A compact vehicle-mounted long-wave infrared lens and electronic equipment

Abstract

This invention discloses a compact automotive long-wave infrared lens, comprising a first lens, an aperture, a second lens, and a third lens arranged sequentially along the optical axis from the object side to the image side. The lenses satisfy the following relationships: 35 < |f1 / f| < 60, 0.8 < |f2 / f| < 2.5, 0.9 < |f3 / f| < 2, where f1 is the focal length of the first lens, f2 is the focal length of the second lens, f3 is the focal length of the third lens, and f is the total focal length of the lens system. This invention, by employing a three-element lens architecture, reduces the overall length of the long-wave infrared lens, facilitating its integration into a space-constrained automotive frame. Furthermore, by rationally allocating the ratios of the first to third lenses to the total focal length, it balances imaging aberrations and achieves high resolution.

Description

Technical Field

[0001] This invention relates to the field of long-wave infrared lens technology, and in particular to a compact vehicle-mounted long-wave infrared lens and electronic device. Background Technology

[0002] With the development of infrared detection technology, uncooled thermal imaging is gradually becoming more common in the automotive field, especially in infrared vehicle night vision systems. Infrared imaging principle: It utilizes the thermal radiation of nature itself for imaging, requiring no illumination source and offering the advantage of long detection distance. In situations with low visibility and poor lighting conditions such as dense fog, heavy rain, and nighttime, compared to visible light imaging, it can clearly detect road conditions ahead, ensuring safe driving and providing road detection capabilities in special environments. However, existing long-wave infrared lenses have at least one of the following drawbacks:

[0003] 1. Generally, long-wave infrared lenses are relatively long and have a large aperture, making them impossible to integrate into the space-constrained car frame.

[0004] 2. Generally, long-wave infrared lenses have high manufacturing costs and high prices, which cannot meet the requirements of the automotive market for low-cost parts.

[0005] 3. Generally, long-wave infrared lenses use sulfur glass for the first lens, which has relatively weak hardness and cannot meet the reliability requirements for hardness of automotive lenses.

[0006] 4. Generally, long-wave infrared lenses are relatively heavy, which cannot meet the current demand for lightweight design.

[0007] 5. Generally, long-wave infrared lenses have poor temperature drift performance and cannot work normally in harsh high and low temperature environments. Summary of the Invention

[0008] In view of this, the object of the present invention is to provide a compact vehicle-mounted long-wave infrared lens and electronic device. This lens can at least solve one of the technical disadvantages mentioned in the background art.

[0009] According to one aspect of the present invention, a compact automotive long-wave infrared lens is provided, comprising a first lens, an aperture, a second lens, and a third lens arranged sequentially along the optical axis from the object side to the image side. The lenses satisfy the following relationships: 35 < |f1 / f| < 60, 0.8 < |f2 / f| < 2.5, 0.9 < |f3 / f| < 2, where f1 is the focal length of the first lens, f2 is the focal length of the second lens, f3 is the focal length of the third lens, and f is the total focal length of the lens system. This invention, by employing a three-element lens architecture, reduces the overall length of the long-wave infrared lens, facilitating its integration into a space-constrained automotive frame. Furthermore, by rationally allocating the ratios of the first to third lenses to the total focal length, it balances imaging aberrations and achieves high resolution.

[0010] According to another aspect of the present invention, an electronic device is provided, comprising the aforementioned compact automotive long-wave infrared lens; and an image sensor configured to receive an image formed by the long-wave infrared lens. In this technical solution, the advantages of the electronic device rely on the long-wave infrared lens, which will not be elaborated upon here. Attached Figure Description

[0011] 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.

[0012] Figure 1 This is a structural diagram of the optical system of Embodiment 1 of the vehicle-mounted long-wave infrared lens of the present invention.

[0013] Figure 2 This is an MTF curve diagram of Embodiment 1 of the vehicle-mounted long-wave infrared lens of the present invention.

[0014] Figure 3 This is a field curvature distortion diagram of Embodiment 1 of the vehicle-mounted long-wave infrared lens of the present invention.

