Folding and super hybrid large-view-field long-wave infrared lens

Abstract

The invention discloses a folding and super hybrid large-view-field long-wave infrared lens, and relates to the technical field of optical engineering. In order to solve the problems of large size, poor semiconductor process compatibility and limited field angle of the existing long-wave infrared lens, the invention provides the following technical scheme: the refraction-super hybrid large-field long-wave infrared lens comprises a first lens, a second lens, a third lens and a fourth lens, the first lens, the second lens, the third lens and the fourth lens are sequentially arranged from the object plane to the phase plane along the optical axis, at least one of the first lens, the second lens, the third lens and the fourth lens is a metasurface lens, and the rest lenses are refraction lenses. According to the refraction and super hybrid type large-view-field long-wave infrared lens, a traditional refraction lens is replaced by the super-surface lens, a refraction and super hybrid optical system is constructed, the size of the lens is greatly reduced, and the manufacturing cost is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of optical engineering, and particularly relates to a refractive and metasurface hybrid large field-of-view long-wave infrared lens. Background Art

[0002] Infrared thermal imaging technology is a technology that detects the thermal radiation of an object to obtain temperature information. In nature, all objects radiate infrared light to varying degrees, and the intensity and spectral distribution of this radiation are closely related to the temperature and surface characteristics of the object. Therefore, infrared thermal imaging technology can provide an image of the temperature distribution of an object without relying on visible light sources, which is of great significance in various application scenarios such as environmental detection, security monitoring, autonomous driving, and military reconnaissance.

[0003] As an important optical device for infrared thermal imaging technology, the performance of an infrared optical lens directly determines the imaging performance of the optical system. A high-quality infrared lens not only needs to have high transmittance, low chromatic aberration, and good optical aberration control, but also needs to be able to adapt to different working environments and application requirements. Among them, large field-of-view long-wave infrared thermal imaging lenses have important application values in multiple fields, especially in high-resolution imaging systems that require covering large areas.

[0004] A metasurface is an artificial structure composed of sub-wavelength-scale micro-nano structure units arranged according to specific rules, which can achieve flexible regulation of incident electromagnetic waves. Its novel characteristics and flexible structure design make it have broad application prospects. In optical design, metasurfaces can be used to replace traditional optical elements, such as lenses, etc., to achieve precise regulation and manipulation of light.

[0005] Traditional infrared thermal imaging lenses use a retrofocus type design to achieve a large field of view. They consist of a front negative lens group and a rear positive lens group along the optical axis from the object plane to the image plane. This results in that this type of lens usually needs to use a combination of multiple lens groups, which not only increases the complexity of the system, but also makes the lens bulky and heavy, not in line with the current development trend of miniaturization and lightweight of optical systems. In order to improve the imaging quality of the lens and achieve higher resolution, it is often necessary to use many aspherical mirrors. The design and manufacture of aspherical mirrors are relatively complex and require high processing accuracy, which not only increases the manufacturing difficulty but also raises the production cost. Summary of the Invention

[0006] The purpose of the present invention is to provide a refractive and metasurface hybrid large field-of-view long-wave infrared lens to solve the problems of large volume, poor semiconductor process compatibility, and limited field of view angle existing in existing long-wave infrared lenses.

[0007] The technical solution of the present invention to solve the above technical problems is as follows: A refractive and metasurface hybrid large field of view long-wave infrared lens, comprising a first lens, a second lens, a third lens and a fourth lens. The first lens, the second lens, the third lens and the fourth lens are sequentially arranged along the optical axis from the object plane to the image plane. At least one of the first lens, the second lens, the third lens and the fourth lens is a metasurface lens, and the remaining lenses are refractive lenses.

[0008] The first lens is a refractive lens with negative optical power, the object side is convex and the image side is concave.

[0009] At least two of the object sides or image sides of the first lens, the second lens, the third lens and the fourth lens are spherical surfaces.

[0010] Both the substrate and the structural unit of the metasurface lens are made of silicon, and infrared antireflection films are coated on both sides of the metasurface lens.

[0011] The structural units of the metasurface lens are arranged in a quasi-periodic or periodic pattern, and the cross-sectional shape of each structural column is a centrally symmetric figure.

[0012] The material of the refractive lens is silicon, germanium or chalcogenide glass.

[0013] The focal length f of the refractive and metasurface hybrid large field of view long-wave infrared lens is less than or equal to 8 mm; the F-number in the image space is less than 2, and the field of view angle of the refractive and metasurface hybrid long-wave infrared lens satisfies that the full field of view angle is greater than 60°.

[0014] The present invention has the following beneficial effects: The refractive and metasurface hybrid large field of view long-wave infrared lens of the present invention replaces traditional refractive lenses with metasurface lenses to construct a refractive and metasurface hybrid optical system, significantly reducing the volume of the lens and the manufacturing cost. The introduction of the metasurface lens significantly reduces the number of aspherical lenses used, simplifies the processing process of complex curved surfaces, and effectively reduces the processing difficulty and assembly complexity. At the same time, a fully dielectric silicon-based metasurface lens is used, and its processing technology is compatible with the CMOS semiconductor process, enabling standardized mass production, with both processing convenience and cost advantages. Compared with traditional large field of view optical lenses, this solution effectively expands the field of view angle under the condition of ensuring infrared imaging resolution, significantly improving the optical performance and applicable scenarios of the system. The present invention combines the characteristics of lightweight, low cost, high resolution and large field of view, providing an efficient solution for the application of infrared imaging technology in the fields of security monitoring, unmanned systems, etc. Description of the Drawings

[0015] Figure 1 It is a schematic structural diagram of the refractive and metasurface hybrid large field of view long-wave infrared lens in the embodiment of the present invention; Figure 2 It is a phase distribution diagram of the metasurface lens in the embodiment of the present invention; Figure 3It is a local structure distribution diagram of the metasurface lens in the embodiment of the present invention; Figure 4 It is the line spread function curve of the refractive-metamaterial hybrid large field of view long-wave infrared lens in the embodiment of the present invention; Figure 5 It is the modulation transfer function (MTF) curve of the refractive-metamaterial hybrid large field of view long-wave infrared lens in the embodiment of the present invention.

