Far infrared camera, shooting device and automobile

Abstract

The application provides a far-infrared lens, a shooting device and a car. It can be used in the technical field of far-infrared technology. The far-infrared lens comprises an incident lens group, a diaphragm and an exit lens group arranged in sequence from an object plane to an image plane. The incident lens group comprises a first lens close to the diaphragm. The first lens is configured as a meniscus aspheric lens with positive focal power. The object side of the first lens is concave, the image side of the first lens is convex, and the edge of the first lens is concave towards the object side. The exit lens group comprises a second lens close to the diaphragm. The second lens is configured as a meniscus aspheric lens with positive focal power. The object side of the second lens is concave, and the object side of the second lens is provided with a diffraction surface. In this way, the aperture of the front lens can be reduced while the field of view is enlarged, and the chromatic aberration and the thermal aberration can be eliminated through the diffraction surface on the concave base of the second lens, so that the effects of large aperture, ultra-wide-angle optical performance, small front end and low-cost manufacturing are achieved.

Description

Technical Field

[0001] This application relates to the field of far-infrared technology, and in particular to a far-infrared lens, a shooting device, and an automobile. Background Technology

[0002] Far-infrared lenses are an important component of intelligent vehicles. A far-infrared lens consists of multiple lenses arranged sequentially from the object plane to the image plane, which can acquire images of the vehicle's external environment through the cooperation of multiple lenses.

[0003] However, in related technologies, the fabrication of some lenses in far-infrared lenses is quite difficult, and far-infrared lenses have a large aperture and require a large assembly space. Summary of the Invention

[0004] This application provides a far-infrared lens, a shooting device, and an automobile to solve the problems of the difficulty in manufacturing some lenses in existing far-infrared lenses, the large aperture of far-infrared lenses, and the large assembly space required for far-infrared lenses.

[0005] On the one hand, this application provides a far-infrared lens, including an incident lens group, an aperture stop, and an exit lens group arranged sequentially along the object plane to the image plane;

[0006] The incident lens group includes a first lens near the aperture stop. The first lens is configured as a meniscus aspherical lens with positive optical power. The object side of the first lens is concave, the image side of the first lens is convex, and the edge of the first lens is concave towards the object side.

[0007] The exit lens group includes a second lens near the aperture stop. The second lens is configured as a meniscus aspherical lens with positive optical power. The object side of the second lens is concave, and a diffraction surface is provided on the object side of the second lens.

[0008] By adopting the above technical solution, the far-infrared lens includes an incident lens group, an aperture stop, and an exit lens group arranged sequentially from the object plane to the image plane. When acquiring an image of the external environment through the far-infrared lens, light can propagate from the incident lens group to the aperture stop, and by adjusting the size of the aperture stop, it can propagate through the exit lens group to the image sensor, thereby realizing the imaging process of the far-infrared lens.

[0009] The incident lens group includes a first lens near the aperture stop. The first lens is configured as a meniscus aspherical lens with positive optical power. The object side of the first lens is concave, the image side of the first lens is convex, and the edge of the first lens is concave towards the object side. This reduces the incident aperture of the far-infrared lens, thereby reducing the aperture of the far-infrared lens and the required assembly space.

[0010] The exit lens group includes a second lens near the aperture stop. This second lens is configured as a meniscus aspherical lens with positive optical power. The object-side surface of the second lens is concave, and a diffraction surface is provided on its object-side surface. When light passing through the aperture stop propagates to the second lens, the diffraction surface on the object-side surface of the second lens reduces chromatic aberration in the far-infrared lens image and provides some thermal compensation. This makes the lens furthest from the aperture stop in the second lens group easier to shape and allows for better correction of axial chromatic aberration and thermal differences within the lens group, thus improving the imaging performance of the far-infrared lens.

[0011] In some possible implementations, the diffraction surface is a binary diffraction surface, and the phase expression of the binary diffraction surface is:

[0012]

[0013] Where ρ = r / r0, r is the radius of the binary diffraction surface, and r0 is the normalized radius of the binary diffraction surface. is the phase coefficient, and n is the number of terms in the polynomial.

[0014] In some possible implementations, the shape factor B of the first lens satisfies:

[0015] -200≤B≤0

[0016] in, C1 is the radius of curvature of the object side of the first lens, and C2 is the radius of curvature of the image side of the first lens.

[0017] In some possible implementations, the incident lens group further includes a third lens located on the side of the first lens away from the aperture stop;

[0018] The third lens is configured as a meniscus spherical lens with negative optical power.

[0019] In some possible implementations, the focal length f1 of the third lens satisfies the same condition as the focal length f of the optical system of the far-infrared lens:

[0020] 1.5≤|f1| / f≤3

[0021] And / or, the focal length f1 of the third lens and the focal length f2 of the first lens satisfy:

[0022] 0.2≤|f1 / f2|≤0.5

[0023] In some possible implementations, the exit lens group further includes a fourth lens located on the side of the second lens away from the aperture stop;

[0024] The fourth lens is configured as a positive lens with both the object-side and image-side surfaces being aspherical.

[0025] In some possible implementations, the incident lens group further includes a third lens, the third lens being made of any one of germanium single crystal, silicon single crystal, and zinc sulfide.

[0026] And / or, at least one of the first lens, the second lens and the fourth lens is made of chalcogenide glass.

[0027] In some possible implementations, the aspherical surface profiles of the first lens, the second lens, and the fourth lens satisfy the following expressions:

[0028]

[0029] Where Z(r) is the distance vector from the vertex of the aspherical surface along the optical axis at a height of r, c is the surface curvature of the aspherical surface, c = 1 / R, R is the radius of curvature of the aspherical surface, k is the conic coefficient, and A, B, C, D... are aspherical coefficients.

[0030] In some possible implementations, the relative aperture of the far-infrared lens is greater than or equal to 1;

[0031] And / or, the maximum field of view of the far-infrared lens is greater than or equal to 120°.

[0032] In some possible implementations, the far-infrared lens satisfies the total optical power condition:

[0033]

[0034] In some possible embodiments, along the direction from the object plane to the image plane, a lens barrel is also included, which is sleeved on the outside of the incident lens group, the aperture stop, and the exit lens group;

[0035] The incident lens group and the exit lens group comprise a plurality of lenses arranged sequentially. Let be the incident height of the paraxial ray at the i-th lens. Let be the optical power of the i-th lens. The total optical power of the far-infrared lens.

[0036] In some possible implementations, the far-infrared lens satisfies the condition for eliminating axial chromatic aberration:

[0037]

[0038] In the direction from the object plane to the image plane, the incident lens group and the exit lens group include a plurality of lenses arranged sequentially. This refers to the amount of on-axis focal position shift at the image-side focal plane of the far-infrared lens caused by chromatic aberration. Let be the incident height of the paraxial ray at the i-th lens. The paraxial ray is at the incident height of the third lens. Let be the optical power of the i-th lens. The total optical power of the far-infrared lens. Let be the achromatic coefficient of the i-th lens;

[0039] And / or, it also includes a lens barrel, which is sleeved on the outside of the incident lens group, the aperture stop and the exit lens group;

[0040] The far-infrared lens meets the thermal difference elimination condition:

[0041]

[0042] in, This refers to the rate at which the focal position of the far-infrared lens at the image-side focal plane shifts with temperature changes. Let be the incident height of the paraxial ray at the i-th lens. The paraxial ray is at the incident height of the third lens. Let be the optical power of the i-th lens. The total optical power of the far-infrared lens. Let be the thermal decompression coefficient of the i-th lens. is the coefficient of linear expansion of the lens barrel material, and L is the length of the lens barrel from the last lens to the image plane.

[0043] In some possible implementations, the second lens includes a flat plate lens and a meniscus aspherical lens with positive optical power, wherein the flat plate lens is configured as a flat plate diffraction lens or a flat plate superlens.

[0044] In some possible implementations, a protective lens is also included, which is disposed between the fourth lens and the image side of the image sensor;

[0045] The protective lens is configured as a monocrystalline silicon flat filter;

[0046] And / or, the incident lens group further includes a third lens;

[0047] At least three of the first lens, the second lens, the third lens, and the fourth lens are made of different materials.

[0048] This application provides a shooting device, including the far-infrared lens described in any of the above claims.

[0049] Since the shooting device includes any of the far-infrared lenses mentioned above, the advantages of the shooting device including any of the far-infrared lenses mentioned above can be found in the relevant descriptions above, and will not be repeated here.

[0050] This application provides a car that includes the far-infrared lens described in any of the above claims.

[0051] Since the car includes any of the above-mentioned far-infrared lenses, the advantages of the car including any of the above-mentioned far-infrared lenses can be found in the relevant descriptions above, and will not be repeated here. Attached Figure Description

[0052] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0053] Figure 1 This is a schematic diagram of the structure of a far-infrared lens provided in an embodiment of this application;

[0054] Figure 2 The field-of-view MTF plot of Example 1;

[0055] Figure 3 This is a relative illumination diagram of Example 1;

[0056] Figure 4 This is the vertical axis color difference diagram of Example 1;

[0057] Figure 5 This is the axial color difference diagram of Example 1;

[0058] Figure 6 This is a schematic diagram of the far-infrared lens in Example 2;

[0059] Figure 7 The field-of-view MTF plot for Example 2;

[0060] Figure 8 This is a relative illumination diagram of Example 2;

[0061] Figure 9 This is the vertical axis color difference diagram of Example 2;

[0062] Figure 10 This is the axial color difference diagram for Example 2;

[0063] Figure 11 This is a schematic diagram of the far-infrared lens in Example 3;

[0064] Figure 12 The field-of-view MTF plot for Example 3;

[0065] Figure 13 This is a relative illumination diagram of Example 3;

[0066] Figure 14 This is the vertical axis color difference diagram of Example 3;

[0067] Figure 15 This is the axial color difference diagram for Example 3.

[0068] Figure label:

[0069] 100. Incident lens group; 110. First lens; 120. Third lens;

[0070] 200. Aperture;

[0071] 300. Outgoing lens group; 310. Second lens; 311. Plane lens; 312. Meniscus aspherical lens with positive optical power; 313. Diffraction surface; 320. Fourth lens;

[0072] 400. Protective lens;

[0073] 500. Image sensor.

[0074] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0075] As described in the background section, with the development of intelligent vehicles, cameras and various sensors have become crucial components as an important part of intelligence. Among them, cameras are a vital part of intelligent vehicles. However, conventional light-sensing cameras struggle to cope with harsh environments such as wind, frost, rain, fog, and low-light conditions, making far-infrared lenses increasingly widely used in these scenarios.

[0076] Far-infrared lenses generally suffer from a small field of view, resulting in a gap in field of view compared to current intelligent driving visible light fusion technology (visible light cameras typically have a field of view of no less than 120 degrees). To improve the field of view of far-infrared lenses, it is usually necessary to increase the aperture size, which in turn requires increasing the outer diameter of the far-infrared lens, thus requiring a larger assembly space.

[0077] In related technologies, far-infrared lenses comprise multiple lenses arranged sequentially from the object plane to the image plane, enabling the acquisition of images of the vehicle's external environment through the coordinated interaction of these lenses. To improve chromatic aberration and thermal aberration issues in far-infrared lens imaging, lenses typically require the use of various optical materials with different refractive indices and Abbe numbers, making the fabrication of some lenses in far-infrared lenses quite challenging.

