A miniaturized thermal imaging folded hyper-hybrid lens and thermal imager

Abstract

The application discloses a folded super-hybrid thermal imaging folded super-hybrid lens with miniaturization and large aperture, and a thermal imager, and belongs to the field of optical lenses, wherein the lens comprises a diaphragm, a first lens, a second lens and a protective window which are sequentially arranged along an optical axis from an object plane to an image plane. The folded super-hybrid system formed by combining the super surface lens and the traditional lens can flexibly regulate the phase, amplitude and polarization of light waves on the sub-wavelength scale, and has mature micro-nano processing technologies such as electron beam lithography and nano-imprinting and diversified materials, so that the characteristics help to reduce the lens volume and weight of the optical system, reduce the raw material cost, and realize the miniaturization, light weight and integrated design of the thermal imaging equipment.

Description

Technical Field

[0001] This invention belongs to the field of optical lenses, and specifically relates to a miniaturized large-aperture thermal imaging hybrid lens and a thermal imager. Background Technology

[0002] Thermal imaging is a technology that uses the infrared radiation emitted by objects to detect and image them, playing a vital role in numerous fields such as military, medical, and industrial applications. The development of thermal imaging technology stemmed from the need for non-contact temperature measurement and nighttime observation. In low-light or no-light environments, traditional optical imaging, which relies on visible light, is severely limited. All objects, as long as their temperature is above absolute zero, emit infrared radiation. By detecting this radiation, imaging can be achieved without visible light. Infrared radiation is a part of the electromagnetic spectrum, with wavelengths ranging from approximately 0.75 micrometers to 1000 micrometers, covering the main bands of thermal radiation.

[0003] Thermal imagers collect infrared radiation through an optical system. A detector converts the radiation into electrical signals, which are then amplified and processed by a signal processing unit before being displayed as a thermal image. The optical system is a crucial component of a thermal imager, and its design and quality directly affect the image quality, detection sensitivity, and other overall performance characteristics. Traditional hybrid thermal imaging lenses rely primarily on multi-element refractive lens groups. However, the infrared materials used are expensive, the multi-element structure results in significant size and weight, and limited functional expandability. These issues hinder the miniaturization, portability, and cost control of thermal imaging equipment.

[0004] With technological advancements, the thin and lightweight characteristics of metasurface technology, along with its potential to utilize mature micro- and nano-fabrication techniques and low-cost dielectric materials, offer a new direction for addressing the shortcomings of traditional lenses. A metasurface is a two-dimensional planar material composed of subwavelength structural units (typically at the nanometer scale). By precisely designing the geometry, size, and arrangement of these structural units, the phase, amplitude, and polarization characteristics of light waves can be flexibly controlled. This allows for the realization of traditional optical element functions at the subwavelength scale, significantly reducing the size and weight of optical systems. Metasurfaces can replace traditional thick lenses, enabling ultra-thin and lightweight optical designs that are easier to integrate into various devices. Furthermore, metasurfaces can be manufactured using mature micro- and nano-fabrication techniques such as electron beam lithography and nanoimprinting. In the future, low-cost mass production can be achieved through wafer-level manufacturing. Moreover, the materials used are diverse, not limited to precious metals (such as gold and silver), but also including dielectric materials such as titanium dioxide and silicon nitride, greatly reducing raw material costs.

[0005] Hybrid refractive-hybrid systems, combining metasurface lenses and traditional lenses, have been proposed as an improvement. These systems can achieve the required optical path length within a compact space through optical path folding, reducing the size of traditional lenses while potentially maintaining high imaging resolution and low manufacturing costs. However, effectively applying hybrid refractive-hybrid systems to thermal imaging and achieving a thermal imaging hybrid refractive-hybrid lens design that simultaneously possesses miniaturization and large aperture characteristics remains a major challenge for current technology. Summary of the Invention

[0006] This invention provides a miniaturized, large-aperture thermal imaging hybrid lens and thermal imager, aiming to reduce the size and cost of the optical system while meeting the requirements of high-quality imaging and achieving a thermal-free design.

