Imaging lens

Abstract

The present invention relates to an imaging lens, which includes a first lens group (G1) with positive optical power, a diaphragm, and a second lens group (G2) with positive optical power, arranged in sequence from the object side to the image side. The first lens group (G1) is a fixed group, and the second lens group (G2) is a focusing lens group that can move along the optical axis. The first lens group (G1) includes at least two lenses with positive optical power and two lenses with negative optical power. Along the direction from the object side to the image side, the first lens of the first lens group (G1) is a lens with positive optical power, and the second lens is a lens with negative optical power. The imaging lens of the present invention can achieve low distortion, large depth of field, uniform image quality, good color restoration, high contrast, and a resolution of up to more than 12 million pixels. At the same time, it has the characteristics of good image quality stability under abnormal conditions such as high temperature and low temperature.

Description

Technical Field

[0001] The present invention relates to the field of optical devices, and particularly to an imaging lens. Background Art

[0002] Machine vision is a rapidly developing branch of artificial intelligence. Briefly speaking, it means using a robot to replace the human eye for measurement and judgment. The target to be captured is converted into an image signal and transmitted to a dedicated image processing system to obtain the morphological information of the captured target. According to the pixel distribution, brightness, color and other information, it is converted into a digital signal. The image system performs various operations on these signals to extract target features, such as position, size and appearance, etc., and then outputs a structure according to preset conditions to achieve functions such as automatic recognition, judgment and measurement. Therefore, the imaging system for machine vision has very high requirements for pixels, picture uniformity, distortion, brightness, color restoration, etc.

[0003] However, the machine vision lenses currently on the market have a small optical magnification, a small imaging picture, and large distortion and uneven brightness. Such machine vision lenses do not image finely, have a low dynamic range during imaging, poor color and contrast, and at the same time have a large deviation in transmittance. Summary of the Invention

[0004] The purpose of the present invention is to solve the above problems and provide an imaging lens with low distortion and uniform image quality.

[0005] To achieve the above purpose, the present invention provides an imaging lens, including a first lens group with positive optical power, a diaphragm, and a second lens group with positive optical power, which are sequentially arranged from the object side to the image side. The first lens group is a fixed group, and the second lens group is a focusing lens group that can move along the optical axis;

[0006] The first lens group includes at least two lenses with positive optical power and two lenses with negative optical power. And along the direction from the object side to the image side, the first lens of the first lens group is a lens with positive optical power, and the second lens is a lens with negative optical power.

[0007] According to one aspect of the present invention, along the direction from the object side to the image side, the first lens of the first lens group is a convex-convex lens or a convex-concave lens;

[0008] The second lens is a concave-concave lens, a convex-concave lens or a plano-concave lens.

[0009] According to one aspect of the present invention, the first lens group includes at least one doublet lens.

[0010] According to one aspect of the present invention, the cemented surface of at least one doublet lens in the first lens group is a convex surface or a plane.

[0011] According to one aspect of the present invention, along the object side to the image side direction, the doublet lens in the first lens group is composed of a lens with a positive optical power and a lens with a negative optical power, or is composed of a lens with a negative optical power and a lens with a positive optical power.

[0012] According to one aspect of the present invention, the second lens group includes at least two lenses with positive optical power and one lens with negative optical power, and the lens closest to the image side in the second lens group is a lens with positive optical power.

[0013] According to one aspect of the present invention, along the object side to the image side direction, the first lens in the second lens group is a convex-convex lens, a concave-convex lens, or a plano-convex lens.

[0014] According to one aspect of the present invention, the second lens group includes at least one doublet lens group, and the doublet lens group is composed of a lens with positive optical power and a lens with negative optical power.

[0015] According to one aspect of the present invention, along the object side to the image side direction, the lens with negative optical power in the doublet lens in the second lens group is a concave-concave lens, a concave-convex lens, or a concave-plano lens.

[0016] According to one aspect of the present invention, the focal length of the first lens group is f G1 , and the focal length of the imaging lens is f, satisfying the relational expression: 1.85 ≤ |f G1 / f| ≤ 4.50.

[0017] According to one aspect of the present invention, the focal length f1 of at least one doublet lens in the first lens group and the focal length f of the first lens group satisfy the relational expression: 0.2 ≤ |f1 / f G1 | ≤ 6.5. G1 | ≤ 6.5.

