Optical lens

Abstract

The present invention provides an optical lens, which is composed of a metalens and three lenses, and includes: a first group, a second lens and a third lens in sequence from the object side to the imaging surface along the optical axis; the first group includes a first lens and a metalens; the first lens has positive focal power, the object side surface of the first lens is convex, and the image side surface of the first lens is concave; the second lens has positive focal power, the object side surface of the second lens is concave, and the image side surface of the second lens is convex; the third lens has negative focal power, the object side surface of the third lens is convex, and the image side surface of the third lens is concave; the metalens has positive focal power, and a stop is provided at the object side end of the metalens. The optical lens provided by the present invention can improve the imaging quality of the optical lens, reduce aberrations, and improve the imaging quality of the optical lens through specific surface shape matching and reasonable optical focal power distribution.

Description

Technical Field

[0001] The present invention relates to the technical field of imaging lenses, and in particular to an optical lens. Background Art

[0002] In the field of vehicle driving, in order to improve the driving safety and intelligent driving of vehicles, it is necessary to monitor the driving room, and the DMS (driver monitoring system) vehicle-mounted lens has developed rapidly. Due to the influence of the driving room environment, infrared lenses can make up for the defects of visible light imaging lenses and can still clearly capture the driver in a dark environment, so they are widely used.

[0003] Existing vehicle-mounted lenses are mainly composed of conventional lenses stacked together, and the structure is relatively large, which cannot meet the requirements of miniaturized design. Superlens, also known as meta-lens, is a two-dimensional planar lens structure made of optical elements that focus light on a super surface. Because superlenses have the advantages of thinner volume, lighter weight, lower cost, better imaging, and easier integration, they provide a potential solution for compact integrated optical systems. In addition, superlens processing technology is becoming increasingly mature. The use of superlenses can not only improve the imaging performance of the lens but also reduce the size of the system. It is a development direction for miniaturized vehicle-mounted lenses in the future. However, how to combine superlenses with lens combination design is still a technical difficulty in this field. Summary of the invention

[0004] In view of the above problems, an object of the present invention is to provide an optical lens which adopts a metalens and has the advantage of excellent imaging quality.

[0005] The technical solution adopted by the present invention is:

[0006] An optical lens, composed of a metalens and three lenses, including: a first group, a second lens and a third lens in sequence from the object side to the imaging surface along the optical axis;

[0007] Wherein, the first group includes a first lens and a super lens;

[0008] The first lens has positive power, the object side surface of the first lens is convex, and the image side surface of the first lens is concave;

[0009] The second lens has positive refractive power, the object side surface of the second lens is concave, and the image side surface of the second lens is convex;

[0010] The third lens has negative optical power, the object side surface of the third lens is convex, and the image side surface of the third lens is concave;

[0011] The superlens has positive optical power, and an aperture is provided at the object side end of the superlens;

[0012] The total optical length TTL of the optical lens and the effective focal length f of the optical lens satisfy: 1.6 <TTL / f<1.9。

[0013] Further preferably, the total optical length TTL of the optical lens and the real image height ih corresponding to the maximum half field angle of the optical lens satisfy: 2.5 <TTL / ih<2.95。

[0014] Further preferably, the effective focal length f of the optical lens, the maximum field of view FOV of the optical lens and the real image height ih corresponding to the maximum half field of view angle of the optical lens satisfy: 102°<(f×FOV) / ih<107°.

[0015] Further preferably, the effective focal length f of the optical lens and the aperture value Fno of the optical lens satisfy: 1.75 mm <f / Fno<1.95mm。

[0016] Further preferably, the back focal length BFL of the optical lens and the total optical length TTL of the optical lens satisfy: 0.27 <BFL / TTL<0.29。

[0017] Further preferably, the effective focal length f of the optical lens and the focal length f3 of the third lens satisfy: -0.85 <f3 / f<-0.75。

[0018] Further preferably, the focal length f1 of the first lens and the focal length f4 of the metalens satisfy: 0.07 <f1 / f4<0.14。

[0019] Further preferably, the effective focal length f of the optical lens and the focal length f4 of the metalens satisfy: <f4 / f<22。

[0020] Further preferably, the effective focal length f of the optical lens, the focal length f1 of the first lens, and the focal length f4 of the metalens satisfy: 74mm<(f1×f4) / f<129mm.

