Low-cost unmanned aerial vehicle airborne infrared temperature measurement lens

Abstract

The invention discloses a low-cost unmanned aerial vehicle airborne infrared temperature measurement lens which comprises a front fixing group and a focusing group which are sequentially arranged from the object side to the eye side. The focal power of the front fixing group is positive; the focal power of the focusing group is negative; a first lens L1 is accommodated in the front fixed group; a second lens L2 is accommodated in the focusing group; the first lens L1 is a positive meniscus lens; the second lens L2 is a biconvex lens; the first lens rear surface S2, the second lens front surface S3 and the second lens rear surface S4 are all aspheric surfaces. The lens is stable in transmission, compact in mechanism and convenient to assemble, and has high imaging quality and high spatial resolution of MTF (on-axis (at) 40lp / mm) greater than or equal to 0.5.

Description

Technical Field

[0001] The present application relates to the technical field of drone lens, and in particular to a low-cost drone-mounted infrared temperature measurement lens. Background Art

[0002] With the continuous development and maturity of drone technology, drones have been widely used in industrial fields such as aerial photography, remote sensing mapping, forest fire prevention, power line inspection, search and rescue, etc. As an important rescue tool in the fields of forest fire prevention and urban fire, in order to achieve these functions, it is often necessary to install infrared temperature measurement lenses on drones to use drones for observation and search.

[0003] Drones not only make up for the shortcomings of traditional emergency firefighting equipment, improve the efficiency of disaster prevention and mitigation, but also reduce the safety risks of firefighters. When installing infrared temperature measuring lenses on existing drones, the weight of the infrared temperature measuring lenses cannot exceed 150 to 180g and the volume cannot exceed Φ100mm×60mm to Φ120mm×80mm. As a result, after the infrared temperature measuring lenses are installed, the overall weight of the drone is too large to affect normal flight, and also affect the control flexibility and sensitivity of the drone.

[0004] Existing infrared temperature measuring lenses cannot be lightweight or miniaturized, and do not meet the requirements of drones. For example, CN202211285138.1 discloses a power emergency repair drone system and its repair method. Although the method discloses that the information collection drone formation is equipped with an image acquisition module (composed of an infrared temperature measuring lens equipped with a visible light camera), which is used for video image information collection in the disaster area before the power emergency repair work is carried out, and for fault inspection and on-site environmental safety inspection during the emergency repair process, it does not specify which type of infrared temperature measuring lens meets the requirements of which type of drone.

[0005] The information disclosed in the background technology section is only intended to enhance the understanding of the overall background of the invention and should not be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art. Summary of the invention

[0006] In view of the above technical problems, the present application provides a low-cost drone-mounted infrared temperature measurement lens, which has stable transmission, compact structure, and is easy to assemble. It has high imaging quality, high spatial resolution, long detection distance, light weight, and resistance to vibration and impact. It eliminates stray light, introduces aspheric and diffraction surface shapes, fully corrects aberrations to make the theoretical design MTF of the optical system close to the diffraction limit, and the diffuse spot meets the detector use requirements, achieving clear imaging from infinite object distance to 0.5m, and can fully compensate for the image plane drift caused by ambient temperature changes, and meet the requirements of no out-of-focus in the temperature range of -40℃ to +60℃. The structural materials are reasonably matched to achieve lightweight lenses.

[0007] The present application provides a low-cost airborne infrared temperature measurement lens for an unmanned aerial vehicle, including a front fixed group and a focusing group arranged in sequence from the object side to the image side; the optical power of the front fixed group is positive; the optical power of the focusing group is negative;

[0008] A first lens L1 is accommodated in the front fixed group; a second lens L2 is accommodated in the focusing group;

[0009] The first lens L1 is a positive meniscus lens;

[0010] The second lens L2 is a biconvex lens;

[0011] The rear surface S2 of the first lens, the front surface S3 of the second lens, and the rear surface S4 of the second lens are all aspherical surfaces, and satisfy the following formula:

