CN212302051U

CN212302051U - Imaging lens

Info

Publication number: CN212302051U
Application number: CN202022162915.6U
Authority: CN
Inventors: 周静; 胡可欣; 刘保东
Original assignee: Sunny Optics Zhongshan Co Ltd
Current assignee: Sunny Optics Zhongshan Co Ltd
Priority date: 2020-09-28
Filing date: 2020-09-28
Publication date: 2021-01-05
Anticipated expiration: 2030-09-28

Abstract

The utility model relates to an imaging lens, include along the first lens battery (G1) that has positive focal power, diaphragm, second lens battery (G2) that have positive focal power and third lens battery (G3) that has positive focal power or negative focal power that the thing side sets gradually to image side, third lens battery (G3) is fixed group, first lens battery (G1) with the focus group that can follow the optical axis removal is constituteed to second lens battery (G2). The utility model discloses an imaging lens sets up according to the injecing more than, can realize that big light ring, high resolution, low distortion, image quality are even, the big depth of field, the color reduction degree is good, the characteristic that the contrast is high.

Description

Imaging lens

Technical Field

The utility model relates to an optical device field especially relates to an imaging lens.

Background

Machine vision means that a robot replaces human eyes to measure and judge, a shot target is converted into an image signal and transmitted to a special image processing system to obtain form information of the shot target, and the form information is converted into a digital signal according to information such as pixel distribution, brightness, color and the like; the image system performs various operations on the signals to extract the characteristics of the target, such as position, size, appearance and the like, and then outputs the result according to preset conditions to realize the functions of automatic identification, judgment, measurement and the like.

Therefore, imaging systems for machine vision have very high requirements on pixels, picture uniformity, distortion, brightness, color rendition, etc. However, the machine vision lens on the market at present has small optical magnification, small imaging frame, large distortion, uneven picture definition, small range of working object distance and the like, and although the machine vision lens has wide shooting range, the machine vision lens has the defects of insufficient imaging fineness, low dynamic range during imaging and insufficient color and contrast.

Along with the wider and wider application range of machine vision, the requirements on a machine vision imaging system are higher and higher, machine vision lenses on the market at present cannot meet the market demands more and more, and are particularly severely limited in some high-precision high-tech fields with higher imaging quality requirements.

SUMMERY OF THE UTILITY MODEL

An object of the utility model is to solve above-mentioned problem, provide an imaging lens that big light ring, high resolution, low distortion, image quality are even, big depth of field, color reduction degree are good, the contrast is high.

In order to realize the objective of the present invention, the present invention provides an imaging lens, including a first lens set with positive focal power, a diaphragm, a second lens set with positive focal power and a third lens set with positive focal power or negative focal power, which are sequentially arranged from an object side to an image side, wherein the third lens set is a fixed set, and the first lens set and the second lens set form a focusing set capable of moving along an optical axis.

According to an aspect of the present invention, the first lens group includes at least two positive power lenses and one negative power lens, and a lens closest to the object side in the first lens group is the positive power lens, and a lens closest to the image side is the negative power lens.

According to an aspect of the present invention, in a direction from the object side to the image side, a lens closest to the object side in the first lens group is one of a biconvex lens, a convex-concave lens, or a convex-flat lens.

According to an aspect of the present invention, the first lens group includes a double cemented lens along the direction from the object side to the image side, and the double cemented lens is formed by combining a positive power lens and a negative power lens.

According to an aspect of the utility model, the refracting index of positive power lens among the two cemented lenses in the first lens group is ND, and the abbe number is VD, satisfies: VD is more than or equal to 60 and less than or equal to 96, ND is more than or equal to 1.43 and less than or equal to 1.65.

According to an aspect of the present invention, the second lens group includes at least two positive power lenses and one negative power lens, and the lens closest to the object side in the second lens group is the negative power lens, and the lens closest to the image side is the positive power lens.

According to an aspect of the present invention, in a direction from the object side to the image side, a lens closest to the image side in the second lens group is one of a biconvex lens, a meniscus lens, or a plano-convex lens.

