CN113917668A

CN113917668A - Fixed focus lens

Info

Publication number: CN113917668A
Application number: CN202111407906.1A
Authority: CN
Inventors: 张圆; 黄斌
Original assignee: Sunny Optics Zhongshan Co Ltd
Current assignee: Sunny Optics Zhongshan Co Ltd
Priority date: 2021-11-19
Filing date: 2021-11-19
Publication date: 2022-01-11

Abstract

The invention relates to a fixed focus lens, comprising: a first lens (L1) and a second lens (L2) which are arranged in order in the direction from the object side to the image side along the optical axis and have negative powers; a third lens (L3), a fourth lens (L4), and a fifth lens (L5) all of which have positive optical power; a sixth lens (L6) having negative optical power; a seventh lens (L7) having positive optical power; an eighth lens (L8); and a ninth lens (L9) having a positive power, further comprising: a Stop (STO) located between the third lens (L3) and the fourth lens (L4) or on an object-side surface of the fourth lens (L4), an optical power of the eighth lens (L8) being positive. The fixed-focus lens can be used for day and night without infrared rays, realizes low-light-level imaging and has F1.0 ultra-large aperture, higher resolving power and larger image height.

Description

Fixed focus lens

Technical Field

The invention relates to the technical field of optical imaging systems, in particular to a fixed-focus lens.

Background

Driven by the digital information era, the demand for fixed focus lenses in the fields of security, public safety and monitoring facilities is increasing day by day. The fixed focus lens is widely applied to various fields by virtue of the advantages of clear imaging, wide monitoring field range and low requirement on required illumination. However, at night or in an environment with insufficient lighting conditions, ensuring clear imaging of the lens is still a technical problem to be overcome in the security field.

The high-image-quality night imaging lens in the market mostly adopts an imaging mode of matching an F1.4 large aperture with an infrared light supplement, but the infrared imaging range is small, so that color information cannot be restored, and the study of the low-light-level lens is imperative.

A fixed focus lens disclosed in prior art CN211293429U includes first to ninth lenses arranged in order from an object side to an image side along an optical axis. The first lens, the second lens, the sixth lens and the eighth lens all have negative focal power, the third lens, the fourth lens, the fifth lens, the seventh lens and the ninth lens all have positive focal power, and the first lens, the second lens, the sixth lens and the ninth lens are all glass spherical lenses. Through the design of the structure, the performance of the lens reaches more than 12 million pixels, the F-Theta confocal lens realizes the confocal of the aperture FNo2.0 and day and night, the imaging target surface reaches 1/2.5 inch, and the F-Theta distortion is less than 10%. However, the fixed focus lens does not have a characteristic of low-light imaging.

Disclosure of Invention

In order to overcome the defects in the prior art, the invention aims to provide a fixed-focus lens which can be used for day and night without infrared rays, realizes low-light-level imaging, and has F1.0 ultra-large aperture, higher resolving power and larger image height.

To achieve the above object, the present invention provides a fixed focus lens, comprising: the first lens and the second lens are sequentially arranged along the direction from the object side to the image side, and the focal powers of the first lens and the second lens are negative; a third lens, a fourth lens and a fifth lens, wherein the focal power of the third lens, the focal power of the fourth lens and the focal power of the fifth lens are all positive; a sixth lens having a negative focal power; a seventh lens, an eighth lens, and a ninth lens each having positive optical power, and further comprising: a stop located between the third lens and the fourth lens or on an object side of the fourth lens.

According to an aspect of the present invention, in a direction from an object side to an image side along an optical axis,

the first lens and the ninth lens are both convex and concave lenses;

the second lens is a concave-convex lens;

the third lens, the fourth lens, the fifth lens and the seventh lens are all convex lenses;

the sixth lens is a concave-concave lens;

the eighth lens is concave-convex in shape at the paraxial region.

According to an aspect of the present invention, the first lens, the second lens, the fourth lens, the eighth lens, and the ninth lens are all aspheric lenses;

the third lens, the fifth lens, the sixth lens and the seventh lens are all spherical lenses.

According to an aspect of the present invention, the first lens, the second lens, the fourth lens, the eighth lens and the ninth lens are all plastic lenses;

the third lens, the fifth lens, the sixth lens and the seventh lens are all glass lenses.