[0012]

[0013] where Z is the distance vector height from the vertex of the aspherical surface at a position with a height of r along the optical axis; c1 = 1 / R, and R represents the paraxial curvature radius of the mirror surface; k is the conic coefficient; A, B, C, and D are high-order aspherical coefficients;

[0014] The aspherical coefficients k of S2, S3, and S4 are all 0; for the S2 surface, A = 9.33856E-06;

[0015] B = 2.11827E-09; C = 3.3711E-010; D = -1.67176E-12;

[0016] For the S3 surface, A = -4.337E-05; B = -2.1299E-07; C = -1.3121E-09;

[0017] D = 2.4734E-10;

[0018] For the S4 surface, A = -7.376E-05; B = -7.0133E-07; C = -6.8347E-09;

[0019] D = 1.12806E-12.

[0020] Preferably, the curvature radius R of the front surface S1 of the first lens L1 is 87 mm; the curvature radius R of the rear surface S2 of the first lens is 71 < R < 80 mm; the curvature radius R of the front surface S3 of the second lens is 25.1 < R < 23.4 mm; the curvature radius R of the rear surface S4 of the second lens is 10 < R < 12 mm.

[0021] Preferably, the material of the first lens L1 is IRG5; the material of the second lens L2 is IRG6.

[0022] Preferably, the diffraction coefficient of surface S4 at a wavelength of 1000 nm is -0.33414E-03.

[0023] Preferably, the focal length of the lens is: f=18mm; field of view angle range: 24.09°×19.37°; relative aperture: 9.84; compatible detector: compatible with an uncooled long-wave infrared detector with a target surface of 640×512 and a pixel size of 12μm; operating temperature: -40℃~+60℃; applicable spectral line range: 8μm~12μm; distortion: <10%; overall dimensions: Φ60mm×32.5mm; weight: 85g.

[0024] Preferably, the front fixing group includes: a first pressing ring and a lens barrel; the first lens L1 is stress-freely bonded in the lens barrel by optical epoxy glue; a first pressing ring is pressed on the other surface of the first lens L1;

[0025] The focusing group includes: a focusing frame and a second pressing ring; the second lens L2 is stress-freely bonded to the focusing frame by optical epoxy glue; and a second pressing ring is pressed on the other surface of the second lens L2;

[0026] It includes: a motor, a cam barrel, and a guide pin; the motor is drivingly connected to the cam barrel; the cam barrel and the guide pin are drivingly connected; and the guide pin is drivingly connected to the focusing lens frame.

[0027] Preferably, it comprises: a motor seat; the motor seat is arranged on the outer wall of the focusing lens frame; the motor is installed in the motor seat; the cam tube and the motor seat are made of hard aluminum alloy.

[0028] Preferably, the lens barrel and the focusing lens frame are made of magnesium-lithium alloy; and the first pressing ring and the second pressing ring are both made of POM.

[0029] Preferably, the lens barrel comprises: a ring body structure and a hollow ring connected to one side of the ring body structure; a plurality of weight-reducing grooves are arranged in pairs and at intervals on the hollow ring in the circumferential direction; the guide pin installation grooves are arranged symmetrically in pairs; a guide pin installation groove is arranged between any two weight-reducing grooves, and the guide pin installation groove is arranged on one side of the weight-reducing groove; the stress at the maximum stress concentration point of the lens barrel (3) is 271.56 MPa;

[0030] The cam barrel includes: a gear ring and a hollow ring; a gear structure meshing with the gear is partially arranged on the outer wall of the gear ring; the gear sleeve is arranged on the output shaft of the motor; one side of the hollow ring is connected to the gear ring; a plurality of weight-reducing grooves are arranged in pairs at intervals circumferentially on the hollow ring; the focusing cam grooves are symmetrically arranged in pairs; the stress at the maximum stress concentration point of the cam barrel is 295.49MPa, which is less than the yield limit requirement of the material.