According to an aspect of the present invention, the second lens group includes a double cemented lens along the direction from the object side to the image side, and the double cemented lens is formed by combining a negative power lens and a positive power lens.

According to an aspect of the present invention, the third lens group includes at least one positive power lens and one negative power lens, and along the direction from the object side to the image side, the two lenses close to the object side in the third lens group are arranged in the order of the positive power lens, the negative power lens or the order of the negative power lens and the positive power lens.

According to an aspect of the present invention, the positive power lens in the third lens group is one of a biconvex lens, a convex-concave lens or a convex-flat lens, and the negative power lens is one of a biconcave lens, a concave-convex lens or a convex-concave lens.

According to the utility model discloses an aspect, the focus of the group of focusing that first battery of lens, diaphragm and second battery of lens are constituteed is fm, imaging lens's focus is f, satisfies the relational expression: fm/f is more than or equal to 1.0 and less than or equal to 1.5.

According to an aspect of the present invention, the focal length of the third lens group is fg3, the focal length of the imaging lens is f, satisfying: the | fg3/f | is more than or equal to 3.5 and less than or equal to 8.5.

According to the utility model discloses an aspect, imaging lens's optical total length is TTL, imaging lens's focus is f, satisfies that TTL/f is not less than 1.35 and is not less than 1.75.

The utility model discloses an imaging lens adopts focal power to be positive first lens system, and collocation focal power is positive second lens system, and the focal power of deuterogamying is positive or negative third lens system for this imaging system possess littleer distortion and littleer chromatic dispersion.

The utility model discloses an imaging lens, first lens system include two piece at least positive focal power lenses and a piece negative focal power lens to the lens that is closest to the thing side in the first lens system is positive focal power lens, and the lens that is closest to the picture side is negative focal power lens. By the arrangement, the matched use of the positive and negative focal powers is beneficial to correcting spherical aberration, astigmatism and distortion in the first lens group, and is beneficial to realizing large aperture and reducing tolerance sensitivity in the group.

The utility model discloses an imaging lens, including a doublet cemented lens in the first lens group, along thing side to image side direction, doublet cemented lens forms for positive focal power lens and negative focal power lens combination. So set up for two cemented lens match suitable focal power, have the correction effect to correcting optical system's distortion, coma and lateral chromatic aberration, thereby can guarantee that optical system has the image quality and the image plane uniformity that are close to diffraction limit.

The utility model discloses an imaging lens, positive focal power lens's among the double-cemented lens in the first lens group refracting index is ND, and the abbe number is VD, satisfies: VD is more than or equal to 60 and less than or equal to 96, ND is more than or equal to 1.43 and less than or equal to 1.65. The condition is met, the focal power and the Abbe number are reasonably matched, the chromatic aberration of the imaging system can be effectively corrected, and the imaging quality of the imaging system is improved. Meanwhile, the lens greatly contributes to maintaining the stability of the image plane of the imaging system in an extremely warm state.

The utility model discloses an imaging lens, including a doublet cemented lens in the second lens system, along thing side to image side direction, doublet cemented lens forms for negative focal power lens and positive focal power lens combination. The use of the double-cemented lens is matched with proper focal power and matched with the first lens group, so that the spherical aberration, astigmatism, coma and distortion in the focusing lens group can be corrected. Meanwhile, the burden proportion of the first lens group to aberration correction is reduced, and the tolerance sensitivity of the movable group can be better reduced, so that the optical system is greatly ensured to have good image plane consistency. The imaging quality of the optical system is comprehensively improved.

The utility model discloses an imaging lens satisfies the relational expression: 1.0-fm/f-1.5, so that the optical system can realize and maintain smaller distortion while rapidly collecting incident light and reducing field curvature and astigmatism.

The utility model discloses an imaging lens satisfies: the absolute value of fg3/f is more than or equal to 3.5 and less than or equal to 8.5, the burden proportion of the first lens group and the second lens group of the optical system on aberration correction can be balanced by reasonably matching the positive and negative focal powers and the focal powers of the first lens group and the second lens group, the focusing performance can be favorably ensured, and the imaging system can be better ensured to meet the high image quality requirement close to the diffraction limit.