[0018] According to one aspect of the present invention, the focal length of the second lens group is f G2 , and the focal length of the imaging lens is f, satisfying the relational expression: 0.53 ≤ |f G2 / f| ≤ 1.85.

[0019] According to one aspect of the present invention, along the object side to the image side direction, the refractive index of the first positive optical power lens in the second lens group is ND, and the Abbe number is VD, satisfying: 50 ≤ VD ≤ 96, 1.43 ≤ ND ≤ 1.70.

[0020] According to one aspect of the present invention, the overall optical length when the imaging lens images from an infinite object to a near object is TTL, and the focal length of the imaging lens is f, satisfying: 3.0 ≤ TTL / f ≤ 4.0.

[0021] The imaging lens of the present invention is provided with the first lens group of the present invention in the above manner, and the first lens group is used as a fixed group. By matching the positive and negative optical powers of the first two lenses close to the object side, the imaging lens of the present invention has the ability to converge light at a large angle. The setting of the double cemented lens has a correction effect on the distortion, coma and chromatic aberration of the imaging system, and at the same time has a correction effect on the tolerance sensitivity of the imaging system, thereby ensuring that the optical system has an image quality close to the diffraction limit and the consistency of the image plane.

[0022] The imaging lens of the present invention, by setting the second lens group of the present invention according to the above definition, can be used to correct the spherical aberration, astigmatism, coma and distortion inside the second lens group through the combination of positive and negative optical power and the setting of the double cemented lens group. The correction of the aberration inside the second lens group is conducive to reducing the burden ratio of the first lens group on the aberration, and can better reduce the tolerance sensitivity of the focus group, thereby greatly ensuring that the optical system has good image surface consistency and comprehensively improving the imaging quality of the optical system. The imaging lens of the present invention adopts an improved double Gaussian structure and a structure similar to reverse telephoto, which can well correct distortion, converge pipelines, eliminate dark corners, and reduce spherical aberration.

[0023] The imaging lens of the present invention has a focal length of the first lens group of f G1 , the focal length of the imaging lens is f, satisfying the relationship: 1.85≤|f G1 / f|≤4.50. Within the above relationship range, the optical system can quickly collect incident light, reduce field curvature and astigmatism, and achieve and maintain small distortion.

[0024] The imaging lens of the present invention has a focal length f1 of at least one doublet lens in the first lens group and a focal length f2 of the first lens group G1. G1 The relationship between them is: 0.2≤|f1 / f G1 |≤6.5. Satisfying the above relationship is conducive to correcting aberrations such as spherical aberration, astigmatism, coma and distortion within the entire lens group, thereby ensuring the imaging quality of the imaging lens of the present invention.

[0025] The imaging lens of the present invention has a focal length of the second lens group of f G2 , the focal length of the imaging lens is f, satisfying the relationship: 0.53≤|f G2 / f|≤1.85. Satisfying the above relationship and reasonably matching the positive and negative focal powers and focal power sizes of the first lens group and the second lens group can balance the burden ratio of the first lens group and the second lens group on the back focal length and CRA, which is conducive to ensuring the focusing performance and a smaller incident angle of the image plane principal ray, thereby ensuring that the imaging system meets the high image quality requirements close to the diffraction limit.

[0026] For the imaging lens of the present invention, along the object side to the image side direction, the refractive index of the first positive refractive power lens in the second lens group is ND, and the Abbe number is VD, satisfying: 50 ≤ VD ≤ 96, 1.43 ≤ ND ≤ 1.70. By setting the refractive index and Abbe number of the first positive refractive power lens in the second lens group in this way, the chromatic aberration of the imaging system can be effectively corrected, and the imaging quality of the imaging system can be improved. At the same time, this lens also bears most of the pressure for correcting the image plane stability of the imaging system in the non-constant temperature state, which is beneficial to ensuring the stability of the image plane of the imaging system in the non-constant temperature state. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematically showing the structural diagram of the imaging lens according to Embodiment 1 of the present invention;

[0028] Figure 2 Schematically showing the MTF graph when the imaging lens according to Embodiment 1 of the present invention is focused at the optimal working object distance;