[0078] To address the aforementioned technical problems, this application provides a far-infrared lens and imaging device. The far-infrared lens includes an incident lens group, an aperture stop, and an exit lens group arranged sequentially from the object plane to the image plane. When acquiring an image of the external environment through the far-infrared lens, light can propagate from the incident lens group to the aperture stop. By adjusting the aperture stop, the light can then propagate through the exit lens group to the image sensor, thereby realizing the imaging process of the far-infrared lens.

[0079] The incident lens group includes a first lens near the aperture stop. The first lens is configured as a meniscus aspherical lens with positive optical power. The object side of the first lens is concave, the image side of the first lens is convex, and the edge of the first lens is concave towards the object side. This reduces the incident aperture of the far-infrared lens, thereby reducing the aperture of the far-infrared lens and the required assembly space.

[0080] The exit lens group includes a second lens near the aperture stop. This second lens is configured as a meniscus aspherical lens with positive optical power. The object-side surface of the second lens is concave, and a diffraction surface is provided on its object-side surface. When light passing through the aperture stop propagates to the second lens, the diffraction surface on the object-side surface of the second lens reduces chromatic aberration in the far-infrared lens image and provides some thermal compensation. This makes the lens furthest from the aperture stop in the second lens group easier to shape and allows for better correction of axial chromatic aberration and thermal differences within the lens group, thus improving the imaging performance of the far-infrared lens.

[0081] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numerals in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses consistent with some aspects of this application as detailed in the appended claims.

[0082] In the embodiments of this application, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the embodiments of this application, unless otherwise stated, "multiple" means two or more.

[0083] Furthermore, in the embodiments of this application, the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0084] In the embodiments of this application, unless otherwise explicitly specified and limited, the terms "installation", "connection", "linking", "fixing", etc., should be interpreted broadly. For example, they can be fixed connections, detachable connections, or integrated; they can be direct connections or indirect connections through an intermediate medium; they can be connections within two components or interactions between two components.

[0085] In embodiments of this application, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, article, or apparatus that includes that element.

[0086] In the embodiments of this application, the terms "exemplary" or "for example" are used to indicate that something is an example, illustration, or description. Any embodiment or design that is described as "exemplary" or "for example" in the embodiments of this application should not be construed as being more preferred or advantageous than other embodiments or design. Specifically, the use of the terms "exemplary" or "for example" is intended to present the relevant concepts in a specific manner.

[0087] The technical solution of this application and how the technical solution of this application solves the above-mentioned technical problems are described in detail below with specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments. The embodiments of this application will now be described with reference to the accompanying drawings.

[0088] See Figure 1 This application provides a far-infrared lens, which may include an incident lens group 100, an aperture 200 and an exit lens group 300 arranged sequentially from the object plane to the image plane.

[0089] The incident lens group 100 refers to the combination of all lenses located on the object side of the aperture stop 200. It is mainly responsible for collecting and initially deflecting light rays from the object side, so as to achieve effective convergence of light rays in a large field of view.

[0090] The exit lens group 300 refers to the combination of all lenses located on the image side of the aperture 200. It is mainly responsible for further converging the light rays passing through the aperture 200 and correcting aberrations in order to form a clear image on the image plane.

[0091] Aperture 200 refers to a solid aperture element used to limit the size of the light beam. It is located between the incident lens group 100 and the exit lens group 300 and can effectively control the amount of light passing through the system and block stray light.

[0092] The incident lens group 100 may include a first lens 110 near the aperture stop 200. The first lens 110 refers to the lens in the incident lens group 100 that is closest to the aperture stop 200 in its axial position.

[0093] The first lens 110 can be configured as a meniscus aspherical lens with positive optical power. Positive optical power means that the lens has the ability to converge light rays, and can work with the front lens to converge the light rays and deflect them towards the aperture 200. A meniscus lens means that the centers of curvature of its two surfaces are located on the same side of the lens, so that the lens as a whole presents a shape that is concave on one side and convex on the other. An aspherical lens means that at least one of its optical surfaces is not spherical, but adopts a surface shape defined by the conic coefficient and the higher order aspherical coefficient, which can more flexibly correct monochromatic aberrations such as spherical aberration and coma.

[0094] The object-side surface of the first lens 110 can be concave, that is, the center of curvature of the surface facing the object is located on the image side of the surface, forming an inward concave shape.

[0095] The image-side surface of the first lens 110 can be a convex surface, that is, the center of curvature of the entire surface facing the image is located on the object side of the surface, forming an outward convex shape.

[0096] The object-side surface refers to the optical surface of a lens facing the object side, that is, the surface on which light first enters the lens. Along the light path from the object plane to the image plane, the object-side surface is located at the front of the lens and is responsible for receiving the light beam from the object side. The surface shape parameters of the object-side surface, such as its radius of curvature and aspheric coefficient, determine the initial degree of refraction of light entering the lens, directly affecting the convergence of off-axis field rays and the entrance pupil position.

[0097] The image-side surface refers to the optical surface of a lens facing the image plane, that is, the surface from which light rays exit the lens. Along the optical path from the object plane to the image plane, the image-side surface is located at the rear end of the lens and serves to output the light beam, after it has passed through the lens, to subsequent optical elements. The surface shape parameters of the image-side surface determine the final refraction state of the light rays as they leave the lens, significantly influencing the incident height of subsequent lenses and the allocation of aberration correction tasks.

[0098] The edge of the first lens 110 can be concave towards the object side. The first lens 110 is not only concave on the object side in the paraxial region, but its edge portion also maintains or enhances the inward concavity tendency towards the object side. This edge shape allows the principal ray of the off-axis beam to be effectively deflected towards the optical axis when passing through the surface, producing negative Seidel coma, thereby shifting the virtual image of the aperture 200 on the object side, i.e., the entrance pupil of the system, forward towards the object side.

[0099] The exit lens group 300 may include a second lens 310 located near the aperture stop 200. The second lens 310 refers to the lens in the exit lens group 300 whose axial position is closest to the aperture stop 200.

[0100] The second lens 310 can be configured as a meniscus aspherical lens with positive optical power, which can be connected to the incident lens group 100 to converge the beam and undertake the main aberration correction function.

[0101] The object-side surface of the second lens 310 is concave, meaning that the entire surface of the lens facing the aperture 200 is concave, with the center of curvature located on the image side of this surface. This meniscus shape with the concave surface facing the aperture 200 helps to gently deflect the light rays in each field of view at the position of maximum beam diameter, reducing the amount of higher-order aberrations.

[0102] The object side of the second lens 310 may be provided with a diffraction surface 313. The diffraction surface 313 refers to an optical surface with specific phase modulation function formed by superimposing microstructures on the substrate surface. Its dispersion characteristics are independent of the temperature coefficient of the refractive index of the material and depend only on the wavelength and the expansion characteristics of the substrate material.

[0103] The diffraction surface 313 is located on the object-side surface of the second lens 310, meaning that the microstructure is directly fabricated on the concave substrate facing the aperture 200. Since the concave surface is located at a position with a large beam diameter, the radial dispersion is linearly superimposed, which can achieve effective chromatic aberration correction with fewer ring bands, while also helping to converge the ring band density, making the surface smoother and reducing the difficulty of fabrication.

[0104] The diffraction surface 313 utilizes its material-independent negative Abbe number characteristic to generate dispersion opposite to that of the refractive lens, which can effectively compensate for the axial chromatic aberration introduced by the first lens 110 and other refractive lenses, and eliminate the system thermal difference caused by changes in ambient temperature, so that the entire lens can maintain stable imaging performance without a focusing mechanism over a wide temperature range.

[0105] By configuring the first lens 110 near the aperture stop 200 as a meniscus aspherical lens with positive optical power and both the object side and edge concave towards the object side, and configuring the second lens 310 near the aperture stop 200 as a meniscus aspherical lens with positive optical power, a concave object side, and a diffraction surface 313, the incident lens group 100 can move the system entrance pupil forward while focusing a large field of view beam, which is beneficial to reducing the front aperture. Meanwhile, the exit lens group 300 can effectively correct chromatic aberration and thermal aberration at a position with a large beam diameter. At the same time, it can achieve good correction of spherical aberration and coma by sharing the residual aberration of the front group. Thus, the miniaturization of the large aperture ultra-wide-angle far-infrared lens and the balanced improvement of system performance are achieved as a whole.

[0106] As a specific embodiment of this application, the diffraction surface 313 can be a binary diffraction surface. A binary diffraction surface is a diffraction optical element that achieves specific phase modulation function by processing multi-level stepped microstructures on the substrate surface. Its step profile is approximately a continuous relief structure, which can precisely control the wavefront of the incident light.

[0107] The phase expression for a binary diffraction surface can be:

[0108]

[0109] Where ρ = r / r0, r is the radius of the binary diffraction plane, and r0 is the normalized radius of diffraction plane 313. is the phase coefficient, and n is the number of terms in the polynomial.

[0110] The phase expression defines the phase delay introduced by the binary diffraction surface at different radial positions. The normalized radius r0 limits the range of the phase function, allowing the phase distribution to be described in normalized coordinates. The phase coefficient... This determines the magnitude of phase changes at each order.

[0111] By adjusting the value of the phase coefficient, the optical power contribution of the binary diffraction surface and its variation with wavelength can be flexibly controlled.

[0112] For example, the binary diffraction surface can be designed as a simple structure containing only the first-order term A1, in which case the diffraction surface 313 mainly provides wavelength-related optical power to compensate for the axial chromatic aberration of the system; it can also be designed as a complex structure containing the second-order term A2, in which case the diffraction surface 313 can simultaneously correct for both axial chromatic aberration and spherical aberration; it can also contain higher-order terms according to the actual system requirements to more finely correct the remaining aberrations.

[0113] The binary diffraction surface, defined by its unique phase expression, possesses a temperature response that is independent of the temperature coefficient of the refractive index of the substrate material and depends only on the material's expansion characteristics. It also has a very small negative equivalent Abbe number, a dispersion characteristic that is the opposite of that of a conventional refractive lens.

[0114] When the binary diffraction surface is set on the concave side of the second lens 310 facing the aperture 200, the surface is located in the region of maximum beam diameter, and the radial dispersion is linearly superimposed. This is beneficial to achieve strong achromatic aberration capability with fewer ring zones and a smoother surface shape, and effectively corrects the thermal difference of the system under different ambient temperatures. As a result, the lens can maintain image clarity over a wide temperature range without the need for an active focusing mechanism, while reducing the processing difficulty and manufacturing cost of the diffraction surface 313.

[0115] As a specific embodiment of this application, the focal length characteristics of a binary diffraction surface can be explained by its approximate focal length formula:

[0116]

[0117] Where f is the focal length of the binary diffraction plane. Let be the normalized radius of the binary diffraction surface. λ is the phase coefficient of the first term in the phase expression of the binary diffraction surface, and λ is the wavelength of the incident infrared light.

[0118] As can be seen from the formula, the focal length of the diffraction surface 313 increases with the increase of wavelength. This means that the convergence of long-wave infrared light after passing through the diffraction surface 313 is weaker than that of short-wave infrared light. This characteristic is the manifestation of negative dispersion, which is exactly the opposite of the positive dispersion characteristic of conventional refracting lenses, where the focal length decreases with the increase of wavelength.

[0119] Furthermore, the equivalent Abbe number V of the diffraction element is defined as follows:

[0120]

[0121] in, The center wavelength, The shortwave reference wavelength, This is the reference wavelength for the long-wavelength end.

