Low-distortion wide-angle lens

Abstract

The utility model discloses a low-distortion wide-angle lens, which is sequentially arranged from an object side to an image side along an optical axis of the lens: a first lens which is a spherical glass lens with negative focal power; the second lens is an aspheric plastic lens with negative focal power; the third lens is an aspheric plastic lens with negative focal power; the fourth lens is a spherical glass lens with negative focal power; a diaphragm sheet; the fifth lens is an aspheric plastic lens with positive focal power; the sixth lens is an aspheric plastic lens with negative focal power; the seventh lens is an aspheric plastic lens with negative focal power; the eighth lens is a spherical glass lens with positive focal power; an optical filter, protective glass and an image acquisition element. According to the utility model, three pieces of spherical glass and five pieces of aspheric plastic are mixed and combined, the lens is matched with a 1 / 1.8 ''chip, the field angle is 120 degrees, the distortion is within 8%, the actually shot picture is clear at the high temperature of + 80 DEG C and the low temperature of-40 DEG C, and the day and night confocal performance is good.

Description

Technical Field

[0001] The utility model relates to the field of optical lenses, in particular to a low-distortion wide-angle lens. Background Art

[0002] In today's digital business environment, video conferencing has become an indispensable part of the daily operations of enterprises. With the increasing demand for efficient communication and collaboration, the requirements for high-quality video conferencing lenses are also getting higher and higher. As a key imaging device, the low-distortion wide-angle video conferencing lens is of great significance for providing clear and real video images. Traditional video conferencing lenses usually have a certain degree of distortion, which may lead to image distortion. Especially at the wide-angle end, a large distortion will cause obvious deformation of the actual shooting image, affecting the visual experience and the meeting effect. Summary of the Utility Model

[0003] Based on this, the purpose of the utility model is to provide a low-distortion wide-angle lens. This lens adopts a hybrid combination of 3 spherical glass lenses and 5 aspherical plastic lenses, can be matched with a 1 / 2.8" inch chip, has a field of view of 120°, a distortion within 8%, has clear actual shooting images at high temperature of +80°C and low temperature of -40°C, and has good day-night confocal performance.

[0004] The purpose of the utility model is achieved through the following technical solutions:

[0005] A low-distortion wide-angle lens is sequentially arranged from the object side to the image side along the optical axis of the lens:

[0006] A first lens, the first lens is a spherical glass lens with negative optical power, its object side is convex, and its image side is concave;

[0007] A second lens, the second lens is an aspherical plastic lens with negative optical power, both its object side and image side are concave;

[0008] A third lens, the third lens is an aspherical plastic lens with negative optical power, its object side is concave, and its image side is convex;

[0009] A fourth lens, the fourth lens is a spherical glass lens with negative optical power, its object side is convex, and its image side is concave;

[0010] An aperture stop;

[0011] A fifth lens, the fifth lens is an aspherical plastic lens with positive optical power, both its object side and image side are convex;

[0012] A sixth lens, the sixth lens is an aspherical plastic lens with negative optical power, both its object side and image side are concave;

[0013] The seventh lens, which is an aspherical plastic lens with a negative focal power, has a concave object side and a convex image side;

[0014] The eighth lens, which is a spherical glass lens with a positive focal power, has convex object and image sides.

[0015] Furthermore, the object side of the second lens is a concave surface with an inflection.

[0016] Furthermore, the object side of the seventh lens is a concave surface with an inflection, and the image side is a convex surface with an inflection.

[0017] Furthermore, the lens is further provided with a filter, a protective glass, and an image acquisition element; the filter is disposed on the image side of the eighth lens; the protective glass is disposed on the image side of the filter, the image acquisition element is disposed on the image side of the protective glass, and the protective glass is integrated on an image sensor.

[0018] Furthermore, the lens satisfies the following relationship:

[0019] IC / TTL≥0.45, TTL / f≤5.4, OBFL / TTL≥0.22,

[0020] In the relationship, f is the total focal length of the lens, TTL is the total optical length of the lens, OBFL is the optical back focal length of the lens, and IC is the full image height of a 1 / 2.8" chip matched with the lens system.