[0021] Further preferably, the object-side surface and the image-side surface of the first lens are both spherical surfaces, and the first lens is made of glass, and the object-side surfaces and the image-side surfaces of the second lens and the third lens are both aspherical surfaces.

[0022] Compared with the prior art, the optical lens provided by the present invention can work in the near-infrared band through a specific surface shape setting and reasonable optical focal length distribution, which improves the monitoring effect at night and in low-light environments; it has a large aperture, which is conducive to increasing the amount of light entering the lens, allowing the lens to achieve high-definition imaging in dim environments. In addition, it can also reasonably correct the overall aberration of the optical lens, has small distortion, and is conducive to reducing the amplitude of deformation and distortion around the image when the optical lens is imaging, and can achieve high-definition imaging and improve the imaging quality of the optical lens. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0024] Figure 1 Schematic diagram of the structure of the optical lens in Example 1 of the present invention.

[0025] Figure 2 It is a field curvature curve diagram of the optical lens in Example 1 of the present invention.

[0026] Figure 3 Graph showing the F-Tan (Theta) distortion of the optical lens in Example 1 of the present invention.

[0027] Figure 4 Graph showing the axial chromatic aberration of the optical lens in Example 1 of the present invention.

[0028] Figure 5 Graph showing the vertical axis chromatic aberration of the optical lens in Example 1 of the present invention.

[0029] Figure 6 This is the MTF curve diagram of the optical lens in Example 1 of the present invention.

[0030] Figure 7 Schematic diagram of the structure of the optical lens in Example 2 of the present invention.

[0031] Figure 8 4 is a field curvature curve diagram of the optical lens in Example 2 of the present invention.

[0032] Fig. 9 Graph showing the F-Tan (Theta) distortion of the optical lens in Example 2 of the present invention.

[0033] Fig.10 Graph showing the axial chromatic aberration of the optical lens in Embodiment 2 of the present invention.

[0034] Fig.11 Graph showing the vertical axis chromatic aberration of the optical lens in Example 2 of the present invention.

[0035] Fig.12This is an MTF curve diagram of the optical lens in Example 2 of the present invention.

[0036] The following specific implementation manner will further illustrate the present invention in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0037] In order to better understand the present application, a more detailed description will be made of various aspects of the present application with reference to the accompanying drawings. It should be understood that these detailed descriptions are only descriptions of the embodiments of the present application, and are not intended to limit the scope of the present application in any way. Throughout the specification, the same reference numerals refer to the same elements. The expression "and / or" includes any and all combinations of one or more of the associated listed items.

[0038] It should be noted that in this specification, the expressions of first, second, third, etc. are only used to distinguish one feature from another feature, and do not represent any limitation on the features. Therefore, without departing from the teaching of the present invention, the first lens discussed below may also be referred to as the second lens or the third lens.

[0039] In the drawings, the thickness, size and shape of the lenses have been slightly exaggerated for ease of explanation. Specifically, the shapes of the spherical or aspherical surfaces shown in the drawings are shown by way of example. That is, the shapes of the spherical or aspherical surfaces are not limited to the shapes of the spherical or aspherical surfaces shown in the drawings. The drawings are only examples and are not drawn strictly to scale.

[0040] In this article, the paraxial region refers to the region near the optical axis. If the lens surface is convex and the position of the convex surface is not defined, it means that the lens surface is convex at least in the paraxial region; if the lens surface is concave and the position of the concave surface is not defined, it means that the lens surface is concave at least in the paraxial region. The surface of each lens closest to the object is called the object side of the lens, and the surface of each lens closest to the imaging plane is called the image side of the lens.

[0041] It should also be understood that the terms "comprises", "including", "having", "includes" and / or "comprising", when used in this specification, indicate the presence of the stated features, elements and / or components, but do not exclude the presence or addition of one or more other features, elements, components and / or combinations thereof. In addition, when expressions such as "at least one of..." appear after a list of listed features, they modify the entire listed features rather than modifying the individual elements in the list. In addition, when describing embodiments of the present application, "may" is used to mean "one or more embodiments of the present application". And, the term "exemplary" is intended to refer to an example or illustration.