[0122] This is a negative constant that is completely independent of the properties of the substrate material of the binary diffraction surface. Its absolute value is much smaller than the Abbe number of conventional infrared refractive materials, indicating that the binary diffraction surface has extremely strong dispersion capability and controllability of dispersion direction.

[0123] When the binary diffraction surface is set on the concave substrate of the object side of the second lens 310 near the aperture 200, this strong negative dispersion characteristic can effectively offset the positive dispersion contribution generated by the third lens 120, the first lens 110 and the fourth lens 320 with a small diffraction power, thereby achieving the chromatic aberration balance of the whole system with a better weighting ratio under the axial chromatic aberration elimination condition.

[0124] From the perspective of low-cost manufacturability, among far-infrared optical materials, apart from chalcogenide glass which can be mass-produced using precision molding processes to achieve aspherical and diffractive surface 313, the most suitable form for low-cost mass production of other infrared crystal materials is the spherical surface, which is ground and polished using traditional optical cold processing techniques.

[0125] In the structural layout of large-aperture ultra-wide-angle lenses, for the sake of compactness and miniaturization, the front of the lens is usually not equipped with an additional protective window. Therefore, the lens closest to the object needs to directly face the external environment. This lens, namely the third lens 120, must be made of a material with sufficient mechanical hardness, scratch resistance, and temperature change resistance. Germanium single crystal, silicon single crystal, or zinc sulfide are suitable choices that meet the above requirements.

[0126] Designing both surfaces of the third lens 120 as spherical means that the lens can be manufactured using mature spherical cold processing technology, without the need to introduce costly aspherical processing methods such as single-point diamond turning or magnetorheological polishing. This is beneficial for achieving low-cost mass production while ensuring the front end's resistance to harsh environments.

[0127] The subsequent first lens 110, second lens 310 and fourth lens 320 can all be made of chalcogenide glass. The aspherical and diffraction surfaces 313 are integrally formed through a precision molding process, so that only the foremost lens in the lens needs to use crystal materials and undergo spherical cold processing, while the rest of the lenses are all included in the molding manufacturing system.

[0128] This combination of materials and processes, while meeting the requirements of large aperture ultra-wide-angle optical performance, minimizes the overall manufacturing difficulty and production cost, providing a feasible manufacturing path for the promotion and popularization of far-infrared lenses in price-sensitive application fields such as automotive and security.

[0129] As a specific embodiment of this application, the shape factor B of the first lens 110 can satisfy:

[0130] -200≤B≤0

[0131] in, C1 is the radius of curvature of the object side surface of the first lens 110, and C2 is the radius of curvature of the image side surface of the first lens 110.

[0132] The shape factor B is a parameter characterizing the bending shape of the first lens 110. The value of the shape factor B reflects the proportional relationship of the optical power distribution between the two surfaces of the lens. When B takes a positive value, the lens tends to be biconvex or convex toward the aperture stop 200. When B takes a negative value, the lens tends to be biconcave or concave toward the aperture stop 200.

[0133] The shape factor B of the first lens 110 is limited to the range of -200≤B≤0. This limitation means that the first lens 110 always maintains a crescent shape with the object side concave to the object side and the image side convex to the image side, and the absolute value of the radius of curvature of the object side is less than or equal to the absolute value of the radius of curvature of the image side, making the concavity of the object side relatively significant.

[0134] The lower limit of the shape factor B, -200, ensures that the object side of the first lens 110 is not excessively curved, thus preventing the generation of advanced aberrations that are difficult to correct. The upper limit, 0, ensures that the first lens 110 at least maintains a basic configuration with the concave side facing the object side, avoiding a shape that tends to be plano-convex or biconvex.

[0135] When the shape factor B of the first lens 110 is in this range, the Seidel coma generated by the lens is negative, that is, it can effectively deflect the principal ray of the off-axis field beam toward the optical axis, so that the entrance pupil position of the system moves toward the object side.

[0136] By limiting the shape factor B to the range of -200 ≤ B ≤ 0, and in conjunction with the positive optical power and meniscus aspherical configuration of the first lens 110, negative coma can be effectively generated while converging off-axis beams, thus shifting the virtual image of the aperture stop 200 on the object side—the system entrance pupil—forward towards the object side. This optical effect allows for a reduction in the aperture required for the lens at the very front of the incident lens group 100 under the same field of view, thereby achieving a large field of view while maintaining a miniaturized design at the front of the lens, and also helping to reduce the weight and size of the front lens.

[0137] As a specific embodiment of this application, the incident lens group 100 may further include a third lens 120, which may be located on the side of the first lens 110 away from the aperture stop 200.

[0138] In the direction from the object plane to the image plane, the third lens 120 is located on the object side of the first lens 110, that is, the third lens 120 is an optical element that is closer to the object side than the first lens 110.

[0139] The third lens 120 can be configured as a meniscus spherical lens with negative optical power. Negative optical power means that the lens has the ability to diverge light, and can quickly converge incident large-angle beams and deflect them towards the optical axis, thereby achieving effective acquisition of a large field of view within a short total optical length.

[0140] A meniscus lens is one in which the centers of curvature of both surfaces are located on the same side of the lens, giving the lens an overall shape that is concave on one side and convex on the other. A spherical lens is one in which both optical surfaces are spherical, meaning that the surface shape is defined only by the radius of curvature, and it can be manufactured using traditional optical cold-working processes.

[0141] For example, both surfaces of the third lens 120 are spherical, which means that low-cost manufacturing can be achieved through mass cold processing without the need for aspherical processing methods such as single-point diamond turning or magnetorheological polishing, which is conducive to the promotion and popularization of the entire lens.

[0142] The third lens 120, as the element closest to the object side in the incident lens group 100, is responsible for collecting light from a wide field of view and resisting harsh external environments. By configuring it as a meniscus spherical lens with negative optical power, it can initially deflect light from the edge field of view with a large radius of curvature, pre-concentrating the beam before it enters the first lens 110, thereby further reducing the aperture requirements of the rear lens. At the same time, the spherical shape allows the lens to be manufactured using high-hardness infrared materials combined with traditional cold-working processes, meeting the requirements of automotive, security, and other applications for impact resistance, scratch resistance, and temperature variation resistance at the lens front end, while also facilitating low-cost mass production.

[0143] As a specific embodiment of this application, the focal length f1 of the third lens 120 and the focal length f of the optical system of the far-infrared lens can satisfy the following:

[0144] 1.5≤|f1| / f≤3

[0145] This ratio reflects the intensity proportion of the negative optical power of the third lens 120 relative to the optical power of the entire system. When the value of |f1| / f is greater than or equal to 1.5, the third lens 120 has a sufficiently strong negative optical power, which can effectively converge a large field-of-view beam before the light enters the first lens 110, thereby reducing the front group optical aperture while ensuring the back cutoff.

[0146] When the value of |f1| / f is less than or equal to 3, the negative optical power of the third lens 120 will not be too strong, thus avoiding the introduction of excessive field curvature and coma, which are difficult to be corrected by the rear lens group, and ensuring that the system imaging quality is within an acceptable range.

[0147] For example, the ratio of the focal length of the third lens 120 to the system focal length can be selected as a value that meets the range, such as 2.0, 2.5 or 2.75. The specific value can be optimized according to the target field of view, front port diameter limitation and image quality requirements.

[0148] And / or, the focal length f1 of the third lens 120 and the focal length f2 of the first lens 110 can satisfy:

[0149] 0.2≤|f1 / f2|≤0.5

[0150] This ratio characterizes the distribution of optical power between the negative lens and the positive lens immediately adjacent to its image side in the incident lens group 100. When the value of |f1 / f2| is greater than or equal to 0.2, the first lens 110 has sufficient optical power contribution relative to the third lens 120. The combination of the two can provide a certain amount of negative field curvature and negative coma for the off-axis field of view, thereby sharing the burden of correcting field curvature and coma in the wide-angle field of view of the exit lens group 300.

[0151] When the value of |f1 / f2| is less than or equal to 0.5, the negative optical power of the third lens 120 is not too weak, so that the front group can still maintain sufficient negative optical power to control the direction of the edge field of view, limit the aperture of the first lens 110 to a small range, and at the same time avoid the inability to effectively compensate for the residual aberrations generated by the third lens 120 due to the weak optical power of the first lens 110.

[0152] For example, the absolute value of the focal length ratio between the third lens 120 and the first lens 110 can be selected as a value that satisfies this range, such as 0.24, 0.35 or 0.46.

[0153] The ratio of the focal length f1 of the third lens 120 to the system focal length f and the ratio of the focal length f1 of the third lens 120 to the focal length f2 of the first lens 110 can work together to coordinate and regulate the overall optical behavior of the incident lens group 100.

[0154] According to aberration theory, the coma produced by a lens is related to its optical power and shape factor. The above two focal length ratio parameters define the working state of the third lens 120 and the first lens 110 from the perspectives of optical power allocation and combined optical power, respectively.

[0155] By controlling |f1| / f and |f1 / f2| within the aforementioned ranges, the incident lens group 100 can generate appropriate amounts of negative coma and negative field curvature while converging a large field-of-view beam, thereby shifting the entrance pupil position of the system towards the object side. This achieves a field-of-view angle of over 120 degrees while maintaining a small optical aperture at the front of the lens and ensuring that the relative illumination of the edge field of view remains at a high level, thus avoiding vignetting.

[0156] As a specific embodiment of this application, the ratio of the focal length f1 of the third lens 120 to the focal length f2 of the first lens 110 can be used to further explain the mechanism by which the optical power allocation and the shape factor B of the first lens 110 coordinately regulate the off-axis coma of the front group and indirectly affect the aperture of the front lens.

[0157] In the far-infrared lens, the ratio of the focal length f1 of the third lens 120 to the focal length f2 of the first lens 110 is limited to the range of 0.2≤|f1 / f2|≤0.5.

[0158] When the value of |f1 / f2| approaches the lower limit of this range, the first lens 110 has a more ample optical power reserve compared to the third lens 120. The incident lens group 100 can generate a certain amount of negative field curvature and negative coma in the off-axis field of view to compensate for subsequent aberrations, while avoiding overcorrection due to excessive negative optical power. This avoids introducing advanced aberrations that are difficult to eliminate by the exit lens group 300, and also helps to control the aperture size of the exit lens group 300.

[0159] When the value of |f1 / f2| approaches the upper limit of this range, the combination of the third lens 120 and the first lens 110 can provide sufficient field curvature and coma correction capabilities for the off-axis field of view, enabling the incident lens group 100 to effectively manage aberrations of the edge field of view rays, thereby limiting the aperture of the third lens 120 to a smaller physical size.

[0160] The effect of the aforementioned focal length ratio on coma and aperture can be explained using aberration theory. According to the coma expression:

[0161]

[0162] in This is the primary spherical difference coefficient. H is the incident height of the principal ray on the lens surface, and H is the incident height of the marginal ray on the lens surface. Let B be the optical power of the lens, and let B be the shape factor of the lens.

[0163] From this expression, we can see that the coma coefficient With optical power The coma is directly proportional to the product of the shape factor B, meaning that the amount of coma produced depends on both the optical power of the lens and the curvature of the lens.

[0164] The shape factor B of the first lens 110 is limited to the range of -200≤B≤0, and the focal length ratio |f1 / f2| of the third lens 120 and the first lens 110 is limited to between 0.2 and 0.5. These two limiting conditions work together to affect the off-axis coma characteristics of the incident lens group 100.