[0029] Figure 3 Schematically showing the MTF defocus graph of the imaging lens according to Embodiment 1 of the present invention at low temperature in the optimal working object distance state;

[0030] Figure 4 Schematically showing the MTF defocus graph of the imaging lens according to Embodiment 1 of the present invention at high temperature in the optimal working object distance state;

[0031] Figure 5 Schematically showing the optical distortion graph of the imaging lens according to Embodiment 1 of the present invention;

[0032] Figure 6 Schematically showing the structural diagram of the imaging lens according to Embodiment 2 of the present invention;

[0033] Figure 7 Schematically showing the MTF graph when the imaging lens according to Embodiment 2 of the present invention is focused at the optimal working object distance;

[0034] Figure 8 Schematically showing the MTF defocus graph of the imaging lens according to Embodiment 2 of the present invention at low temperature in the optimal working object distance state;

[0035] Figure 9 Schematically showing the MTF defocus graph of the imaging lens according to Embodiment 2 of the present invention at high temperature in the optimal working object distance state;

[0036] Figure 10 Schematically showing the optical distortion graph of the imaging lens according to Embodiment 2 of the present invention;

[0037] Figure 11 Schematically showing the structural diagram of the imaging lens according to Embodiment 3 of the present invention;

[0038] Figure 12 Schematically shows the MTF graph when the imaging lens according to Embodiment 3 of the present invention is focused at the optimal working object distance;

[0039] Figure 13 Schematically shows the MTF defocus graph of the imaging lens according to Embodiment 3 of the present invention at low temperature in the optimal working object distance state;

[0040] Figure 14 Schematically shows the MTF defocus graph of the imaging lens according to Embodiment 3 of the present invention at low and high temperatures in the optimal working object distance state;

[0041] Figure 15 Schematically shows the optical distortion graph of the imaging lens according to Embodiment 3 of the present invention;

[0042] Figure 16 Schematically shows the structural schematic diagram of the imaging lens according to Embodiment 4 of the present invention;

[0043] Figure 17 Schematically shows the MTF graph when the imaging lens according to Embodiment 4 of the present invention is focused at the optimal working object distance;

[0044] Figure 18 Schematically shows the MTF defocus graph of the imaging lens according to Embodiment 4 of the present invention at low temperature in the optimal working object distance state;

[0045] Figure 19 Schematically shows the MTF defocus graph of the imaging lens according to Embodiment 4 of the present invention at low and high temperatures in the optimal working object distance state;

[0046] Figure 20 Schematically shows the optical distortion graph of the imaging lens according to Embodiment 4 of the present invention;

[0047] Figure 21 Schematically shows the structural schematic diagram of the imaging lens according to Embodiment 5 of the present invention;

[0048] Figure 22 Schematically shows the MTF graph when the imaging lens according to Embodiment 5 of the present invention is focused at the optimal working object distance;

[0049] Figure 23 Schematically shows the MTF defocus graph of the imaging lens according to Embodiment 5 of the present invention at low temperature in the optimal working object distance state;

[0050] Figure 24 Schematically shows the MTF defocus graph of the imaging lens according to Embodiment 5 of the present invention at low and high temperatures in the optimal working object distance state;

[0051] Figure 25 Schematically shows the optical distortion graph of the imaging lens according to Embodiment 5 of the present invention. Detailed Embodiments

[0052] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or in the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0053] The present invention will be described in detail below in conjunction with the drawings and specific embodiments. The embodiments cannot be enumerated one by one here, but the embodiments of the present invention are not limited to the following embodiments.

[0054] Referring to Figure 1 As shown, the present invention provides an imaging lens, which includes a first lens group G1 with positive optical power, a diaphragm, and a second lens group G2 with positive optical power, which are arranged in sequence from the object side to the image side. Among them, the first transparent group G1 is a fixed group, and the second lens group is an internal focusing lens group. When imaging from an infinitely distant object to a near-distance object, the second transparent group G2 moves along the optical axis. The imaging lens of the present invention, by combining the first lens group G1 with positive optical power with the second lens group G2 with positive optical power, makes the imaging lens of the present invention conducive to reducing distortion.