[0042] Unless otherwise defined, all terms (including technical terms and scientific terms) used in this article have the same meaning as commonly understood by ordinary technicians in the field to which this application belongs. It should also be understood that terms (such as terms defined in commonly used dictionaries) should be interpreted as having the same meaning as their meaning in the context of the relevant technology, and will not be interpreted in an idealized or overly formal sense unless explicitly defined in this article.

[0043] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0044] The optical lens provided by the embodiment of the present invention is composed of a metalens and three lenses, and includes: a first group, a second lens, and a third lens in sequence from the object side to the imaging surface along the optical axis. The lens of the present invention is mainly used for DMS (driver monitoring system) vehicle lenses with functions such as driver fatigue detection and face recognition. In order to clearly shoot the driver in a dark environment, the optical lens of the present invention is mainly suitable for working in the infrared band to improve the clarity of indoor shooting of the driver to cope with the complex indoor environment of the driving room.

[0045] Specifically, the first group includes a first lens and a super lens. The first lens has positive optical power, the object side surface of the first lens is a convex surface, and the image side surface of the first lens is a concave surface. The super lens has positive optical power, the object side surface of the super lens is a plane, the image side surface of the super lens is a super transparent surface, and an aperture is provided at the object side end of the super lens. Specifically, the first group may include an aperture, a super lens and a first lens in sequence from the object side to the imaging surface along the optical axis, or the first group may include a first lens, an aperture and a super lens in sequence from the object side to the imaging surface along the optical axis.

[0046] In the present application, the superlens is composed of a substrate and a micro-nano structure arranged on the substrate, and the micro-nano structure can adjust the direction of light. The micro-nano structure is arranged on the image side of the substrate, and the image side of the superlens is a supersurface. The superlens, also known as the superstructure lens, is a two-dimensional planar lens structure made of an optical element that focuses light on a supersurface (i.e., a planar two-dimensional structure with sub-wavelength thickness). The superlens has the advantages of thinner volume, lighter weight, lower cost, better imaging, and easier integration, providing a potential solution for compact integrated optical systems. And the properties of light such as polarization, phase and amplitude can be controlled by adjusting the shape, rotation direction, height and other parameters of the structure.

[0047] Specifically, the second lens has positive power, the object side surface of the second lens is concave, and the image side surface of the second lens is convex. The third lens may have negative power, the object side surface of the third lens is convex, and the image side surface of the third lens is concave.

[0048] In some embodiments, the total optical length TTL of the optical lens and the effective focal length f of the optical lens satisfy: 1.6 < TTL / f < 1.9. Meeting the above conditions, by reasonably setting the ratio of the total optical length to the effective focal length of the optical lens, not only can the length of the optical lens be effectively limited to achieve miniaturization of the optical lens, but also it is beneficial for light to converge better on the imaging surface, which is conducive to reducing the amplitude of distortion around the image of the optical lens during imaging and improving the imaging quality of the optical lens.

[0049] In some embodiments, the total optical length TTL of the optical lens and the true image height ih corresponding to the maximum half field of view angle of the optical lens satisfy: 2.5 < TTL / ih < 2.95. Meeting the above conditions and within the above range can effectively balance the requirements of the image height and miniaturization of the optical lens.

[0050] In some embodiments, the effective focal length f of the optical lens, the maximum field of view angle FOV of the optical lens, and the true image height ih corresponding to the maximum half field of view angle of the optical lens satisfy: 102° < (f × FOV) / ih < 107°. Meeting the above conditions enables the optical lens to take into account the characteristics of long focal length and large field of view angle.

[0051] In some embodiments, the effective focal length f of the optical lens and the aperture value Fno of the optical lens satisfy: 1.75mm < f / Fno < 1.95mm. Meeting the above conditions ensures that the optical lens has a large aperture, enabling the lens to achieve high-definition imaging even in a relatively dim environment at night, reducing the noise impact caused by too weak light, and thus improving the imaging quality.