[0165] A negative shape factor B causes the first lens 110 to produce negative coma, and the value of |f1 / f2| determines the intensity ratio of the positive optical power of the first lens 110 to the negative optical power of the third lens 120, which in turn affects the specific value of the product of φ and B, that is, determines the magnitude of the negative coma.

[0166] When |f1 / f2| takes an appropriate value within the defined range, the negative coma generated by the first lens 110 can effectively deflect the principal ray of the off-axis field of view toward the optical axis, and through the principal ray height The geometric relationship with the aperture of the front lens indirectly affects the aperture requirement of the third lens 120.

[0167] Specifically, the incident height of the principal ray on the surface of the front lens after it is deflected. This allows for a smaller physical aperture for the third lens 120 while maintaining the required relative aperture, thus enabling a miniaturized design of the lens front end.

[0168] As a specific embodiment of this application, the exit lens group 300 may further include a fourth lens 320, which may be located on the side of the second lens 310 away from the aperture stop 200. In the direction from the object plane to the image plane, the fourth lens 320 is located in the image-side direction of the second lens 310, that is, the fourth lens 320 is an optical element that is closer to the image plane than the second lens 310.

[0169] The fourth lens 320 can be configured as a positive lens with both the object-side and image-side surfaces being aspherical. A positive lens means that the lens has the ability to converge light rays, and can further converge the light beam after passing through the second lens 310 onto the image plane.

[0170] Both the object-side and image-side surfaces are aspherical, meaning that both optical surfaces of the lens adopt a surface shape defined by the conic coefficient and higher-order aspherical coefficient, enabling independent and precise correction of monochromatic aberrations such as spherical aberration, coma, astigmatism, and distortion for each field of view.

[0171] For example, the object side of the fourth lens 320 can be convex or concave, and the image side can be convex or concave. The radii of curvature and aspherical coefficients of the two surfaces can be flexibly configured according to the residual aberration state of the outgoing lens group 300, so as to complete the final compensation of aberration at the last refractive surface in front of the image.

[0172] The fourth lens 320 can be made of infrared optical materials with low softening point, such as chalcogenide glass, which facilitates the mass production of aspherical surfaces at low cost through precision molding processes.

[0173] The fourth lens 320, with its aspherical configuration on both surfaces, provides ample aberration correction freedom in the final stage of the beam approaching the image plane. Combined with the meniscus aspherical configuration of the second lens 310 located on its object side and its achromatic and thermal correction capabilities based on the diffraction surface 313, the exit lens group 300 can achieve large aperture and ultra-wide-angle optical performance while correcting the image quality of each field of view to a diffraction-limited level, and ensuring uniform relative illumination distribution across the entire field of view with no obvious vignetting at the edges.

[0174] As a specific embodiment of this application, the incident lens group 100 may further include a third lens 120, which is made of any one of germanium single crystal, silicon single crystal and zinc sulfide.

[0175] Germanium single crystal, silicon single crystal, and zinc sulfide are all infrared optical crystal materials with high hardness and high strength. Among them, germanium single crystal and silicon single crystal have high refractive index and low dispersion in the wavelength range of 8 to 14 micrometers, while zinc sulfide has a wide transmission range and good chemical stability in this band.

[0176] Choosing any of the above materials to manufacture the third lens 120 ensures that the lens at the front of the lens has sufficient mechanical strength and environmental resistance to withstand the erosion and impact of harsh conditions such as wind, sand, rain, snow, and temperature changes on the lens surface, and can be used directly in the external environment without the need for an additional protective window in front.

[0177] And / or, at least one of the first lens 110, the second lens 310 and the fourth lens 320 may be made of chalcogenide glass.

[0178] Chalcogenide glass is a non-oxide glass material with chalcogen elements as the main components. It has good light transmittance in the far-infrared band, and its softening temperature is significantly lower than that of crystalline materials such as germanium single crystal and silicon single crystal.

[0179] Using chalcogenide glass to fabricate the first lens 110, the second lens 310, or the fourth lens 320 allows these lenses to be processed into aspherical shapes through precision molding, avoiding the use of inefficient aspherical manufacturing methods such as single-point diamond turning, thus facilitating low-cost mass production.

[0180] For example, the first lens 110, the second lens 310, and the fourth lens 320 can all be made of chalcogenide glass. In this case, only the foremost third lens 120 in the lens needs to use a crystal material, and all other lenses can be made by molding. Alternatively, only the first lens 110 and the second lens 310 can be made of chalcogenide glass, while the fourth lens 320 can be made of other infrared materials. Furthermore, depending on the actual optical design requirements, some lenses can be made of chalcogenide glass, while others can be made of materials such as zinc selenide.

[0181] By using high-hardness crystal materials such as germanium single crystal, silicon single crystal, or zinc sulfide for the third lens 120, and at least one of the first lens 110, second lens 310, and fourth lens 320 using chalcogenide glass, the lens can expand the processing method of aspherical lenses from cold working to precision molding while meeting the requirements of front-end resistance to harsh environments, effectively reducing manufacturing costs. In addition, chalcogenide glass differs significantly from crystal materials such as germanium and silicon in Abbe number and refractive index temperature coefficient. The combination of multiple materials is beneficial to achieving material matching conditions for achromatic and thermal aberration correction in the optical system, thereby avoiding the limitations of traditional anechoic designs that must rely on more than three materials with different refractive indices and Abbe numbers to correct chromatic and thermal aberrations, and reducing dependence on scarce and expensive materials.

[0182] As a specific embodiment of this application, the aspherical surface shape expressions of the first lens 110, the second lens 310, and the fourth lens 320 can satisfy:

[0183]

[0184] Where Z(r) is the distance vector from the vertex of the aspherical surface along the optical axis at a height of r, c is the surface curvature of the aspherical surface, c = 1 / R, R is the radius of curvature of the aspherical surface, and k is the conic coefficient. A, B, C, D... are the aspherical coefficients.

[0185] The radius of curvature R determines the basic optical power contribution of an aspherical surface in the paraxial region. The smaller the absolute value of R, the greater the curvature of the surface and the stronger the deflection of light on that surface.

[0186] r is the radial distance from any point on the surface to the optical axis. When r is equal to zero, the point is located at the vertex of the aspherical surface, and Z(r) is equal to zero.

[0187] The conic coefficient k determines the type of conic section of the non-spherical base. When k equals 0, the base surface is spherical; when k is less than -1, the base surface is hyperboloid; when k equals -1, the base surface is parabolic; when k is between -1 and 0, the base surface is a long ellipsoid; and when k is greater than 0, the base surface is an oblate ellipsoid.

[0188] For example, the object-side and image-side surfaces of the second lens 310 can be selected with different conic coefficient values ​​to specifically correct coma and astigmatism in the off-axis field of view based on the meniscus shape. The object-side surface of the fourth lens 320 can be selected with a conic coefficient close to -1, making the substrate approach a parabolic shape, which is beneficial for completing the correction of residual spherical aberration with a smaller increment of higher-order coefficients on the final refractive surface.

[0189] Higher-order aspherical coefficients A, B, C, and D are used to describe the deviation of the surface shape from the base conic section during the transition from the paraxial region to the edge region. They correspond to the 4th, 6th, 8th, and 10th powers of r, respectively, and higher-order terms can be added in the same way. These terms increase progressively with even powers of the radial distance r, describing the offset of the aspherical surface relative to the reference quadratic surface at various radial positions.

[0190] The coefficient A dominates the surface profile correction from the paraxial region to the medium aperture region. When A is positive, the surface rises relative to the quadratic surface in this region, and when A is negative, the surface sinks downward. The absolute value of A determines the correction intensity of spherical aberration and primary coma.

[0191] Coefficient B dominates the surface correction in the medium aperture region, mainly used to control the advanced spherical aberration in the middle of the aperture and the advanced coma in the off-axis field of view. Its range of action is more peripheral than that of option A.

[0192] The coefficient C dominates the surface correction in the larger aperture region, and is used to balance the residual aberrations near the edge aperture.

[0193] The coefficients D and higher-order terms are specifically designed to finely control the minute aberrations at the maximum aperture, avoiding a sharp drop in resolution at the edge field of view with full aperture.

[0194] For example, the aspherical coefficients of the first lens 110 can be enabled only in orders A and B, because the first lens 110 is located where the light diameter has not yet fully expanded, and the range of surface shape fine-tuning is limited. Low-order corrections are sufficient to meet the initial correction requirements for coma and field curvature. The aspherical coefficients of the second lens 310 can be enabled up to order C, because the second lens 310 is located in the region of larger beam diameter and serves as the substrate of the diffraction surface 313. More degrees of freedom for correction are needed to coordinate the matching relationship between monochromatic aberration correction and the phase distribution of the diffraction surface 313. The aspherical coefficients of the fourth lens 320 can be enabled up to order D or higher, because the fourth lens 320, as the last refractive element in front of the image, needs to eliminate all residual aberrations accumulated in the previous group with the highest precision to achieve diffraction-limited imaging quality at the maximum aperture and maximum field of view.

[0195] By employing the aforementioned unified aspherical surface shape expression on the first lens 110, the second lens 310, and the fourth lens 320, each lens can flexibly configure its conic coefficient and aspherical coefficients of various orders according to its own task of correcting ray height and aberrations in the optical path. This allows for comprehensive correction of spherical aberration, coma, astigmatism, and field curvature with a relatively small number of lenses. In particular, when the second lens 310 is an aspherical meniscus lens and its object-side surface is provided with a diffraction surface 313, its aspherical substrate can independently undertake the task of monochromatic aberration correction, while the diffraction surface 313 is specifically responsible for chromatic aberration and thermal aberration correction. The two have clear division of labor and do not interfere with each other, enabling the lens to obtain high-quality imaging performance even under large aperture ultra-wide-angle conditions.

[0196] As a specific embodiment of this application, the relative aperture of the far-infrared lens can be greater than or equal to 1.

[0197] Relative aperture is the ratio of the lens's entrance pupil diameter to the optical system's focal length, and its reciprocal is the aperture f-number. When the relative aperture is greater than or equal to 1, it means that the lens's aperture f-number is less than or equal to 1. The system has strong light-gathering capabilities and can receive sufficient infrared radiation energy from the target in low-light environments or short exposure times, thereby achieving clear image output in conjunction with the high-sensitivity far-infrared image sensor 500.

[0198] The closer the relative aperture is to 1 or greater than 1, the stronger the light transmission capability of the lens. However, at the same time, the difference in light height between each lens increases, and the difficulty of correcting on-axis and off-axis aberrations also increases.

[0199] By configuring the first lens 110 as a meniscus aspherical lens with positive optical power and concave edges facing the object side, and configuring the second lens 310 as a meniscus aspherical lens with positive optical power and a diffraction surface 313 on the concave surface of the object side, the system can effectively deflect and balance the light rays of each aperture under the condition that the relative aperture is greater than or equal to 1, so that the higher-order aberrations caused by the large aperture are reasonably distributed to multiple lens surfaces for step-by-step correction.

[0200] And / or, the maximum field of view of the far-infrared lens can be greater than or equal to 120°.

[0201] The maximum field of view refers to the full angle of the object that the lens can clearly image. When the maximum field of view reaches 120 degrees or more, the lens enters the ultra-wide-angle category, and a single shot can cover a wide range of scenes. It is suitable for application scenarios that require large-area scene perception, such as vehicle-mounted assisted driving, security monitoring, and traffic monitoring.