[0016] Figures 1 to 3 The reference numerals shown in the figure are respectively represented as: 1 - the first lens, 2 - the second lens, 3 - the third lens, 4 - the fourth lens, 5 - the detector protection window, 6 - the image plane. Detailed implementation manners

[0017] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0018] Embodiment: A refractive-metamaterial hybrid large field of view long-wave infrared lens includes a first lens 1, a second lens 2, a third lens 3 and a fourth lens 4. The first lens 1, the second lens 2, the third lens 3 and the fourth lens 4 are arranged in sequence along the optical axis from the object surface to the image surface 6. At least one of the first lens 1, the second lens 2, the third lens 3 and the fourth lens 4 is a metasurface lens, and the remaining lenses are refractive lenses.

[0019] In this embodiment, a scheme of three refractive lenses plus one metasurface lens is adopted. The specific structure is as shown in the attached Figure 1 figure. The introduction of the metasurface lens reduces the volume and weight of the entire optical system. The first lens 1, the second lens 2 and the fourth lens 4 are all refractive lenses, and the third lens 3 is a metasurface lens.

[0020] Among them, the first lens 1 has a negative optical power. Its object side is convex and its image side is concave, and it is used for converging large-angle incident light. The object side and the image side of the first lens 1 are both spherical surfaces.

[0021] The second lens 2, the third lens 3 and the fourth lens 4 all have positive optical powers. Among them, the object side of the second lens 2 is a spherical surface and the image side is an aspherical surface. The object side of the third lens 3 is a plane and the image side is a microstructured surface. The object side of the fourth lens 4 is an aspherical surface and the image side is a spherical surface.

[0022] The refractive lens material is silicon, germanium, or chalcogenide glass. In this embodiment, all refractive lenses (i.e., the first lens 1, the second lens 2, and the fourth lens 4) are made of germanium material. The metasurface lens (i.e., the third lens 3) is formed by arranging silicon square columns with different side lengths, having a structural unit height of 6.2 μm and a period of 4.3 μm. The phase distribution of the metasurface lens satisfies:

[0023] where is the normalized radius of the metasurface lens, and is the coefficient. The phase distribution is as shown in Appendix Figure 2 . According to the phase distribution at different positions, structural units of different sizes are arranged, and finally, the two-dimensional topography distribution of the entire metasurface structure array can be obtained. The local distribution is as shown in Appendix Figure 3 .

[0024] The performance of the entire refractive-metasurface hybrid large field-of-view long-wave infrared lens is as follows. High-resolution imaging with a focal length of 5.4 mm, an image space F-number of 1.0, and a full field-of-view angle of approximately 100° is achieved in the wavelength range of 8 - 12 μm. This lens is matched with a 512×512 infrared detector target surface with a pixel size of 12 μm. Appendix Figure 4 shows the line spread function distribution curve of the lens. Appendix Figure 5 shows the modulation transfer function curve of the lens. The design realizes that the average value of the MTF at 20 lp / mm is greater than 0.4 and the average value at 40 lp / mm is greater than 0.2 at different field-of-view angles, demonstrating high-resolution imaging capabilities.

[0025] Both the substrate and the structural units of the metasurface lens are made of silicon material, and infrared antireflection films are coated on both sides of the metasurface lens.

[0026] Furthermore, the structural units of the metasurface lens are arranged in a quasi-periodic or periodic manner, and the cross-sectional shape of each structural column is a centrosymmetric figure, such as a circle, a square, a cross, etc. In this embodiment, the cross-sectional shape of the structural column is a circle.

[0027] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A refractive and diffractive hybrid large field of view long wave infrared lens, characterized in that, It includes a first lens (1), a second lens (2), a third lens (3) and a fourth lens (4). The first lens (1), the second lens (2), the third lens (3) and the fourth lens (4) are sequentially arranged along the optical axis from the object surface to the image surface (6). At least one of the first lens (1), the second lens (2), the third lens (3) and the fourth lens (4) is a metasurface lens, and the remaining lenses are refractive lenses.

2. The folded and refracted hybrid long-wave infrared lens according to claim 1, wherein The first lens (1) is a refractive lens with a negative optical power. The object side is convex and the image side is concave.

3. The folded and refractive hybrid large field of view long wave infrared lens according to claim 1, wherein At least two of the object sides or image sides of the first lens (1), the second lens (2), the third lens (3) and the fourth lens (4) are spherical surfaces.

4. The folding and ultra-wide hybrid long-wave infrared lens according to claim 1, wherein Both the substrate and the structural unit of the metasurface lens are made of silicon, and infrared antireflection films are coated on both sides of the metasurface lens.

5. The folded and refractive hybrid long-wave infrared lens according to claim 1, wherein The structural units of the metasurface lens are arranged in a quasi-periodic or periodic manner, and the cross-sectional shape of each structural column is a centrosymmetric figure.

6. The folded and refractive hybrid large field of view long wave infrared lens according to claim 1, wherein The material of the refractive lens is silicon, germanium or chalcogenide glass.

7. The folded and refractive hybrid long-wave infrared lens according to claim 1, wherein The focal length f of the refractive and metasurface hybrid large field of view long-wave infrared lens is less than or equal to 8 mm; the image space F number is less than 2, and the field of view angle of the refractive and metasurface hybrid long-wave infrared lens satisfies that the full field of view angle is greater than 60°.

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