[0055] In the present invention, the first lens group G1 includes at least two positive optical power lenses and two negative optical power lenses. And along the direction from the object side to the image side, the first lens of the first lens group G1 is a positive optical power lens, and the second lens is a negative optical power lens. According to an embodiment of the present invention, along the direction from the object side to the image side, the first lens of the first lens group G1 is a convex-convex lens or a convex-concave lens; the second lens is a concave-concave lens, a convex-concave lens or a plano-concave lens. In addition, in the present invention, the first lens group G1 includes at least one doublet lens, and at least one doublet lens has a convex or flat cemented surface. Along the direction from the object side to the image side, the doublet lens is composed of a lens with positive optical power and a lens with negative optical power or is composed of a lens with negative optical power and a lens with positive optical power.

[0056] For the imaging lens of the present invention, by arranging the first lens group G1 of the present invention in the above manner, the first lens group G1, as a fixed group, through the combination of the positive and negative optical powers of the first two lenses close to the object side, enables the imaging lens of the present invention to have the ability to converge large-angle light rays at the same time. And the setting of the doublet lens has a corrective effect on correcting the distortion, coma and chromatic aberration of the imaging system, and at the same time has a corrective effect on the tolerance sensitivity of the imaging system, so as to ensure that the optical system has an image quality and image plane consistency close to the diffraction limit.

[0057] In the imaging lens of the present invention, the second lens group G2 includes at least two positive-power lenses and one negative-power lens, and the lens closest to the image side in the second lens group G2 is a positive-power lens. Along the object side to the image side direction, the first lens in the second lens group G2 is a convex-convex lens, a concave-convex lens, or a plano-convex lens. The second lens group G2 includes at least one doublet lens group, and the doublet lens group is composed of a lens with positive power and a lens with negative power. According to an embodiment of the present invention, along the object side to the image side direction, the negative-power lens in the doublet lens of the second lens group G2 can be a concave-concave lens, a concave-convex lens, or a concave-plano lens.

[0058] For the imaging lens of the present invention, by arranging the second lens group G2 of the present invention according to the above limitations, through the combination of positive and negative powers and the setting of the doublet lens group, it is beneficial to correct spherical aberration, astigmatism, coma, and distortion inside the second lens group G2. The correction of the internal aberration of the second lens group G2 is beneficial to reducing the burden ratio of the first lens group G1 on aberration, and can better reduce the tolerance sensitivity of the focusing group, thereby greatly ensuring that the optical system has good image plane consistency and comprehensively improving the imaging quality of the optical system. The imaging lens of the present invention adopts an improved double Gauss structure and a structure similar to a reverse telephoto lens, which can well correct distortion, converge light rays, eliminate vignetting, and reduce spherical aberration.

[0059] For the imaging lens of the present invention, the focal length of the first lens group G1 is f G1 , and the focal length of the imaging lens is f, satisfying the relationship: 1.85 ≤ |f G1 / f| ≤ 4.50. Within the above relationship range, the optical system can quickly collect incident light, reduce field curvature and astigmatism, and at the same time achieve and maintain small distortion.

[0060] For the imaging lens of the present invention, the focal length f1 of at least one doublet lens in the first lens group G1 and the focal length f of the first lens group G1 G1 satisfy the relationship: 0.2 ≤ |f1 / f G1 | ≤ 6.5. Satisfying the above relationship is beneficial to correcting aberrations such as spherical aberration, astigmatism, coma, and distortion inside the entire lens group, and ensuring the imaging quality of the imaging lens of the present invention.

[0061] For the imaging lens of the present invention, the focal length of the second lens group G2 is f G2 , and the focal length of the imaging lens is f, satisfying the relationship: 0.53 ≤ |f G2| / f| ≤ 1.85. By satisfying the above relational expression and reasonably matching the positive and negative optical powers and the magnitudes of the optical powers of the first lens group G1 and the second lens group G2, the burden ratios of the first lens group G1 and the second lens group G2 on the back focal length and CRA can be balanced, which is beneficial to ensuring the focusing performance and a small incident angle of the chief ray on the image plane, thereby ensuring that the imaging system meets the high image quality requirements close to the diffraction limit.