[0202] Under ultra-wide-angle conditions, the incident angle of the principal ray in the off-axis field of view increases significantly. The front lens needs to use a large surface curvature to converge the edge rays to the aperture stop 200, while suppressing the resulting field curvature and distortion.

[0203] By configuring the first lens 110 as a meniscus aspherical lens with both the object side and edge concave towards the object side, negative coma is generated to move the entrance pupil of the system forward. Combined with the negative optical power of the third lens 120, the off-axis beam is pre-contracted. The incident lens group 100 can maintain a small front port diameter under a field of view of 120 degrees or more, while the relative illumination of the edge field of view is maintained at a high level, avoiding vignetting.

[0204] The limitations of a relative aperture greater than or equal to 1 and a maximum field of view greater than or equal to 120 degrees can be applied independently or in combination. When the two are applied in combination, the lens simultaneously possesses the optical characteristics of a large aperture and an ultra-wide angle, meeting stringent application requirements in both low-light environments and a wide field of view. At the same time, it also places higher comprehensive demands on the system's aberration correction, chromatic aberration correction, and thermal aberration correction.

[0205] By combining the negative and positive optical power of the third lens 120 and the first lens 110 in the incident lens group 100 to gather light rays across a large field of view and move the entrance pupil forward, and by effectively correcting axial chromatic aberration and thermal aberration through the aspherical diffraction surface 313 of the second lens 310 in the exit lens group 300, and by finally compensating for residual monochromatic aberration through the double-sided aspherical surface of the fourth lens 320, the lens can obtain uniform and clear imaging quality across the entire field of view under the condition that the relative aperture is greater than or equal to 1 and the maximum field of view is greater than or equal to 120 degrees.

[0206] As a specific embodiment of this application, the far-infrared lens can meet the total optical power requirement:

[0207]

[0208] In the direction from the object plane to the image plane, the incident lens group 100 and the exit lens group 300 include a plurality of lenses arranged sequentially. Let be the incident height of the paraxial ray at the i-th lens. Let be the optical power of the i-th lens. This refers to the total optical power of the far-infrared lens.

[0209] Paraxial ray incident height This describes the radial distance from the optical axis of a paraxial ray in the on-axis field of view when it reaches the i-th lens. This height varies from lens to lens as the beam propagates, influenced by the optical power of each preceding lens. When the ray passes through a positive power lens, its height tends to decrease, while when it passes through a negative power lens, its height tends to increase or the decreasing trend slows down.

[0210] Optical power The refractive power of the i-th lens is defined. A positive power lens causes light rays to converge toward the optical axis, while a negative power lens causes light rays to diverge away from the optical axis.

[0211] Product of the two It represents the effective weight of the i-th lens in the overall optical power composition of the system. This weight depends on both the optical power of the lens itself and the beam aperture when the light reaches the lens.

[0212] Total optical power The condition essentially expresses the linear superposition relationship of the optical power contributions of each lens in an optical system. When light passes through each lens in sequence, the phase modulation applied to the wavefront by each lens is proportional to the product of its optical power and the incident height of the light. Summing up the contributions of all lenses gives the total optical power of the system.

[0213] In the practical design of far-infrared lenses, this condition provides a basic constraint framework for optical power allocation. By configuring the third lens 120 in the incident lens group 100 with negative optical power and the first lens 110 with positive optical power and positioned at a level that remains relatively horizontal after the light incident height has diverged through the third lens 120, this negative-positive combination can achieve... Under the mutual constraints, an effective contribution to the total optical power is achieved while controlling the aperture of the front lens. In the exit lens group 300, the second lens 310 is located after the aperture stop 200, at a position where the light beam height is re-spread. Its positive optical power is relatively high at this point. Combined, they make a major contribution to the total optical power. The fourth lens 320 is located near the image plane where the light rays gradually converge, so its contribution to the positive optical power is relatively reduced, making it suitable for final aberration fine-tuning.

[0214] By satisfying the above total optical power conditions, the optical power and relative axial position of each lens can be configured in a coordinated manner, so that the absolute value of the optical power of each lens is not too strong or too weak while meeting the imaging focal length requirements. This is beneficial to reduce the curvature of each surface, reduce the amount of higher aberrations, and keep the material selection and processing difficulty of each lens within a reasonable range.

[0215] As a specific embodiment of this application, the far-infrared lens can meet the condition of eliminating axial chromatic aberration:

[0216]

[0217] In the direction from the object plane to the image plane, the incident lens group 100 and the exit lens group 300 include a plurality of lenses arranged sequentially. This refers to the on-axis focal position shift of the far-infrared lens at the image-side focal plane caused by chromatic aberration. Let be the incident height of the paraxial ray at the i-th lens. The paraxial ray is at the incident height of the third lens 120. Let be the optical power of the i-th lens. This refers to the total optical power of the far-infrared lens. Let be the achromatic coefficient of the i-th lens. This represents the focal length difference caused by axial chromatic aberration between different wavelengths. When this value is equal to 0, it means that the focal positions of paraxial rays of different wavelengths tend to be consistent on the image plane, and the axial chromatic aberration of the system is corrected.

[0218] achromatic coefficient This is a parameter characterizing the degree of dispersion of a lens material between different wavelengths; its value is determined by the difference in refractive index of the material within the 8-14 micrometer operating wavelength range. Conventional refractive lenses... The positive value indicates that the difference in achromatic coefficient between different infrared materials is the basis for achieving color difference correction.

[0219] Paraxial ray incident height With lens power The product of these factors determines the weight of the lens's contribution to optical power, while squared multiplied by Multiply This determines the total contribution of the lens to axial chromatic aberration. Since this summation includes... The square factor of the achromatic coefficient and optical power of a lens located at a higher beam height significantly amplifies the contribution of these factors to axial chromatic aberration.

[0220] The condition for eliminating axial chromatic aberration requires that the summation result equals 0, meaning the total contribution of each lens in the system to axial chromatic aberration is zero, causing paraxial rays of different wavelengths to converge at their focal points on the image plane. In far-infrared lenses, this condition can be achieved through the combination of diffraction surface 313 and a refractive lens. Diffraction surface 313 has the characteristic of a negative equivalent Abbe number with a very small absolute value, and its dispersion direction is opposite to that of a traditional refractive lens. and The product of these two elements exhibits the opposite sign to that of the refractive lens on the diffraction surface 313. The diffraction surface 313 is positioned on the concave surface of the object side of the second lens 310 near the aperture stop 200, a location where the beam diameter is relatively large. The value is relatively high, and the achromatic contribution of diffraction plane 313 is... The square-weighted magnification can produce a significant axial chromatic aberration reduction effect with a small diffraction power, thereby compensating for the chromatic aberration generated by the third lens 120, the first lens 110 and the fourth lens 320.

[0221] By satisfying the aforementioned conditions for eliminating axial chromatic aberration, far-infrared lenses can ensure that the focal points of light rays of all wavelengths in the on-axis field of view coincide across a wide spectral range, eliminating image blurring and false color phenomena caused by chromatic aberration. This condition, combined with the condition for eliminating thermal aberration, allows the system to achieve this without relying on a combination of multiple expensive infrared materials to simultaneously correct chromatic and thermal aberrations. It can be accomplished simply by introducing a single-sided diffraction element at a suitable location, thereby simplifying the material system and reducing manufacturing costs.

[0222] As a specific embodiment of this application, it may also include a lens barrel, which may be sleeved on the outside of the incident lens group 100, the aperture 200 and the exit lens group 300.

[0223] The lens barrel is a mechanical structural component used to support and position the lenses and aperture 200. Its inner wall can be provided with multiple spacers and support steps, which respectively mate with the outer edge of each lens to ensure that the axial spacing and coaxiality between the lenses remain stable during assembly and service. The lens barrel also serves to block external stray light and protect the internal optical components.

[0224] Far-infrared lenses can meet the requirements for heat dissipation:

[0225]

[0226] in, This refers to the rate at which the focal position of the far-infrared lens at the image-side focal plane shifts with temperature changes. Let be the incident height of the paraxial ray at the i-th lens. The paraxial ray is at the incident height of the third lens 120. Let be the optical power of the i-th lens. This refers to the total optical power of the far-infrared lens. Let be the thermal decompression coefficient of the i-th lens. is the coefficient of linear expansion of the lens barrel material, and L is the length of the lens barrel.

[0227] This represents the differential change in the focal position shift at the image plane of a far-infrared lens due to variations in ambient temperature. When the optical power of the lenses and the lens barrel structure within the optical system change with temperature, the image plane position will correspondingly defocus. This refers to the minute change in the amount of temperature-induced defocusing.

[0228] dt represents the differential change in ambient temperature, that is, the tiny increment of temperature change. The ratio of dt to dt represents the rate of shift of the system's focal position with temperature, i.e., the temperature drift sensitivity. This equation requires that the sum of the optical power drifts caused by temperature changes in all lenses within the optical system be exactly compensated by the thermal expansion and contraction of the lens barrel's mechanical structure, thereby achieving passive calorimetry.

[0229] Heat dissipation coefficient It is a parameter characterizing the degree of optical power shift of a lens as a function of temperature. For refractive lenses, the thermal ablation coefficient is determined by both the linear expansion coefficient and the temperature coefficient of refractive index of the material. ,in Let n be the coefficient of linear expansion of the lens material, and n be the refractive index of the lens material. The refractive index of the environmental medium, The temperature coefficient of refractive index of the lens material. The temperature coefficient of refractive index of the ambient medium.

[0230] For diffraction plane 313, the thermal ablation coefficient is independent of the temperature coefficient of the refractive index of the material and depends only on the coefficient of linear expansion of the substrate material. .

[0231] This difference means that the temperature response characteristics of the diffraction surface 313 are independent of the refractive index change of the substrate material. It can only affect the period of the diffraction microstructure and thus change the optical power through the thermal expansion and contraction of the substrate material. Therefore, its thermal degradation coefficient is usually significantly smaller than that of the refractive lens.

[0232] Coefficient of linear expansion of the lens tube The coefficient of linear expansion is determined by the metal material used for the lens barrel; for example, aluminum has a coefficient of linear expansion of approximately [missing value]. / ℃, this value is moderately high among commonly used metallic materials, and can provide appropriate mechanical compensation under thermal difference conditions in conjunction with the thermal drift characteristics of the optical system. L is the structural length of the lens barrel in the back intercept direction, that is, the length of the lens barrel section corresponding to the mechanical gap between the last lens and the image plane. The expansion and contraction of this section length during temperature changes directly cause the image plane to defocus.

[0233] The summation term on the left-hand side of the pyrolysis condition equation characterizes the defocusing effect on the image plane of the sum of optical power drifts caused by temperature changes in each lens in the optical system. This value is determined by the pyrolysis coefficient of each lens. Optical power and the incident height of light at the location of the lens. The square-weighted decision is made. Because it includes... The square factor is significant for lenses located at higher beam heights, where the thermal drift contribution is amplified. (Right side of equation) Multiplying by L represents the mechanical expansion and contraction of the lens barrel structure when the temperature changes. When the two are equal, it means that the optical power temperature drift of the optical system is exactly compensated by the change in the length of the lens barrel, and the position of the image plane relative to the last lens remains unchanged when the temperature changes.