[0021] Furthermore, the lens also satisfies the following relationship:

[0022] -7.50<f1 / f<9.00,

[0023] -3.70<f2 / f<3.60,

[0024] -29.50<f3 / f<49.5,

[0025] -5.00<f4 / f<4.30,

[0026] -1.15<f5 / f<1.5,

[0027] -1.60<f6 / f<1.40,

[0028] -4.85<f7 / f<5.60,

[0029] -5.20<f8 / f<4.90;

[0030] In the relational expression, f is the total focal length of the lens, f1 is the focal length of the first lens, f2 is the focal length of the second lens, f3 is the focal length of the third lens, f4 is the focal length of the fourth lens, f5 is the focal length of the fifth lens, f6 is the focal length of the sixth lens, f7 is the focal length of the seventh lens, and f8 is the focal length of the eighth lens.

[0031] Furthermore, the lens also satisfies: F# ≤ 2.0, where F# is the aperture of the lens.

[0032] Furthermore, the optical system satisfies: TTL / ImageH < 9.375, where TTL is the total optical length of the lens and ImageH is half of the diagonal length of the effective pixel area on the imaging surface.

[0033] Furthermore, the lens also satisfies: f ≤ 2.0 mm, where f is the total focal length of the lens.

[0034] Furthermore, the lens also satisfies: TTL ≤ 30 mm, where TTL is the total optical length of the lens.

[0035] Furthermore, the aspheres of the second lens, the third lens, the fifth lens, the sixth lens, and the seventh lens satisfy the following formula:

[0036]

[0037] In the formula, Z is the sag height of the lens along the optical axis direction, k is the conic coefficient of the quadratic surface, γ is the lens height, c is the lens curvature, and A, B, C, D, E, F, G are the coefficients of the 4th, 6th, 8th, 10th, 12th, 14th, and 16th order terms of the aspheric polynomial

[0038] The beneficial effects of the present utility model are:

[0039] The low-distortion wide-angle lens of the present utility model has a total focal length f ≤ 2.0 mm of the optical lens and an aperture F# ≤ 2.0, and can provide high-definition image quality under the condition of a large field of view angle.

[0040] In terms of manufacturability, the lens adopts a hybrid combination of 3 spherical glass lenses and 5 aspheric plastic lenses. Each lens is insensitive, easy to mold and manufacture, has a compact structure, and can achieve the characteristics of small volume, light weight, good performance, and low cost, with a high cost performance.

[0041] By reasonably setting the optical power and surface shape of each lens, the present utility model is beneficial to reducing the aberration and chromatic aberration of the lens imaging. When the field of view angle is 120°, the distortion can be controlled within 8%. It can be paired with a 1 / 2.8" chip to achieve 24-hour all-weather high-definition monitoring with day and night confocal, and has good reliability and stability. Description of the Drawings

[0042] Figure 1 Schematic diagram of the optical path structure of Embodiment 1 of the present utility model;

[0043] Figure 2 Defocus curve graph of visible light of 0.435 - 0.656μm (125lp / mm) at normal temperature +20°C of Embodiment 1 of the present utility model;

[0044] Figure 3 Defocus curve graph of visible light of 0.435 - 0.656μm (125lp / mm) at low temperature -40°C of Embodiment 1 of the present utility model;

[0045] Figure 4 Defocus curve graph of visible light of 0.435 - 0.656μm (125lp / mm) at high temperature +80°C of Embodiment 1 of the present utility model;

[0046] Figure 5 Defocus curve graph of infrared light of 0.850μm (125lp / mm) of Embodiment 1 of the present utility model;

[0047] Figure 6 Relative illuminance graph of visible light of 0.546μm of Embodiment 1 of the present utility model;

[0048] Figure 7 FFT MTF curve graph of visible light of 0.435 - 0.656μm of Embodiment 1 of the present utility model;

[0049] Figure 8 F - Tan(Theta) distortion curve graph of visible light of 0.546μm of Embodiment 1 of the present utility model;

[0050] Figure 9 Axial chromatic aberration curve graph of visible light of 0.435 - 0.656μm of Embodiment 1 of the present utility model;

[0051] Figure 10 Schematic diagram of the optical path structure of Embodiment 2 of the present utility model;

[0052] Figure 11 Defocus curve graph of visible light of 0.435 - 0.656μm (125lp / mm) at normal temperature +20°C of Embodiment 2 of the present utility model;

[0053] Figure 12 Defocus curve graph of visible light of 0.435 - 0.656μm (125lp / mm) at low temperature -40°C of Embodiment 2 of the present utility model;