According to an aspect of the present invention, the fifth lens, the sixth lens and the seventh lens are cemented to constitute a cemented lens.

According to an aspect of the present invention, a focal length F567 of the cemented lens and a focal length F of the prime lens satisfy the relation: F567/F is more than or equal to 5.2 and less than or equal to 7.6.

According to an aspect of the present invention, the focal length F567 of the cemented lens and the center thickness db1 of the cemented lens satisfy the relation: db1/F567 is more than or equal to 0.2 and less than or equal to 0.3.

According to an aspect of the present invention, the total optical length TTL of the fixed focus lens and the focal length F of the fixed focus lens satisfy the following relation: TTL/F is more than or equal to 6.5 and less than or equal to 7.3.

According to an aspect of the present invention, the optical back focus BFL of the fixed-focus lens and the focal length F of the fixed-focus lens satisfy the following relation: BFL/F is more than or equal to 0.9 and less than or equal to 1.1.

According to an aspect of the invention, the focal length of the first lens F1 and the focal length of the fourth lens F4 satisfy the relation: F4/F1 is less than or equal to-2.4 and less than or equal to-2.

According to an aspect of the present invention, a focal length F8 of the eighth lens and a focal length F of the prime lens satisfy the relation: F8/F is more than or equal to 8.6 and less than or equal to 12.2.

According to an aspect of the present invention, a focal length F9 of the ninth lens and a focal length F of the prime lens satisfy the relation: F9/F is more than or equal to 14.6 and less than or equal to 24.4.

According to an aspect of the present invention, a combined focal length F89 of the eighth lens and the ninth lens and a focal length F of the prime lens satisfy the relation: F89/F is more than or equal to 5.3 and less than or equal to 6.9.

According to an aspect of the present invention, a center length d23 of the image-side surface of the second lens from the object-side surface of the third lens, a center length d34 of the image-side surface of the third lens from the object-side surface of the fourth lens, and a combined focal length F89 of the eighth lens and the ninth lens satisfy the following relations: (d23+ d34)/F89 is more than or equal to 0.1 and less than or equal to 0.2.

According to the scheme of the invention, a fixed focus lens comprising 9 lenses and a diaphragm is provided, the focal powers of the first lens to the ninth lens are negative-positive in sequence, the diaphragm is arranged between the third lens and the fourth lens or on the object side surface of the fourth lens, F1.0 ultra-large aperture, large target surface and low-light imaging are realized, the day and night dual-purpose can be realized without infrared rays, and virtual focus is avoided in the temperature range of-40 ℃ to 80 ℃.

According to one scheme of the invention, concave-convex shapes are respectively designed on the object side surface and the image side surface of the 9 lenses, and the cemented lens composed of the fifth lens to the seventh lens is adopted, so that chromatic aberration and aberration of imaging are effectively corrected. On the basis, the assembly tolerance sensitivity of the whole optical system is low, and the high resolution of 500 ten thousand pixels is realized. In addition, through the reasonable collocation of the glass-plastic mixed lens, relevant parameters of the specific lens and parameters such as the optical total length, the optical back focus and the like of the fixed-focus lens are reasonably set, and the low cost, the miniaturization and the light weight of the fixed-focus lens are realized.

Drawings

Fig. 1 is a schematic view showing an optical structure of a fixed focus lens according to embodiment 1 of the present invention;

fig. 2 is a schematic view showing an optical structure of a fixed-focus lens according to embodiment 2 of the present invention;

fig. 3 is a schematic view of an optical configuration of a fixed-focus lens according to embodiment 3 of the present invention;

fig. 4 is a schematic view showing an optical configuration of a fixed-focus lens according to embodiment 4 of the present invention;

fig. 5 is a schematic view of an optical configuration of a fixed-focus 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.

In describing embodiments of the present invention, the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like are used in an orientation or positional relationship that is based on the orientation or positional relationship shown in the associated drawings, which is for convenience and simplicity of description only, and does not indicate or imply that the referenced device or element must have a particular orientation, be constructed and operated in a particular orientation, and thus, the above-described terms should not be construed as limiting the present invention.