[0052] In some embodiments, the back focal length BFL of the optical lens and the total optical length TTL of the optical lens satisfy: 0.27 < BFL / TTL < 0.29. Meeting the above conditions, maintaining a long back focus is beneficial for adjusting the distribution of the optical power of each lens, providing more optimization space for various aberrations of the optical lens.

[0053] In some embodiments, the effective focal length f of the optical lens and the focal length f3 of the third lens satisfy: -0.85 < f3 / f < -0.75. The third lens is the last lens of the optical lens. By providing negative refractive power through the third lens, it is beneficial to expand the width of the light beam, increasing the angle of the light rays refracted by the first group and the second lens and filling the pupil, so that the light can be fully transmitted to the imaging surface, obtaining a wider field of view range, which is conducive to achieving high-pixel imaging of the optical lens; exceeding the range of the above relationship is not conducive to the correction of the aberrations of the optical lens, resulting in a reduction in the imaging quality of the optical lens.

[0054] In some embodiments, the focal length f1 of the first lens and the focal length f4 of the metalens satisfy: 0.07 < f1 / f4 < 0.14. When the above conditional formula is satisfied, the effective focal lengths of the first lens and the metalens in the first group can be reasonably configured to effectively balance the chromatic aberration of the optical lens, reduce the performance sensitivity of the optical lens, make the performance of the optical lens more stable, facilitate the correction of chromatic aberration, and improve the imaging quality.

[0055] In some embodiments, the effective focal length f of the optical lens and the focal length f4 of the metalens satisfy: 12 < f4 / f < 22. Setting the metalens to have a positive optical power can provide a positive refractive power for the optical lens. Satisfying the above relational formula is beneficial to suppressing the high-order aberrations caused by the light beams around the imaging area and correcting the marginal aberrations, thereby effectively improving the resolution performance of the optical lens.

[0056] In some embodiments, the effective focal length f of the optical lens, the focal length f1 of the first lens, and the focal length f4 of the metalens satisfy: 74 mm < (f1 × f4) / f < 129 mm. When the above conditional formula is satisfied, the negative refractive power intensities provided by the first lens and the metalens in the first group are reasonable. On the one hand, it is beneficial to collect incident light at large angles, enabling the optical lens to have further large viewing angle characteristics; on the other hand, it is also beneficial to share the refractive power loads of the first lens and the metalens with each other, preventing the refractive power intensities of the two from being too large and generating aberrations such as astigmatism and chromatic aberration that are difficult to correct, and further facilitating the reduction of the burden on the image-side lens group for correcting aberrations.

[0057] In some embodiments, the effective focal length f of the optical lens and the true image height ih corresponding to the maximum half field angle of the optical lens satisfy: 0.62 < ih / f < 0.68. Satisfying the above conditions can not only achieve the long focal length characteristics of the optical lens to meet local shooting requirements, but also achieve the large image plane characteristics of the optical lens, be able to match larger-sized chips, achieve high-pixel imaging of the optical lens, and be applicable to driver monitoring.

[0058] In some embodiments, the effective focal length f of the optical lens and the focal length f1 of the first lens satisfy: 1.62 < f1 / f < 1.68. When the above conditional formula is satisfied, the proportion of the refractive power of the first lens in the optical lens can be reasonably configured, which is beneficial to correcting the aberrations of the optical lens and improving the imaging resolution of the optical lens.

[0059] In some embodiments, the air gap CT12 between the first group and the second lens on the optical axis and the air gap CT23 between the second lens and the third lens on the optical axis satisfy: 13 < CT12 / CT23 < 25. By satisfying the above conditional formula, by restricting the ratio of the distance between the first group and the second lens on the optical axis and the distance between the second lens and the third lens on the optical axis, the distances between the first group, the second lens, and the third lens can be reasonably configured, so that the structure of the first group including the meta-lens is more stable and reliable; at the same time, the air gaps between the first group, the second lens, and the third lens can be ensured, and the assembly space of each lens can be reasonably configured, thereby avoiding interference, which is beneficial to improving the assembly yield, and at the same time, the space utilization rate of the lens barrel can also be improved.

