Near-infrared narrow-band camera lens, camera module and facial recognition optical system

Abstract

The invention relates to a near-infrared narrow-band pick-up lens based on refraction and super hybrid design, a pick-up module and a facial recognition optical system, and belongs to the field of optical lenses, and the near-infrared narrow-band pick-up lens comprises a first lens, a second lens, a third lens and a fourth lens which are sequentially arranged from an object plane to an image plane along an optical axis. The submillimeter-level thickness characteristic of the metasurface lens is utilized, so that the optical module is small in size and can be suitable for high-security identity authentication scenes such as mobile terminals and the like. Meanwhile, the metasurface nanostructure is designed in a customized mode, narrow-band spectrum filtering, off-axis aberration correction and speckle suppression can be completed in a single-layer element, and the biological characteristic signal-to-noise ratio under complex illumination scenes (such as strong backlight and multi-source interference) is remarkably improved.

Description

Technical Field

[0001] This invention belongs to the field of optical lenses, specifically relating to a near-infrared narrowband camera lens, camera module, and facial recognition optical system based on a hybrid design of refracting and hyperbolic lenses. Background Technology

[0002] Near-infrared narrowband facial recognition technology achieves liveness detection and 3D contour reconstruction by collecting biometric reflected light of specific wavelengths. Its optical system needs to maintain high signal-to-noise ratio imaging under complex ambient light interference, while also meeting the requirements for miniaturization and low power consumption in terminal integration. Traditional solutions face multiple challenges in maintaining spectral purity, adapting to dynamic light environments, and controlling hardware costs, which restricts the widespread application of high-security identity authentication systems.

[0003] Metasurfaces are two-dimensional planar optical materials composed of periodically arranged submicron-scale artificial microstructures. Compared to traditional refractive optical elements, metasurfaces can be mass-produced using micro / nano fabrication techniques such as photolithography and nanoimprinting, offering significant advantages in manufacturing cost and process complexity. By optimizing parameters such as the configuration and periodicity of their microstructure units, the phase distribution and propagation path of incident light waves can be precisely controlled, thereby achieving efficient light field modulation and imaging functions in the near-infrared band.

[0004] In the hybrid face recognition system, the innovative value of metasurface technology is reflected in the integration of optical functions and the improvement of system performance: First, its sub-millimeter thickness characteristics break through the spatial limitations of the traditional filter-imaging separation architecture, reducing the thickness of the optical module; Second, through customized design of metasurface nanostructures, narrowband spectral filtering, off-axis aberration correction and speckle suppression can be completed in a single-layer element, significantly improving the signal-to-noise ratio of biometrics in complex lighting scenarios (such as strong backlight and multi-source interference).

[0005] Compared to traditional multi-chip infrared imaging systems, the hybrid refracto-metasurface design effectively reduces optical crosstalk and system power consumption. With the iteration of computational optics design and nanofabrication technologies, metasurfaces are driving the evolution of biometric optical systems towards chip-level integration. In the future, this technology is expected to achieve breakthroughs in areas such as wide dynamic range response, multi-band spectral fusion, and enhanced anti-counterfeiting optical features, opening up new technological paths for building a highly secure and low-cost intelligent identity authentication system. Summary of the Invention

[0006] This invention provides a near-infrared narrowband camera lens, camera module, and facial recognition optical system based on a hybrid design of refractive and superconducting lenses. While ensuring focal length and F-number, it reduces the number of lenses, TTL (total optical length), volume, and cost, thereby achieving high-resolution imaging.

[0007] This application provides a near-infrared narrowband camera lens based on a hybrid refractive-superconducting design. The lens includes a first lens, a second lens, a third lens, and a fourth lens arranged sequentially along the optical axis from the object plane to the image plane.

[0008] The first lens is an aspherical lens with positive optical power, its object side is convex and its image side is concave. Both the object side and the image side of the first lens are aspherical.

[0009] The second lens is a metasurface lens with positive optical power, whose object-side and image-side are both planar, and whose image-side has a metasurface microstructure.

[0010] The third lens is an aspherical lens with positive optical power, its object side is concave and its image side is convex, and both the object side and the image side of the third lens are aspherical.