[0054] Figure 13 Defocus curve graph of visible light of 0.435 - 0.656μm (125lp / mm) at high temperature +80°C of Embodiment 2 of the present utility model;

[0055] Figure 14 It is the defocus curve graph of the infrared light of 0.850μm (125lp / mm) in Embodiment 2 of the present utility model;

[0056] Figure 15 It is the relative illuminance graph of the visible light of 0.546μm in Embodiment 2 of the present utility model;

[0057] Figure 16 It is the FFT MTF curve graph of the visible light of 0.435 - 0.656μm in Embodiment 2 of the present utility model;

[0058] Figure 17 It is the F - Tan(Theta) distortion curve graph of the visible light of 0.546μm in Embodiment 2 of the present utility model;

[0059] Figure 18 It is the longitudinal chromatic aberration curve graph of the visible light of 0.435 - 0.656μm in Embodiment 2 of the present utility model;

[0060] Reference numerals:

[0061] 1. First lens; 2. Second lens; 3. Third lens; 4. Fourth lens; 5. Fifth lens; 6. Sixth lens; 7. Seventh lens; 8. Eighth lens; 9. Filter; 10. Protective glass; 11. Image acquisition element; 12. Aperture stop; Detailed implementation manners

[0062] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. In this specification, the expressions such as the first, the second, and the third are only used to distinguish one feature from another feature, and do not represent any limitation on the feature. The shape of the spherical or aspherical surface is not limited to the spherical or aspherical shape shown in the drawings. The drawings are only for illustration and are not drawn strictly to scale.

[0063] In the present invention, 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; if the lens surface is not defined as convex, concave or flat, it means that the lens surface can be convex, concave or flat. The surface of each lens closest to the object to be photographed is called the object side surface of the lens, and the surface of each lens closest to the imaging surface is called the image side surface of the lens.

[0064] Unless otherwise defined, all terms (including technical and scientific terms) used in the present invention have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. It should also be understood that terms (such as those defined in a commonly used dictionary) should be interpreted as having a meaning consistent with their meaning in the context of the relevant art, and will not be interpreted in an idealized or overly formal sense unless expressly so defined in the present invention.

[0065] It should be noted that, without conflict, the embodiments in this application and the features in the embodiments may be combined with each other. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the scope of protection of the present invention. For better understanding and implementation, the present invention will be described in detail below with reference to the accompanying drawings.

[0066] The present utility model provides a low-distortion wide-angle lens. Along the optical axis of the lens, a first lens 1, a second lens 2, a third lens 3, a fourth lens 4, an aperture stop 12, a fifth lens 5, a sixth lens 6, a seventh lens 7, an eighth lens 8, a filter 9, a protective glass 10, and an image acquisition element 11 are sequentially arranged from the object side to the image side. The aperture stop 12 is arranged between the fourth lens 4 and the fifth lens 5; the filter 9 is arranged on the image side surface of the eighth lens 8, and the filter 9 is made of H-K9L glass; the protective glass 10 is integrated on the image acquisition element 11, and the image acquisition element 11 is arranged on the image side surface of the filter 9.

[0067] Wherein:

[0068] The first lens 1 is a spherical glass lens with a negative optical power. Its object side surface is convex, and its image side surface is concave.

[0069] The second lens 2 is an aspherical plastic lens with a negative optical power. Both its object side surface and image side surface are concave.

[0070] The third lens 3 is an aspherical plastic lens with a negative optical power. Its object side surface is concave, and its image side surface is convex.

[0071] The fourth lens 4 is a spherical glass lens with a negative optical power. Its object side surface is convex, and its image side surface is concave.

[0072] The fifth lens 5 is an aspherical plastic lens with a positive optical power. Both its object side surface and image side surface are convex.

[0073] The sixth lens 6 is an aspherical plastic lens with a negative optical power. Both its object side surface and image side surface are concave.

[0074] The seventh lens 7 is an aspherical plastic lens with a negative optical power. Its object side surface is concave, and its image side surface is convex.

[0075] The eighth lens 8, a spherical glass lens with a positive optical power, having convex surfaces on both the object side and the image side.