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

Fig. 1 schematically shows an optical structure of a fixed focus lens according to an embodiment of the present invention. As shown in fig. 1, the fixed-focus lens of the present invention includes, in order along an optical axis from an object side to an image side: a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, a sixth lens L6, a seventh lens L7, an eighth lens L8, and a ninth lens L9. Among them, the first lens L1, the second lens L2, and the sixth lens L6 all have negative power, and the remaining third lens L3, the fourth lens L4, the fifth lens L5, the seventh lens L7, the eighth lens L8, and the ninth lens L9 all have positive power. In addition, the fixed focus lens further includes a stop STO. The stop STO may be disposed between the third lens L3 and the fourth lens L4, or may be disposed on the object-side surface of the fourth lens L4.

In the nine lenses, the object-side surfaces of the first lens L1 and the ninth lens L9 are both convex, and the image-side surfaces are both concave. The object-side surface of the second lens L2 is concave, and the image-side surface is convex. The object-side and image-side surfaces of the third lens L3, the fourth lens L4, the fifth lens L5, and the seventh lens L7 are convex. The object-side surface and the image-side surface of the sixth lens L6 are both concave. The eighth lens element L8 has a concave object-side surface and a convex image-side surface in the vicinity of the optical axis region of the lens.

It can be seen that the fixed focus lens adopts an optical structure of 9 lenses, and a stop STO is disposed between the third lens L3 and the fourth lens L4 or on the object-side surface of the fourth lens L4. As shown in fig. 1, a parallel plate CG having a certain thickness is also provided on the image side. Therefore, the whole fixed-focus lens is formed, the image degradation and the focus leakage of the fixed-focus lens at high and low temperatures can be avoided, and the F1.0 ultra-large aperture design is realized. Meanwhile, through specific combination design of the positive and negative focal powers of the 9 lenses and different shapes of the object side surface and the image side surface, aberration and chromatic aberration can be corrected, tolerance sensitivity of an optical imaging system is reduced, assembly tolerance sensitivity is low, high-pixel low-light imaging is achieved, and imaging is higher in image height. Moreover, the prime lens can realize dual purposes of day and night without infrared rays, and has the performance of no virtual focus within the temperature range of minus 40-80 ℃.

In terms of the surface design and material selection of the lenses, it is preferable that the first lens L1, the second lens L2, the fourth lens L4, the eighth lens L8 and the ninth lens L9 in the fixed focus lens all use aspherical lenses, and the materials of the lenses all use plastic materials. In addition, the third lens L3, the fifth lens L5, the sixth lens L6, and the seventh lens L7 in the fixed focus lens are all spherical lenses, and the materials of the lenses are all glass materials. The spherical lens is arranged in the fixed-focus lens at the position, and the distance between the spherical lens and the fixed-focus lens is designed to compensate aberration to a certain extent. In combination with the above aspheric lens, the aspheric lens can compensate for various aberrations such as spherical aberration, coma aberration, and distortion aberration, and the direction of incident light is controlled by adjusting the value of the radius of curvature R of the aspheric lens surface, thereby suppressing the aberration at a low level. By reasonably combining the spherical lens and the aspheric lens, the imaging performance of the large-aperture fixed-focus lens can be improved. In addition, the optical framework of 4 glass lenses and 5 plastic lenses can balance the high and low temperature performance of the prime lens, so that the lens is low in cost and light in weight.

Further, the fifth lens L5, the sixth lens L6, and the seventh lens L7 may be cemented into one cemented lens. By adopting the cemented lens, the aberration and chromatic aberration of the whole optical imaging system of the fixed-focus lens can be corrected, the tolerance sensitivity of the optical imaging system is effectively reduced, the high resolution of 500 ten thousand pixels of the fixed-focus lens can be realized, and the fixed-focus lens is free from virtual focus within the temperature range of minus 40 ℃ to 80 ℃.

The focal length F567 of the cemented lens and the focal length F of the fixed-focus lens satisfy the relation: F567/F is more than or equal to 5.2 and less than or equal to 7.6. The focal length F567 of the cemented lens and its center thickness db1 satisfy the relation: db1/F567 is more than or equal to 0.2 and less than or equal to 0.3. By defining the relationship between the focal length of the cemented lens and the focal length of the prime lens and the relationship between the focal length of the cemented lens and the center thickness and setting a reasonable range, chromatic aberration and aberration caused by light entering through the stop STO and the fourth lens L4 can be effectively corrected.