The utility model discloses an imaging lens sets up according to the injecing more than, can realize that big light ring, high resolution, low distortion, image quality are even, the big depth of field, the color reduction degree is good, the characteristic that the contrast is high.

Drawings

Fig. 1 schematically shows a schematic structural view of an imaging lens according to embodiment 1 of the present invention;

fig. 2 schematically shows an MTF chart when the best working object distance of the imaging lens according to embodiment 1 of the present invention is focused;

fig. 3 schematically shows an MTF defocus diagram of an imaging lens in an optimal working object distance low temperature state according to embodiment 1 of the present invention;

fig. 4 schematically shows an MTF defocus diagram of an imaging lens in an optimal working object distance high temperature state according to embodiment 1 of the present invention;

fig. 5 schematically shows an optical distortion diagram of an imaging lens according to embodiment 1 of the present invention;

fig. 6 schematically shows a schematic structural view of an imaging lens according to embodiment 2 of the present invention;

fig. 7 schematically shows an MTF chart when the best working object distance of the imaging lens according to embodiment 2 of the present invention is focused;

fig. 8 schematically shows an MTF defocus diagram of an imaging lens in an optimal working object distance low temperature state according to embodiment 2 of the present invention;

fig. 9 schematically shows an MTF defocus diagram of an imaging lens in an optimal working object distance high temperature state according to embodiment 2 of the present invention;

fig. 10 schematically shows an optical distortion diagram of an imaging lens according to embodiment 2 of the present invention;

fig. 11 schematically shows a schematic structural view of an imaging lens according to embodiment 3 of the present invention;

fig. 12 schematically shows an MTF chart when the best working object distance of the imaging lens according to embodiment 3 of the present invention is focused;

fig. 13 schematically shows an MTF defocus diagram of an imaging lens in an optimal working object distance low temperature state according to embodiment 3 of the present invention;

fig. 14 schematically shows an MTF defocus diagram of an imaging lens in an optimal working object distance high temperature state according to embodiment 3 of the present invention;

fig. 15 schematically shows an optical distortion diagram of an imaging lens according to embodiment 3 of the present invention;

fig. 16 is a schematic structural view of an imaging lens according to embodiment 4 of the present invention;

fig. 17 schematically shows an MTF chart when the best working object distance of the imaging lens according to embodiment 4 of the present invention is focused;

fig. 18 schematically shows an MTF defocus diagram of an imaging lens in an optimal working object distance low temperature state according to embodiment 4 of the present invention;

fig. 19 schematically shows an MTF defocus diagram of an imaging lens in an optimal working object distance high temperature state according to embodiment 4 of the present invention;

fig. 20 schematically shows an optical distortion diagram of an imaging lens according to embodiment 4 of the present invention;

fig. 21 is a schematic structural view of an imaging lens according to embodiment 5 of the present invention;

fig. 22 schematically shows an MTF chart when the best working object distance of the imaging lens according to embodiment 5 of the present invention is focused;

fig. 23 schematically shows MTF defocus diagrams of an imaging lens in an optimal working object distance low temperature state according to embodiment 5 of the present invention;

fig. 24 schematically shows an MTF defocus diagram of an imaging lens in an optimal working object distance high temperature state according to embodiment 5 of the present invention;

fig. 25 schematically shows an optical distortion diagram of an imaging lens according to embodiment 5 of the present invention.

Detailed Description

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the embodiments will be briefly described below. It is obvious that the drawings in the following description are only some embodiments of the invention, and that for a person skilled in the art, other drawings can be derived from them without inventive effort.

The present invention will be described in detail with reference to the accompanying drawings and specific embodiments, which are not repeated herein, but the present invention is not limited to the following embodiments.