[0015] Figure 4 This is a wavefront image of Embodiment 1 of the vehicle-mounted long-wave infrared lens of the present invention.

[0016] Figure 5 This is a structural diagram of the optical system of Embodiment 2 of the vehicle-mounted long-wave infrared lens of the present invention.

[0017] Figure 6 This is the MTF curve of Embodiment 2 of the vehicle-mounted long-wave infrared lens of the present invention.

[0018] Figure 7 This is a field curvature distortion diagram of Embodiment 2 of the vehicle-mounted long-wave infrared lens of the present invention.

[0019] Figure 8 This is a wavefront image of embodiment 2 of the vehicle-mounted long-wave infrared lens of the present invention.

[0020] Figure 9 This is a schematic diagram of the structure of the electronic device of the present invention.

[0021] The above figures include the following reference numerals:

[0022] L1, first lens; L2, second lens; L3, third lens; ST, aperture stop; G, protective glass; IMA, imaging plane. Detailed Implementation

[0023] 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.

[0024] According to one aspect of the present invention, a compact vehicle-mounted long-wave infrared lens is provided, comprising a first lens L1, an aperture ST, a second lens L2, and a third lens L3 arranged sequentially along the optical axis from the object side to the image side.

[0025] The lens satisfies the following relationships: 35 < |f1 / f| < 60, 0.8 < |f2 / f| < 2.5, 0.9 < |f3 / f| < 2, where f1 is the focal length of the first lens L1, f2 is the focal length of the second lens L2, f3 is the focal length of the third lens L3, and f is the total focal length of the lens system.

[0026] The beneficial effects of the above embodiments are as follows: By adopting a three-element lens architecture, the present invention can reduce material costs, shorten the total length of the long-wave infrared lens, and facilitate its integration into a space-constrained automotive frame. Furthermore, by rationally allocating the ratio of the first lens L1 to the third lens L3 to the total focal length, the imaging aberrations of the lens can be balanced, thereby achieving high resolution of the lens.

[0027] Furthermore,

[0028] The first lens L1 has negative refractive power, the object side of the first lens L1 is convex, and the image side of the first lens L1 is concave.

[0029] The second lens L2 has positive refractive power, the object side of the second lens L2 is concave, and the image side of the second lens L2 is convex.

[0030] The third lens L3 has positive refractive power, the object side of the third lens L3 is concave, and the image side of the third lens L3 is convex.

[0031] The beneficial effects of the above embodiment are: image clarity is ensured by reasonably allocating refractive power, and overall image quality is uniform. The aperture stop ST is located between the first lens L1 and the second lens L2. All lenses on both sides of the aperture stop ST are bent towards it, minimizing the angle of incidence and achieving near-symmetry. The overall light path is as follows: the light diverges slightly after passing through the first lens L1, then gradually increases in aperture after passing through the second lens L2, and finally converges to the imaging plane IMA after passing through the third lens L3. The advantage of near-symmetry is that it can reduce aberrations, improve image quality, improve luminous flux distribution, simplify design and manufacturing, improve system stability, and enhance the symmetry of the optical system.

[0032] Furthermore, the lens satisfies the following relationship:

[0033] 1.5<TTL / f<2.5, 0.4<BFL / f<1.5,

[0034] Where TTL is the distance from the vertex of the object side of the first lens L1 to the imaging surface IMA, BFL is the distance from the vertex of the image side of the third lens L3 to the imaging surface IMA, and f is the total focal length of the lens system.

[0035] The beneficial effects of the above embodiments are: the total length of the lens is extremely short and the back focal length is long, and the optical system occupies a very small total length, which meets the miniaturization requirements of vehicle-mounted equipment for lenses.

[0036] Furthermore, the lens satisfies the following relationship:

[0037] f1 < 0, f2 > 0, f3 > 0

[0038] Where f1 is the focal length of the first lens L1, f2 is the focal length of the second lens L2, and f3 is the focal length of the third lens L3.