In the invention, the total optical length TTL and the focal length F of the fixed-focus lens satisfy the relation: TTL/F is more than or equal to 6.5 and less than or equal to 7.3. The total optical length TTL is a distance from the center of the object-side surface to the center of the image-side surface of the first lens element L1 of the fixed focus lens. The optical back focus BFL of the fixed focus lens and the focal length F thereof satisfy the relation: BFL/F is more than or equal to 0.9 and less than or equal to 1.1. The optical back focus BFL is a distance from the center of the image-side surface of the ninth lens L9 to the center of the image plane, which is the last lens of the fixed focus lens. By limiting the range, the fixed-focus lens can be miniaturized, and has the characteristics of small volume and high performance.

In the present invention, the focal length F1 of the first lens L1 and the focal length F4 of the fourth lens L4 satisfy the relationship: F4/F1 is less than or equal to-2.4 and less than or equal to-2. This allows to control the light tendencies of the whole optical imaging system and to reduce aberrations due to high angle light rays entering through the stop STO.

In the present invention, the focal length F8 of the eighth lens L8 and the focal length F of the fixed-focus lens satisfy the relationship: F8/F is more than or equal to 8.6 and less than or equal to 12.2. The focal length F9 of the ninth lens L9 and the focal length F of the fixed focus lens satisfy the relation: F9/F is more than or equal to 14.6 and less than or equal to 24.4. Meanwhile, the combined focal length F89 of the eighth lens L8 and the ninth lens L9 and the focal length F of the fixed-focus lens satisfy the relationship: F89/F is more than or equal to 5.3 and less than or equal to 6.9. Therefore, the distortion can be controlled, the distortion is reduced, and the design of a large target surface is facilitated.

In the present invention, the center length d23 of the image-side surface of the second lens L2 from the object-side surface of the third lens L3, the center length d34 of the image-side surface of the third lens L3 from the object-side surface of the fourth lens L4, and the combined focal length F89 of the eighth lens L8 and the ninth lens L9 satisfy the relation: (d23+ d34)/F89 is more than or equal to 0.1 and less than or equal to 0.2. The sensitivity of the three lenses, namely the second lens L2, the third lens L3 and the fourth lens L4, to the Modulation Transfer Function (MTF) of the fixed-focus lens is favorably reduced, the structure of the fixed-focus lens is compact, and the miniaturization is favorably realized.

In conclusion, the prime lens provided by the invention has an F1.0 super-large aperture, realizes large-target-surface and low-light-level imaging, can realize day and night dual-purpose without infrared rays, and does not have virtual focus within the temperature range of-40-80 ℃. The use of the cemented lens can effectively correct chromatic aberration and aberration of imaging. Also, the sensitivity of the assembly tolerance of the entire optical system is low. On the basis, the high resolution of 500 ten thousand pixels is realized. Meanwhile, the prime lens realizes low cost, miniaturization and light weight.

The following five embodiments specifically describe the fixed focus lens of the present invention. In the following embodiments, the prime lens of the present invention comprises nine lenses, stop STO, a parallel plate CG and an image side surface IMA. Here, the stop STO is referred to as a first surface STO, the image side surface IMA is referred to as a first surface IMA, and the cemented surfaces of the cemented triplet including the fifth lens L5, the sixth lens L6, and the seventh lens L7 are referred to as two surfaces. The nine lenses and the parallel plate CG have two surfaces, respectively.

The parameters of each example specifically corresponding to the above relationship are shown in table 1 below:

TABLE 1

In the present invention, the aspherical lens of the fixed focus lens satisfies the following formula:

in the above formula, z is the axial distance from the curved surface to the vertex at the position of the height h perpendicular to the optical axis along the optical axis direction; c represents the curvature at the apex of the aspherical surface; k is the conic constant of the surface; a. the₄、A₆、A₈、A₁₀、A₁₂、A₁₄、A₁₆The aspherical coefficients of the fourth, sixth, eighth, tenth, twelfth, fourteenth and sixteenth orders are expressed respectively.

Example 1

Referring to fig. 1, in the present embodiment, a stop STO is disposed between the third lens L3 and the fourth lens L4.

