CN211786325U

CN211786325U - Fixed-focus optical imaging lens

Info

Publication number: CN211786325U
Application number: CN202020472709.2U
Authority: CN
Inventors: 上官秋和; 刘青天; 李雪慧
Original assignee: Xiamen Leading Optics Co Ltd
Current assignee: Xiamen Leading Optics Co Ltd
Priority date: 2020-04-03
Filing date: 2020-04-03
Publication date: 2020-10-27
Anticipated expiration: 2030-04-03

Abstract

The utility model relates to a camera lens technical field. The utility model discloses a fixed focus optical imaging lens, which comprises six lenses, wherein the first lens is a convex-concave lens with negative refractive index; the second lens is a concave lens with negative refractive index; the third lens element, the fifth lens element and the sixth lens element are convex lenses with positive refractive index; the fourth lens element with negative refractive index has a concave image-side surface; the first lens, the third lens, the fourth lens and the fifth lens are all made of glass materials, the second lens and the sixth lens are both plastic aspheric lens, and the fourth lens and the fifth lens are mutually glued. The utility model has high resolution and high imaging quality; the chromatic aberration is low, and the color reducibility is high; the aperture is large; the temperature drift control is good; low cost.

Description

Fixed-focus optical imaging lens

Technical Field

The utility model belongs to the technical field of the camera lens, specifically relate to a tight optical imaging camera lens.

Background

With the continuous progress of scientific technology and the continuous development of society, in recent years, optical imaging lenses are also rapidly developed, and the optical imaging lenses are widely applied to various fields such as smart phones, tablet computers, video conferences, vehicle-mounted monitoring, security monitoring, unmanned aerial vehicle aerial photography and the like, so that the requirements on the optical imaging lenses are higher and higher.

However, the existing fixed-focus optical imaging lens applied to the monitoring field has many defects, such as difficult improvement of pixels, poor imaging quality and obvious difference; the aperture is small, the brightness of the picture is not high, and the definition is damaged; color cast phenomenon exists, stray light is obvious under strong light, and imaging effect and picture purity are influenced; the focus running is serious under severe working environments such as high and low temperature, and the image quality is poor; in order to meet the requirements of higher performance, glass lenses are adopted, so that the cost is high, the volume is larger, and the like, and therefore, the improvement is needed to meet the increasing requirements of consumers.

Disclosure of Invention

An object of the utility model is to provide a tight shot optical imaging lens is used for solving the technical problem that above-mentioned exists.

In order to achieve the above object, the utility model adopts the following technical scheme: a fixed-focus optical imaging lens sequentially comprises a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens and a fourth lens from an object side to an image side along an optical axis; the first lens, the second lens, the third lens and the fourth lens are respectively arranged on the object side and the image side, and the object side faces towards the object side and enables the imaging light rays to pass through;

the first lens element with negative refractive index has a convex object-side surface and a concave image-side surface;

the second lens element has negative refractive index, the object-side surface of the second lens element is concave, the image-side surface of the second lens element is concave, and both the object-side surface and the image-side surface of the second lens element are aspheric surfaces;

the third lens element with positive refractive index has a convex object-side surface and a convex image-side surface;

the fourth lens element with negative refractive index has a concave image-side surface;

the fifth lens element with positive refractive index has a convex object-side surface and a convex image-side surface;

the sixth lens element with positive refractive index has a convex object-side surface and a convex image-side surface, and both the object-side surface and the image-side surface are aspheric;

the fourth lens and the fifth lens are mutually glued, the second lens and the sixth lens are made of plastic materials, and the first lens, the third lens, the fourth lens and the fifth lens are made of glass materials;

the fixed-focus optical imaging lens has only the first lens element to the sixth lens element.

Further, the fixed-focus optical imaging lens further satisfies the following conditions: 0.8< | f3/f4 | <1.2, wherein f3 and f4 are focal lengths of the third lens and the fourth lens, respectively.