[0234] By satisfying the aforementioned pyrolysis conditions, the far-infrared lens can maintain a stable image plane position over a wide temperature range without the need for an active focusing mechanism, achieving passive pyrolysis. By placing the diffraction surface 313 on the object-side concave surface of the second lens 310, which is close to the aperture stop 200 and has a relatively large beam diameter, due to… The thermal differential coefficient at this location is relatively high and is also relevant to diffraction plane 313. The smaller size allows for significant thermal compensation with a smaller diffraction power. At the same time, the refractive part of the meniscus lens provides the main positive power and maintains low thermal sensitivity. The two work together to effectively compensate for the total thermal difference of the output lens group 300. With the appropriate selection of lens barrel material, the image plane defocusing amount of the entire lens is controlled within the depth of focus range when the temperature changes.

[0235] As a specific embodiment of this application, a protective lens 400 is also included, which may be disposed between the fourth lens 320 and the image side of the image sensor 500.

[0236] The protective lens 400 refers to a parallel plane optical plate with both the object side and the image side being flat. It does not contribute to optical power and its main function is to isolate the sensitive surface of the image sensor 500 from the external environment.

[0237] The protective lens 400 can be configured as a monocrystalline silicon flat filter. Monocrystalline silicon, as a substrate material, has high transmittance in the far-infrared band, as well as good mechanical strength and chemical stability, and can provide physical protection for the image sensor 500 without introducing significant light energy loss.

[0238] For example, the protective lens 400 can achieve spectral selection by depositing a narrow-band filter layer on its object side or image side, such as limiting infrared radiation in the 8 to 14 micrometer band to reach the image sensor 500, suppressing background radiation outside the working band, thereby improving the image contrast and signal-to-noise ratio.

[0239] The protective lens 400 may also be without a functional coating, serving only as a physical isolation element to prevent dust, moisture, or particulate matter generated during assembly from contaminating the sensitive surface of the image sensor 500. The thickness of the protective lens 400 can be flexibly determined based on the axial distance from the image side of the fourth lens 320 to the image plane, typically ranging from a few tenths of a millimeter to one millimeter, to ensure sufficient mechanical strength without occupying excessive back focal length space.

[0240] By setting the protective lens 400 as a single-crystal silicon flat filter and placing it between the fourth lens 320 and the image sensor 500, the protective lens 400 provides a reliable physical barrier for the image sensor 500 without changing the system's optical power distribution or introducing additional aberrations. At the same time, its planar shape makes manufacturing and assembly simple, reducing the risk of image defects caused by contamination at the rear of the lens and helping to extend the lens's service life in complex working conditions such as automotive and security applications.

[0241] As a specific embodiment of this application, at least three of the first lens 110, the second lens 310, the third lens 120 and the fourth lens 320 may be made of different materials.

[0242] Of the four lenses that make up a far-infrared lens, three or four can be made of different infrared optical materials. Different materials can refer to differences in at least one of the optical and thermal properties, such as refractive index, Abbe number, temperature coefficient of refractive index, and coefficient of linear expansion.

[0243] Since different infrared materials have their own characteristics in terms of dispersion and temperature response, by combining multiple materials in the system, sufficient degree of parameter freedom can be provided for the joint correction of color difference and thermal difference.

[0244] For example, the third lens 120 can be made of germanium single crystal or silicon single crystal. These crystal materials have a high refractive index, relatively low dispersion in the 8 to 14 micrometer wavelength range, and high mechanical hardness and chemical resistance, making them suitable as the frontmost element of the lens that faces the external environment directly.

[0245] The second lens 310 can be made of chalcogenide glass, whose refractive index temperature coefficient and dispersion characteristics complement those of crystalline materials such as germanium and silicon. At the same time, its low softening point characteristic allows the lens to be processed into a complex surface with aspherical and diffraction surfaces 313 through precision molding.

[0246] The first lens 110 and the fourth lens 320 can be made of different grades of chalcogenide glass. The slight differences between the two in Abbe number and temperature coefficient of refractive index can provide a more precise adjustment margin for achromatic and thermal aberration conditions.

[0247] Alternatively, the fourth lens 320 can also be made of infrared materials such as zinc selenide, which have a wide transmission band and a suitable refractive index, thereby enriching the material combination of the system while achieving the final correction of aberrations.

[0248] Based on the mechanism of achromatic and thermal aberration correction, traditional refractive optical systems typically require the use of three or more optical materials with different refractive indices, Abbe numbers, and temperature coefficients of refractive index to compensate for each other by utilizing the differences in thermal properties between the materials.

[0249] By combining crystal materials such as germanium or silicon, which have a high temperature coefficient of refractive index and a relatively low refractive index, with chalcogenide glasses, which have different temperature coefficients of refractive index and relatively high refractive indexes, the thermal compensation relationship can be established between multiple lenses by utilizing the different photofocus shifts of the three or more materials under temperature changes. This allows the defocusing caused by temperature changes in each lens to cancel each other out.

[0250] By using at least three of the first lens 110, second lens 310, third lens 120, and fourth lens 320 made of different materials, the lens can establish a combination of optical properties of various materials within the limited space of the four lenses, avoiding excessive reliance on rare and expensive materials. This material differentiation configuration, combined with the equivalent negative Abbe number characteristics provided by the diffraction surface 313, can meet the constraints on the combination of material parameters for total optical power, axial chromatic aberration elimination, and thermal aberration elimination. Passive calorimetry can be achieved over a wide temperature range without introducing additional material types, thereby reducing material costs and coating complexity.

[0251] As a specific embodiment of this application, the second lens 310 includes a flat plate lens 311 and a meniscus aspherical lens 312 with positive optical power. The flat plate lens 311 is configured as a flat plate diffraction lens or a flat plate superlens.

[0252] The second lens 310 may include a flat diffraction lens and a meniscus aspherical lens 312 with positive optical power.

[0253] Specifically, the second lens 310 may include a flat diffraction lens and a meniscus aspherical lens 312 with positive optical power, which are arranged sequentially along the optical axis to form the lens unit near the aperture in the output lens group.

[0254] A flat diffractive lens is a diffractive optical element with a flat, parallel plate as its substrate. Both its object-side and image-side surfaces are flat, and the diffractive microstructure is fabricated on one of these planes. The required dispersion correction and thermal compensation functions are achieved through phase modulation.

[0255] A meniscus aspherical lens is an aspherical lens with positive optical power and a concave object side and a convex image side. Both of its surfaces are aspherical and it is mainly used to provide the required converging optical power of the system and to correct monochromatic aberrations.

[0256] A flat diffractive lens can be placed on the side of a meniscus aspherical lens closer to the aperture, or on the side of a meniscus aspherical lens farther from the aperture. The two work together to achieve functional separation of optical power contribution and chromatic aberration and thermal aberration correction.

[0257] Alternatively, the second lens 310 may include a flat superlens and a meniscus aspherical lens 312 with positive optical power.

[0258] A planar metalens is an optical element based on metasurface technology. Its substrate is a parallel planar plate with subwavelength-scale micro- and nano-structure units arranged on its surface. Arbitrary phase modulation of the incident light wavefront can be achieved by adjusting the geometry and arrangement of each structural unit.

[0259] Flat plate superlenses also possess negative dispersion characteristics, and can replace the aforementioned flat plate diffraction lenses. While achieving axial chromatic aberration elimination and thermal compensation, they also offer greater design freedom due to their subwavelength structural characteristics.

[0260] By configuring the second lens 310 as a combination of a flat diffractive lens or a flat superlens and a meniscus aspherical lens, the diffractive or superlens element is specifically responsible for chromatic aberration and thermal aberration correction, while the refractive element is specifically responsible for optical power and monochromatic aberration correction. These two functional elements are independent of each other, and their parameters can be optimized separately, facilitating modular design and manufacturing. Compared to directly fabricating the diffractive surface on a meniscus aspherical substrate, the flat diffractive lens or superlens further reduces the technological difficulty of surface composite processing, which is beneficial for improving production efficiency and yield.

[0261] The following describes two specific embodiments:

[0262] Example 1:

[0263] See Figure 1 The far-infrared lens includes an incident lens group 100, an aperture 200, and an exit lens group 300 arranged sequentially from the object plane to the image plane. The incident lens group 100 includes a first lens 110 near the aperture 200 and a third lens 120 located on the side of the first lens 110 away from the aperture 200. The exit lens group 300 includes a second lens 310 near the aperture 200 and a fourth lens 320 located on the side of the second lens 310 away from the aperture 200. A protective lens 400 and the image side of an image sensor 500 are sequentially arranged behind the image side of the fourth lens 320. The lens barrel is fitted outside each lens and the aperture 200.

[0264] In this embodiment, the third lens 120 is configured as a meniscus spherical lens with negative optical power, and its material is single crystal silicon. The first lens 110 is configured as a meniscus aspherical lens with positive optical power, its object-side surface is concave, its image-side surface is convex, and the edge of the first lens 110 is concave towards the object side, and its material is chalcogenide glass. The second lens 310 is configured as a meniscus aspherical lens with positive optical power, its object-side surface is concave and faces the aperture stop 200, its image-side surface is convex, and its material is chalcogenide glass. The object-side surface of the second lens 310 is provided with a binary diffraction surface. The fourth lens 320 is configured as a positive lens with both the object-side and image-side surfaces aspherical, and its material is chalcogenide glass. The protective lens 400 is configured as a single-crystal silicon flat filter.

[0265] The surface parameters, thickness, spacing, material, and aperture parameters of each lens in this embodiment are detailed in Table 1, the aspherical coefficients are detailed in Table 2, and the phase parameters of diffraction surface 313 are detailed in Table 3.

[0266]

[0267] Table 1

[0268] In Table 1, r1 represents the radius of curvature of the object side of the lens, and r2 represents the radius of curvature of the image side of the lens. A positive value indicates that the center of curvature is on the image side of the surface, and a negative value indicates that the center of curvature is on the object side of the surface. The spacing represents the axial distance along the optical axis from the image side of the current lens to the object side of the next lens.

[0269]

[0270] Table 2

[0271] In Table 2, k is the conic coefficient, and A, B, C, and D are aspheric coefficients of each order. The symbol " / " indicates that the surface is a sphere in the sense of an aspheric expression or that the coefficient of that order is not enabled.

[0272]

[0273] Table 3

[0274] In Table 3, n is the number of polynomial terms, r0 is the normalized radius of diffraction surface 313, and A1 and A2 are phase coefficients.

[0275] Among them, the two surfaces of the first lens 110, the image-side surface of the second lens 310, and the two surfaces of the fourth lens 320 are all aspherical surfaces. The expression for an aspherical surface is:

[0276]

[0277] Where Z(r) is the distance vector from the vertex of the aspherical surface along the optical axis at a height of r, c is the surface curvature of the aspherical surface, c = 1 / R, R is the radius of curvature of the aspherical surface, k is the conic coefficient, and A, B, C, D... are aspherical coefficients.

[0278] The object-side surface of the second lens 310 is a diffraction surface 313 on an aspherical substrate. Its surface shape expression is based on the above aspherical expression with the addition of a phase term for the diffraction surface 313, and the expression is as follows:

[0279]

[0280] in, ρ = r / r0, where r is the radial distance from any point on diffraction plane 313 to the optical axis, and r0 is the normalized radius of diffraction plane 313. is the phase coefficient, and n is the number of terms in the polynomial.