The parameters of each lens of the fixed focus lens of the present embodiment include a curvature radius R value, a thickness d, a refractive index Nd of a material, and an abbe number Vd, and S1 to S19 represent each surface of each lens, a cemented lens, a stop STO, and a parallel plate CG in the fixed focus lens, as shown in table 2 below.

Number of noodles	Radius of curvature R value	Thickness d	Refractive index Nd	Abbe number Vd
					1	13.842	2.600	1.54	55.7
2	5.018	4.899
					3	-7.320	3.340	1.64	23.4
4	-15.427	2.976
					5	28.845	4.720	1.85	23.8
6	-28.845	4.500
					7(STO)	Infinity	-0.527
8	80.000	3.730	1.54	55.7
					9	-27.223	0.120
10	31.023	4.430	1.62	63.4
					11	-11.850	1.000	1.85	23.8
12	15.834	5.795	1.59	68.6
					13	-15.834	0.118
14	-24.344	3.375	1.64	23.4
					15	-18.176	0.120
16	9.165	3.300	1.54	55.7
					17	9.274	6.336
18	Infinity	0.800	1.52	64.2
					19	Infinity	0.200
Image plane	Infinity	-

TABLE 2

The aspheric coefficients of the aspheric lenses of the prime lens of the present embodiment include the fourth-order aspheric coefficient A of the surface₄Sixth order aspherical surface coefficient A₆Eighth order aspheric surface coefficient A₈Ten-order aspheric surface coefficient A₁₀Twelve-order aspheric surface coefficient A₁₂And the conic constant K, as shown in Table 3 belowAs shown.

Surf

A₄

A₆

A₈

A₁₀

A₁₂

Value of K

1

-7.125E-04

1.202E-05

-1.167E-07

6.636E-10

-1.604E-12

-3.371

2

-1.619E-03

1.935E-05

-7.879E-07

1.915E-08

-3.400E-10

-0.426

3

2.301E-04

-3.375E-06

1.029E-07

-3.251E-09

4.672E-11

-1.110

4

3.366E-04

1.666E-07

-2.602E-08

1.324E-09

-1.797E-11

-1.484

8

1.333E-04

-4.277E-07

-1.482E-08

2.053E-10

-1.686E-12

38.493

9

2.203E-04

-8.110E-07

-1.948E-08

2.728E-10

-2.255E-12

-6.517

14

3.360E-04

-9.030E-06

8.476E-08

-8.762E-10

1.993E-12

-70.822

15

7.568E-05

-5.854E-06

4.884E-08

-2.797E-10

3.559E-13

-12.081

16

-4.228E-04

2.194E-07

5.091E-08

-3.567E-11

-9.472E-13

-5.033

17

-5.333E-04

5.867E-06

-1.246E-08

-4.244E-10

6.334E-12

-5.208

TABLE 3

As shown in fig. 1, and by combining the relevant parameters and data in tables 1, 2 and 3, the prime lens of the present embodiment has an ultra-large aperture of 1.0, realizes large target surface and low light level imaging, can realize dual purposes of day and night without infrared, and has no virtual focus in a temperature range of-40 ℃ to 80 ℃. The use of the cemented lens can effectively correct chromatic aberration and aberration of imaging. Also, the sensitivity of the assembly tolerance of the entire optical system is low. On the basis, the high resolution of 500 ten thousand pixels is realized. Meanwhile, the prime lens realizes low cost, miniaturization and light weight.

Example 2

Referring to fig. 2, in the present embodiment, the stop STO is disposed on the object side of the fourth lens L4.

The parameters of each lens of the fixed focus lens of the present embodiment include a curvature radius R value, a thickness d, a refractive index Nd of a material, and an abbe number Vd, and S1 to S18 represent each surface of each lens, a cemented lens, a stop STO, and a parallel plate CG in the fixed focus lens, as shown in table 4 below.