[0007] To solve the above-mentioned technical problems, the purpose of this invention is achieved through the following technical solution: a thermal imaging superconducting lens is provided, comprising an aperture stop, a first lens, a second lens, and a protective window arranged sequentially along the optical axis from the object plane to the image plane; The first lens is an aspherical Fresnel lens; the second lens is a metasurface lens; The thermal imaging hyper-refractive hybrid lens satisfies: ; in, This indicates the aperture value of a thermal imaging hybrid lens. The back focal length of the optical system is the distance from the image-side surface of the second lens to the imaging plane. The effective area size of the image-side surface of the first lens.

[0008] Furthermore, the first lens is an aspherical Fresnel lens, with the object side being an even-order aspherical surface and the image side being a Fresnel surface.

[0009] Furthermore, the first lens has positive optical power, the object side of the first lens is convex, and the image side of the first lens is concave.

[0010] Furthermore, the object-side surface of the first lens has a positive radius of curvature, and the image-side surface of the first lens also has a positive radius of curvature.

[0011] Furthermore, the second lens is a metasurface lens, with microstructures arranged on the object side and a plane on the image side.

[0012] Furthermore, the distance from the center of the optical axis on the side of the first lens to the image plane is the total length of the optical system. TTL The effective focal length of the optical system is ,in .

[0013] Furthermore, the material of the first lens is a chalcogenide material.

[0014] Furthermore, the substrate thickness of the second lens metasurface satisfies The substrate materials include, but are not limited to, amorphous silicon, crystalline silicon, borosilicate, silicon dioxide, quartz, glass, and other materials.

[0015] Furthermore, the microstructure material of the second lens metasurface includes, but is not limited to, amorphous silicon, crystalline silicon, silicon dioxide, silicon nitride, titanium dioxide, and other materials.

[0016] Furthermore, the aperture value of the thermal imaging hyperspectral hybrid lens satisfies It has a large aperture and allows a large amount of light to enter, meeting the requirements for high-quality imaging.

[0017] Furthermore, the MTF of the thermal imaging hyperspectral hybrid lens satisfies the following condition: at 21 lp / mm, At 42 lp / mm, It has a high imaging resolution and can acquire clear images.

[0018] The present invention also provides a thermal imager, including any of the above-mentioned thermal imaging hyperspectral hybrid lenses.

[0019] The thermal imaging refracto-hyper-lens hybrid lens provided in this embodiment of the invention employs two lenses, one a chalcogenide aspherical lens and the other a metalens. This design achieves a small size and cost-effectiveness while maintaining a wide operating temperature range. Furthermore, by setting the first lens to an aspherical Fresnel lens and rationally allocating the phase of the metasurface, the thermal imaging refracto-hyper-lens hybrid lens satisfies… , It has a small overall size, and the thermal imaging superconducting lens has a high resolution, while also meeting the required F-number. Version 1.0 features a large light intake, addressing the issues of large size and high cost in existing thermal imaging technologies. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the structure of a thermal imaging hyperspectral hybrid lens provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the MTF of a thermal imaging hyperspectral hybrid lens provided in Embodiment 1 of the present invention; Figure 3 This is a schematic diagram of distortion in a thermal imaging hyperspectral hybrid lens provided in Embodiment 1 of the present invention; Figure 4 This is a schematic diagram of the MTF of a thermal imaging hyperspectral hybrid lens provided in Embodiment 2 of the present invention; Figure 5 This is a schematic diagram of distortion in a thermal imaging hyperspectral hybrid lens provided in Embodiment 2 of the present invention.

[0022] Explanation of reference numerals in the attached figures: 110. Aperture stop; 120. First lens; 130. Second lens; 140. Protective window; 150. Imaging plane. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] It should be understood that, when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0026] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0027] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0028] Please see Figure 1 The present invention provides a miniaturized large-aperture thermal imaging superconducting lens, comprising an aperture stop 110, a first lens 120, a second lens 130, and a protective window 140 arranged sequentially along the optical axis from the object plane to the image plane.