[0031] Preferably, the focusing lens frame comprises: a mounting ring and a waist-shaped tube; the mounting ring is arranged at one end of the waist-shaped tube; the diameter of the mounting ring is larger than the maximum diameter of any cross section of the waist-shaped tube; the cross-sectional diameter of the waist-shaped tube first shrinks and then expands from one end connected to the mounting ring to the other end;

[0032] A plurality of weight-reducing grooves are arranged in pairs along the circumference of the waist-shaped tube; the guide straight grooves are symmetrically arranged in pairs; the stress at the maximum stress concentration point of the focusing frame is 281.68MPa.

[0033] The beneficial effects of this application include:

[0034] 1) The low-cost drone-mounted infrared temperature measurement lens provided in this application has stable transmission, compact structure, and is easy to assemble. It has high imaging quality and high spatial resolution of MTF (on-axis @40lp / mm): ≥0.5. It also has long detection distance, light weight, and resistance to vibration and impact. It can eliminate stray light, introduce aspheric and diffraction surface shapes, fully correct aberrations to make the theoretical design MTF of the optical system close to the diffraction limit, and the diffuse spot meets the detector use requirements, achieving clear imaging from infinite object distance to 0.5m, and can fully compensate for the image plane drift caused by ambient temperature changes, and meet the requirement of no out-of-focus in the temperature range of -40℃ to +60℃. The structural materials are reasonably matched to achieve lightweight lenses.

[0035] 2) The low-cost drone-mounted infrared temperature measurement lens provided in this application adopts an optical system that reasonably distributes the optical focal length of each group: a total of 3 aspherical surfaces are used to correct phase differences, so that the lens achieves high imaging quality and compact structure while reducing the number of lenses used, thereby reducing the overall quality and meeting the needs of drone mounting.

[0036] 3) The low-cost drone airborne infrared temperature measurement lens provided by this application reasonably matches the infrared materials of the selected lenses in the optical system, fully eliminates the system aberration, corrects the image plane drift, and obtains excellent imaging quality, such as Figure 5 shown.

[0037] 4) The low-cost UAV airborne infrared temperature measurement lens provided in this application optimizes the overall structure of the lens in the lens structure design, and uses magnesium-lithium alloy to make the lens barrel, frame, and interface, uses hard aluminum alloy to make the cam barrel and motor seat, and uses POM material to make the pressure ring, which can meet the requirements of -40℃~+60℃ to ensure the lens surface shape and the overall imaging reliability of the lens. The main lens barrel, cam barrel, and frame are designed to be lightweight respectively, which effectively reduces the total mass of the lens while ensuring the reliability of the imaging results during flight. This structure can focus normally and improve the compactness of the structure. Stress analysis is performed on the lens barrel, cam barrel, and focusing frame respectively, and compared with the material limit stress, which proves that the lightweight structure meets the working strength requirements in the flight environment. The structure obtained after the weight reduction of the lens structure can meet the stress requirements of use.

[0038] 6) The low-cost drone airborne infrared temperature measurement lens provided by this application optimizes the frame aspect ratio, lens position and guide pin depth in the lens structure design, wherein the frame aspect ratio is within the range of 1:1.8 to 1:2, the lens is located within the frame position range of 1:2 to 1:2.5, and the guide pin depth is within the range of 0.3 to 0.5 mm. In the lens structure design, the focusing frame is designed with a matte thread structure to effectively eliminate certain stray light.

[0039] 7) The low-cost UAV airborne infrared temperature measurement lens provided in this application has a gap adjustment block between the cam tube and the interface in the lens structure design, which can effectively eliminate the axial gap, ensure the consistency before and after focusing, and improve the focusing accuracy and the image quality after focusing. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is a structural schematic diagram of a low-cost airborne infrared temperature measurement lens in at least one embodiment of the present application. a) is a side view and a cross-sectional view; b) is a main view;.

[0041] Figure 2 This is a structural axonometric diagram of a low-cost airborne infrared temperature measurement lens in at least one embodiment of the present application.