[0011] The fourth lens is an aspherical lens with negative optical power; the object-side surface of the fourth lens is convex in the near-optical axis region and concave in the edge region; the image-side surface of the fourth lens is concave in the near-optical axis region and convex in the edge region; both the object-side surface and the image-side surface of the fourth lens are aspherical.

[0012] Furthermore, the near-infrared narrowband camera lens also includes a fifth lens, which is a protective glass and is located after the fourth lens.

[0013] Optionally, the near-infrared narrowband camera lens satisfies:

[0014]

[0015] Where Fno is the aperture number, EFL is the focal length, TTL is the distance from the center of the optical axis on the object side of the first lens to the image plane, and FOV is the diagonal field of view.

[0016] Optionally, the near-infrared narrowband camera lens satisfies:

[0017]

[0018] Optionally, the near-infrared narrowband camera lens further includes an aperture stop; the aperture stop is located in front of the first lens, or the aperture stop is located in the optical path between the first lens and the second lens, or the aperture stop is located in the optical path between the second lens and the third lens.

[0019] Furthermore, the aperture stop is located between the first lens and the second lens.

[0020] Optionally, the focal length of the near-infrared narrowband camera lens satisfies f≥2.45mm.

[0021] Optionally, the field of view of the near-infrared narrowband camera lens satisfies FOV≤80°.

[0022] Optionally, the operating temperature of the near-infrared narrowband camera lens is -30℃ to 70℃.

[0023] The present invention also provides a camera module, which includes the above-described near-infrared narrowband camera lens.

[0024] The present invention also provides a facial recognition optical system, which includes the above-mentioned camera module and is suitable for high-security identity authentication scenarios such as mobile terminals.

[0025] This invention provides a near-infrared narrowband camera lens based on a hybrid refractive-supersurface design, employing only five lenses: three aspherical lenses, one metasurface lens, and one protective glass lens. Its simple structure, small size, and cost-effectiveness are achieved while maintaining an operating temperature range (-30℃ to 70℃). Furthermore, the second lens is a supersurface lens, and the phase of the metasurface is rationally allocated, enabling this near-infrared narrowband camera lens based on a hybrid refractive-supersurface design to meet [the required specifications / standards]. The near-infrared narrowband camera lens with a fold-over-hybrid architecture has a focal length of 2.5mm in the central region, ensuring a compact overall optical length; the overall field of view of the near-infrared narrowband camera lens with a fold-over-hybrid architecture can reach up to 80°, which is suitable for the needs of facial recognition.

[0026] This invention solves the problems of large size, many lenses, and long optical length in the existing technology, and improves the response rate and resolution of the imaging system, realizing high-resolution imaging for facial recognition. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the structure of a near-infrared narrowband camera lens based on a folding-super-folding hybrid design, provided in an embodiment of this application.

[0028] Figure 2 This is a schematic diagram of the MTF of a near-infrared narrowband camera lens based on a folding-super-hybrid design provided in an embodiment of this application;

[0029] Figure 3 This is a schematic diagram of the blur pattern of a near-infrared narrowband camera lens based on a folding-super-hybrid design provided in an embodiment of this application;

[0030] Figure 4 This is a schematic diagram of the relative illumination of a near-infrared narrowband camera lens based on a folding-super-folding hybrid design, provided in an embodiment of this application.

[0031] Explanation of reference numerals in the attached figures:

[0032] 110. First lens; 120. Second lens; 130. Third lens; 140. Fourth lens; 150. Fifth lens; 160. Aperture stop; 170. Imaging plane. Detailed Implementation

[0033] The present invention will now be described in further detail with reference to the accompanying drawings.