[0029] The first lens 120 is an aspherical Fresnel lens with positive optical power, and the second lens 130 is a metasurface lens. The object-side surface of the first lens is convex, and the image-side surface is concave. The object-side surface is an even-order aspherical surface, and the image-side surface is a Fresnel surface. The object-side surface of the first lens is defined as the first surface, and the image-side surface is defined as the second surface.

[0030] In this experimental case, the object-side surface of the first lens 120 is designed as a convex even-order aspherical surface, primarily responsible for the initial convergence of light rays and the correction of some higher-order aberrations. The image-side surface of the first lens 120 is designed as a Fresnel surface, exhibiting a concave shape macroscopically, with a microstructure consisting of a series of concentric, precise annular steps. This precise design of the object-side and image-side surfaces of the first lens maintains high optical imaging quality while significantly reducing the lens's central thickness and overall volume, thus significantly improving the overall imaging sharpness and contrast of the system, while also meeting the requirements of miniaturization and cost control. The second lens 130, as a metasurface lens, through its planar object-side surface, binary image-side surface, and the microstructures arranged on the image-side surface, can achieve more precise control of light rays, further improving imaging quality. The period of the microstructure in the second lens 130 ranges from 350 to 500 nm, with an optimal period of 450 nm selected in this embodiment; the height of the microstructure ranges from 500 to 1500 nm, with an optimal height of 700 nm selected in this embodiment; the diameter of the microstructure covers 100 to 350 nm, and the material is silicon dioxide, arranged in square, hexagonal, and other shapes. Overall, this preferred embodiment demonstrates excellent performance in terms of imaging quality, optical performance, and applicability.

[0031] This implementation example uses a thermal imaging hyperfocal hybrid lens to meet the requirements. , Under these specified parameters, the hybrid lens not only has a small overall size but also boasts excellent image quality and high resolution.

[0032] In this embodiment, the aperture value (F-number) of the thermal imaging hyperspectral hybrid lens satisfies: 1.0. A large aperture significantly increases the lens's light-gathering diameter, and the amount of infrared radiation energy received per unit time (light intake) is directly proportional to the aperture area. In thermal imaging, this directly improves the detector's signal strength, enhances sensitivity, increases the signal-to-noise ratio, accelerates response speed, and meets the requirements for high-quality imaging.

[0033] In this embodiment, the metasurface lens can effectively correct aberrations. By setting at least one lens in the thermal imaging hyper-reflex lens as a metasurface lens, high-quality imaging results can be provided. Furthermore, the hyper-reflex lens can achieve a higher focal length and better optical path folding effect, thus achieving the required optical path length within a relatively small optical system. This characteristic helps to significantly reduce the volume and size of the optical system, while potentially maintaining high imaging resolution and low manufacturing costs.

[0034] As a feasible implementation, the first lens 120 is made of a chalcogenide material, and the substrate material of the second lens 130 includes, but is not limited to, amorphous silicon, crystalline silicon, borosilicate, silicon dioxide, quartz, and glass. The microstructure material of the second lens 130 includes, but is not limited to, amorphous silicon, crystalline silicon, silicon dioxide, silicon nitride, and titanium dioxide. By matching and combining lenses with positive and negative focal length temperature coefficients, the overall focal length drift is offset, and the optical power ratio of each lens is adjusted, making the total optical power of the system insensitive to temperature changes. This achieves a heatless design, reducing material costs and system size.

[0035] In this embodiment, the thermal imaging hyperspectral hybrid lens also includes an aperture stop 110. The aperture stop 110 is located in front of the first lens 120, and its main function is to intercept and limit light. The specific position can be adjusted according to actual needs. Preferably, the aperture stop 110 is attached to the object side of the first lens 120, that is, the aperture stop 110 is located on the first surface of the first lens 120, in order to achieve the best imaging effect.