[0042] Figure 3 Schematic diagram of light propagation of a low-cost airborne infrared temperature measurement lens in at least one embodiment of the present application.

[0043] Figure 4 This is a diagram marking relevant parameters of each lens in at least one embodiment of the present application.

[0044] Figure 5 This is a schematic diagram of the MTF of a low-cost airborne infrared temperature measurement lens in at least one embodiment of the present application.

[0045] Figure 6Schematic diagram of field curvature and distortion of a low-cost airborne infrared temperature measurement lens in at least one embodiment of the present application; a) is field curvature; b) distortion.

[0046] Figure 7 This is a spot diagram of a low-cost airborne infrared temperature measurement lens in at least one embodiment of the present application.

[0047] Figure 8 This is a relative illumination diagram of a low-cost airborne infrared temperature measurement lens in at least one embodiment of the present application.

[0048] Fig. 9 This is a barrel stress analysis diagram of a low-cost airborne infrared temperature measurement lens in at least one embodiment of the present application.

[0049] Fig.10 This is a stress analysis diagram of the cam barrel of a low-cost airborne infrared temperature measurement lens in at least one embodiment of the present application.

[0050] Fig.11 This is a stress analysis diagram of the focusing lens frame of a low-cost airborne infrared temperature measurement lens in an embodiment of the present invention.

[0051] Legend:

[0052] first lens L1, second lens L2, first lens front surface S1, first lens rear surface S2, second lens front surface S3, second lens rear surface S4,

[0053] Front mirror cover 1, first pressure ring 2, lens barrel 3, cam barrel 4, focusing lens frame 5, gear 6, motor seat 7, motor 8, guide pin 9, interface 10, rear mirror cover 11, second pressure ring 12, limit switch 13, limit block 14, gap focusing block 15. DETAILED DESCRIPTION

[0054] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0055] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0056] The technical means that are not described in detail in this application and are not used to solve the technical problems of this application are all set according to the common knowledge in the field, and can be implemented in a variety of common knowledge settings.

[0057] See also Figures 1 to 11 The low-cost drone-mounted infrared temperature measurement lens provided in the present application includes: a front fixed group with positive optical focal length and a focusing group with negative optical focal length, which are arranged in sequence along the incident direction of light from left to right; a first lens L1 is arranged in the front fixed group, and the first lens L1 is a positive meniscus lens; a second lens L2 is arranged in the focusing group for focusing, and the second lens L2 is a double convex lens.

[0058] The first lens rear surface S2, the second lens front surface S3, and the second lens rear surface S4 are all aspherical surfaces.

[0059] The aspherical surfaces of the first lens rear surface S2, the second lens front surface S3, and the second lens rear surface S4 all satisfy the following formula:

[0060]

[0061] Among them, Z is the distance vector height from the vertex of the aspherical surface at a height of r along the optical axis; c1=1 / R, R represents the paraxial curvature radius of the mirror; k is the cone coefficient; A, B, C, and D are high-order aspherical coefficients.

[0062] The parameters of the first lens L1 and the second lens L2 are shown in the following table:

[0063] surface

[0064]

[0065]

[0066] The radius of curvature R in the above table refers to the radius of curvature of each surface.

[0067] The following table lists the aspheric coefficients of surfaces S2, S3, and S4:

[0068] surface

[0069] Surface number k A B C D S2 0 9.33856E-06 2.11827E-09 3.3711E-010 -1.67176E-12 S3 0 -4.337E-05 -2.1299E-07 -1.3121E-09 2.4734E-10 S4 0 -7.376E-05 -7.0133E-07 -6.8347E-09 1.12806E-12

[0070] The following table shows the diffraction coefficients of surface S4:

[0071] surface wavelength First-order diffraction coefficient S4 1000nm -0.33414E-03

[0072] In a specific embodiment, the lens materials of the optical system in the lens are arranged in order along the incident direction of the light, i.e., IRG5 and IRG6. The lens material used for the first lens L1 is i.e., IRG5; and the lens material used for the second lens L2 is i.e., IRG6.