[0034] The near-infrared narrowband camera lens provided in this embodiment of the invention includes a first lens 110, a second lens 120, a third lens 130, and a fourth lens 140 arranged sequentially along the optical axis from the object plane to the image plane. The first lens 110 is an aspherical lens with positive optical power, its object-side surface is convex, and its image-side surface is concave; both the object-side and image-side surfaces of the first lens 110 are aspherical. The second lens 120 is a metasurface lens with positive optical power, its object-side and image-side surfaces are both planar, and its image-side surface has a metasurface surface. The design incorporates a microstructure: the third lens 130 is an aspherical lens with positive optical power, featuring a concave object-side surface and a convex image-side surface; both the object-side and image-side surfaces of the third lens 130 are aspherical. The fourth lens 140 is an aspherical lens with negative optical power; its object-side surface is convex near the optical axis and concave at the edges; its image-side surface is concave near the optical axis and convex at the edges; both the object-side and image-side surfaces of the fourth lens 140 are aspherical. This design enables the near-infrared narrowband camera lens to have achromatic capabilities, thus maintaining consistent image quality within a certain range.

[0035] In addition, to protect the sensor, the near-infrared narrowband camera lens also includes a fifth lens 150. In this invention, the fifth lens 150 is configured as a protective glass, which is fixed in front of the image sensor, and the detector can be placed at the imaging surface 170.

[0036] The protective glass is preferably made of optical glass with a refractive index of 1.5168 and an Abbe number of 64.199. Its main function is to provide a physical barrier for the image sensor while ensuring high transmittance, effectively blocking the intrusion of dust and particles, and resisting a certain degree of mechanical impact or scratches, significantly reducing the risk of sensor damage and ensuring stable image quality.

[0037] In this invention, the second lens 120 consists of a substrate and microstructures disposed on the substrate. These microstructures are composed of a subwavelength-scale micro / nano unit array, each with a specific shape, size, and arrangement to achieve precise control over the phase, amplitude, or polarization state of the incident light wave. Through the design of the microstructures, the metasurface lens can achieve optical performance comparable to or even superior to traditional lenses while maintaining a thin and light volume, such as high transmittance, low chromatic aberration, and low distortion. The period of the micro / nano units in the second lens 120 ranges from 350 to 500 nm, with an optimal period of 450 nm selected in this embodiment; the height of the micro / nano units ranges from 500 to 1500 nm, with an optimal height of 700 nm selected in this embodiment; the diameter of the microstructures covers 100-350 nm, the material is silicon dioxide, and they are arranged in square, hexagonal, or other shapes.

[0038] As a feasible implementation method, the first lens 110, the third lens 130, and the fourth lens 140 are made of plastic, while the second lens 120 and the fifth lens 150 are made of glass. By matching the materials and the optical power of each lens, a heatless design is achieved, which reduces material costs and shrinks the size of the system.

[0039] In addition, in order to control the path of light through the lens and reduce stray light interference, thereby improving image quality, the near-infrared narrowband camera lens also includes an aperture of 160.

[0040] The aperture stop 160 can be located in front of the first lens, or it can be located in the optical path between the first lens 110 and the second lens 120, or it can be located in the optical path between the second lens 120 and the third lens 130. Preferably, in this embodiment, the aperture stop 160 is adjusted according to actual needs and is selected to be located between the first lens 110 and the second lens 120, so as to more precisely control the light passing through the aperture and achieve the best imaging effect.

[0041] Based on the above solutions, near-infrared narrowband camera lenses meet the requirements. The focal length in the central region is 2.5mm, ensuring a compact overall optical length; the near-infrared narrowband camera lens has a maximum field of view of 80°, suitable for facial recognition applications. In this embodiment, the lens operates at temperatures ranging from -30℃ to 70℃, exhibiting high reliability and stability.

[0042] Example 1

[0043] Table 1 shows the parameters of a near-infrared narrowband camera lens based on a folding-super-hybrid design provided in Example 1.

[0044] Table 1

[0045]

[0046] Wherein, BFL is the axial distance from the vertex of the last optical surface in the optical system to the image-side focal point (focal plane) of the system.

[0047] refer to Figure 1 The near-infrared narrowband camera lens provided in this embodiment of the invention includes a first lens 110, an aperture 160, a second lens 120, a third lens 130, a fourth lens 140, a fifth lens 150, and an imaging plane 170 arranged sequentially along the optical axis from the object plane to the image plane.