Further, the fixed-focus optical imaging lens further satisfies the following conditions: 0.8< | f1/f2 | <1.2, wherein f1 and f2 are focal lengths of the first lens and the second lens, respectively.

Further, the fixed-focus optical imaging lens further satisfies the following conditions: nd1 > 1.8, where nd1 is the refractive index of the first lens.

Further, the fixed-focus optical imaging lens further satisfies the following conditions: nd3 is greater than 1.9, wherein nd3 is the refractive index of the third lens.

Further, the fixed-focus optical imaging lens further satisfies the following conditions: vd5 > 50, vd4 < 30, and vd5-vd4 > 25, where vd4 and vd5 represent the abbe numbers of the fourth and fifth lenses, respectively.

Further, the fixed-focus optical imaging lens further satisfies the following conditions: vd2 is more than or equal to 50, vd6 is more than or equal to 50, wherein vd2 and vd6 respectively represent the abbe number of the second lens and the sixth lens.

Furthermore, a soma sheet is adopted between the first lens and the second lens and between the second lens and the third lens for bearing.

Further, the lens further comprises a diaphragm, and the diaphragm is arranged between the third lens and the fourth lens.

Furthermore, the diaphragm is formed by a soma plate directly against the fourth lens.

The utility model has the advantages of:

the utility model adopts the mixed design of six lenses, glass and plastic, and has low cost by correspondingly designing each lens; the total length is short; the imaging quality is good, the performance is high, and high-definition image quality is realized; the aperture is large, the light incoming quantity is large, the picture brightness is high, and the low-light effect is good; the chromatic aberration control is good, and stray light is improved and avoided, so that a monitoring picture is pure, and color restoration is high; the defocusing is small or not under the high and low temperature conditions, and the clear and bright stable image quality is realized.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.

Fig. 1 is a schematic structural diagram of a first embodiment of the present invention;

FIG. 2 is a graph of MTF of 0.425-0.675 μm according to the first embodiment of the present invention;

fig. 3 is a schematic view of a chromatic aberration curve according to a first embodiment of the present invention;

FIG. 4 is a defocus plot of 425 and 675nm visible light at 20 ℃ at 60lp/mm in the first embodiment of the present invention;

FIG. 5 is a defocus plot of 425 and 675nm visible light at-30 ℃ at 60lp/mm in the first embodiment of the present invention;

FIG. 6 is a defocus plot of visible light 425 and 675nm at 70 ℃ at 60lp/mm in the first embodiment of the present invention;

fig. 7 is a schematic structural diagram of a second embodiment of the present invention;

FIG. 8 is a graph of MTF of 0.425-0.675 μm according to example II of the present invention;

fig. 9 is a schematic view of a color difference curve according to a second embodiment of the present invention;

FIG. 10 is a defocus plot of 425 and 675nm visible light at 20 ℃ at 60lp/mm in the second embodiment of the present invention;

FIG. 11 is a defocus plot of 425 and 675nm visible light at-30 ℃ at 60lp/mm in the second embodiment of the present invention;

FIG. 12 is a defocus plot of visible light 425 and 675nm at 70 ℃ at 60lp/mm in the second embodiment of the present invention;

fig. 13 is a schematic structural view of a third embodiment of the present invention;

FIG. 14 is a graph of MTF of 0.425-0.675 μm according to the third embodiment of the present invention;

fig. 15 is a schematic view of a color difference curve according to a third embodiment of the present invention;

FIG. 16 is a defocus plot of 425 and 675nm visible light at 20 ℃ at 60lp/mm in the third embodiment of the present invention;

FIG. 17 is a defocus plot of 425 and 675nm visible light at-30 ℃ at 60lp/mm in a third embodiment of the present invention;

FIG. 18 is a defocus plot of visible light 425 and 675nm at 70 ℃ at 60lp/mm in the third embodiment of the present invention;

fig. 19 is a schematic structural diagram of a fourth embodiment of the present invention;

FIG. 20 is a graph of MTF of 0.425-0.675 μm according to example four of the present invention;

fig. 21 is a schematic view of a color difference curve according to a fourth embodiment of the present invention;

FIG. 22 is a defocus plot of 425 and 675nm visible light at 20 ℃ at 60lp/mm in the fourth embodiment of the present invention;

FIG. 23 is a defocus plot of 425 and 675nm visible light at-30 ℃ at 60lp/mm in the fourth embodiment of the present invention;

FIG. 24 is a defocus plot of visible light 425 and 675nm at 70 ℃ at 60lp/mm in accordance with the fourth embodiment of the present invention.