[0073] In a specific embodiment, the optical system composed of the above-mentioned lenses achieves the following optomechanical indicators:

[0074] (1) Focal length: f = 18 mm;

[0075] (2) Field of view: 24.09°×19.37°;

[0076] (3) Relative aperture: 9.84;

[0077] (4) Suitable detector: Suitable for uncooled long-wave infrared detector with a target area of ​​640×512 and a pixel size of 12μm;

[0078] (5) Working temperature: -40℃~+60℃;

[0079] (6) Applicable spectral range: 8μm~12μm;

[0080] (7) Distortion: <10%

[0081] (8) Overall dimensions: Φ60mm×32.5mm;

[0082] (9)Weight: 85g.

[0083] In this example, the optical system is sensitive to temperature to a certain extent. The lens material is selected reasonably, and the influence of temperature on the system is considered during the design process. Among the common infrared materials, the refractive index temperature variation coefficient of IRG5 and IRG6 is relatively low, and the price is relatively lower than Ge, and the weight is lighter. Therefore, based on the comprehensive consideration of cost and quality, IRG5 and IRG6 are selected as the main materials. Since infrared materials have greater absorption than visible light materials, but higher refractive index, in order to ensure the imaging effect, only two lenses with the above parameters are selected for use to ensure the comprehensive performance of the optical system. At the same time, by introducing the aspheric lens structure designed according to the above formula to balance the system aberration, the optical system structure is simplified and the imaging quality is better.

[0084] The front fixing group includes: a first lens L1 and a first pressing ring 2, and the first lens L1 is stress-free bonded to the front end of the lens barrel 3 by optical epoxy glue; the focusing group includes: a second lens L2, a focusing lens frame 5 and a second pressing ring 12, and is fixed and pressed by the first pressing ring 2, and the second lens L2 is stress-free bonded to the focusing lens frame 5 by optical epoxy glue and fixed and pressed by the second pressing ring 12.

[0085] The focusing assembly is installed in the lens barrel 3, a focusing guide groove is provided on the lens barrel 3, a cam barrel 4 is provided outside the lens barrel 3, a focusing cam groove is provided on the outer surface of the cam barrel 4, and a plurality of guide pins 9 are provided on the cam barrel 4 and extend into the focusing guide groove from the focusing cam groove in sequence, and are connected to the focusing assembly. The gap focusing block 15 is installed on the lens barrel 3, and contacts with the cam barrel 4 and the interface 10 respectively, and then the interface 10 is fixed to the rear end of the lens barrel 3 by screws.

[0086] The motor 8 is arranged on the motor seat 7. When the rotor of the motor 8 rotates, the gear 6 sleeved on the output shaft of the motor 8 drives the cam barrel 4 to rotate. The cam barrel 4 transmits the motion to the focusing lens frame 5 through the guide pin 9. The focusing lens frame 5 converts the rotational motion of the cam barrel 4 into parallel movement of the focusing lens frame 5 along the optical axis along the guide straight groove, thereby realizing focusing. The motor 8 automatically stops at the front and rear focusing end points, and the focusing stroke is controlled by the limit block 14 arranged on the focusing lens frame 5 touching the contact of the limit switch 13.

[0087] In a specific embodiment, in order to better adapt to the use environment, the lens uses reasonable structural material, so the lens barrel 3, the focusing lens frame 5 and the interfaces of each part are made of magnesium-lithium alloy.

[0088] In a specific embodiment, the cam barrel 4 and the motor seat 7 are both made of hard aluminum alloy, and the first pressing ring 2 and the second pressing ring 12 are both made of POM. The processing technology and stability are increased, and the first pressing ring 2 and the second pressing ring 12 are provided with matte threads on the inner wall, which reduces the weight of the lens and reduces the influence of stray light.

[0089] In a specific embodiment, the lens barrel 3 accommodates a front fixing group and a focusing group; the front fixing group and the focusing group are arranged in sequence along the incident direction of the light from left to right.