[0060] In some embodiments, the air gap ET12 in the optical axis direction between the position of the maximum effective semi-aperture on the image side of the first group and the position of the maximum effective semi-aperture on the object side of the second lens and the air gap ET23 in the optical axis direction between the position of the maximum effective semi-aperture on the image side of the second lens and the position of the maximum effective semi-aperture on the object side of the third lens satisfy: 0.08 < ET12 / ET23 < 0.24. By satisfying the above conditional formula, the overall size of the optical lens can be effectively reduced, which is beneficial to realizing the design of the optical lens to be thinner, lighter and smaller.

[0061] In some embodiments, the effective focal length f of the optical lens and the clear aperture semi-diameter CSD11 of the object side of the first lens satisfy: 2.5 < f / CSD11 < 2.9. By satisfying the above conditional formula, the light incident amount of the optical lens is effectively increased, so that the optical lens has a high light incident amount and a high light energy utilization rate.

[0062] In some embodiments, the back focal length BFL of the optical lens and the overall optical length TTL of the optical lens satisfy: 0.27 < BFL / TTL < 0.29. By satisfying the above conditional formula, the proportion of the back focal length of the optical lens in the overall optical length is restricted. Since this ratio is small, the miniaturization of the optical lens can be achieved.

[0063] In some embodiments, the optical lens satisfies the conditional formula: 3mm < f < 4mm, 1.8mm < EPD < 2mm, 6mm < TTL < 7mm, 1.9 < Fno < 2.1, 15° < CRA < 21°, 1.7mm < BFL < 1.9mm, 65° < FOV < 70°, 2mm < ih < 2.5mm; where f represents the effective focal length of the optical lens, EPD represents the entrance pupil diameter of the optical lens, TTL represents the total optical length of the optical lens, Fno represents the aperture value of the optical lens, CRA represents the principal ray incident angle at the maximum image height of the optical lens, BFL represents the back focal length of the optical lens, FOV represents the maximum field of view angle of the optical lens, and ih represents the true image height corresponding to the maximum semi-field angle of the optical lens. Meeting the above conditions indicates that the optical lens provided by the embodiments of the present invention has at least the characteristics of miniaturization and large aperture.

[0064] In some embodiments, the first lens, the second lens, and the third lens can adopt spherical lenses or aspherical lenses. Compared with the spherical structure, the aspherical structure can effectively reduce the aberration of the optical system, thereby reducing the number of lenses and the size of the lenses, and better realizing the miniaturization of the lens. More specifically, the first lens of the present invention can adopt a spherical lens; the second lens and the third lens can adopt aspherical lenses.

[0065] In some embodiments, the lens material in the optical lens provided by the present invention can be glass or plastic. When the lens material is plastic, the production cost can be effectively reduced. When the lens material is glass, the geometric chromatic aberration of the optical system can be effectively corrected by the low dispersion characteristic of the glass itself. More specifically, the first lens of the present invention can be a glass lens, and the second lens and the third lens can be plastic lenses.

[0066] In various embodiments of the present invention, when the lens adopts an aspherical lens, the shapes of the aspherical surfaces of the optical lens satisfy the following equations:

[0067] ;

[0068] where z is the distance between the surface and the vertex of the surface in the optical axis direction, h is the distance from the optical axis to the surface, c is the curvature of the vertex of the surface, K is the conic coefficient, and B, C, D, E, F, G, H are the surface coefficients of the fourth order, sixth order, eighth order, tenth order, twelfth order, fourteenth order, and sixteenth order respectively.

[0069] The present invention is further described below in multiple embodiments. In each embodiment, the thickness, radius of curvature, and material selection of each lens in the optical lens are different. For specific differences, please refer to the parameter table of each embodiment. The following embodiments are only preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the following embodiments. Any other changes, substitutions, combinations or simplifications that do not deviate from the innovative points of the present invention should be regarded as equivalent replacement methods and are included in the protection scope of the present invention.

[0070] Example 1

[0071] See also Figure 1 , which is a schematic diagram of the structure of the optical lens 100 provided in Embodiment 1 of the present invention, wherein the optical lens comprises, in sequence from the object side to the imaging surface along the optical axis: a first group, a second lens L2, a third lens L3, a filter G1 and a protective glass G2.