[0048] The first lens 110 is an aspherical lens with positive optical power, its object-side surface is convex, and its image-side surface is concave. Both the object-side and image-side surfaces of the first lens 110 are aspherical. The second lens 120 is a metasurface lens with positive optical power, its object-side surface is planar, and its image-side surface has metasurface microstructures. The third lens 130 is an aspherical lens with positive optical power, its object-side surface is concave, and its image-side surface is convex. Both the object-side and image-side surfaces of the third lens 130 are aspherical. The fourth lens 140 is an aspherical lens with negative optical power. The object-side surface of the fourth lens 140 is convex in the near-optical axis region and concave in the edge region. The image-side surface of the fourth lens 140 is concave in the near-optical axis region and convex in the edge region. Both the object-side and image-side surfaces of the fourth lens 140 are aspherical. The fifth lens 150 is a protective glass that protects the sensor.

[0049] like Figure 1 As shown, the incident light enters through the object side of the first lens 110, passes through the aperture 160, and then enters the second lens 120, the third lens 130, the fourth lens 140 and the fifth lens 150 before converging on the imaging surface 170.

[0050] Table 2 shows the parameters of each surface in the near-infrared narrowband camera lens provided in Example 1.

[0051] Table 2

[0052]

[0053]

[0054] The surface numbering is based on the order of the lenses' surfaces. For example, surface number 1 represents the object-side surface of the first lens 110, surface number 2 represents the image-side surface of the first lens 110, and so on, until surface number 11 represents the imaging surface 170. 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. "Infinity" indicates that the surface is planar, "Even asphere" indicates an aspherical surface, and "Metasurface" indicates a binary surface. 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).

[0055] Even-order aspherical surfaces satisfy the following equations:

[0056]

[0057] Where z is the distance from the even-order aspherical surface to its vertex along the optical axis, r is the height from the optical axis, c is the curvature 1 / R, and R is the radius of curvature at the vertex of the lens; N is the number of polynomial coefficients in the series, k is the conic coefficient, and a i For aspherical higher-order terms, the coefficients are given.

[0058] For example, Table 3 details the conic coefficient k and higher-order coefficient a of the aspherical lens surface in this embodiment, using a feasible implementation method. i .

[0059] Table 3

[0060] Face number k R1 <![CDATA[a2]]> <![CDATA[a3]]> <![CDATA[a4]]> 1 12.306 0 0.340 -0.304 -0.756 2 13.265 0 0.044 0.658 0.511 5 21.654 0 0.012 -0.73 -0.175 6 -5.652 0 -0.120 0.051 2.2E-4 7 -45.65 0 -0.235 0.198 -0.0123 8 -6.654 0 -0.084 0.025 -0.0042

[0061] Face number <![CDATA[a5]]> <![CDATA[a6]]> <![CDATA[a7]]> <![CDATA[a8]]> 1 0.748 0.606 -0.835 1.209 2 -0.549 0.377 0.229 1.672 5 0.243 0.154 0.018 -0.086 6 0.024 0.012 1.3E-3 1.4E-3 7 0.02 0.0053 -1.2E-3 -4.9E-4 8 -9E-4 6.5E-5 1.86E-4 -3.5E-5

[0062] Where R1 is the normalized radius of the binary surface, 0.340 means that the coefficient a2 of surface number 1 is 0.340, and so on.

[0063] For example, Table 4 details the phase of the metasurface in this embodiment with a feasible implementation.

[0064] Table 4

[0065] Face number R1 <![CDATA[a1]]> <![CDATA[a2]]> <![CDATA[a3]]> <![CDATA[a4]]> 4 1 -238.8 127.41 -99.59 56.357

[0066] Face number <![CDATA[a5]]> <![CDATA[a6]]> <![CDATA[a7]]> <![CDATA[a8]]> 4 -468.4 618.63 1743.01 -3493.6

[0067] The near-infrared narrowband camera lens provided in this embodiment operates in the near-infrared band, has an F-number of 1.6, a focal length of 2.52mm, and a maximum overall field of view of 78°.