[0090] In a specific embodiment, the automatic stop action of the motor 8 at the end point of the front and rear focusing is controlled by the upper limit post on the focusing lens frame 5 touching the limit switch contact.

[0091] In a specific embodiment, the axial clearance of the lens can be adjusted by replacing the clearance block according to the actual structural requirements to ensure the stability of the focusing process, thereby ensuring the consistency and accuracy of the temperature calibration.

[0092] Application examples:

[0093] The lens imaging using the above structure can achieve the following effects:

[0094] MTF (on-axis @10lp / mm): ≥0.85

[0095] MTF (on-axis @20lp / mm): ≥0.75

[0096] MTF (on-axis @30lp / mm): ≥0.6;

[0097] MTF (on-axis @40lp / mm): ≥0.5

[0098] Distortion ≤7%;

[0099] Relative illumination ≥97%;

[0100] The lens barrel and lens frame structure are lightweighted by using lightweight materials and topology optimization. The stress analysis results of the lens barrel 3 are as follows: Fig. 9 As shown; the stress analysis results of the cam tube 4 are as shown Fig.10 As shown; the stress analysis results of the focusing frame 5 are as shown Fig.11 As shown;

[0101] Depend on Figures 9-10 It can be seen that the lens barrel 3 includes: a ring body structure and a hollow ring connected to one side of the ring body structure; a plurality of weight-reducing grooves are arranged in pairs at intervals in the circumferential direction on the hollow ring; the guide nail mounting grooves are symmetrically arranged in pairs; the stress at the maximum stress concentration point of the lens barrel 3 is 271.56 MPa; specifically, the weight-reducing grooves are arranged in pairs of 3 groups, and the guide nail mounting grooves are symmetrically arranged in pairs of 1 group; while achieving a better weight-reducing effect, it can ensure the safety of use in various temperature environments.

[0102] The cam barrel 4 includes: a gear ring and a hollow ring; a gear structure meshing with the gear is partially arranged on the outer wall of the gear ring; the gear is sleeved on the output shaft of the motor; one side of the hollow ring is connected to the gear ring; multiple weight-reducing grooves are arranged in pairs and at intervals on the hollow ring in the circumferential direction; the focusing cam grooves are arranged symmetrically in pairs; the stress at the maximum stress concentration point of the cam barrel 4 is 295.49MPa, which is less than the yield limit requirement of the material. Specifically, the weight-reducing grooves are arranged in pairs of 3 groups, and the focusing cam grooves are arranged in pairs of 1 group, which can achieve a good weight-reducing effect while ensuring the safety of use in various temperature environments.

[0103] The focusing lens frame 5 comprises: a mounting ring and a waist-shaped tube; the mounting ring is arranged at one end of the waist-shaped tube; the diameter of the mounting ring is larger than the maximum diameter of any cross section of the waist-shaped tube; the cross-sectional diameter of the waist-shaped tube first shrinks and then expands from one end connected to the mounting ring to the other end;

[0104] A plurality of weight-reducing grooves are arranged in pairs along the circumference of the waist-shaped tube; the guide straight grooves are arranged symmetrically in pairs; the stress at the maximum stress concentration point of the focusing frame 5 is 281.68MPa. Specifically, one group of guide straight grooves and three groups of weight-reducing grooves are arranged, which can achieve a good weight-reducing effect while ensuring the safety of use in various temperature environments.

[0105] Depend on Figures 9-10It can be seen that when the ambient temperature decreases or increases, the structural parts will experience corresponding thermal stress. Under the condition of an ambient temperature of -40°C, the thermal stress of the frame is relatively uniform as a whole, among which the maximum thermal stress is distributed at the weight reduction position, and the maximum value is 271.56Mpa, which is less than the material yield limit. Under the condition of an ambient temperature of -40°C, the thermal stress of the cam barrel is relatively uniform as a whole, among which the maximum thermal stress is distributed at the cam curve position, and the maximum value is 295.49Mpa, which is less than the material yield limit. Under the condition of an ambient temperature of -40°C, the thermal stress of the lens barrel is relatively uniform as a whole, among which the maximum thermal stress is distributed at the rear end threaded connection position of the lens barrel, and the maximum value is 281.68Mpa, which is less than the material yield limit. The lens barrel, cam barrel and frame meet the requirements for normal operation at -40°C.