Referring to fig. 1, the present invention provides an imaging lens including a first lens group G1 having positive refractive power, a diaphragm, a second lens group G2 having positive refractive power, and a third lens group G3 having positive or negative refractive power, which are disposed in order from an object side to an image side. The third lens group G3 is a fixed group, and the first lens group G1, the stop and the second lens group G2 form a focusing group, which can move along the optical axis when imaging from an infinite object to a close object. The utility model discloses an imaging lens adopts focal power to be positive first lens group G1, and collocation focal power is positive second lens group G2, deuterogamies focal power and is positive or negative third lens group G3 for this imaging system possess littleer distortion and littleer chromatic dispersion.

In the present invention, the first lens group G1 includes at least two positive power lenses and one negative power lens, and the lens closest to the object side in the first lens group G1 is a positive power lens, and the lens closest to the image side is a negative power lens.

By the arrangement, the spherical aberration, astigmatism and distortion in the first lens group G1 can be corrected by matching the positive and negative focal powers, the large aperture can be realized, and meanwhile, the tolerance sensitivity in the group can be reduced.

According to an embodiment of the present invention, a lens closest to the object side in the first lens group G1 is one of a biconvex lens, a convex-concave lens, or a convex-flat lens in a direction from the object side to the image side.

In the present invention, the first lens group G1 includes a double cemented lens, which is formed by combining a positive focal power lens and a negative focal power lens along the direction from the object side to the image side. So set up for two cemented lens match suitable focal power, have the correction effect to correcting optical system's distortion, coma and lateral chromatic aberration, thereby can guarantee that optical system has the image quality and the image plane uniformity that are close to diffraction limit.

The utility model discloses in, positive focal power lens's among the two cemented lens in the first lens group G1 refracting index is ND, and the abbe number is VD, satisfies: VD is more than or equal to 60 and less than or equal to 96, ND is more than or equal to 1.43 and less than or equal to 1.65. The condition is met, the focal power and the Abbe number are reasonably matched, the chromatic aberration of the imaging system can be effectively corrected, and the imaging quality of the imaging system is improved. Meanwhile, the lens greatly contributes to maintaining the stability of the image plane of the imaging system in an extremely warm state.

In 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 object side in the second lens group G2 is the negative power lens, and the lens closest to the image side is the positive power lens. In the object-to-image direction, the lens closest to the image side in the second lens group G2 is one of a biconvex lens, a meniscus lens, or a plano-convex lens. The second lens group G2 includes a double cemented lens formed by a combination of a negative power lens and a positive power lens along the object-to-image direction. The use of the double-cemented lens is matched with proper focal power and matched with the first lens group, so that the spherical aberration, astigmatism, coma and distortion in the focusing lens group can be corrected. Meanwhile, the burden proportion of the first lens group G1 on aberration correction is reduced, the tolerance sensitivity of the movable group can be better reduced, and the optical system is greatly ensured to have good image plane consistency. The imaging quality of the optical system is comprehensively improved.

In the present invention, the third lens group G3 includes at least one positive focal power lens and one negative focal power lens, and two lenses close to the object side in the third lens group G3 are arranged in the order of the positive focal power lens and the negative focal power lens or in the order of the negative focal power lens and the positive focal power lens along the direction from the object side to the image side. The positive power lens in the third lens group G3 is one of a biconvex lens, a convex-concave lens, or a convex-flat lens, and the negative power lens is one of a biconcave lens, a convex-concave lens, or a convex-concave lens.

The utility model discloses an imaging lens, according to the above-mentioned setting of injecing the utility model discloses a first lens group G1, second lens group G2 and third lens group G3, thereby make the utility model discloses an imaging lens's imaging system forms the gauss structure, can rectify the distortion well, receive and restraint light, eliminates the vignetting, reduces the spherical aberration.

The utility model discloses in, the focus of the group of focusing that first lens group G1, diaphragm and second lens group G2 constitute is fm, and imaging lens's focus is f, satisfies the relational expression: fm/f is more than or equal to 1.0 and less than or equal to 1.5. Within the above relationship, the optical system is able to achieve and maintain less distortion while collecting incident light rays quickly, reducing curvature of field and astigmatism.