[0281] Based on the parameters in Table 1, the following relational data table 4 for this embodiment can be derived:

[0282]

[0283] Table 4

[0284] Where f1 is the focal length of the third lens 120, f is the focal length of the lens optical system, f2 is the focal length of the first lens 110, and the shape factor B = (C1 + C2) / (C1 - C2), where C1 and C2 are the radii of curvature of the object side and image side of the first lens 110, respectively.

[0285] As shown in Table 4, the ratio of the focal length of the third lens 120 to the system focal length, |f1| / f, is 2.75, satisfying the constraint 1.5 ≤ |f1| / f ≤ 3. Within this range, the negative optical power of the third lens 120 can effectively gather light rays from a large field of view. While ensuring the backstop meets requirements, the front optical aperture is controlled at 19 mm, while avoiding the introduction of difficult-to-correct advanced aberrations due to excessive negative optical power.

[0286] The shape factor B of the first lens 110 is -185.89, satisfying the constraint -200≤B≤0. The meniscus shape of the first lens 110 causes its concave surface to face the object side, generating negative Seidel coma. This bends the principal ray of the off-axis beam towards the optical axis, shifting the entrance pupil position forward towards the object side, thereby reducing the aperture requirement of the front-end third lens 120. Simultaneously, the aberrations of the front group composed of the first lens 110 and the second lens 310 are partially corrected, sharing the burden of correcting field curvature, chromatic aberration, and coma in the exit lens group 300, which is beneficial for obtaining a more compact structure and better image quality.

[0287] The ratio of the focal length of the third lens 120 to that of the first lens 110, |f1 / f2|, is 0.46, satisfying the constraint 0.2 ≤ |f1 / f2| ≤ 0.5. This lower limit of the ratio ensures that the off-axis field of view has a certain degree of negative field curvature and negative coma, while avoiding overcorrection that would lead to difficult-to-correct higher-order aberrations. It also facilitates control of the aperture of the exit lens group 300. This upper limit of the ratio ensures that the preceding group has sufficient field curvature and coma correction capabilities, allowing the aperture of the third lens 120 to be controlled within a relatively small range.

[0288] According to the coma expression in aberration theory:

[0289]

[0290] in This is the primary spherical difference coefficient. H is the incident height of the principal ray on the lens surface, and H is the incident height of the marginal ray on the lens surface. Let B be the optical power of the lens, and let B be the shape factor of the lens.

[0291] From this expression, we can see that the coma coefficient is related to... It is proportional to the product of B. The aforementioned focal length ratio limit and shape factor limit work together to synergistically regulate the off-axis coma of the incident lens group 100, and indirectly affect the aperture of the third lens 120 through the principal ray height relationship.

[0292] The second lens 310 has a binary diffraction surface on the object side near the aperture 200. By utilizing the negative dispersion characteristics of the diffraction surface 313 and the low equivalent Abbe number that is independent of the material, the axial chromatic aberration of the entire system can be effectively corrected.

[0293] The key optical performance parameters of this embodiment are as follows: system focal length f is 4.79 mm, aperture Fn0. is 0.9, relative aperture is approximately 1.11, total optical length ttl is 40.057 mm, front optical diameter is 19 mm, maximum image ring is 12 mm, and maximum field of view (FOV) is 145 degrees.

[0294] Figure 2 This is the field-of-view MTF diagram for this embodiment. Figure 3 This is a relative illumination diagram for this embodiment. Figure 4 This is the vertical axis color difference diagram of this embodiment. Figure 5 This is the axial color difference diagram for this embodiment. (From...) Figures 2 to 5 As can be seen, under the conditions of a 145-degree ultra-wide-angle field of view and a large aperture of f / 0.9, the MTF curves of each field of view are concentrated and have high values, indicating that the image quality is uniform and the resolution is good across the entire field of view. The relative illumination diagram shows that the illumination at the edge of the field of view is maintained at a high level, with no obvious vignetting. The transverse chromatic aberration and axial chromatic aberration diagrams show that the system has excellent chromatic aberration correction.

[0295] Example 2:

[0296] See Figure 6 The far-infrared lens includes an incident lens group 100, an aperture 200, and an exit lens group 300 arranged sequentially from the object plane to the image plane. The incident lens group 100 includes a first lens 110 near the aperture 200 and a third lens 120 located on the side of the first lens 110 away from the aperture 200. The exit lens group 300 includes a second lens 310 near the aperture 200 and a fourth lens 320 located on the side of the second lens 310 away from the aperture 200. A protective lens 400 and the image side of an image sensor 500 are sequentially arranged behind the image side of the fourth lens 320. The lens barrel is fitted outside each lens and the aperture 200.

[0297] In this embodiment, the third lens 120 is configured as a meniscus spherical lens with negative optical power. The first lens 110 is configured as a meniscus aspherical lens with positive optical power, its object-side surface is concave, its image-side surface is convex, and the edge of the first lens 110 is concave towards the object side. The second lens 310 is configured as a meniscus aspherical lens with positive optical power, its object-side surface is concave and faces the aperture stop 200, its image-side surface is convex, and the object-side surface of the second lens 310 is provided with a binary diffraction surface. The fourth lens 320 is configured as a positive lens with both its object-side and image-side surfaces aspherical. The protective lens 400 is configured as a single-crystal silicon flat filter.

[0298] The surface parameters, thickness, spacing, material, and aperture parameters of each lens in this embodiment are detailed in Table 5, the aspherical coefficients are detailed in Table 6, and the phase parameters of diffraction surface 313 are detailed in Table 7.

[0299]

[0300] Table 5

[0301] In Table 5, r1 represents the radius of curvature of the object side of the lens, and r2 represents the radius of curvature of the image side of the lens. A positive value indicates that the center of curvature is on the image side of the surface, and a negative value indicates that the center of curvature is on the object side of the surface. The spacing represents the axial distance along the optical axis from the image side of the current lens to the object side of the next lens.

[0302]

[0303] Table 6

[0304] In Table 6, k is the conic coefficient, and A, B, C, and D are aspheric coefficients of each order. The symbol " / " indicates that the surface is a sphere in the sense of an aspheric expression or that the coefficient of that order is not enabled.

[0305]

[0306] Table 7

[0307] In Table 7, n is the number of polynomial terms, r0 is the normalized radius of diffraction surface 313, and A1 and A2 are phase coefficients.

[0308] In this embodiment, the two surfaces of the first lens 110, the image-side surface of the second lens 310, and the two surfaces of the fourth lens 320 are all aspherical surfaces, and their aspherical surface expressions are the same as in Embodiment 1. The object-side surface of the second lens 310 is the diffraction surface 313 of the aspherical substrate, and its surface shape expression is the same as in Embodiment 1.

[0309] The following relational data table 8 can be derived from the parameters in Table 5:

[0310]

[0311] Table 8

[0312] Where f1 is the focal length of the third lens 120, f is the focal length of the lens optical system, f2 is the focal length of the first lens 110, and the shape factor B = (C1 + C2) / (C1 - C2), where C1 and C2 are the radii of curvature of the object side and image side of the first lens 110, respectively.

[0313] As shown in Table 8, the ratio of the focal length of the third lens 120 to the system focal length, |f1| / f, is 2.01, satisfying the constraint 1.5 ≤ |f1| / f ≤ 3. Within this range, the negative optical power of the third lens 120 can effectively gather light rays from a large field of view. While ensuring the backstop meets requirements, the front optical aperture is controlled at 22.6 mm, while avoiding the introduction of difficult-to-correct advanced aberrations due to excessive negative optical power.

[0314] The shape factor B of the first lens 110 is -13.91, satisfying the constraint -200 ≤ B ≤ 0. The meniscus shape of the first lens 110 causes its concave surface to face the object side, generating negative Seidel coma. This bends the principal ray of the off-axis beam towards the optical axis, shifting the entrance pupil position forward towards the object side, thereby reducing the aperture requirement of the front-end third lens 120. Simultaneously, the aberrations of the incident lens group 100 are partially corrected, relieving some of the correction burden on the exit lens group 300.

[0315] The ratio of the focal length of the third lens 120 to that of the first lens 110, |f1 / f2|, is 0.24, satisfying the constraint that 0.2 ≤ |f1 / f2| ≤ 0.5. This ratio ensures that the off-axis field of view of the front group has an appropriate amount of negative field curvature and negative coma, which is neither overcorrected nor lacks sufficient correction capability, thus benefiting the control of the rear aperture and the miniaturization of the front lens aperture.

[0316] The second lens 310 has a binary diffraction surface on the object side near the aperture 200. By utilizing the negative dispersion characteristics of the diffraction surface 313, the axial chromatic aberration of the entire system can be effectively corrected.

[0317] According to the coma expression in aberration theory:

[0318]

[0319] in This is the primary spherical difference coefficient. H is the incident height of the principal ray on the lens surface, and H is the incident height of the marginal ray on the lens surface. Let B be the optical power of the lens, and let B be the shape factor of the lens.

[0320] From this expression, we can see that the coma coefficient is related to... It is proportional to the product of B. The aforementioned focal length ratio limit and shape factor limit work together to synergistically regulate the off-axis coma of the incident lens group 100, and indirectly affect the aperture of the third lens 120 through the principal ray height relationship.

[0321] The second lens 310 has a binary diffraction surface on the object side near the aperture 200. By utilizing the negative dispersion characteristics of the diffraction surface 313 and the low equivalent Abbe number that is independent of the material, the axial chromatic aberration of the entire system can be effectively corrected.

[0322] The key optical performance parameters of this embodiment are as follows: system focal length f is 4.81 mm, aperture Fn0. is 0.9, relative aperture is approximately 1.11, total optical length is 41.037 mm, front optical diameter is 22.6 mm, maximum image circle is 12 mm, and maximum field of view is 140 degrees.

[0323] Figure 7 This is the field-of-view MTF diagram for this embodiment. Figure 8 This is a relative illumination diagram for this embodiment. Figure 9 This is the vertical axis color difference diagram of this embodiment. Figure 10 This is the axial color difference diagram for this embodiment. (From...) Figures 7 to 10 As can be seen, under the conditions of a 140-degree ultra-wide-angle field of view and a large aperture of f / 0.9, the MTF curves of each field of view are concentrated and have high values, and the image quality is uniform across the entire field of view. The relative illumination diagram shows no obvious vignetting at the edge of the field of view. The transverse chromatic aberration and axial chromatic aberration diagrams show that the system has excellent chromatic aberration correction.

[0324] Combining the above two embodiments, the far-infrared lens provided in this application, through the combination of negative and positive optical power of the third lens 120 and the first lens 110 in the incident lens group 100, and the specific shape factor and focal length ratio of the first lens 110 bent towards the object side, shifts the system's entrance pupil forward to reduce the front aperture. Simultaneously, achromatic and thermal aberrations are eliminated through the binary diffraction surface on the aspherical substrate of the second lens 310 in the exit lens group 300, and the final aberration correction is completed by the double-sided aspherical surface of the fourth lens 320. Thus, high-quality imaging with a relative aperture greater than or equal to 1 and a maximum field of view greater than or equal to 120 degrees is achieved in a compact structure. The front-end third lens 120 adopts a spherical design and can be manufactured using traditional cold-working processes, while the rear lens group can be manufactured using a chalcogenide glass molding process, which is beneficial for low-cost mass production.

[0325] This application provides a shooting device, including a far-infrared lens as described in any of the above embodiments.

[0326] Since the shooting device includes the far-infrared lens of any of the above embodiments, the advantages of the shooting device including the far-infrared lens of any of the above embodiments can be specifically referred to in the relevant description above, and will not be repeated here.