[0062] For the imaging lens of the present invention, along the object side to the image side direction, the refractive index of the first positive optical power lens in the second lens group G2 is ND, and the Abbe number is VD, satisfying: 50 ≤ VD ≤ 96, 1.43 ≤ ND ≤ 1.70. By setting the refractive index and Abbe number of the first positive optical power lens in the second lens group in this way, the chromatic aberration of the imaging system can be effectively corrected, and the imaging quality of the imaging system can be improved. At the same time, this lens also bears most of the pressure for correcting the image plane stability of the imaging system in the non-constant temperature state, which is beneficial to ensuring the stability of the image plane of the imaging system in the non-constant temperature state.

[0063] For the imaging lens of the present invention, when the imaging lens images from an infinite object to a near object, the overall optical length is TTL, and the focal length of the imaging lens is f, satisfying: 3.0 ≤ TTL / f ≤ 4.0.

[0064] In summary, by setting the imaging lens of the present invention according to the above limitations, it can achieve low distortion, large depth of field, uniform image quality, good color restoration, high contrast, and a resolution of up to more than 12 million pixels. At the same time, it also has the characteristics of good image quality stability of the image in abnormal states such as high temperature and low temperature.

[0065] The following gives five specific embodiments according to the above settings of the present invention to specifically illustrate the imaging lens according to the present invention.

[0066] The data of the five embodiments are as follows in Table 1:

[0067]

[0068]

[0069] Table 1

[0070] Embodiment 1:

[0071] Figure 1 It schematically shows the structural diagram of the imaging lens according to Embodiment 1 of the present invention.

[0072] In Embodiment 1, the overall optical length of the optical system TTL = 50.9 mm, the system focal length f = 16 mm, the system imaging object distance range is 0.1 m - inf, the system picture size Y = 12 mm, and the F number FNO = 2.8.

[0073] The relevant parameters of each lens in the present embodiment are listed in Table 2 below, including surface type, radius of curvature, thickness, refractive index of the material, and Abbe number:

[0074] Surface number Surface type R value Thickness Refractive index Abbe number sur1 standard 80.45 2.24 1.70 50.34 sur2 standard -200.1 0.15 sur3 standard 85.5 1.5 1.55 60.5 sur4 standard 15.3 16.5 sur5 standard 20.45 1.95 1.85 42.5 sur6 standard 80.5 0.18 sur7 standard 14.5 5.1 1.43 90.0 sur8 standard -51.62 1.3 1.72 30.5 sur9 standard 8.51 2.24 Stop standard infinity 1.96 sur11 standard 540.16 1.26 1.43 96.0 sur12 standard -25.84 1.79 sur13 standard -8.34 1.56 1.70 35.5 sur14 standard -121.8 2.85 1.75 60.5 sur15 standard -11.1 0.3 sur16 standard 42.23 2.5 1.85 40.73 sur17 standard -25.12 8.5 Image plane ФI standard infinity

[0075] Table 2

[0076] Combined with Figure 1 As shown, in the present embodiment, the first lens group G1 includes five lenses (L1-L5), where lenses L4 and L5 are doublet lenses. The second lens group G2 includes four lenses (L6-L9), where lenses L7 and L8 are doublet lenses, and lenses L6 and L9 are positive power lenses.

[0077] Figures 2 - 5 Respectively schematically show the MTF graph when the imaging lens according to Embodiment 1 of the present invention is focused at the optimal working object distance, the MTF defocus graph at low temperature in the optimal working object distance state, the MTF defocus graph at high and low temperature in the optimal working object distance state, and the optical distortion graph. It can be known from the accompanying drawings that the imaging lens obtained according to Embodiment 1 of the present invention can achieve low distortion, large depth of field, uniform image quality, good color restoration, high contrast, and a resolution of up to more than 12 million pixels, and at the same time has good image quality stability in abnormal states such as high temperature and low temperature.

[0078] Embodiment 2:

[0079] Figure 6 Is a schematic structural diagram of an imaging lens according to Embodiment 2 of the present invention.

[0080] In Embodiment 2, the total optical system length TTL = 59 mm, the system focal length f = 16 mm, the system imaging object distance range is 0.1 m - inf, the system picture size Y = 14 mm, and the F number FNO = 2.4.