Detailed Description

To further illustrate the embodiments, the present invention provides the accompanying drawings. The accompanying drawings, which are incorporated in and constitute a part of this disclosure, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the embodiments. With these references, one of ordinary skill in the art will appreciate other possible embodiments and advantages of the present invention. Elements in the figures are not drawn to scale and like reference numerals are generally used to indicate like elements.

The present invention will now be further described with reference to the accompanying drawings and detailed description.

The term "a lens element having positive refractive index (or negative refractive index)" means that the paraxial refractive index of the lens element calculated by Gaussian optics theory is positive (or negative). The term "object-side (or image-side) of a lens" is defined as the specific range of imaging light rays passing through the lens surface. The determination of the surface shape of the lens can be performed by the judgment method of a person skilled in the art, i.e., by the sign of the curvature radius (abbreviated as R value). The R value may be commonly used in optical design software, such as Zemax or CodeV. The R value is also commonly found in lens data sheets (lens data sheets) of optical design software. When the R value is positive, the object side is judged to be a convex surface; and when the R value is negative, judging that the object side surface is a concave surface. On the contrary, regarding the image side surface, when the R value is positive, the image side surface is judged to be a concave surface; when the R value is negative, the image side surface is judged to be convex.

The utility model discloses a fixed focus optical imaging lens, which comprises a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens and a fifth lens from the object side to the image side along an optical axis; the first lens element to the sixth lens element each include an object-side surface facing the object side and passing the image light, and an image-side surface facing the image side and passing the image light.

The first lens element with negative refractive index has a convex object-side surface and a concave image-side surface.

The second lens element has a negative refractive index, the object-side surface of the second lens element is concave, the image-side surface of the second lens element is concave, and both the object-side surface and the image-side surface of the second lens element are aspheric surfaces.

The third lens element with positive refractive power has a convex object-side surface and a convex image-side surface.

The fourth lens element with negative refractive index has a concave image-side surface.

The fifth lens element with positive refractive power has a convex object-side surface and a convex image-side surface.

The sixth lens element with positive refractive index has a convex object-side surface and a convex image-side surface, and both the object-side surface and the image-side surface are aspheric.

The fourth lens and the fifth lens are cemented to each other, and are preferably achromatic.

The second lens and the sixth lens are made of plastic materials, the first lens, the third lens, the fourth lens and the fifth lens are made of glass materials, 2 plastic lenses are adopted, 4 glass lenses are matched, high optical performance is guaranteed, cost is greatly controlled, and the length of a lens system is shortened.

The fixed-focus optical imaging lens has only the first lens element to the sixth lens element. The utility model adopts the six lenses and the glass-plastic mixed design, thereby having low cost; the total length is short; the imaging quality is good, the performance is high, and high-definition image quality is realized; the aperture is large, the light incoming quantity is large, the picture brightness is high, and the low-light effect is good; the chromatic aberration control is good, and stray light is improved and avoided, so that a monitoring picture is pure, and color restoration is high; the defocusing is small or not under the high and low temperature conditions, and the clear and bright stable image quality is realized.

Preferably, the fixed-focus optical imaging lens further satisfies: 0.8< | f3/f4 | <1.2, wherein f3 and f4 are focal lengths of the third lens and the fourth lens, respectively, to further control the back focus offset under high and low temperature conditions.