[0076] For the low-distortion wide-angle lens provided by the present utility model, F# is the aperture of the lens, f is the total focal length of the lens, TTL is the total optical length of the lens, OBFL is the optical back focal length of the lens, and the optical back focal length of the lens is the distance from the point on the image side of the eighth lens 8 closest to the image plane to the image plane. IC is the total image height of the 1 / 2.8” chip matched with the lens system, and ImageH is half of the diagonal length of the effective pixel area on the imaging plane; the lens satisfies the following conditions:

[0077] F# ≤ 2.0, f ≤ 2.0 mm, TTL ≤ 30 mm, IC / TTL ≥ 0.45, TTL / f ≤ 5.4, OBFL / TTL ≥ 0.22, TTL / ImageH < 9.375.

[0078] For the low-distortion wide-angle lens provided by the present utility model, f is the total focal length of the lens, f1 is the focal length of the first lens 1, f2 is the focal length of the second lens 2, f3 is the focal length of the third lens 3, f4 is the focal length of the fourth lens 4, f5 is the focal length of the fifth lens 5, f6 is the focal length of the sixth lens 6, f7 is the focal length of the seventh lens 7, and f8 is the focal length of the eighth lens 8. The total focal length of the entire lens is f, and the ratio of the focal length of each lens to the total focal length of the lens satisfies the following conditions:

[0079] -7.50 < f1 / f < 9.00,

[0080] -3.70 < f2 / f < 3.60,

[0081] -29.50 < f3 / f < 49.5,

[0082] -5.00 < f4 / f < 4.30,

[0083] -1.15 < f5 / f < 1.5,

[0084] -1.60 < f6 / f < 1.40,

[0085] -4.85 < f7 / f < 5.60,

[0086] -5.20 < f8 / f < 4.90.

[0087] For the low-distortion wide-angle lens provided by the present utility model, the aspheric surfaces of the second lens 2, the third lens 3, the fifth lens 5, the sixth lens 6, and the seventh lens 7 can all be defined by the following equation of even-order aspheric surfaces:

[0088]

[0089] Wherein, Z is the sag height of the lens along the optical axis direction, k is the conic coefficient of the conic surface, γ is the lens height, c is the lens curvature, and A, B, C, D, E, F, G are the coefficients of the 4th, 6th, 8th, 10th, 12th, 14th, and 16th order terms of the aspheric polynomial.

[0090] The main element symbols in the specific embodiments of the present utility model are shown in Table 1.

[0091] Table 1

[0092]

[0093]

[0094] Embodiment 1

[0095] As Figure 1 shown is the schematic optical path structure diagram of Embodiment 1, wherein the first lens 1 and the second lens 2 adopt meniscus negative optical power lenses with the convex surface facing the object side, and their function is to quickly converge light. The fourth lens 4 and the eighth lens 8 are made of materials with an Abbe number greater than 68. Such a combination can reduce the chromatic aberration of the system, and thus solve problems such as day and night confocal; the second lens 2, the third lens 3, the fifth lens 5, the sixth lens 6, and the seventh lens 7 are all plastic aspheric lenses, and their main function is to correct various optical aberrations, and finally optimize the performance of the optical system.

[0096] In this embodiment, considering the problem of the aberration of the optical system, the curvature radius, central thickness, refractive index, Abbe constant, and aspheric K value of each lens are designed as shown in Table 2.

[0097] Table 2 gives the curvature radius R (unit: mm) of each lens, the central thickness d (unit: mm) of each lens, the refractive index (ND) of each lens, the Abbe constant (VD), and the aspheric K value (Conic) of each lens.

[0098] Table 2

[0099] Surface number Radius of curvature R Central thickness D Refractive index ND Abbe number VD K S1 15.11 1.50 1.80 46.5 S2 6.59 3.47 S3 -29.11 1.15 1.53 55.7 -0.2783 S4 4.20 4.66 -0.0618 S5 -5.22 3.96 1.53 55.7 6.025E-03 S6 -5.84 0.15 3.189E-03 S7 6.98 2.55 1.59 68.5 S8 78.76 3.70 S9 (stop surface) Infinity 0.94 S10 7.96 1.63 1.53 55.7 0.034E-03 S11 -2.18 0.10 1.602E-03 S12 -2.14 0.83 1.63 23.9 -2.671E-03 S13 8.55 0.28 0.2658 S14 -10.32 1.28 1.53 55.7 4.224E-03 S15 -3.81 0.13 0.0177 S16 10.80 1.19 1.59 68.5 S17 -80.79 0.32 S18 Infinity 0.30 1.51 64.2 S19 Infinity 1.30 S20 Infinity 0.40 1.51 64.2 S21 Infinity 0.15