[0081] The relevant parameters of each lens in the present embodiment are listed in Table 3 below, including surface type, radius of curvature, thickness, refractive index of the material, and Abbe number:

[0082] Surface number Surface type R value Thickness Refractive index Abbe number sur1 standard 65.52 2.45 1.85 52.35 sur2 standard 180.57 0.1 sur3 standard 164.27 1.1 1.55 60.21 sur4 standard 16.52 17.53 sur5 standard 20.23 1.97 1.90 45.73 sur6 standard 82.5 0.53 sur7 standard 15.75 5.0 1.85 42.3 sur8 standard -46.78 1.35 1.75 30.12 Sur9 standard 10.46 2.3 Stop standard infinity 2.3 sur10 standard -210.01 1.38 1.63 52.6 sur11 standard -29.45 1.5 sur12 standard -8.62 2.2 1.76 25.5 sur13 standard 188.78 2.5 1.77 52.6 sur14 standard -11.18 0.1 sur15 standard 48.19 2.1 1.55 60.5 sur16 standard -33.56 14.0 Image plane ФI standard infinity

[0083] Table 3

[0084] Combined with Figure 6 As shown, in the present embodiment, the first lens group G1 includes five lenses (L1-L5), where lenses L4 and L5 are doublet lenses. The second lens group G2 includes four lenses (L6-L9), where lenses L7 and L8 are doublet lenses, and lenses L6 and L9 are positive power lenses.

[0085] Figures 7 - 10 Schematically show the MTF graph when the imaging lens according to Embodiment 2 of the present invention is focused at the optimal working object distance, the MTF defocus graph in the low-temperature state at the optimal working object distance, the MTF defocus graph in the low-high temperature state at the optimal working object distance, and the optical distortion graph. It can be seen from the accompanying drawings that the imaging lens obtained according to Embodiment 2 of the present invention can achieve low distortion, large depth of field, uniform image quality, good color restoration, high contrast, and a resolution of up to more than 12 million pixels, and at the same time has good image quality stability in abnormal states such as high temperature and low temperature.

[0086] Embodiment 3:

[0087] Figure 11 Schematically show the structural diagram of the imaging lens according to Embodiment 3 of the present invention.

[0088] In Embodiment 3, the total optical system length TTL = 54 mm, the system focal length f = 16 mm, the system imaging object distance range is 0.1 m - inf, the system image frame Y = 14 mm, and the F number FNO = 2.5.

[0089] The following Table 4 lists the relevant parameters of each lens in this embodiment, including the surface type, radius of curvature, thickness, refractive index of the material, and Abbe number:

[0090] Surface number Surface type R value Thickness Refractive index Abbe number sur1 standard 280.8 1.90 1.52 65.21 sur2 standard -115.9 0.1 sur3 standard 33.66 1.2 1.73 56.82 sur4 standard 15.31 15.71 sur5 standard 20.35 2.5 1.85 45.73 sur6 standard -765.5 3.24 sur7 standard 10.18 2.5 1.63 64.45 sur8 standard infinity 1.12 1.65 34.85 sur9 standard 7.5 2.13 Stop standard infinity 3.51 sur11 standard -9.51 0.52 1.75 30.27 sur12 standard -120.09 2.07 1.65 50.0 sur13 standard -10.3 0.1 sur14 standard 22.38 2.25 1.73 55.75 sur15 standard -35.32 14.45 Image plane ФI standard infinity

[0091] Table 4

[0092] Combined with Figure 11 As shown, in this embodiment, the first lens group G1 includes 5 lenses (L1 - L5), where lenses L4 and L5 are doublet lenses. The second lens group G2 includes 3 lenses (L6 - L8), where lenses L6 and L7 are doublet lenses, and lens L8 is a positive focal length lens.

[0093] Figures 12 - 15 Schematically show the MTF graph when the imaging lens according to Embodiment 3 of the present invention is focused at the optimal working object distance, the MTF defocus graph in the low-temperature state at the optimal working object distance, the MTF defocus graph in the low-high temperature state at the optimal working object distance, and the optical distortion graph. It can be seen from the accompanying drawings that the imaging lens obtained according to Embodiment 3 of the present invention can achieve low distortion, large depth of field, uniform image quality, good color restoration, high contrast, and a resolution of up to more than 12 million pixels, and at the same time has good image quality stability in abnormal states such as high temperature and low temperature.