[0036] Based on the above scheme, the operating temperature range of the thermal imaging hyperspectral hybrid lens can be achieved from -45℃ to 105℃, maintaining stable performance and imaging quality, and adapting to various extreme environmental conditions.

[0037] The following are two preferred embodiments based on the above examples, which detail the specific optical data parameters of each lens in the thermal imaging hyperspectral hybrid lens provided by the embodiments of the present invention.

[0038] The first preferred embodiment, specifically, is as follows: Figure 1 As shown, the thermal imaging hybrid lens includes an aperture stop 110, a first lens 120, a second lens 130, a protective window 140, and an imaging surface 150 arranged sequentially along the optical axis from the object plane to the image plane. The first lens 120 is an aspherical Fresnel lens with positive optical power, its object-side surface is convex, its image-side surface is concave, its object-side surface is an even-order aspherical, and its image-side surface is a Fresnel surface. The second lens 130 is a metasurface lens, its object-side surface has microstructures arranged, and its image-side surface is planar. The aperture stop 110 is located on the first surface of the first lens 120. The incident light is restricted by the aperture stop 110, enters through the object-side surface of the first lens 120, passes through the second lens 130 and the protective window 140, and finally converges on the imaging surface 150.

[0039] The optical parameters of this thermal imaging hyperspectral hybrid lens can be found in the example in Table 1. The optical data parameters in Table 1 correspond to... Figure 1 The thermal imaging super-hybrid lens shown.

[0040] Table 1

[0041] In Table 1, the surface numbers are assigned according to the surface sequence of each lens. For example, surface number 1 represents the object side of the first lens 120, which is also the aperture stop 110; surface number 2 represents the image side of the first lens 120, and so on, with the final surface number 7 representing the imaging plane 150. The radius of curvature represents the degree of curvature of the lens surface; a positive value indicates that the surface bends towards the image plane, and a negative value indicates that the surface bends towards the object plane. "Standard" represents the standard surface, "Extended sphere" represents the extended aspherical surface, "Binary2" represents the binary surface, and "Infinity" represents the surface as a plane. The spacing represents the central axial distance from the current surface to the next surface. Both the radius of curvature and the spacing are in millimeters (mm).

[0042] Its even-order aspherical surface type and Fresnel surface basic surface type satisfy the following equations:

[0043] Where z represents the distance of the aspherical surface from its vertex along the optical axis, r represents the height from the optical axis, c represents the curvature 1 / R, R represents the radius of curvature at the vertex of the lens, and k represents the conic coefficient. Ai Represents the higher-order coefficients of aspherical surfaces. ρ This represents the normalized radial coordinate.

[0044] Among them, the conic coefficient of each extended aspherical lens k and coefficients of higher-order terms Ai See the example in Table 2 below.

[0045] Table 2

[0046] In Table 2, 1.06E-004 indicates that the coefficient a2 of face number 1 is 1.06E-004, and so on.

[0047] The phase of the Fresnel surface of the first lens 110 and the metasurface of the second lens 120 can be referenced in the example in Table 3.

[0048] Table 3

[0049] In Table 3, R1 represents the normalized radius of the Fresnel surface or metasurface lens binary surface.

[0050] In the preferred embodiment of this example, the aperture value, the back focal length of the optical system, and the effective area size of the second surface of the first lens satisfy the following relationship: The total optical length and effective focal length satisfy the following conditions: .

[0051] The preferred embodiment of this example provides a thermal imaging hyperspectral hybrid lens with an operating wavelength of 8-12 μm and an F-number of [missing information]. It has a large entrance pupil diameter, sufficient light intake, and high resolution, meeting the requirements for thermal imaging technology.

[0052] Figure 2 This is a schematic diagram of the MTF of a thermal imaging refractive-hypermagnetic hybrid lens provided in an embodiment of the present invention. The MTF of the thermal imaging refractive-hypermagnetic hybrid lens provided in this embodiment of the present invention satisfies the following condition: at 21 lp / mm, At 42 lp / mm, It has a high imaging resolution and can acquire clear images.