[0100] In Table 2, the curvature radius R represents the degree of curvature of the lens surface. A positive value represents that the surface bends towards the image side, and a negative value represents that the surface bends towards the object side. Among them, "INFINITY" represents that the surface is a plane; the central thickness D represents the central axial distance from the current surface to the next surface, the refractive index ND represents the light deflection ability of the current lens material, the Abbe number VD represents the light dispersion characteristic of the current lens material; the k value represents the numerical value of the best-fit conic coefficient of the aspheric surface.

[0101] In this embodiment, the aspherical surfaces of the second lens 2, the third lens 3, the fifth lens 5, the sixth lens 6, and the seventh lens 7 can all be defined by the above equation of the even aspherical surface. Among them, the coefficients of the aspherical surfaces of each optical surface of the second lens 2, the third lens 3, the fifth lens 5, and the sixth lens 6 are shown in Table 3.

[0102] Table 3

[0103] Surface number A B C D E F S3 2.825E-03 -6.204E-04 9.540E-09 5.190E-08 -1.563E-03 1.534E-11 S4 -1.445E-04 1.504E-04 5.828E-06 -1.963E-06 9.290E-03 -2.433E-09 S5 -1.974E-03 2.870E-04 -2.268E-05 1.602E-06 -6.196E-03 1.134E-09 S6 1.277E-04 4.052E-05 -1.275E-08 6.567E-08 -1.550E-03 5.234E-11 S10 -6.608E-03 -4.112E-04 -7.359E-03 -6.089E-04 1.128E-03 -1.347E-04 S11 0.031 -5.389E-04 -7.701E-03 4.778E-03 1.460E-03 4.470E-05 S12 6.115E-03 2.714E-03 -6.579E-03 3.041E-03 -5.263E-03 -2.758E-06 S13 -0.011 3.529E-03 -1.267E-04 -5.466E-05 1.061E-03 1.080E-07 S14 0.042 -8.034E-03 1.982E-03 -4.502E-04 5.428E-03 -2.700E-06 S15 0.027 1.543E-04 -6.451E-04 7.253E-05 -1.938E-03 -5.007E-08

[0104] In this embodiment:

[0105] As Figure 2 - 4 shown, the defocus amounts of the lens at high temperature of +80 °C and low temperature of -40 °C are less than 9 μm and 5 μm respectively. Such defocus amounts ensure that the lens can capture high-definition images at high temperature of +80 °C and low temperature of -40 °C.

[0106] As Figure 5 shown, the defocus amount of the lens at infrared of 0.850 μm is less than 7 μm, which ensures that the actual captured image is clear during night shooting.

[0107] As Figure 6 shown, the relative illuminance of the lens at the maximum field of view is greater than 43%, and the light input is sufficient, ensuring that there is no vignetting in the actual captured image even when the lens is used in a relatively dim environment.

[0108] As Figure 7 shown, it is the MTF curve graph of the lens in this embodiment. The horizontal axis represents the spatial frequency (unit: lp / mm), and the vertical axis represents the MTF value. It can be seen from the figure that at a spatial frequency of 200 lp / mm, the MTF value of the lens within the full field of view matching the 1 / 2.8" chip is above 0.3, indicating that the lens has a high resolution.

[0109] As Figure 8 shown, it is the F-Tan(Theta) distortion graph of the lens in this embodiment. The horizontal axis represents the F-Tan(Theta) distortion (unit: %), and the vertical axis represents the semi-field angle (unit: °). It can be seen from the figure that the F-Tan(Theta) distortion of the lens is small and less than 8%, which can keep the magnification of different positions of the actual captured image consistent.

[0110] As Figure 9 shown, it is the axial chromatic aberration curve graph of the lens in this embodiment. The axial chromatic aberration at the center axis with a wavelength of 0.546 μm is within 0.025 mm, indicating that the lens system has good aberration correction and small axial chromatic aberration.