[0106] At the same time, the deformation of the structural parts is less than 0.07mm, the equivalent stress is less than 400MPa, and the overall weight is only 85g, which can effectively reduce the overall weight and meet the imaging requirements in the drone recording environment.

[0107] The light in this lens propagates as Figure 3 As shown; it can be seen from the figure that the lens can achieve effective focusing of light.

[0108] The MTF results of this lens are as follows: Figure 5 As shown in the figure, the lens imaging can achieve the following effects: MTF (on-axis @10lp / mm): ≥0.85, MTF (on-axis @20lp / mm): ≥0.75, MTF (on-axis @30lp / mm): ≥0.6, MTF (on-axis @40lp / mm): ≥0.5, proving that the lens meets the imaging quality requirements.

[0109] The field curvature and distortion of this lens ( Figure 6 b) respectively as Figure 6 The field curvature of the lens imaging is less than 0.01, and the distortion is ≤7%, which proves that the field curvature and distortion of the lens meet the industry standard requirements of UAV airborne thermal imagers, which are field curvature less than 0.10 and distortion ≤10%.

[0110] The imaging point sequence of this lens is as follows Figure 7 The diffuse spot result of this lens is as follows Figure 7 The RMS diffuse spot radius of the lens is less than 12μm in the central field of view, proving that the lens has good imaging quality at all positions.

[0111] The relative illumination results of the lens are as follows: Figure 8 As shown; the diffuse spot result of this lens is as follows Figure 7 The relative illumination of the lens is > 95%, which proves that the lens has good uniformity at all positions and meets the relative illumination > 90% requirement of the industry standard for UAV airborne thermal imagers.

[0112] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A low-cost drone-mounted infrared temperature measurement lens, characterized in that: It includes a front fixed group and a focusing group arranged in sequence from the object side to the image side; the optical power of the front fixed group is positive; the optical power of the focusing group is negative; The first lens L1 is accommodated in the front fixed group; the second lens L2 is accommodated in the focusing group; The first lens L1 is a positive meniscus lens; The second lens L2 is a biconvex lens; The rear surface S2 of the first lens, the front surface S3 of the second lens, and the rear surface S4 of the second lens are all aspherical surfaces and satisfy the following formula: Where, Z is the distance vector height from the vertex of the aspherical surface at the position with a height of r along the optical axis direction; c1 = 1 / R, R represents the paraxial curvature radius of the mirror surface; k is the conic coefficient; A, B, C, D are high-order aspherical coefficients; The conic coefficients k of S2, S3, and S4 are all 0; for the S2 surface, A = 9.33856E-06; B = 2.11827E-09; C = 3.3711E-010; D = -1.67176E-12; For the S3 surface, A = -4.337E-05; B = -2.1299E-07; C = -1.3121E-09; D = 2.4734E-10; For the S4 surface, A = -7.376E-05; B = -7.0133E-07; C = -6.8347E-09; D = 1.12806E-12.

2. The low-cost UAV airborne infrared temperature measuring lens according to claim 1 is characterized in that: The curvature radius R of the front surface S1 of the first lens L1 is 87mm; the curvature radius R of the rear surface S2 of the first lens is 71 < R < 80mm; the curvature radius R of the front surface S3 of the second lens is 25.1 < R < 23.4mm; the curvature radius R of the rear surface S4 of the second lens is 10 < R < 12mm.

3. The low-cost UAV airborne infrared temperature measuring lens according to claim 1 is characterized in that: The material of the first lens L1 is IRG5; the material of the second lens L2 is IRG6.