[0039] The beneficial effects of the above embodiments are as follows: the first lens L1 and the second lens L2 adopt a reverse telephoto structure with negative focal length and positive focal length respectively, which can effectively enable the lens to achieve a short focal length and a long optical back focal length, making it convenient to place auxiliary elements behind the lens, so that the lens can obtain a large field of view and obtain a wide shooting field of view.

[0040] Furthermore, the lens satisfies the following relationship:

[0041] 3.5<Nd1<4.5, 2<Nd2<3.5, 2<Nd3<3.5,

[0042] The first lens L1 has a refractive index of Nd1 at a wavelength of 10 μm, the second lens L2 has a refractive index of Nd2 at a wavelength of 10 μm, and the third lens L3 has a refractive index of Nd3 at a wavelength of 10 μm.

[0043] The beneficial effects of the above embodiments are as follows: By setting the refractive indices of the first lens L1 to the third lens L3, if the refractive index of the first lens L1 is higher than the upper limit, the incident angle of light from the lens increases, and the lens sensitivity increases. However, if the refractive index of the first lens L1 is lower than the lower limit, the first lens cannot be coated with a DLC film; if the refractive index of the second lens L2 is higher than the upper limit, the temperature drift performance of the optical system deteriorates. However, if the refractive index of the second lens L2 is lower than the lower limit, the lens sensitivity increases; if the refractive index of the third lens L3 is higher than the upper limit, the temperature drift performance of the optical system deteriorates. However, if the refractive index of the third lens L3 is lower than the lower limit, the lens sensitivity increases; satisfying the above formula helps to reduce the sensitivity of each lens, improve temperature drift performance, and simultaneously increase the hardness of the first lens.

[0044] Furthermore, the object-side and image-side surfaces of the first lens L1, the second lens L2, and the third lens L3 are all aspherical, and the object-side surface of the third lens L3 is a binary diffraction surface.

[0045] The binary diffraction surface satisfies the following relationship:

[0046] 5.3<r<6, -35<A1<-5, 0<A2<10, N<4,

[0047] The normalized radius of the binary diffraction surface is r, the first phase coefficient of the binary diffraction surface is A1, the second phase coefficient of the binary diffraction surface is A2, and the series of the polynomial of the binary diffraction surface is N.

[0048] The beneficial effects of the above embodiments are as follows: by designing the object-side and image-side surfaces of the first lens L1, the second lens L2, and the third lens L3 as aspherical surfaces, the pyrodynamic performance of the optical system can be effectively improved. Furthermore, designing the relationship satisfied by the binary diffraction surface is beneficial for improving the imaging performance of the optical system at both high and low temperatures, ensuring that the image plane remains focused.

[0049] Furthermore, the lens satisfies the following relationship:

[0050] 1.4mm < d1 < 2.7mm, 1.3mm < d2 < 2.6mm, 2.2mm < d3 < 3.7mm, where the center thickness of the first lens L1 is d1, the center thickness of the second lens L2 is d2, and the center thickness of the third lens L3 is d3.

[0051] The beneficial effects of the above embodiments are as follows: By setting the center thicknesses of the first lens L1 to the third lens L3, if the center thickness of the first lens L1 is higher than the upper limit, the lens weight increases, and the cost increases. However, if the center thickness of the first lens L1 is lower than the lower limit, the optical imaging performance decreases, the edge thickness is insufficient, and it is easy to break. If the center thickness of the second lens L2 is higher than the upper limit, the lens weight increases, and the cost increases. However, if the center thickness of the second lens L2 is lower than the lower limit, the optical imaging performance decreases, the edge thickness is insufficient, and it is easy to break. If the center thickness of the third lens L3 is higher than the upper limit, the lens weight increases, and the cost increases. However, if the center thickness of the third lens L3 is lower than the lower limit, the image quality deteriorates. By satisfying the above formula, it is beneficial to obtain good image quality performance while reducing the weight and cost of the optical system.