[0068] Figure 2The modulation function curves of the near-infrared narrowband camera lens provided in this embodiment of the invention are shown. Different colored curves represent different fields of view. The higher the value of the curve, the larger the blank area below the curve, and the smoother the curve, the better the image quality and the clearer the image. The near-infrared narrowband camera lens provided in this embodiment of the invention has an edge field of view modulation function curve value greater than 45% at a frequency of 100 line pairs per millimeter, which has excellent imaging effect and can meet the requirements of high-resolution and high-quality facial recognition imaging.

[0069] Figure 3 This is a schematic diagram of the blur pattern of the near-infrared narrowband camera lens provided in an embodiment of the present invention. The near-infrared narrowband camera lens provided in this embodiment of the present invention has a relatively concentrated and uniformly distributed blur pattern across the entire long-wavelength band, which can meet the requirements of high-resolution imaging.

[0070] Figure 4 This is a schematic diagram of the relative illumination of a near-infrared narrowband camera lens provided in an embodiment of the present invention, which represents the relative illumination values ​​corresponding to different fields of view, such as... Figure 4 As shown, the near-infrared narrowband camera lens provided in this embodiment of the invention has an edge field of view relative illumination of over 40% in the working band, which meets the needs of most usage scenarios.

[0071] The present invention also provides a camera module, which includes the above-described near-infrared narrowband camera lens.

[0072] The present invention also provides a facial recognition optical system, which includes the above-mentioned camera module and is suitable for high-security identity authentication scenarios such as mobile terminals.

[0073] In the description of this application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "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 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 this application.

[0074] 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 near-infrared narrowband camera lens based on a hybrid folding and hyper-folding design, characterized in that, include: The first lens, the second lens, the third lens, and the fourth lens are arranged sequentially along the optical axis from the object plane to the image plane; The first lens is an aspherical lens with positive optical power, its object side is convex and its image side is concave. Both the object side and the image side of the first lens are aspherical. The second lens is a metasurface lens with positive optical power, whose object-side and image-side are both planar, and whose image-side has a metasurface microstructure. The third lens is an aspherical lens with positive optical power, its object side is concave and its image side is convex, and both the object side and the image side of the third lens are aspherical. The fourth lens is an aspherical lens with negative optical power; the object-side surface of the fourth lens is convex in the near-optical axis region and concave in the edge region; the image-side surface of the fourth lens is concave in the near-optical axis region and convex in the edge region; both the object-side surface and the image-side surface of the fourth lens are aspherical.

2. The near-infrared narrowband camera lens according to claim 1, characterized in that, It also includes a fifth lens, which is a protective glass and is located after the fourth lens.

3. The near-infrared narrowband camera lens according to claim 1, characterized in that, The near-infrared narrowband camera lens meets the following requirements: Where Fno is the aperture number, EFL is the focal length, TTL is the distance from the center of the optical axis on the object side of the first lens to the image plane, and FOV is the diagonal field of view.

4. The near-infrared narrowband camera lens according to claim 1, characterized in that, The near-infrared narrowband camera lens meets the following requirements:

5. The near-infrared narrowband camera lens according to claim 1, characterized in that, The near-infrared narrowband camera lens further includes an aperture stop; the aperture stop is located in front of the first lens, or the aperture stop is located in the optical path between the first lens and the second lens, or the aperture stop is located in the optical path between the second lens and the third lens.

6. The near-infrared narrowband camera lens according to claim 5, characterized in that, The aperture stop is located between the first lens and the second lens.

7. The near-infrared narrowband camera lens according to claim 1, characterized in that, The focal length f of the near-infrared narrowband camera lens satisfies: f≥2.45m.

8. The near-infrared narrowband camera lens according to claim 1, characterized in that, The field of view (FOV) of the near-infrared narrowband camera lens satisfies: FOV≤80°.

9. The near-infrared narrowband camera lens according to claim 1, characterized in that, The operating temperature of the near-infrared narrowband camera lens is -30℃ to 70℃.

10. A camera module, characterized in that, Including the near-infrared narrowband camera lens as described in claims 1 to 9.

11. A facial recognition optical system, characterized in that, Includes the camera module as described in claim 10.

Images