Preferably, the fixed-focus optical imaging lens further satisfies: 0.8< | f1/f2 | <1.2, wherein f1 and f2 are focal lengths of the first lens and the second lens, respectively, to further control the back focus offset under high and low temperature conditions.

Preferably, the fixed-focus optical imaging lens further satisfies: nd1 is more than 1.8, wherein nd1 is the refractive index of the first lens, and the material with high refractive index is adopted, so that the image quality is optimized, and the system performance is improved.

Preferably, the fixed-focus optical imaging lens further satisfies: nd3 is more than 1.9, wherein nd3 is the refractive index of the third lens, and the material with high refractive index is adopted, so that the image quality is optimized, and the system performance is improved.

Preferably, the fixed-focus optical imaging lens further satisfies: vd5 > 50, vd4 < 30, and vd5-vd4 > 25, where vd4 and vd5 represent the abbe numbers of the fourth and fifth lenses, respectively, further achromatizing.

Preferably, the fixed-focus optical imaging lens further satisfies: vd2 is more than or equal to 50, vd6 is more than or equal to 50, wherein vd2 and vd6 respectively represent the abbe number of the second lens and the sixth lens, and chromatic aberration is further corrected.

Preferably, the first lens and the second lens and the third lens are supported by the soma sheet, so that stray light can be further avoided, tolerance control is easy, system performance is improved, and offset of a back focus is controlled.

Preferably, the optical system further comprises a diaphragm, and the diaphragm is arranged between the third lens and the fourth lens, so that the system performance is further improved.

More preferably, the diaphragm is formed with a soma plate directly against the fourth lens, greatly suppressing stray light.

The optical imaging lens of the present invention will be described in detail with reference to specific embodiments.

Example one

As shown in fig. 1, a fixed-focus optical imaging lens includes, in order along an optical axis I, a first lens element 1, a second lens element 2, a third lens element 3, a stop 7, a fourth lens element 4, a fifth lens element 5, a sixth lens element 6, a protective glass 8, and an image plane 9 from an object side a1 to an image side a 2; the first lens element 1 to the sixth lens element 6 each include an object-side surface facing the object side a1 and passing the imaging light rays, and an image-side surface facing the image side a2 and passing the imaging light rays.

The first lens element 1 has a negative refractive index, and an object-side surface 11 of the first lens element 1 is convex and an image-side surface 12 of the first lens element 1 is concave.

The second lens element 2 has a negative refractive index, the object-side surface 21 of the second lens element 2 is concave, the image-side surface 22 of the second lens element 2 is concave, and both the object-side surface 21 and the image-side surface 22 of the second lens element 2 are aspheric.

The third lens element 3 has a positive refractive index, and an object-side surface 31 of the third lens element 3 is convex and an image-side surface 32 of the third lens element 3 is convex.

The fourth lens element 4 has a negative refractive index, and an object-side surface 41 of the fourth lens element 4 is concave and an image-side surface 42 of the fourth lens element 4 is concave. Of course, in other embodiments, the object side surface 41 of the fourth lens element 4 may be convex or planar.

The fifth lens element 5 has a positive refractive index, and an object-side surface 51 of the fifth lens element 5 is convex and an image-side surface 52 of the fifth lens element 5 is convex.

The sixth lens element 6 has a positive refractive index, an object-side surface 61 of the sixth lens element 6 is convex, an image-side surface 62 of the sixth lens element 6 is convex, and both the object-side surface 61 and the image-side surface 62 of the sixth lens element 6 are aspheric.

The fourth lens 4 and the fifth lens 5 are cemented to each other.

In this embodiment, the first lens 1 and the second lens 2 and the third lens 3 are supported by the soma sheet.

In this particular embodiment, the diaphragm 7 is formed by a soma plate resting directly on the fourth lens 4.

Of course, in other embodiments, the diaphragm 7 may be disposed at other suitable positions.

The detailed optical data of this embodiment are shown in Table 1-1.