[0052] Furthermore, the lens satisfies the following relationship:

[0053] 4g / cm 3 <ρ1<6.5g / cm 3 2.5g / cm 3 <ρ2<5.6g / cm 3 2.5g / cm 3 <ρ3<5.6g / cm 3 The first lens L1 uses glass material with a density of ρ1 (grams per cubic centimeter), the second lens L2 uses glass material with a density of ρ2 (grams per cubic centimeter), and the third lens L3 uses glass material with a density of ρ3 (grams per cubic centimeter).

[0054] The beneficial effects of the above embodiments are as follows: By setting the glass density of the first lens L1 to the third lens L3, if the glass density of the first lens L1 is higher than the upper limit, the lens weight increases, and the cost increases. However, if the glass density of the first lens L1 is lower than the lower limit, the optical system aberration increases. Similarly, if the glass density of the second lens L2 is higher than the upper limit, the weight increases, and the cost increases. However, if the glass density of the second lens L2 is lower than the lower limit, the optical system aberration increases. Furthermore, if the glass density of the third lens L3 is higher than the upper limit, the lens weight increases, and the cost increases. However, if the glass density of the third lens L3 is lower than the lower limit, the optical system aberration increases. Satisfying the above formulas facilitates the acquisition of lightweight and low-cost lenses.

[0055] Furthermore, the lens satisfies the following relationship:

[0056] 5 < FOV / f < 9,

[0057] Where FOV is the field of view of the lens, and f is the total focal length of the lens system.

[0058] The beneficial effects of the above embodiments are as follows: by setting the ratio range of FOV to f, if the ratio range is higher than the upper limit, the optical system has a large field of view, a small focal length, and a smaller magnification of the detected object, resulting in blurred details. However, if the ratio range is lower than the lower limit, the optical system has an insufficient field of view and a small detection area. By satisfying the above formula, it is beneficial to obtain a suitable detection field of view, and when shooting objects with magnification, the details are clear.

[0059] Furthermore, an aperture stop ST is provided between the first lens L1 and the second lens L2, and a protective glass G is provided on the image-side side of the third lens L3. Preferably, the first lens L1 is made of germanium, which can effectively enhance the coating strength of the first material. The second lens L2 and the third lens L3 are made of chalcogenide glass, which can be molded, facilitating mass production and greatly reducing manufacturing costs.

[0060] Furthermore, the lens satisfies the following relationship:

[0061] D1≤D2≤D3,

[0062] The maximum outer diameter of the first lens L1 is D1, the maximum outer diameter of the second lens L2 is D2, and the maximum outer diameter of the third lens L3 is D3.

[0063] The advantages of the above embodiments are as follows: Unlike conventional lenses, the first lens L1, the second lens L2, and the third lens L3 are assembled with the lens frame from right to left, with the first lens L1 directly resting on the lens frame. The third lens L3 is locked in place by a pressure ring. The maximum outer diameter of the first lens L1 to the third lens L3 increases sequentially, which is beneficial for miniaturization requirements, resulting in small lens dimensions and low material costs. The lens frame can be well designed as a waterproof structure.

[0064] Furthermore, the finished lens's external dimensions satisfy the following relationship:

[0065] 12.5mm<L<14.5mm, Φ18.5mm<D<Φ20mm,

[0066] The length from the front end to the rear end of the mechanical component in the finished lens is L, and the maximum diameter of the finished lens is D.

[0067] The beneficial effect of the above embodiments is that by limiting the length from the foremost end to the tail end of the finished lens mechanical component and the maximum diameter of the finished lens, the miniaturization requirements of vehicle-mounted equipment for lenses are met.

[0068] The following will provide a detailed description of the shots described in this case using specific examples. It should be noted that the following table is merely a specific embodiment of the present invention and not a limiting example.

[0069] For ease of description, in the table, surface number 1 and surface number 2 are the object-side and image-side surfaces of the first lens L1, respectively; surface number 3 is the surface of the aperture STST; surface number 4 and surface number 5 are the object-side and image-side surfaces of the second lens L2, respectively; surface number 6 and surface number 7 are the object-side and image-side surfaces of the third lens L3, respectively; surface number 8 and surface number 9 are the object-side and image-side surfaces of the protective glass G, respectively; and surface number 10 is the surface of the imaging plane IMA.