[0072] The first group includes, from the object side to the imaging surface, the aperture ST, the super lens L4, and the first lens L1;

[0073] The superlens L4 has positive optical power, its object side surface S1 is a plane, and its image side surface S2 is a super-transparent surface;

[0074] The first lens L1 has positive refractive power, its object side surface S3 is convex, and its image side surface S4 is concave;

[0075] The second lens L2 has positive refractive power, its object side surface S5 is concave, and its image side surface S6 is convex;

[0076] The third lens L3 has negative refractive power, its object-side surface S7 is convex, and its image-side surface S8 is concave;

[0077] The object side surface S9 and the image side surface S10 of the filter G1 are both planes;

[0078] The object side surface S11 and the image side surface S12 of the protective glass G2 are both flat surfaces;

[0079] The imaging surface S13 is a plane.

[0080] The first lens L1 is a glass spherical lens, and the second lens L2 and the third lens L3 are plastic aspherical lenses.

[0081] The relevant parameters of each lens in the optical lens 100 in Example 1 are shown in Table 1-1.

[0082] Table 1-1

[0083]

[0084] The surface parameters of the aspheric lens of the optical lens 100 in Example 1 are shown in Table 1-2.

[0085] Table 1-2

[0086]

[0087] Specifically, the phase distribution function of the metalens is as follows:

[0088]

[0089] in,

[0090] is the phase distribution function of the entire metalens, N is the number of polynomial coefficients in the series, Ai is the coefficient of ρ raised to an even power, ρ is the normalized radial aperture, and M is the diffraction order.

[0091] The metalens in the application uses six even-order terms, so N=6; when i=1, the corresponding The coefficient of When it is -6.0079E+01 and i=2, the corresponding The coefficient of is 2.4742E+00……; is the normalized radial aperture, with a value range of [0, 1]. The hypersurface is a circle-centered area, from the center to the edge, corresponding to The value ranges from 0 to 1. The calculated phase value is different, so the phase distribution of the metasurface changes from the center to the edge. changes; M is +1 in both instances of this scheme.

[0092] In this embodiment, the normalized radius r of the metasurface of the metalens is: 1.188 mm; the coefficients of the phase distribution parameters of the metasurface of the metalens in the quadratic term, the quartic term, the sixth term...the twelfth term are respectively:

[0093]

[0094] In this embodiment, the field curvature curve, F-Tan (Theta) distortion curve, axial chromatic aberration curve, vertical chromatic aberration curve, and MTF curve of the optical lens 100 are shown in FIG. Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 shown.

[0095] Figure 2The field curvature curve of Example 1 is shown, which represents the field curvature of light of different wavelengths on the meridional image plane and the sagittal image plane, the horizontal axis represents the offset (unit: mm), and the vertical axis represents the field angle (unit: °). It can be seen from the figure that the field curvature of the meridional image plane and the sagittal image plane is controlled within ±0.04mm, indicating that the optical lens 100 can well correct the field curvature.

[0096] Figure 3 The F-Tan (Theta) distortion curve of Example 1 is shown, which represents the distortion of different field angles on the imaging plane, with the horizontal axis representing the distortion value (unit: %) and the vertical axis representing the field angle (unit: °). It can be seen from the figure that the distortion value is controlled within ±6%, indicating that the optical lens 100 can correct the distortion well.

[0097] Figure 4 The axial chromatic aberration curve of Example 1 is shown, which represents the chromatic aberration of each wavelength on the optical axis at the imaging plane, the horizontal axis represents the axial chromatic aberration value (unit: mm), and the vertical axis represents the normalized pupil radius. It can be seen from the figure that the offset of the axial chromatic aberration is controlled within ±0.012mm, indicating that the optical lens 100 can correct the axial chromatic aberration well.