Table 1-1 detailed optical data for example one

Surface of		Radius of curvature/mm	Thickness/spacing/mm	Material of	Refractive index	Coefficient of dispersion	Focal length/mm
								-	OBJ	Infinity	Infinity
11	First lens	21.698	0.99	Glass	1.83	37.23	-5.2
								12		3.551	2.93
21	Second lens	-5.055	2.7	Plastic material	1.54	55.98	-5.3
								22		8.001	0.1
31	Third lens	5.834	2.4	Glass	2.00	25.44	4.4
								32		-15.111	1.7
7	Diaphragm	Infinity	0.3
								41	Fourth lens	-22.454	1.76	Glass	1.95	17.94	-4.8
42		6.088	0
								51	Fifth lens element	6.088	1.95	Glass	1.59	68.52	5.5
52		-6.264	0.2
								61	Sixth lens element	7.601	2.75	Plastic material	1.54	55.98	7.3
62		-7.118	4.5
								8	Cover glass	Infinity	0.7	Glass	1.52	64.21	-
-		Infinity	0.5
								9	Image plane	Infinity

In this embodiment, the object-side surface 21, the object-side surface 61, the image-side surface 22 and the image-side surface 62 are defined by the following aspheric curve formulas:

wherein:

z: depth of the aspheric surface (the vertical distance between a point on the aspheric surface that is y from the optical axis and a tangent plane tangent to the vertex on the optical axis of the aspheric surface);

c: curvature of aspheric vertex (the vertex curvature);

k: cone coefficient (Conic Constant);

radial distance (radial distance);

r_n: normalized radius (normalysis radius (NRADIUS));

u：r/r_n；

a_m: mth order Q^conCoefficient (is the m)^thQ^concoefficient)；

Q_m ^con: mth order Q^conPolynomial (the m)^thQ^conpolynomial)；

For details of parameters of each aspheric surface, please refer to the following table:

please refer to table 5 for the values of the conditional expressions related to this embodiment.

The MTF transfer function graph of the present embodiment is detailed in fig. 2, and it can be seen that the resolution is high and the pixels are high; referring to fig. 3, it can be seen that the color difference is small and the color reducibility is high; the high-low temperature defocusing graphs are shown in figures 4-6 in detail, and it can be seen that the back focus movement is small under the high-low temperature condition.

In this specific embodiment, the focal length f of the fixed-focus optical imaging lens is 2.5 mm; f-number FNO 1.6; the field angle FOV is 150 degrees; the distance TTL between the object-side surface 11 of the first lens element 1 and the image forming surface 9 on the optical axis I is 23.5 mm.

Example two

As shown in fig. 7, the surface convexoconcave and the refractive index of each lens element of this embodiment are substantially the same as those of the first embodiment, only the object-side surface 41 of the fourth lens element 4 is a convex surface, and the optical parameters such as the curvature radius of each lens element surface and the lens thickness are different.

The detailed optical data of this embodiment is shown in Table 2-1.

TABLE 2-1 detailed optical data for example two

Surface of		Radius of curvature/mm	Thickness/spacing/mm	Material of	Refractive index	Coefficient of dispersion	Focal length/mm
								-	OBJ	Infinity	Infinity
11	First lens	16.776	0.6	Glass	1.9	31.32	-5.1
								12		3.584	3.15
21	Second lens	-3.711	2.92	Plastic material	1.54	55.98	-6.1
								22		35.227	0.1
31	Third lens	7.476	3.1	Glass	2.00	25.44	4.7
								32		-10.711	1.76
7	Diaphragm	Infinity	0.43
								41	Fourth lens	173.516	1	Glass	1.95	17.94	-4.6
42		4.281	0
								51	Fifth lens element	4.281	2.16	Glass	1.62	63.41	4.2
52		-5.479	1.08
								61	Sixth lens element	16.691	2.16	Plastic material	1.54	55.98	11.2
62		-9.103	3.5
								8	Cover glass	Infinity	0.7	Glass	1.52	64.21	-
-		Infinity	0.5
								9	Image plane	Infinity

For the detailed data of the parameters of each aspheric surface of this embodiment, refer to the following table:

The MTF transfer function graph of the present embodiment is detailed in fig. 8, and it can be seen that the resolution is high and the pixels are high; referring to fig. 9, it can be seen that the color difference is small and the color reproducibility is high; the high and low temperature defocusing graphs are shown in fig. 10-12 in detail, and it can be seen that the back focus movement is small under the high and low temperature conditions.