[0094] Embodiment 4:

[0095] Figure 11 Schematically show the structural diagram of the imaging lens according to Embodiment 4 of the present invention.

[0096] In Embodiment 4, the total optical system length TTL = 60 mm, the system focal length f = 15 mm, the object distance range for system imaging is 0.1 m - inf, the system image size Y = 12 mm, and the F - number FNO = 2.6.

[0097] The following Table 5 lists the relevant parameters of each lens in this embodiment, including surface type, radius of curvature, thickness, refractive index of the material, and Abbe number:

[0098] Surface number Surface type R value Thickness Refractive index Abbe number sur1 standard 75 2.95 1.80 45.73 sur2 standard -45.21 1.5 1.65 37.75 sur3 standard 14.13 18.65 sur4 standard 19.7 3.0 1.90 35.40 sur5 standard -235.7 1.05 sur6 standard 13.5 3.65 1.72 65.65 sur7 standard -36.33 1.32 1.50 32.35 sur8 standard 8.5 2.42 Stop standard infinity 3.14 sur11 standard 118.5 1.32 1.65 50.71 sur12 standard -36.28 0.88 sur13 standard -9.52 1.3 1.75 36.35 sur14 standard 16.42 2.75 1.55 50.61 sur15 standard -16.32 0.9 sur16 standard 30.4 1.2 1.55 63.12 sur17 standard -21.1 13.8 Image plane ФI standard infinity

[0099] Table 5

[0100] Combined with Figure 16 As shown, in this embodiment, the first lens group G1 includes 5 lenses (L1 - L5), where lenses L1 and L2, and lenses L4 and L5 are doublet lenses. The second lens group G2 includes 4 lenses (L6 - L9), where lenses L7 and L8 are doublet lenses, and lenses L6 and L9 are positive - power lenses.

[0101] Figures 17 - 20 Respectively, they schematically show the MTF graph when the imaging lens according to Embodiment 4 of the present invention is focused at the optimal working object distance, the MTF defocus graph at low - temperature state with the optimal working object distance, the MTF defocus graph at high - temperature state with the optimal working object distance, and the optical distortion graph. Combining with the attached drawings, it can be known that the imaging lens obtained according to Embodiment 4 of the present invention can achieve low distortion, large depth of field, uniform image quality, good color restoration, high contrast, and a resolution of up to more than 12 million pixels, and at the same time has the characteristic of good image quality stability in abnormal states such as high temperature and low temperature.

[0102] Embodiment 5:

[0103] Figure 21 It is a schematic structural diagram of the imaging lens according to Embodiment 5 of the present invention.

[0104] In Embodiment 5, the total optical system length TTL = 58 mm, the system focal length f = 17 mm, the object distance range for system imaging is 0.1 m - inf, the system image size Y = 12 mm, and the F - number FNO = 2.86.

[0105] The following Table 6 lists the relevant parameters of each lens in this embodiment, including surface type, radius of curvature, thickness, refractive index of the material, and Abbe number:

[0106] Surface number Surface type R value Thickness Refractive index Abbe number sur1 standard 51.98 2.78 1.62 58.7 sur2 standard -85.23 2.86 sur3 standard -283.75 0.90 1.51 65.2 sur4 standard 12.57 14.35 sur5 standard 17.5 2.50 1.70 55.12 sur6 standard 360.2 0.15 sur7 standard 9.55 4.01 1.72 54.57 sur8 standard -45.35 0.65 1.60 35.35 sur9 standard 6.58 1.75 Stop standard infinity 4.25 sur11 standard infinity 1.35 1.70 55.0 sur12 standard -18.19 1.12 sur13 standard -7.5 0.6 1.60 36.45 sur14 standard infinity 2.75 1.70 54.6 sur15 standard -8.97 0.15 sur16 standard 23.73 2.48 1.52 63.12 sur17 standard infinity 15.2 Image plane ФI standard infinity

[0107] Table 6

[0108] Combined with Figure 21As shown, in this embodiment, the first lens group G1 includes five lenses (L1-L5), wherein lenses L4 and L5 are doublet lenses. The second lens group G2 includes four lenses (L6-L9), wherein lenses L7 and L8 are doublet lenses, and lenses L6 and L9 are positive power lenses.