[0070] Please refer to the optical structure of Example 1. Figure 1 The specific parameters of this embodiment 1 are shown in Table 1 below. In this embodiment 1, the lens focal length f' = 9mm, aperture F = 1.0, field of view FOV = 62.5°, back focal length BFL = 7.9mm, and total length TTL = 18.4mm.

[0071] Table 1 Lens Parameter Table for Example 1

[0072]

[0073] Table 2. Arrangement of Aspheric Coefficients on Lens Surfaces in Example 1

[0074] Face number K A4 A6 A8 A10 A12 1 0.00 2.737E-04 -4.786E-05 2.577E-06 -1.076E-07 1.780E-09 2 0.00 7.788E-04 -1.389E-04 8.229E-06 -4.043E-07 7.317E-09 4 0.00 4.372E-04 -6.553E-05 3.575E-06 -1.740E-07 -6.866E-10 5 0.00 9.333E-04 -9.658E-05 8.131E-06 -4.101E-07 8.110E-09 6 0.00 7.261E-04 -5.050E-05 2.632E-06 -7.945E-08 1.034E-09 7 0.00 3.222E-04 -2.725E-05 1.314E-06 -3.370E-08 3.468E-10

[0075] Table 3. Arrangement of Aspheric Coefficients on Lens Surfaces in Example 1

[0076] Face number Normalized radius polynomial coefficients A1 A2 6 5.50 2.00 -25.219 3.9

[0077] According to Table 1-3, the conditional expression of Embodiment 1 of the present invention can be read as follows:

[0078] (1)TTL / f=2.044, BFL / f=0.878

[0079] (2)f1=-421mm, f2=14mm, f3=12mm, f′=9mm

[0080] (3)Nd1=4.0, Nd2=2.8, Nd3=2.8

[0081] (4)r=5.5, A1=-25.219, A2=3.900, N=2

[0082] (5)d1=2.1mm, d2=2.1mm, d3=3.2mm

[0083] (6) ρ1=5.33g / cm 3 ρ2=4.63g / cm 3 ρ3=4.63g / cm 3

[0084] (7) FOV / f = 6.944

[0085] (8)D1=11.2mm, D2=11.9mm, D3=12.6mm

[0086] (9) L=13.5mm, D=Φ19mm

[0087] The following is an explanation of the various figures in Embodiment 1:

[0088] Figure 1 This is a structural diagram of the optical system of the lens in Example 1. As can be seen from the diagram, the aperture stop ST is located between the first lens L1 and the second lens L2. All the lenses on both sides of the aperture stop ST are bent towards it, minimizing the angle of incidence and achieving near symmetry. The overall direction of the light rays is as follows: after passing through the first lens L1, the light rays diverge slightly; after passing through the second lens L2, the light aperture gradually increases; and after passing through the third lens L3, the light aperture narrows and converges to the imaging plane IMA. A protective glass G for the detector window is placed between the third lens L3 and the imaging plane IMA.

[0089] Figure 2 This is the MTF curve for Example 1. The horizontal axis represents frequency, in line pairs. The vertical axis represents the MTF value, with no unit. As can be seen from the graph, in the 8-12µm long-wave infrared band, the MTF curve is very concentrated, with most of the MTF across the entire field of view concentrated around 0.3 at 42 Lp / mm. The imaging quality is good and suitable for use with a 12µm long-wave infrared sensor.

[0090] Figure 3 The left image shows the field curvature distortion diagram for Example 1. The horizontal axis represents the field curvature value in millimeters, and the vertical axis represents the normalized field of view in infinitesimal. The diagram shows that the field curvature of this lens is within 0.2 mm. The right image shows the relative optical distortion diagram. The horizontal axis represents the percentage of relative optical distortion in % (%), and the vertical axis represents the normalized field of view in infinitesimal. The diagram shows that the relative optical distortion of the lens is approximately -10.5%, which meets practical application requirements.