[0053] Figure 3 This is a schematic diagram of the distortion of a thermal imaging refractometer-hybrid lens provided in an embodiment of the present invention. The thermal imaging refractometer-hybrid lens provided in this embodiment of the present invention has small distortion and minimal image deformation, which can meet the requirements of high-quality imaging.

[0054] In a second preferred embodiment, exemplarily, the thermal imaging hyperspectral hybrid lens includes an aperture stop 110, a first lens 120, a second lens 130, a protective window 140, and an imaging surface 150 arranged sequentially along the optical axis from the object plane to the image plane. The first lens 120 is an aspherical Fresnel lens with positive optical power, its object-side surface is convex, its image-side surface is concave, its object-side surface is an even-order aspherical, and its image-side surface is a Fresnel surface. The second lens 130 is a metasurface lens, its object-side surface has microstructures arranged, and its image-side surface is planar. The aperture stop 110 is located on the first surface of the first lens 120. The incident light is restricted by the aperture stop 110, enters through the object-side surface of the first lens 120, passes through the second lens 130 and the protective window 140, and finally converges on the imaging surface 150.

[0055] The optical parameters of this thermal imaging hyperspectral hybrid lens can be found in the example in Table 1, and the optical data parameters in Table 4 correspond to... Figure 1 The thermal imaging super-hybrid lens shown.

[0056] Table 4

[0057] In Table 4, the surface numbers are assigned according to the surface sequence of each lens. For example, surface number 1 represents the object side of the first lens 120, which is also the aperture stop 110; surface number 2 represents the image side of the first lens 120, and so on, with the final surface number 7 representing the imaging plane 150. The radius of curvature represents the degree of curvature of the lens surface; a positive value indicates that the surface bends towards the image plane, and a negative value indicates that the surface bends towards the object plane. "Standard" represents the standard surface, "Extended sphere" represents the extended aspherical surface, "Binary2" represents the binary surface, and "Infinity" represents the surface as a plane. The spacing represents the central axial distance from the current surface to the next surface. Both the radius of curvature and the spacing are in millimeters (mm).

[0058] Its even-order aspherical surface type and Fresnel surface basic surface type satisfy the following equations:

[0059] Where z represents the distance of the aspherical surface from its vertex along the optical axis, r represents the height from the optical axis, c represents the curvature 1 / R, R represents the radius of curvature at the vertex of the lens, and k represents the conic coefficient. Ai Represents the higher-order coefficients of aspherical surfaces. ρ This represents the normalized radial coordinate.

[0060] Among them, the conic coefficient of each extended aspherical lens k and coefficients of higher-order terms Ai See the example in Table 5 below.

[0061] Table 5

[0062] In Table 5, 1.30E-004 represents the coefficient with face number 1. A2 For example, 1.30E-004, and so on.

[0063] The phase of the Fresnel surface of the first lens 110 and the metasurface of the second lens 120 can be referenced in the example in Table 6.

[0064] Table 6

[0065] In Table 6, R1 represents the normalized radius of the Fresnel surface or metasurface lens binary surface.

[0066] In the preferred embodiment of this example, the aperture value, the back focal length of the optical system, and the effective area size of the second surface of the first lens satisfy the following relationship: The total optical length and effective focal length satisfy the following conditions: .

[0067] The thermal imaging hyperspectral hybrid lens provided in this embodiment operates in the 8-12μm wavelength range and has an F-number of [missing information]. It has a large entrance pupil diameter, sufficient light intake, and high resolution, meeting the requirements for thermal imaging technology.

[0068] Figure 4 This is a schematic diagram of the MTF of a thermal imaging refractive-hypermagnetic hybrid lens provided in an embodiment of the present invention. The MTF of the thermal imaging refractive-hypermagnetic hybrid lens provided in this embodiment of the present invention satisfies the following condition: at 21 lp / mm, At 42 lp / mm, It has a high imaging resolution and can acquire clear images.