In the specific embodiment, f is 2.5 mm; FNO 1.6; FOV 150 °; TTL 23.2 mm.

EXAMPLE III

As shown in fig. 13, the lens elements of this embodiment have the same surface irregularities and refractive index as those of the first embodiment, and only the optical parameters such as the curvature radius of the surface of each lens element and the lens thickness are different.

The detailed optical data of this embodiment is shown in Table 3-1.

TABLE 3-1 detailed optical data for EXAMPLE III

Surface of		Radius of curvature/mm	Thickness/spacing/mm	Material of	Refractive index	Coefficient of dispersion	Focal length/mm
								-	OBJ	Infinity	Infinity
11	First lens	22.3	1.07	Glass	1.83	37.17	-5.3
								12		3.61	2.91
21	Second lens	-5.037	2.75	Plastic material	1.54	55.98	-5.3
								22		7.824	0.09
31	Third lens	5.927	2.19	Glass	2.00	25.44	4.4
								32		-14.679	1.61
7	Diaphragm	Infinity	0.36
								41	Fourth lens	-23.142	1.92	Glass	1.95	17.94	-5
42		6.156	0
								51	Fifth lens element	6.156	2.02	Glass	1.59	68.52	5.5
52		-6.211	0.16
								61	Sixth lens element	7.853	2.63	Plastic material	1.54	55.98	7.3
62		-7.035	4.52
								8	Cover glass	Infinity	0.7	Glass	1.52	64.21	-
-		Infinity	0.5
								9	Image plane	Infinity

surface of

K＝

a₄＝

a₆＝

a₈＝

a₁₀＝

a₁₂＝

a₁₄＝

21

-1.05E+00

5.24E-03

-4.28E-04

2.36E-05

-7.09E-07

1.36E-09

-4.64E-10

22

1.17E+00

5.75E-03

-3.76E-04

1.35E-05

-2.78E-07

2.00E-08

-5.94E-09

61

1.23E+00

-1.58E-03

-6.39E-05

2.74E-06

-4.38E-07

-4.96E-10

-1.57E-09

62

1.77E+00

3.51E-04

-3.10E-05

4.51E-06

-3.41E-07

-3.20E-09

-4.17E-11

The MTF transfer function graph of the present embodiment is detailed in fig. 14, and it can be seen that the resolution is high and the pixels are high; referring to fig. 15, it can be seen that the color difference is small and the color reproducibility is high; the high and low temperature defocusing graphs are shown in fig. 16-18 in detail, and it can be seen that the back focus movement is small under the high and low temperature conditions.

In the specific embodiment, f is 2.5 mm; FNO 1.6; FOV 150 °; TTL 23.4 mm.

Example four

As shown in fig. 19, the lens elements of this embodiment have the same surface irregularities and refractive index as those of the first embodiment, and only the optical parameters such as the curvature radius of the surface of each lens element and the lens thickness are different.

The detailed optical data of this embodiment is shown in Table 4-1.

TABLE 4-1 detailed optical data for example four

Surface of		Radius of curvature/mm	Thickness/spacing/mm	Material of	Refractive index	Coefficient of dispersion	Focal length/mm
								-	OBJ	Infinity	Infinity
11	First lens	19.349	0.6	Glass	1.83	37.16686	-5.3
								12		3.537	2.85
21	Second lens	-4.983	2.62	Plastic material	1.54	55.98069	-5.2
								22		7.588	0.1
31	Third lens	5.862	2.37	Glass	2.00	25.43506	4.4
								32		-13.291	1.39
7	Diaphragm	Infinity	0.8
								41	Fourth lens	-19.534	1	Glass	1.95	17.94	-4.8
42		6.09	0
								51	Fifth lens element	6.09	2.22	Glass	1.59	68.52	5.4
52		-5.845	0.1
								61	Sixth lens element	8.001	2.78	Plastic material	1.54	55.98	7.4
62		-7	4.4
								8	Cover glass	Infinity	0.7	Glass	1.52	64.21	-
-		Infinity	0.5
								9	Image plane	Infinity