The utility model discloses in, the focus of third lens group G3 is fg3, and imaging lens's focus is f, satisfies: the | fg3/f | is more than or equal to 3.5 and less than or equal to 8.5. The limitation of the relational expression is met, the burden proportion of the first lens group G1 and the second lens group G2 of the optical system on aberration correction can be balanced by reasonably matching the positive and negative focal powers and the focal powers of the first lens group G1 and the second lens group G2, the focusing performance can be favorably ensured, and the imaging system can be better ensured to meet the high image quality requirement close to the diffraction limit.

Furthermore, the utility model discloses in, imaging lens's optical total length is TTL, and imaging lens's focus is f, satisfies that TTL/f is not less than 1.35 and is not less than 1.75.

To sum up, the utility model discloses an imaging lens sets up according to the above injecing, can realize that big light ring, high resolution, low distortion, image quality are even, and big depth of field, the color reduction degree is good, the characteristic that the contrast is high.

The imaging lens according to the present invention is specifically described below by giving five groups of embodiments according to the above-described arrangement of the present invention.

Five sets of embodiment data are as in table 1 below:

conditional formula (II)	Example 1	Example 2	Example 3	Example 4	Example 5
						1.0≤fm/f≤1.5	1.0	1.3	1.28	1.5	1.38
3.5≤\|fg3/f\|≤8.5	3.5	4.2	4.5	6.8	8.45
						1.35≤TTL/f≤1.75	1.71	1.64	1.58	1.39	1.56
60≤VD≤96	68	75	80	96	68
						1.43≤ND≤1.65	1.60	1.55	1.50	1.43	1.55

TABLE 1

The first implementation mode comprises the following steps:

fig. 1 is a schematic diagram illustrating an imaging lens structure according to a first embodiment of the present invention.

In the first embodiment, the total optical system length TTL is 42.9mm, the system focal length F is 25.1mm, the system imaging object distance range is 0.15m to inf, the system frame Y is 12mm, and the F number FNO is 3.1.

Table 2 below lists relevant parameters of each lens of the present embodiment, including surface type, radius of curvature, thickness, refractive index of material, abbe number:

number of noodles	Surface type	R value	Thickness of	Refractive index	Abbe number
						sur1	standard	20.54	2.35	1.85	52.35
sur2	standard	52.41	0.5
						sur3	standard	8.45	2.95	1.6	68.0
sur4	standard	25.71	1.2	1.58	46.17
						sur5	standard	6.88	5.57
Stop	standard	infinity	3.15
						Sur7	standard	-8.84	0.8	1.68	33.85
Sur8	standard	-45.37	2.5	1.76	50.35
						Sur9	standard	-8.34	0.3
Sur10	standard	75.35	1.7	1.76	50.35
						sur11	standard	-45.65	3.13
sur12	standard	30.22	1.6	1.68	35.85
						sur13	standard	18.34	0.5
sur14	standard	25.73	3.5	1.64	60.4
						sur15	standard	95.37	13.1
Image plane phi I	standard	infinity	-

TABLE 2

In the present embodiment, as shown in fig. 1, the first lens group G1 includes 3 lenses (L1-L3), wherein the lens L2 and the lens L3 form a double cemented lens. The second lens group G2 comprises 3 lenses (L4-L6), wherein the lens L4 and the lens L5 are double cemented lenses. The third lens group G3 includes 2 lenses (L7 and L8).

Fig. 2 to 5 schematically show an MTF chart, an MTF defocus chart in a low temperature state, an MTF defocus chart in a high temperature state, and an optical distortion chart in focusing of the optimal working object distance of the imaging lens according to embodiment 1 of the present invention. Can learn in combination with the attached drawing, according to the utility model discloses the imaging lens who obtains according to embodiment 1 realizes that big light ring, high resolution, low distortion, image quality are even, and big depth of field, the color reduction degree is good, the characteristic that the contrast is high.