[0091] Figure 4 The image shows the wavefront diagram of Example 1. As can be seen from the diagram, the wavefront to trough length of this optical system is 0.0336 wavelengths, and the RMS length is 0.011 wavelengths, which meets the requirements for practical use.

[0092] Please refer to the optical structure of Example 2. Figure 5 The specific parameters of this embodiment 2 are shown in Table 1 below. In this embodiment 2, the lens focal length f' = 9mm, aperture F = 1.0, field of view FOV = 62.5°, back focal length BFL = 7.86mm, and total length TTL = 18.4mm.

[0093] Table 4 Lens Parameter Table for Example 2

[0094]

[0095] Table 5. Arrangement of Aspheric Coefficients on Lens Surfaces in Example 2

[0096]

[0097] Table 6. Arrangement of Aspheric Coefficients on Lens Surfaces in Example 2

[0098] Face number Normalized radius polynomial coefficients A1 A2 6 5.50 2.00 -25.08 3.09

[0099] According to Table 4-6, the conditional expression of Embodiment 2 of the present invention can be read as follows:

[0100] (1)TTL / f=2.044, BFL / f=0.873

[0101] (2)f1=-460mm, f2=14mm, f3=12mm, f′=9mm

[0102] (3)Nd1=4.0, Nd2=2.8, Nd3=2.8

[0103] (4)r=5.5, A1=-25.080, A2=3.090, N=2

[0104] (5)d1=2.1mm, d2=2.1mm, d3=3.2mm

[0105] (6) ρ1=5.33g / cm 3 ρ2=4.63g / cm 3 ρ3=4.63g / cm 3

[0106] (7) FOV / f = 6.944

[0107] (8)D1=11mm, D2=11.8mm, D3=12.6mm

[0108] (9) L=13.5mm, D=Φ19mm

[0109] The following is an explanation of the various figures in Embodiment 2:

[0110] Figure 5This is a structural diagram of the optical system of the lens in Example 2. As can be seen from the diagram, the aperture stop ST is located between the first lens L1 and the second lens L2. All the lenses on both sides of the aperture stop ST are bent towards it, minimizing the angle of incidence and achieving near symmetry. The overall direction of the light rays is as follows: after passing through the first lens L1, the light rays diverge slightly; after passing through the second lens L2, the light aperture gradually increases; and after passing through the third lens L3, the light aperture narrows and converges to the imaging plane IMA. A protective glass G for the detector window is placed between the third lens L3 and the imaging plane IMA.

[0111] Figure 6 This is the MTF curve for Example 2. The horizontal axis represents frequency, in line pairs. The vertical axis represents the MTF value, with no unit. The graph shows that in the 8-12µm long-wave infrared band, the MTF curve is highly concentrated, with most of the MTF across the entire field of view concentrated around 0.3 at 42 Lp / mm. The imaging quality is good and suitable for use with a 12µm long-wave infrared sensor.

[0112] Figure 7 The image shows the field curvature distortion diagram for Example 2. The left image is the field curvature diagram, with the horizontal axis representing the field curvature value in millimeters and the vertical axis representing the normalized field of view in infinitesimal. The image shows that the field curvature of this lens is within 0.13 mm. The right image is the relative optical distortion diagram, with the horizontal axis representing the percentage of relative optical distortion in % and the vertical axis representing the normalized field of view in infinitesimal. The image shows that the relative optical distortion of the lens is approximately -10.5%, which meets practical usage requirements.

[0113] Figure 8 The wavefront diagram for Example 2 is shown. As can be seen from the diagram, the wavefront to trough length of the optical system is 0.0422 wavelengths, and the RMS length is 0.0145 wavelengths, which meets the requirements for practical use.

[0114] On the other hand, now refer to Figure 9 A schematic diagram of the structure of the electronic device A according to the present invention will be given. Figure 9 This is a schematic diagram of an electronic device (camera) for a camera optical system, which is one of the compact long-wave infrared lenses according to Embodiments 1 to 2.