[0098] Figure 5 The vertical axis chromatic aberration curve of Example 1 is shown, which represents the chromatic aberration of each wavelength relative to the central wavelength (0.94 μm) at different image heights on the imaging surface, the horizontal axis represents the vertical axis chromatic aberration value of each wavelength relative to the central wavelength (unit: μm), and the vertical axis represents the field angle (unit: °). It can be seen from the figure that the vertical axis chromatic aberration of the longest wavelength and the shortest wavelength is controlled within ±1 μm, indicating that the optical lens 100 can correct chromatic aberration well.

[0099] Figure 6 The MTF (Modulation Transfer Function) curve of Example 1 is shown, which represents the imaging modulation degree of the lens at different spatial frequencies under each field of view, the horizontal axis represents the spatial frequency (unit: cycle / mm), and the vertical axis represents the MTF value. It can be seen from the figure that the MTF value of this embodiment is above 0.5 in the whole field of view, and the MTF curve decreases evenly and smoothly from the center to the edge of the field of view, and has good imaging quality and good detail resolution ability in both low-frequency and high-frequency conditions.

[0100] from Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 It can be seen that the aberration of the optical lens 100 is well balanced and has good imaging quality in the infrared band.

[0101] Example 2

[0102] See also Figure 7 , which is a schematic diagram of the structure of the optical lens 200 provided in Example 2 of the present invention. Compared with Example 1, the main difference between this embodiment and Example 1 is that: the first group includes the first lens L1, the aperture ST, and the super lens L4 in sequence from the object side to the imaging surface; the optical parameters such as the curvature radius of each lens surface and the lens thickness are different.

[0103] The relevant parameters of each lens in the optical lens 200 in Example 2 are shown in Table 2-1.

[0104] Table 2-1

[0105]

[0106] The surface parameters of the aspheric lens of the optical lens 200 in Example 2 are shown in Table 2-2.

[0107] Table 2-2

[0108]

[0109] In this embodiment, the normalized radius r of the metasurface of the metalens is: 1.046 mm; the coefficients of the phase distribution parameters of the metasurface of the metalens in the quadratic term, the quartic term, the sixth term...the twelfth term are respectively:

[0110]

[0111] In this embodiment, the field curvature curve, F-Tan (Theta) distortion curve, axial chromatic aberration curve, vertical chromatic aberration curve, and MTF curve of the optical lens 200 are shown in FIG. Figure 8 , Fig. 9 , Fig.10 , Fig.11 , Fig.12 shown.

[0112] Figure 8 The field curvature curve of Example 2 is shown, which represents the field curvature of light of different wavelengths on the meridional image plane and the sagittal image plane, the horizontal axis represents the offset (unit: mm), and the vertical axis represents the field angle (unit: °). It can be seen from the figure that the field curvature of the meridional image plane and the sagittal image plane is controlled within ±0.04mm, indicating that the optical lens 200 can well correct the field curvature.

[0113] Fig. 9 The F-Tan (Theta) distortion curve of Example 2 is shown, which represents the distortion of different field angles on the imaging plane, with the horizontal axis representing the distortion value (unit: %) and the vertical axis representing the field angle (unit: °). It can be seen from the figure that the distortion value is controlled within ±3%, indicating that the optical lens 200 can correct the distortion well.

[0114] Fig.10 The axial chromatic aberration curve of Example 2 is shown, which represents the chromatic aberration of each wavelength on the optical axis at the imaging plane, the horizontal axis represents the axial chromatic aberration value (unit: mm), and the vertical axis represents the normalized pupil radius. It can be seen from the figure that the offset of the axial chromatic aberration is controlled within ±0.012mm, indicating that the optical lens 200 can correct the axial chromatic aberration well.

[0115] Fig.11 The vertical axis chromatic aberration curve of Example 2 is shown, which represents the chromatic aberration of each wavelength relative to the central wavelength (0.94 μm) at different image heights on the imaging surface, the horizontal axis represents the vertical axis chromatic aberration value of each wavelength relative to the central wavelength (unit: μm), and the vertical axis represents the field angle (unit: °). It can be seen from the figure that the vertical axis chromatic aberration of the longest wavelength and the shortest wavelength is controlled within ±2 μm, indicating that the optical lens 200 can correct chromatic aberration well.