[0069] Figure 5 This is a schematic diagram of the distortion of a thermal imaging refractometer-hybrid lens provided in an embodiment of the present invention. The thermal imaging refractometer-hybrid lens provided in this embodiment of the present invention has small distortion and minimal image deformation, which can meet the requirements of high-quality imaging.

[0070] In summary, the thermal imaging hyperspectral hybrid lens provided in this embodiment of the invention is small in size, low in cost, and produces clear images, meeting the requirements for high-quality imaging and lightweight integration.

[0071] Example 1 and Example 2 respectively satisfy the relationships shown in Table 7 below: Table 7

[0072] This invention also provides a thermal imager, which includes the above-described thermal imaging hyperspectral hybrid lens.

[0073] The above are merely specific embodiments of this disclosure, but the scope of protection of this disclosure is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this disclosure should be included within the scope of protection of this disclosure. Therefore, the scope of protection of this disclosure should be determined by the scope of the claims.

Claims

1. A miniaturized, large-aperture thermal imaging hybrid lens, characterized in that, It includes an aperture stop, a first lens, a second lens, and a protective window arranged sequentially along the optical axis from the object plane to the image plane; at least one of the first lens and the second lens is a metasurface lens; The thermal imaging hyperspectral hybrid lens satisfies: ; in, This indicates the aperture value of a thermal imaging hybrid lens. The back focal length of the optical system is the distance from the image-side surface of the second lens to the image plane. This indicates the effective area size of the image-side surface of the first lens.

2. The thermal imaging hyperspectral hybrid lens according to claim 1, characterized in that, The first lens is an aspherical Fresnel lens, with the object side being an even-order aspherical surface and the image side being a Fresnel surface; The first lens has positive optical power, the object side of the first lens is convex, and the image side of the first lens is concave. The object-side surface of the first lens has a positive radius of curvature, and the image-side surface of the first lens has a positive radius of curvature.

3. The thermal imaging hyperspectral hybrid lens according to claim 1, characterized in that, The second lens is a metasurface lens, which includes a substrate and microstructures disposed on the substrate; The object side of the second lens has a microstructure arrangement, and the image side of the second lens is a plane.

4. The thermal imaging hyperspectral hybrid lens according to claim 3, characterized in that, The substrate material of the second lens is one of amorphous silicon, crystalline silicon, borosilicate, silicon dioxide, quartz, and glass, and the substrate thickness meets the following requirements. The microstructure material of the second lens is one of amorphous silicon, crystalline silicon, silicon dioxide, silicon nitride, and titanium dioxide.

5. The thermal imaging hyperspectral hybrid lens according to claim 2, characterized in that, The first lens is made of a chalcogenide material.

6. The thermal imaging hyperspectral hybrid lens according to claim 1, characterized in that, The thermal imaging hyperspectral hybrid lens satisfies: ; in, TTL This represents the distance from the center of the optical axis on the object side of the first lens to the image plane. This indicates the effective focal length of the optical system.

7. The thermal imaging hyperspectral hybrid lens according to claim 1, characterized in that, The thermal imaging superconducting lens also includes an aperture stop, which is located in front of the first lens.

8. The thermal imaging hyperspectral hybrid lens according to claim 7, characterized in that, The aperture is attached to the object side of the first lens.

9. The thermal imaging hyperspectral hybrid lens according to claim 1, characterized in that, The aperture value of the thermal imaging superconducting lens satisfies .

10. The thermal imaging hyperspectral hybrid lens according to claim 1, characterized in that, The MTF of the thermal imaging refractive-hybrid lens satisfies the following condition: when the resolution of the thermal imaging refractive-hybrid lens is 21 lp / mm. ; When the resolution of the thermal imaging hyperspectral hybrid lens is 42 lp / mm .

11. The thermal imaging hyperspectral hybrid lens according to claim 1, characterized in that, The operating temperature range of the thermal imaging superconducting lens is -45℃ to 105℃.

12. A thermal imager, characterized in that, Includes any one of the thermal imaging hyper-hybrid lenses according to claims 1-11.

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