[0109] Figures 22 - 25 Schematically show the MTF graph when the imaging lens according to Embodiment 5 of the present invention is focused at the optimal working object distance, the MTF defocus graph at low temperature in the optimal working object distance state, the MTF defocus graph at high and low temperature in the optimal working object distance state, and the optical distortion graph respectively. It can be seen from the accompanying drawings that the imaging lens obtained according to Embodiment 5 of the present invention can achieve low distortion, large depth of field, uniform image quality, good color restoration, high contrast, and a resolution of up to more than 12 million pixels, and at the same time has the characteristics of good image quality stability in abnormal states such as high temperature and low temperature.

[0110] The above description is only one embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. An imaging lens, characterized in that, it includes a first lens group (G1) with positive optical power, a diaphragm, and a second lens group (G2) with positive optical power, which are arranged in sequence from the object side to the image side, totaling two lens groups. The first lens group (G1) is a fixed group, and the second lens group (G2) is a focusing lens group that can move along the optical axis; Along the direction from the object side to the image side, the first lens group (G1) includes a first lens with positive optical power, a second lens with negative optical power, a third lens with positive optical power, a fourth lens with positive optical power, and a fifth lens with negative optical power, totaling five lenses; The second lens group (G2) includes a sixth lens with positive optical power, a seventh lens with negative optical power, an eighth lens with positive optical power, and a ninth lens with positive optical power, totaling four lenses, or The second lens group (G2) includes a sixth lens with negative optical power, a seventh lens with positive optical power, and an eighth lens with positive optical power, totaling three lenses.

2. The imaging lens according to claim 1, characterized in that, Along the direction from the object side to the image side, the first lens of the first lens group (G1) is a convex-convex lens or a convex-concave lens; The second lens is a concave-concave lens, a convex-concave lens, or a plano-concave lens.

3. The imaging lens according to claim 1 or 2, characterized in that, The first lens group (G1) includes at least one doublet lens.

4. The imaging lens according to claim 3, characterized in that, The cemented surface of at least one doublet lens in the first lens group (G1) is a convex surface or a plane surface.

5. The imaging lens according to claim 4, characterized in that, Along the direction from the object side to the image side, the doublet lens in the first lens group (G1) is composed of a lens with positive optical power and a lens with negative optical power.

6. The imaging lens according to claim 1, characterized in that, Along the direction from the object side to the image side, the first lens of the second lens group (G2) is a convex-convex lens, a concave-convex lens, or a plano-convex lens.

7. The imaging lens according to claim 1 or 6, characterized in that, The second lens group (G2) includes at least one doublet lens group, and the doublet lens group is composed of a lens with positive optical power and a lens with negative optical power.

8. The imaging lens according to claim 7, characterized in that, Along the direction from the object side to the image side, the lens with negative optical power in the doublet lens of the second lens group (G2) is a concave-concave lens, a concave-convex lens, or a concave-plano lens.

9. The imaging lens according to claim 1 or 5, characterized in that, The focal length of the first lens group (G1) is f G1 , the focal length of the imaging lens is f, and the following relationship is satisfied: 1.85 ≤ |f G1 / f| ≤ 4.

50.

10. The imaging lens according to claim 9, characterized in that, The focal length f1 of at least one doublet lens in the first lens group (G1) and the focal length f of the first lens group (G1) G1 satisfy the relationship: 0.2 ≤ |f1 / f G1 | ≤ 6.

5.

11. The imaging lens according to claim 1 or 8, characterized in that, The focal length of the second lens group (G2) is f G2 , the focal length of the imaging lens is f, and the following relationship is satisfied: 0.53 ≤ |f G2 / f| ≤ 1.

85.

12. The imaging lens according to claim 8, characterized in that, Along the direction from the object side to the image side, the refractive index of the first positive-optical-power lens in the second lens group (G2) is ND, and the Abbe number is VD, satisfying: 50 ≤ VD ≤ 96, 1.43 ≤ ND ≤ 1.

70.

13. The imaging lens according to claim 1, wherein, when the imaging lens images from an infinite object to a close object, the overall optical length is TTL, and the focal length of the imaging lens is f, satisfying: 3.0 ≤ TTL / f ≤ 4.0.

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