[0116] Fig.12 The MTF (Modulation Transfer Function) curve of Example 2 is shown, which represents the imaging modulation degree of the lens at different spatial frequencies under each field of view, the horizontal axis represents the spatial frequency (unit: cycle / mm), and the vertical axis represents the MTF value. It can be seen from the figure that the MTF value of this embodiment is above 0.5 in the entire field of view, and the MTF curve decreases evenly and smoothly from the center to the edge of the field of view, and has good imaging quality and good detail resolution ability in both low-frequency and high-frequency conditions.

[0117] from Figure 8 , Fig. 9 , Fig.10 , Fig.11 , Fig.12 It can be seen that the aberration of the optical lens 200 is well balanced and has good imaging quality in the infrared band.

[0118] Please refer to Table 3, which shows the optical characteristics corresponding to the above embodiments, including the effective focal length f of the optical lens, the total optical length TTL, the aperture value Fno, the entrance pupil diameter EPDI, the real image height ih corresponding to the maximum half field of view angle, the maximum field of view angle FOV, and the numerical value corresponding to each conditional expression in each embodiment.

[0119] Table 3

[0120]

[0121] In summary of the above embodiments, the optical lens provided by the present invention has the following advantages: through a specific surface shape setting and a reasonable distribution of optical focal length, it works in the near-infrared band, improving the monitoring effect at night and in low-light environments; it has a large aperture, which is conducive to increasing the amount of light entering the lens, allowing the lens to achieve high-definition imaging in a dim environment. In addition, it can also reasonably correct the overall aberration of the optical lens, has a small distortion, and is conducive to reducing the amplitude of deformation and distortion around the image when the optical lens is imaging, and can achieve high-definition imaging and improve the imaging quality of the optical lens.

[0122] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0123] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. An optical lens, consisting of a metalens and three lenses, characterized in that: The lens comprises a first lens group, a second lens group and a third lens group in sequence from the object side to the imaging surface along the optical axis; Wherein, the first group includes a first lens and a super lens; The first lens has positive power, the object side surface of the first lens is convex, and the image side surface of the first lens is concave; The second lens has positive refractive power, the object side surface of the second lens is concave, and the image side surface of the second lens is convex; The third lens has negative optical power, the object side surface of the third lens is convex, and the image side surface of the third lens is concave; The superlens has positive optical power, and an aperture is provided at the object side end of the superlens; The total optical length TTL of the optical lens and the effective focal length f of the optical lens satisfy: 1.6 <TTL / f<1.9; The effective focal length f of the optical lens and the focal length f3 of the third lens satisfy: -0.85 <f3 / f<-0.75。 2. The optical lens according to claim 1, characterized in that: The total optical length TTL of the optical lens and the real image height ih corresponding to the maximum half field angle of the optical lens satisfy: 2.5 <TTL / ih<2.95。 3. The optical lens according to claim 1, characterized in that: The effective focal length f of the optical lens, the maximum field of view FOV of the optical lens and the real image height ih corresponding to the maximum half field of view of the optical lens satisfy: 102°<(f×FOV) / ih<107°.

4. The optical lens according to claim 1, characterized in that: The effective focal length f of the optical lens and the aperture value Fno of the optical lens satisfy: 1.75mm <f / Fno<1.95mm。 5. The optical lens according to claim 1, characterized in that: The back focal length BFL of the optical lens and the total optical length TTL of the optical lens satisfy: 0.27 <BFL / TTL<0.29。 6. The optical lens according to claim 1, characterized in that: The focal length f1 of the first lens and the focal length f4 of the super lens satisfy: 0.07 <f1 / f4<0.14。 7. The optical lens according to claim 1, characterized in that: The effective focal length f of the optical lens and the focal length f4 of the metalens satisfy: 12 <f4 / f<22。 8. The optical lens according to claim 1, characterized in that: The effective focal length f of the optical lens, the focal length f1 of the first lens and the focal length f4 of the metalens satisfy: 74mm<(f1×f4) / f<129mm.

9. The optical lens according to claim 1, characterized in that: The object side surface and the image side surface of the first lens are both spherical surfaces, and the first lens is made of glass. The object side surfaces and the image side surfaces of the second lens and the third lens are both aspherical surfaces.

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