[0115] exist Figure 9In the figures, reference numeral A2 indicates the main body of the electronic device, and reference numeral A1 indicates a camera optical system (interchangeable lens) including any of the compact long-wave infrared lenses according to Embodiments 1 and 2. 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 (optical image formed by the camera optical system A1) from the camera optical system A1 and performs photoelectric conversion.

[0116] By using the compact long-wave infrared lens according to any one of Embodiments 1 to 2 in electronic devices such as digital still cameras, an electronic device with a line scan lens having high optical performance can be obtained.

[0117] Each example can provide electronic devices with high optical performance.

[0118] 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 compact vehicle-mounted long-wave infrared lens, characterized in that, It consists of a first lens, an aperture stop, a second lens, and a third lens arranged sequentially along the optical axis from the object side to the image side. The lens satisfies the following relationship: |f1 / f|=46.778, |f2 / f|=1.556, |f3 / f|=1.333, Where f1 is the focal length of the first lens, f2 is the focal length of the second lens, f3 is the focal length of the third lens, and f is the total focal length of the lens system. The first lens has negative refractive power, the object side of the first lens is convex, and the image side of the first lens is concave. The second lens has positive refractive power, the object side of the second lens is concave, and the image side of the second lens is convex. The third lens has positive diopter, the object side of the third lens is concave, and the image side of the third lens is convex.

2. A compact vehicle-mounted long-wave infrared lens as described in claim 1, characterized in that, The lens satisfies the following relationship: TTL / f = 2.044, BFL / f = 0.873 Where TTL is the distance from the vertex of the object side of the first lens to the imaging plane, BFL is the distance from the vertex of the image side of the third lens to the imaging plane, and f is the total focal length of the lens system.

3. A compact vehicle-mounted long-wave infrared lens as described in claim 1, characterized in that, The lens satisfies the following relationship: f1 < 0, f2 > 0, f3 > 0 Where f1 is the focal length of the first lens, f2 is the focal length of the second lens, and f3 is the focal length of the third lens.

4. A compact vehicle-mounted long-wave infrared lens as described in claim 1, characterized in that, The lens satisfies the following relationship: Nd1=4.0, Nd2=2.8, Nd3=2.8, The first lens has a refractive index of Nd1 at a wavelength of 10 μm, the second lens has a refractive index of Nd2 at a wavelength of 10 μm, and the third lens has a refractive index of Nd3 at a wavelength of 10 μm.

5. A compact vehicle-mounted long-wave infrared lens as described in claim 1, characterized in that, The object-side and image-side surfaces of the first, second, and third lenses are all aspherical, and the object-side surface of the third lens is a binary diffraction surface. The binary diffraction surface satisfies the following relationship: r=5.5, -25.219<A1<-25.080, 3.09<A2<3.9, N=2, The normalized radius of the binary diffraction surface is r, the first phase coefficient of the binary diffraction surface is A1, the second phase coefficient of the binary diffraction surface is A2, and the series of the polynomial of the binary diffraction surface is N.

6. A compact vehicle-mounted long-wave infrared lens as described in claim 1, characterized in that, The lens satisfies the following relationship: d1=2.1mm, d2=2.1mm, d3=3.2mm, The center thickness of the first lens is d1, the center thickness of the second lens is d2, and the center thickness of the third lens is d3.

7. A compact vehicle-mounted long-wave infrared lens as described in claim 1, characterized in that, The lens satisfies the following relationship: ρ1=5.33g / cm 3 ,ρ2 =4.63g / cm 3 ,ρ3 =4.63g / cm 3 , The glass material used in the first lens has a density of ρ1 (grams per cubic centimeter), the glass material used in the second lens has a density of ρ2 (grams per cubic centimeter), and the glass material used in the third lens has a density of ρ3 (grams per cubic centimeter).

8. A compact vehicle-mounted long-wave infrared lens as described in claim 1, characterized in that, The lens satisfies the following relationship: FOV / f = 6.944 Where FOV is the field of view of the lens, and f is the total focal length of the lens system.

9. An electronic device, characterized in that, A compact vehicle-mounted long-wave infrared lens according to any one of claims 1-8; and an image sensor configured to receive an image formed by the long-wave infrared lens.

Images