surface of

K＝

a₄＝

a₆＝

a₈＝

a₁₀＝

a₁₂＝

a₁₄＝

21

-1.46E+00

5.21E-03

-4.72E-04

2.77E-05

-8.99E-07

4.30E-21

1.83E-23

22

2.47E+00

5.69E-03

-3.57E-04

1.45E-05

-8.46E-07

6.44E-21

1.84E-23

61

1.19E+00

-1.53E-03

-4.94E-05

3.71E-06

-4.59E-07

2.19E-20

1.97E-23

62

1.45E+00

3.85E-04

-3.03E-05

4.35E-06

-2.75E-07

-2.31E-20

-3.62E-24

The MTF transfer function graph of the present embodiment is detailed in fig. 20, and it can be seen that the resolution is high and the pixels are high; referring to fig. 21, it can be seen that the color difference is small and the color reproducibility is high; the high and low temperature defocusing graphs are shown in fig. 22-24 in detail, and it can be seen that the back focus movement is small under the high and low temperature conditions.

In the specific embodiment, f is 2.5 mm; FNO 1.6; FOV 150 °; TTL is 22.4 mm.

Table 5 values of relevant important parameters of four embodiments of the present invention

	Example one	Example two	EXAMPLE III	Example four
					∣f3/f4∣	0.92	1.02	0.88	0.92
∣f1/f2∣	0.98	0.84	1.00	1.02
					vd5-vd4	50.58	45.47	50.58	50.58

While the invention has been particularly shown and described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

1. A fixed focus optical imaging lens is characterized in that: the lens comprises a first lens, a second lens, a third lens, a fourth lens, a fifth lens and a sixth lens in sequence from the object side to the image side along an optical axis; the first lens, the second lens, the third lens and the fourth lens are respectively arranged on the object side and the image side, and the object side faces towards the object side and enables the imaging light rays to pass through;

2. The fixed focus optical imaging lens according to claim 1, further satisfying: 0.8< | f3/f4 | <1.2, wherein f3 and f4 are focal lengths of the third lens and the fourth lens, respectively.

3. The fixed focus optical imaging lens according to claim 1, further satisfying: 0.8< | f1/f2 | <1.2, wherein f1 and f2 are focal lengths of the first lens and the second lens, respectively.

4. The fixed focus optical imaging lens according to claim 1, further satisfying: nd1 > 1.8, where nd1 is the refractive index of the first lens.

5. The fixed focus optical imaging lens according to claim 1, further satisfying: nd3 is greater than 1.9, wherein nd3 is the refractive index of the third lens.

6. The fixed focus optical imaging lens according to claim 1, further satisfying: vd5 > 50, vd4 < 30, and vd5-vd4 > 25, where vd4 and vd5 represent the abbe numbers of the fourth and fifth lenses, respectively.

7. The fixed focus optical imaging lens according to claim 1, further satisfying: vd2 is more than or equal to 50, vd6 is more than or equal to 50, wherein vd2 and vd6 respectively represent the abbe number of the second lens and the sixth lens.

8. The fixed-focus optical imaging lens according to claim 1, characterized in that: and a soma sheet is adopted between the first lens and the second lens and between the second lens and the third lens for bearing.

9. The fixed-focus optical imaging lens according to claim 1, characterized in that: the diaphragm is arranged between the third lens and the fourth lens.

10. The fixed-focus optical imaging lens according to claim 9, characterized in that: the diaphragm is formed by a soma plate directly against the fourth lens.