The second embodiment:

fig. 6 is a view schematically showing the structure of an imaging lens according to the second embodiment of the present invention.

In the second embodiment, the total optical system length TTL is 43.5mm, the system focal length F is 26.4mm, the system imaging object distance range is 0.15m to inf, the system frame Y is 12.5mm, and the F number FNO is 2.5.

Table 3 below lists relevant parameters of each lens of the present embodiment, including surface type, radius of curvature, thickness, refractive index of material, abbe number:

number of noodles	Surface type	R value	Thickness of	Refractive index	Abbe number
						sur1	standard	22.5	2.45	1.78	60.23
sur2	standard	64.2	0.15
						sur3	standard	10.73	3.56	1.55	75.0
sur4	standard	-54.07	2.0	1.58	49.2
						sur5	standard	8.83	2.38
Stop	standard	infinity	4.80
						Sur7	standard	-10.24	1.2	1.65	33.84
Sur8	standard	43.81	3.88	1.79	47.52
						Sur9	standard	-12.91	0.15
Sur10	standard	infinity	2.2	1.65	50.12
						sur11	standard	-26.12	2.61
sur12	standard	108.75	2.0	1.72	49.61
						sur13	standard	15.68	1.13
sur14	standard	20.51	4.9	1.80	46.57
						sur15	standard	infinity	9.6
Image plane phi I	standard	infinity	-

TABLE 3

Referring to fig. 6, in the present embodiment, the first lens group G1 includes 3 lenses (L1-L3), wherein the lens L2 and the lens L3 form a double cemented lens. The second lens group G2 comprises 3 lenses (L4-L6), wherein the lens L4 and the lens L5 are double cemented lenses. The third lens group G3 includes 2 lenses (L7 and L8).

Fig. 7 to 10 schematically show an MTF chart, an MTF defocus chart in a low temperature state, an MTF defocus chart in a high temperature state, and an optical distortion chart in focusing of the optimal working object distance of the imaging lens according to embodiment 2 of the present invention. Can learn in combination with the attached drawing, according to the utility model discloses the imaging lens who obtains according to the embodiment 2 realizes that big light ring, high resolution, low distortion, image quality are even, and big depth of field, the color reduction degree is good, the characteristic that the contrast is high.

The third embodiment is as follows:

fig. 11 is a view schematically showing the configuration of an imaging lens according to a third embodiment of the present invention.

In the third embodiment, the total optical system length TTL is 53.00mm, the system focal length F is 33.5mm, the system imaging object distance range is 0.15m to inf, the system frame Y is 11.5mm, and the F number FNO is 2.6.

Table 4 below lists relevant parameters of each lens of the present embodiment, including surface type, radius of curvature, thickness, refractive index of material, abbe number:

number of noodles	Surface type	R value	Thickness of	Refractive index	Abbe number
						sur1	standard	35.02	4.2	1.85	37.5
sur2	standard	165.14	0.2
						sur3	standard	18.2	4.1	1.50	80.2
sur4	standard	infinity	3.85	1.70	35.15
						sur5	standard	13.5	4.89
Stop	standard	infinity	4.5
						Sur7	standard	-15.75	2.54	1.62	36.35
Sur8	standard	96.57	2.35	1.76	53.34
						Sur9	standard	-25.26	0.2
Sur10	standard	79.25	3.82	1.90	40.2
						Sur11	standard	-82.35	5.45
Sur12	standard	45.47	3.62	1.78	50.61
						sur13	standard	-45.28	2.08
sur14	standard	-35.03	1.1	1.62	45.35
						sur15	standard	38.13	10.3
Image plane phi I	standard	infinity	-

TABLE 4

As shown in fig. 11, in the present embodiment, the first lens group G1 includes 3 lenses (L1-L3), wherein the lens L2 and the lens L3 form a double cemented lens. The second lens group G2 comprises 3 lenses (L4-L6), wherein the lens L4 and the lens L5 are double cemented lenses. The third lens group G3 includes 2 lenses (L7 and L8).