[0111] Embodiment 2

[0112] As Figure 10The following is a schematic diagram of the optical path structure of Embodiment 2. The first lens 1 and the second lens 2 are meniscus negative lenses with convex surfaces facing the object side, and their function is to quickly converge light. The fourth lens 4 and the eighth lens 8 are made of materials with an Abbe number greater than 68. Such a combination can reduce the chromatic aberration of the system and thus solve problems such as day-night confocal imaging. The second lens 2, the third lens 3, the fifth lens 5, the sixth lens 6, and the seventh lens 7 are all plastic aspherical lenses, and their main function is to correct various optical aberrations, ultimately optimizing the performance of the optical system.

[0113] In this embodiment, considering the problem of optical aberrations in the optical system, the curvature radii, central thicknesses, refractive indices, Abbe constants, and aspherical K values of each lens are designed as shown in Table 4.

[0114] Table 4 shows the curvature radius R (unit: mm) of each lens, the central thickness d (unit: mm) of each lens, the refractive index (ND) of each lens, the Abbe constant (VD) of each lens, and the aspherical K value (Conic) of each lens.

[0115] Table 4

[0116]

[0117]

[0118] In Table 4, the curvature radius R represents the degree of curvature of the lens surface. A positive value indicates that the surface is curved towards the image side, and a negative value indicates that the surface is curved towards the object side. "INFINITY" indicates that the surface is a plane. The central thickness D represents the central axial distance from the current surface to the next surface. The refractive index ND represents the ability of the current lens material to refract light. The Abbe number VD represents the dispersion characteristics of the current lens material with respect to light. The k value represents the numerical value of the best-fit conic coefficient of the aspherical surface.

[0119] In this embodiment, the aspherical surfaces of the second lens 2, the third lens 3, the fifth lens 5, the sixth lens 6, and the seventh lens 7 can all be defined by the above equation of the even-order aspherical surface. Among them, the coefficients of the aspherical surfaces of each optical surface of the second lens 2, the third lens 3, the fifth lens 5, and the sixth lens 6 are shown in Table 5.

[0120] Table 5

[0121]

[0122]

[0123] In this embodiment:

[0124] As shown in Figures 11 - 13, the defocus amounts of this lens at high temperature of +80°C and low temperature of -40°C are less than 9μm and 4.5μm respectively. Such defocus amounts ensure that the lens can capture high-definition images at high temperature of +80°C and low temperature of -40°C.

[0125] As Figure 14 shown, the defocus amount of this lens at infrared wavelength of 0.850μm is less than 7.5μm, which ensures clear real-shot images during night shooting.

[0126] As Figure 15 shown, the relative illuminance of this lens at the maximum field of view is greater than 45%, with sufficient light input, ensuring that there is no vignetting in the real-shot images even when the lens is used in a relatively dim environment.

[0127] As Figure 16 shown, it is the MTF curve graph of the lens in this embodiment. The horizontal axis represents the spatial frequency (unit: lp / mm), and the vertical axis represents the MTF value. It can be seen from the graph that at a spatial frequency of 200 lp / mm, the MTF value of the lens within the full field of view matching a 1 / 2.8” chip is above 0.2, indicating that the lens has a high resolution.

[0128] As Figure 17 shown, it is the F-Tan(Theta) distortion graph of the lens in this embodiment. The horizontal axis represents the F-Tan(Theta) distortion (unit: %), and the vertical axis represents the semi-field angle (unit: °). It can be seen from the graph that the F-Tan(Theta) distortion of the lens is small and less than 8%, enabling the magnification ratios at different positions of the real-shot images to be consistent.

[0129] As Figure 18 shown, it is the axial chromatic aberration curve graph of the lens in this embodiment. The axial chromatic aberration at the center axis with a wavelength of 0.546μm is within 0.025mm, indicating that the aberration correction of this lens system is good and the axial chromatic aberration is small.

[0130] In summary, for the low-distortion wide-angle lens provided by the present utility model, the total focal length f of the optical lens ≤ 2.0mm, and the aperture F# ≤ 2.0. It can provide high-definition image quality under the condition of a large field of view. In terms of manufacturability, this lens adopts a hybrid combination of 3 spherical glasses and 5 aspherical plastics. Each lens is insensitive and easy to form, achieving the characteristics of small volume, light weight, good performance, and low cost, with a high cost performance ratio. Through reasonable selection of lens materials, distribution of optical power, and optimization of optical design, the present utility model can be paired with a 1 / 2.8” chip to achieve 24-hour all-weather high-definition monitoring with coaxial focus day and night, and has good reliability and stability.