4. The low-cost UAV airborne infrared temperature measuring lens according to claim 1 is characterized in that: The diffraction surface coefficient of the surface S4 at a wavelength of 1000nm is -0.33414E-03.

5. The low-cost UAV airborne infrared temperature measuring lens according to claim 1 is characterized in that: The focal length of this lens: f = 18mm; the field of view angle range: 24.09°×19.37°; the relative aperture: 9.84; the adapted detector: adapted to a non-cooled long-wave infrared detector with a target surface of 640×512 and a pixel size of 12μm; the operating temperature: -40°C to +60°C; the applicable spectral line range: 8μm to 12μm; the distortion: <10%; The external dimensions: Φ60mm×32.5mm; the weight: 85g.

6. The low-cost UAV airborne infrared temperature measuring lens according to claim 1, characterized in that: The front fixed group includes: the first retaining ring (2), the lens barrel (3); the first lens L1 is adhesively bonded in the lens barrel (3) without stress by optical epoxy; the first retaining ring (2) is pressed on the other surface of the first lens L1; The focusing group includes: the focusing lens frame (5), the second retaining ring (12); the second lens L2 is adhesively bonded in the focusing lens frame (5) without stress by optical epoxy; the second retaining ring (12) is pressed on the other surface of the second lens L2; It includes: the motor (8), the cam barrel (4), the guide pin (9); the motor (8) is drivingly connected to the cam barrel (4); the cam barrel (4) and the guide pin (9) are drivingly connected; the guide pin (9) is drivingly connected to the focusing lens frame (5).

7. The low-cost drone-mounted infrared temperature measuring lens according to claim 6 is characterized in that: It includes: The motor seat (7) is arranged on the outer wall of the focusing lens frame (5); the motor (8) is installed in the motor seat (7); the cam tube (4) and the motor seat (7) are made of hard aluminum alloy.

8. The low-cost UAV airborne infrared temperature measuring lens according to claim 6, characterized in that: The lens barrel (3) and the focusing lens frame (5) are made of magnesium-lithium alloy; the first pressing ring (2) and the second pressing ring (12) are both made of POM.

9. The low-cost UAV airborne infrared temperature measuring lens according to claim 1, characterized in that: The lens barrel (3) comprises: a ring body structure and a hollow ring connected to one side of the ring body structure; a plurality of weight-reducing grooves are arranged in pairs at intervals in the circumferential direction on the hollow ring; the guide pin installation grooves are arranged symmetrically in pairs; a guide pin installation groove is arranged between any two weight-reducing grooves, and the guide pin installation groove is arranged on one side of the weight-reducing groove; the stress at the maximum stress concentration point of the lens barrel (3) is 271.56 MPa; The cam barrel (4) comprises: a gear ring and a hollow ring; a gear structure meshing with a gear (6) is partially arranged on the outer wall of the gear ring; the gear (6) is sleeved on the output shaft of the motor (8); one side of the hollow ring is connected to the gear ring; a plurality of weight-reducing grooves are arranged in pairs and at intervals on the hollow ring in a circumferential direction; the focusing cam grooves are symmetrically arranged in pairs; and the stress at the maximum stress concentration point of the cam barrel (4) is 295.49 MPa, which is less than the yield limit requirement of the material.

10. The low-cost UAV airborne infrared temperature measuring lens according to claim 1, characterized in that: The focusing lens frame (5) comprises: a mounting ring and a waist-shaped tube; the mounting ring is arranged at one end of the waist-shaped tube; the diameter of the mounting ring is larger than the maximum diameter of any cross section of the waist-shaped tube; the cross-sectional diameter of the waist-shaped tube first shrinks and then expands from one end connected to the mounting ring to the other end; A plurality of weight-reducing grooves are arranged in pairs and at intervals along the circumference of the waist-shaped tube; the guide straight grooves are arranged symmetrically in pairs; and the stress at the maximum stress concentration point of the focusing lens frame (5) is 281.68 MPa.

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