Fig. 12 to 15 schematically show an MTF chart, an MTF defocus chart in a low temperature state, an MTF defocus chart in a high temperature state, and an optical distortion chart in focusing of the optimal working object distance of the imaging lens according to embodiment 3 of the present invention. Can learn in combination with the attached drawing, according to the utility model discloses the imaging lens who obtains realizes big light ring, high resolution, low distortion, the image quality is even, and big depth of field, the color reduction degree is good, the characteristic that the contrast is high.

The fourth embodiment:

fig. 16 is a view schematically showing the configuration of an imaging lens according to a fourth embodiment of the present invention.

In the fourth embodiment, the total optical system length TTL is 49.1mm, the system focal length F is 35.1mm, the system imaging object distance range is 0.15m to inf, the system frame Y is 12mm, and the F number FNO is 2.8.

Table 5 below lists relevant parameters of each lens of the present embodiment, including surface type, radius of curvature, thickness, refractive index of material, abbe number:

number of noodles	Surface type	R value	Thickness of	Refractive index	Abbe number
						sur1	standard	27.5	2.12	1.85	43.5
sur2	standard	-80.2	0.2
						sur3	standard	14.035	3.7	1.43	96.0
sur4	standard	infinity	3.0	1.85	35.4
						sur5	standard	10.08	3.5
Stop	standard	infinity	3.6
						Sur7	standard	-15.2	1.45	1.70	31.25
Sur8	standard	-30.1	1.90	1.78	45.21
						Sur9	standard	-14.2	0.21
Sur10	standard	35.7	1.78	1.75	50.34
						Sur11	standard	-402.2	6.85
sur12	standard	-153.06	1.5	1.82	30.1
						sur13	standard	-21.1	3.78
sur14	standard	-25.8	1.2	1.78	23.5
						sur15	standard	-300.5	13.4
Image plane phi I	standard	infinity	-

TABLE 5

Referring to fig. 16, in the present embodiment, the first lens group G1 includes 3 lenses (L1-L3), wherein the lens L2 and the lens L3 form a double cemented lens. The second lens group G2 comprises 3 lenses (L4-L6), wherein the lens L4 and the lens L5 are double cemented lenses. The third lens group G3 includes 2 lenses (L7 and L8).

Fig. 17 to 20 schematically show an MTF chart, an MTF defocus chart in a low temperature state, an MTF defocus chart in a high temperature state, and an optical distortion chart in focusing of the optimal working object distance of the imaging lens according to embodiment 4 of the present invention. Can learn in combination with the attached drawing, according to the utility model discloses the imaging lens who obtains, realize big light ring, high resolution, low distortion, the image quality is even, and big depth of field, the color reduction degree is good, the characteristic that the contrast is high.

The fifth embodiment:

fig. 21 is a view schematically showing an imaging lens structure according to a fifth embodiment of the present invention.

In the fifth embodiment, the total optical system length TTL is 47.83mm, the system focal length F is 30.6mm, the system imaging object distance range is 0.15m to inf, the system frame Y is 11.6mm, and the F number FNO is 2.5.

Table 6 below lists relevant parameters of each lens of the present embodiment, including surface type, radius of curvature, thickness, refractive index of material, abbe number:

number of noodles	Surface type	R value	Thickness of	Refractive index	Abbe number
						sur1	standard	25.6	2.14	1.75	42.5
sur2	standard	75.33	0.18
						sur3	standard	12.03	3.5	1.55	68.0
sur4	standard	20.12	2.0	1.67	40.2
						sur5	standard	11.0	3.1
Stop	standard	infinity	3.25
						Sur7	standard	-13.97	1.32	1.69	37.5
Sur8	standard	-32.61	1.85	1.75	42.5
						Sur9	standard	-14.47	1.1
Sur10	standard	436.1	1.5	1.78	42.5
						sur11	standard	-34.5	7.5
sur12	standard	-195.06	2.2	1.85	25.1
						sur13	standard	-35.78	4.0
sur14	standard	-24.65	1.2	1.81	23.7
						sur15	standard	infinity	13
Image plane phi I	standard	infinity	-

TABLE 6

Referring to fig. 21, in the present embodiment, the first lens group G1 includes 3 lenses (L1-L3), wherein the lens L2 and the lens L3 form a double cemented lens. The second lens group G2 comprises 3 lenses (L4-L6), wherein the lens L4 and the lens L5 are double cemented lenses. The third lens group G3 includes 2 lenses (L7 and L8).