[0327] This application provides a car that includes an infrared lens as described in any of the above embodiments.

[0328] A car can be an intelligent connected vehicle. An intelligent connected vehicle refers to a car equipped with advanced on-board sensors, controllers, actuators and other devices, and integrated with modern communication and network technologies to achieve information exchange and sharing between vehicles, between vehicles and roads, between vehicles and people, and between vehicles and the cloud, and has functions such as complex environment perception, intelligent decision-making and collaborative control.

[0329] Among them, the vehicle vision perception system is a core component of the environmental perception layer of intelligent connected vehicles. Due to its imaging advantages in low visibility conditions such as night, fog, haze, rain and snow, far-infrared lenses have become one of the indispensable sensor types in the vehicle vision perception system.

[0330] The far-infrared lens can be installed on the exterior of a car body, such as in the front grille, roof shark fin antenna module, rearview mirror base, or both sides of the bumper. This far-infrared lens, in conjunction with the onboard image sensor and image processing unit, forms an onboard far-infrared sensing module.

[0331] As part of the intelligent connected vehicle environmental perception system, this vehicle-mounted far-infrared sensing module achieves data fusion and collaboration with other on-board sensors through the Internet of Vehicles.

[0332] During vehicle operation, far-infrared cameras collect infrared radiation information from the scene in front of or around the vehicle. Subsequent processing units then perform target detection, recognition, and tracking. Combined with roadside perception information obtained from the vehicle-to-everything (V2X) network and high-precision map data from the cloud, this provides all-weather, highly reliable perception input for autonomous driving or assisted driving systems, supporting the realization of intelligent driving functions such as automatic emergency braking, adaptive cruise control, and blind spot monitoring.

[0333] Since the automobile includes the far-infrared lens of any of the above embodiments, the advantages of the automobile including the far-infrared lens of any of the above embodiments can be specifically referred to in the relevant description above, and will not be repeated here.

[0334] Example 3:

[0335] See Figure 11The far-infrared lens includes an incident lens group 100, an aperture 200, and an exit lens group 300 arranged sequentially from the object plane to the image plane. The incident lens group 100 includes a first lens 110 near the aperture 200 and a third lens 120 located on the side of the first lens 110 away from the aperture 200. The exit lens group 300 includes a second lens 310 near the aperture 200 and a fourth lens 320 located on the side of the second lens 310 away from the aperture 200. The second lens 310 includes a flat plate lens 311 and a meniscus aspherical lens 312 with positive optical power. A protective lens 400 and the image side of an image sensor 500 are sequentially arranged behind the image side of the fourth lens 320. The lens barrel is fitted around the outside of each lens and the aperture 200.

[0336] The surface parameters, thickness, spacing, material, and aperture parameters of each lens in this embodiment are detailed in Table 9, the aspherical coefficients are detailed in Table 10, and the phase parameters of diffraction surface 313 are detailed in Table 11.

[0337]

[0338] Table 9

[0339] In Table 9, r1 represents the radius of curvature of the object side of the lens, and r2 represents the radius of curvature of the image side of the lens. A positive value indicates that the center of curvature is on the image side of the surface, and a negative value indicates that the center of curvature is on the object side of the surface. The spacing represents the axial distance along the optical axis from the image side of the current lens to the object side of the next lens.

[0340]

[0341] Table 10

[0342] In Table 10, k is the conic coefficient, and A, B, C, and D are aspheric coefficients of each order. The symbol " / " indicates that the surface is a sphere in the sense of an aspheric expression or that the coefficient of that order is not enabled.

[0343]

[0344] Table 11

[0345] In Table 11, n is the number of polynomial terms, r0 is the normalized radius of diffraction surface 313, and A1 and A2 are phase coefficients.

[0346] In this embodiment, the two surfaces of the first lens 110, the image-side surface of the second lens 310, and the two surfaces of the fourth lens 320 are all aspherical surfaces, and their aspherical surface expressions are the same as in Embodiment 1. The object-side surface of the second lens 310 is the diffraction surface 313 of the aspherical substrate, and its surface shape expression is the same as in Embodiment 1.

[0347] The following relational data table 12 can be derived from the parameters in Table 9:

[0348]

[0349] Table 12

[0350] Figure 12 This is the field-of-view MTF diagram for this embodiment. Figure 13 This is a relative illumination diagram for this embodiment. Figure 14 This is the vertical axis color difference diagram of this embodiment. Figure 15 This is the axial color difference diagram for this embodiment. (From...) Figures 2 to 5 As can be seen, the MTF curves for each field of view in this embodiment are concentrated and have high values, indicating uniform image quality and good resolution across the entire field of view. The relative illumination map shows that the edge field of view illumination remains at a high level with no obvious vignetting. The transverse and axial chromatic aberration maps show that the system has excellent chromatic aberration correction.

[0351] The above technical description is illustrated with reference to the accompanying drawings, which form a part of this application, and which show implementations according to the described embodiments. While these embodiments are described in sufficient detail to enable those skilled in the art to implement them, these embodiments are not limiting; thus, other embodiments can be used, and variations can be made without departing from the scope of the described embodiments.

[0352] Furthermore, terminology is used in the above technical description to provide a thorough understanding of the described embodiments. However, excessive detail is not required to implement the described embodiments. Therefore, the above description of the embodiments is presented for illustrative and descriptive purposes. The embodiments presented in the above description, as well as the examples disclosed according to these embodiments, are provided separately to add context and aid in understanding the described embodiments. The above specification is not intended to be exhaustive or to limit the described embodiments to the precise form of this application. Based on the above teachings, several modifications, selections, and variations are possible. In some cases, well-known processing steps have not been described in detail to avoid unnecessarily affecting the described embodiments.

[0353] This application uses specific embodiments to illustrate the principles and implementation methods of this application. The description of the above embodiments is only for the purpose of helping to understand the core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

[0354] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A far-infrared lens, characterized in that, It includes an incident lens group (100), an aperture (200), and an exit lens group (300) arranged sequentially from the object plane to the image plane. The incident lens group (100) includes a first lens (110) near the aperture stop (200). The first lens (110) is configured as a meniscus aspherical lens with positive optical power. The object side of the first lens (110) is concave, the image side of the first lens (110) is convex, and the edge of the first lens (110) is concave towards the object side. The exit lens group (300) includes a second lens (310) near the aperture stop (200). The second lens (310) is configured as a meniscus aspherical lens with positive optical power. The object side of the second lens (310) is concave, and a diffraction surface (311) is provided on the object side of the second lens (310).

2. The far-infrared lens according to claim 1, characterized in that, The diffraction surface (311) is a binary diffraction surface, and the phase expression of the binary diffraction surface is: Where ρ = r / r0, r is the radius of the binary diffraction surface, r0 is the normalized radius of the binary diffraction surface, A_i is the phase coefficient, and n is the number of terms in the polynomial.

3. The far-infrared lens according to claim 1, characterized in that, The shape factor B of the first lens (110) satisfies: -200≤B≤0 in, C1 is the radius of curvature of the object side of the first lens (110), and C2 is the radius of curvature of the image side of the first lens (110).

4. The far-infrared lens according to claim 1, characterized in that, The incident lens group (100) further includes a third lens (120), which is located on the side of the first lens (110) away from the aperture stop (200); The third lens (120) is configured as a meniscus spherical lens with negative optical power.

5. The far-infrared lens according to claim 4, characterized in that, The focal length f1 of the third lens (120) satisfies the following with the focal length f of the optical system of the far-infrared lens: 1.5≤|f1| / f≤3 And / or, the focal length f1 of the third lens (120) and the focal length f2 of the first lens (110) satisfy: 0.2≤|f1 / f2|≤0.

5.

6. The far-infrared lens according to claim 1, characterized in that, The exit lens group (300) further includes a fourth lens (320), which is located on the side of the second lens (310) away from the aperture stop (200); The fourth lens (320) is configured as a positive lens with both the object-side surface and the image-side surface being aspherical.

7. The far-infrared lens according to claim 6, characterized in that, The incident lens group (100) also includes a third lens (120), the third lens (120) being made of any one of germanium single crystal, silicon single crystal and zinc sulfide; And / or, at least one of the first lens (110), the second lens (310) and the fourth lens (320) is made of chalcogenide glass.

8. The far-infrared lens according to claim 6, characterized in that, The aspherical surface shape expressions of the first lens (110), the second lens (310), and the fourth lens (320) satisfy: Where Z(r) is the distance vector from the vertex of the aspherical surface along the optical axis at a height of r, c is the surface curvature of the aspherical surface, c = 1 / R, R is the radius of curvature of the aspherical surface, k is the conic coefficient, and A, B, C, D... are aspherical coefficients.

9. The far-infrared lens according to any one of claims 1-8, characterized in that, The relative aperture of the far-infrared lens is greater than or equal to 1. And / or, the maximum field of view of the far-infrared lens is greater than or equal to 120°.

10. The far-infrared lens according to any one of claims 1-8, characterized in that, The far-infrared lens meets the total optical power requirement: In the direction from the object plane to the image plane, the incident lens group (100) and the exit lens group (300) include a plurality of lenses arranged sequentially. Let be the incident height of the paraxial ray at the i-th lens. Let be the optical power of the i-th lens. The total optical power of the far-infrared lens.

11. The far-infrared lens according to any one of claims 4 or 5, characterized in that, The far-infrared lens meets the condition for eliminating axial chromatic aberration: In the direction from the object plane to the image plane, the incident lens group (100) and the exit lens group (300) include a plurality of lenses arranged sequentially. This refers to the amount of on-axis focal position shift of the far-infrared lens at the image-side focal plane caused by chromatic aberration. Let be the incident height of the paraxial ray at the i-th lens. The paraxial ray is at the incident height of the third lens (120). Let be the optical power of the i-th lens. The total optical power of the far-infrared lens. Let be the achromatic coefficient of the i-th lens; And / or, it also includes a lens barrel, which is sleeved on the outside of the incident lens group (100), the aperture stop (200) and the exit lens group (300); The far-infrared lens meets the thermal difference elimination condition: in, This refers to the rate at which the focal position of the far-infrared lens at the image-side focal plane shifts with temperature changes. Let be the incident height of the paraxial ray at the i-th lens. The paraxial ray is at the incident height of the third lens (120). Let be the optical power of the i-th lens. The total optical power of the far-infrared lens. Let be the thermal decompression coefficient of the i-th lens. is the coefficient of linear expansion of the lens barrel material, and L is the length of the lens barrel from the last lens to the image plane.

12. The far-infrared lens according to any one of claims 1-8, characterized in that, The second lens (310) includes a flat plate lens (311) and a meniscus aspherical lens (312) with positive optical power, wherein the flat plate lens is configured as a flat plate diffraction lens or a flat plate superlens.

13. The far-infrared lens according to any one of claims 6-8, characterized in that, It also includes a protective lens (400) disposed between the fourth lens (320) and the image side of the image sensor (500); The protective lens (400) is configured as a monocrystalline silicon flat filter; And / or, the incident lens group (100) further includes a third lens (120). At least three of the first lens (110), the second lens (310), the third lens (120), and the fourth lens (320) are made of different materials.

14. A shooting device, characterized in that, Including the far-infrared lens as described in any one of claims 1-13.

15. A car, characterized in that, Including the far-infrared lens as described in any one of claims 1-13.

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