[0131] The above only expresses the preferred technical solutions of the present utility model, and its description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the utility model patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present utility model, several modifications and improvements can still be made, and the present utility model also intends to include these modifications and variations.

Claims

1. A low-distortion wide-angle lens, characterized in that: Set along the lens optical axis from the object side to the image side in order: A first lens, wherein the first lens is a spherical glass lens with negative optical power, the object side surface of which is convex and the image side surface of which is concave; A second lens, wherein the second lens is an aspherical plastic lens with negative optical power, and both the object side surface and the image side surface thereof are concave; A third lens, wherein the third lens is an aspheric plastic lens with negative optical power, the object side surface of which is concave and the image side surface of which is convex; a fourth lens, wherein the fourth lens is a spherical glass lens with negative optical power, the object side surface of which is convex and the image side surface of which is concave; Aperture diaphragm; a fifth lens, wherein the fifth lens is an aspherical plastic lens with positive refractive power, and both the object side surface and the image side surface thereof are convex; a sixth lens, wherein the sixth lens is an aspherical plastic lens with negative optical power, and both the object side surface and the image side surface thereof are concave; A seventh lens, wherein the seventh lens is an aspherical plastic lens with negative optical power, the object side surface of which is concave and the image side surface of which is convex; an eighth lens, wherein the eighth lens is a spherical glass lens with positive refractive power, and both the object side surface and the image side surface thereof are convex; The lens satisfies the following relationship: IC / TTL≥0.45, TTL / f≤5.4, OBFL / TTL≥0.22, In the relationship, f is the total focal length of the lens, TTL is the total optical length of the lens, OBFL is the optical back focus of the lens, and IC is the total image height of the chip matched with the lens system.

2. The low-distortion wide-angle lens according to claim 1, characterized in that: The object side surface of the second lens is a concave surface with reverse curvature.

3. The low distortion wide-angle lens according to claim 1, characterized in that: The object side surface of the seventh lens is a concave surface with a reverse curve, and the image side surface is a convex surface with a reverse curve.

4. The low-distortion wide-angle lens according to claim 1, characterized in that: The lens also satisfies the following relationship: -7.50<f1 / f<9.00, -3.70<f2 / f<3.60, -29.50<f3 / f<49.5, -5.00<f4 / f<4.30, -1.15<f5 / f<1.5, -1.60<f6 / f<1.40, -4.85<f7 / f<5.60, -5.20<f8 / f<4.90; In the relationship, f is the total focal length of the lens, f1 is the focal length of the first lens, f2 is the focal length of the second lens, f3 is the focal length of the third lens, f4 is the focal length of the fourth lens, f5 is the focal length of the fifth lens, f6 is the focal length of the sixth lens, f7 is the focal length of the seventh lens, and f8 is the focal length of the eighth lens.

5. The low distortion wide-angle lens according to claim 1, characterized in that: The lens also satisfies: F#≤2.0, where F# is the aperture of the lens.

6. The low distortion wide-angle lens according to claim 1, characterized in that: The lens also satisfies: TTL / ImageH<9.375, TTL is the total optical length of the lens, and ImageH is half of the diagonal length of the effective pixel area on the imaging surface.

7. The low distortion wide-angle lens according to claim 1, characterized in that: The lens also satisfies: f≤2.0 mm, where f is the total focal length of the lens.

8. The low distortion wide-angle lens according to claim 1, characterized in that: The lens also satisfies: TTL≤30mm, where TTL is the total optical length of the lens.

9. The low distortion wide-angle lens according to claim 1, characterized in that: A filter, a protective glass and an image acquisition element are also provided; the filter is provided on the image side of the eighth lens; the protective glass is provided on the image side of the filter, the image acquisition element is provided on the image side of the protective glass, and the protective glass is integrated on the image sensor.

10. The low distortion wide-angle lens according to any one of claims 1 to 9, characterized in that: The aspheric surfaces of the second lens, the third lens, the fifth lens, the sixth lens and the seventh lens satisfy the following formula: Wherein, Z is the vector height of the lens along the optical axis, k is the quadratic cone coefficient, γ is the lens height, c is the lens curvature, A, B, C, D, E, F, G are the 4th, 6th, 8th, 10th, 12th, 14th, and 16th order coefficients of the aspheric polynomial.

Images