Fig. 22 to 25 schematically show an MTF chart, an MTF defocus chart in a low temperature state, an MTF defocus chart in a high temperature state, and an optical distortion chart in focusing of the optimal working object distance of the imaging lens according to embodiment 5 of the present invention. Can learn in combination with the attached drawing, according to the utility model discloses imaging lens who obtains, realize big light ring, high resolution, low distortion, the image quality is even, big depth of field, the color rendition degree is good, the characteristic that the contrast is high.

The above description is only one embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. An imaging lens includes, in order from an object side to an image side, a first lens group (G1) having positive power, a stop, a second lens group (G2) having positive power, and a third lens group (G3) having positive power or negative power, the third lens group (G3) being a fixed group, and the first lens group (G1) and the second lens group (G2) constituting a focusing group movable along an optical axis.

2. The imaging lens according to claim 1, wherein the first lens group (G1) includes at least two positive power lenses and one negative power lens, and a lens closest to the object side in the first lens group (G1) is a positive power lens, and a lens closest to the image side is a negative power lens.

3. The imaging lens according to claim 2, wherein a lens closest to the object side in the first lens group (G1) is one of a biconvex lens, a convex-concave lens, or a convex-flat lens in an object-to-image direction.

4. The imaging lens according to claim 3, wherein the first lens group (G1) comprises a double cemented lens formed by a combination of positive power lens and negative power lens along the object-to-image direction.

5. An imaging lens according to claim 4, characterized in that the positive power lens of the cemented doublet in the first lens group (G1) has a refractive index ND and an Abbe number VD, satisfying: VD is more than or equal to 60 and less than or equal to 96, ND is more than or equal to 1.43 and less than or equal to 1.65.

6. The imaging lens according to claim 1 or 5, wherein the second lens group (G2) includes at least two positive power lenses and one negative power lens, and a lens closest to the object side in the second lens group (G2) is a negative power lens, and a lens closest to the image side is a positive power lens.

7. The imaging lens according to claim 6, wherein a lens closest to an image side in the second lens group (G2) is one of a biconvex lens, a meniscus lens, or a plano-convex lens in an object-to-image direction.

8. The imaging lens according to claim 7, wherein the second lens group (G2) comprises a double cemented lens formed by a combination of negative power lens and positive power lens along the object-to-image direction.

9. The imaging lens according to claim 1 or 8, wherein the third lens group (G3) includes at least one positive power lens and one negative power lens, and two lenses close to the object side in the third lens group (G3) are arranged in the order of the positive power lens, the negative power lens, or the order of the negative power lens and the positive power lens in the object-to-image direction.

10. The imaging lens according to claim 9, characterized in that the positive power lens in the third lens group (G3) is one of a biconvex lens, a convex-concave lens, or a convex-flat lens, and the negative power lens is one of a biconcave lens, a convex-concave lens, or a convex-concave lens.

11. An imaging lens according to claim 1, wherein a focal length of a focusing group consisting of the first lens group (G1), the stop, and the second lens group (G2) is fm, and a focal length of the imaging lens is f, satisfying the relation: fm/f is more than or equal to 1.0 and less than or equal to 1.5.

12. An imaging lens according to claim 1, characterized in that the focal length of the third lens group (G3) is fg3 and the focal length of the imaging lens is f, satisfying: the | fg3/f | is more than or equal to 3.5 and less than or equal to 8.5.

13. The imaging lens of claim 1, wherein the total optical length of the imaging lens is TTL, and the focal length of the imaging lens is f, which satisfies TTL/f 1.35 ≤ 1.75.