Number of noodles	Radius of curvature R value	Thickness d	Refractive index Nd	Abbe number Vd
					1	17.331	2.600	1.54	55.7
2	5.256	4.899
					3	-7.567	3.340	1.64	23.4
4	-17.688	2.976
					5	27.739	4.720	1.85	23.8
6	-27.739	4.500
					7(STO)	80.000	3.730	1.54	55.7
8	-21.316	0.120
					9	52.693	4.430	1.62	63.4
10	-12.128	1.000	1.85	23.8
					11	14.744	5.795	1.59	68.6
12	-14.744	0.118
					13	-18.693	3.375	1.64	23.4
14	-14.022	0.120
					15	10.044	3.300	1.54	55.7
16	10.341	7.017
					17	Infinity	0.800	1.52	64.2
18	Infinity	0.200
					Image plane	Infinity	-

TABLE 4

The aspheric coefficients of the aspheric lenses of the prime lens of the present embodiment include the fourth-order aspheric coefficient A of the surface₄Sixth order aspherical surface coefficient A₆Eighth order aspheric surface coefficient A₈Ten-order aspheric surface coefficient A₁₀Twelve-order aspheric surface coefficient A₁₂And the conic constant K values, as shown in table 5 below.

TABLE 5

As shown in fig. 2, and by combining the relevant parameters and data in tables 1, 4, and 5, the prime lens of the present embodiment has an F1.0 super large aperture, realizes large target surface and low light level imaging, can be used for both day and night without infrared, and has no virtual focus in a temperature range of-40 ℃ to 80 ℃. The use of the cemented lens can effectively correct chromatic aberration and aberration of imaging. Also, the sensitivity of the assembly tolerance of the entire optical system is low. On the basis, the high resolution of 500 ten thousand pixels is realized. Meanwhile, the prime lens realizes low cost, miniaturization and light weight.

Example 3

Referring to fig. 3, in the present embodiment, a stop STO is disposed between the third lens L3 and the fourth lens L4.

The parameters of each lens of the fixed focus lens of the present embodiment include a curvature radius R value, a thickness d, a refractive index Nd of a material, and an abbe number Vd, and S1 to S19 represent each surface of each lens, a cemented lens, a stop STO, and a parallel plate CG in the fixed focus lens, as shown in table 6 below.

Number of noodles	Radius of curvature R value	Thickness d	Refractive index Nd	Abbe number Vd
					1	14.841	2.600	1.54	55.7
2	5.094	4.899
					3	-7.308	3.340	1.64	23.4
4	-15.382	2.976
					5	28.781	4.720	1.85	23.8
6	-28.781	4.500
					7(STO)	Infinity	-0.527
8	80.000	3.730	1.54	55.7
					9	-25.443	0.120
10	31.933	4.430	1.62	63.4
					11	-11.935	1.000	1.85	23.8
12	15.665	5.795	1.59	68.6
					13	-15.665	0.118
14	-23.251	3.375	1.64	23.4
					15	-17.266	0.120
16	9.693	3.300	1.54	55.7
					17	9.667	6.318
18	Infinity	0.800	1.52	64.2
					19	Infinity	0.200
Image plane	Infinity	-

TABLE 6

The aspheric coefficients of the aspheric lenses of the prime lens of the present embodiment include the fourth-order aspheric coefficient A of the surface₄Sixth order aspherical surface coefficient A₆Eighth order aspheric surface coefficientA₈Ten-order aspheric surface coefficient A₁₀Twelve-order aspheric surface coefficient A₁₂Fourteen-order aspheric surface coefficient A₁₄And the conic constant K values, as shown in table 7 below.

TABLE 7

As shown in fig. 3, and by combining the relevant parameters and data in tables 1, 6, and 7, the prime lens of the present embodiment has an ultra-large aperture of 1.0, realizes large target surface and low light level imaging, can be used for both day and night without infrared, and has no virtual focus in a temperature range of-40 ℃ to 80 ℃. The use of the cemented lens can effectively correct chromatic aberration and aberration of imaging. Also, the sensitivity of the assembly tolerance of the entire optical system is low. On the basis, the high resolution of 500 ten thousand pixels is realized. Meanwhile, the prime lens realizes low cost, miniaturization and light weight.

Example 4

Referring to fig. 4, in the present embodiment, a stop STO is disposed between the third lens L3 and the fourth lens L4.

The parameters of each lens of the fixed focus lens of the present embodiment include a curvature radius R value, a thickness d, a refractive index Nd of a material, and an abbe number Vd, and S1 to S19 represent each surface of each lens, a cemented lens, a stop STO, and a parallel plate CG in the fixed focus lens, as shown in table 8 below.

Number of noodles	Radius of curvature R value	Thickness d	Refractive index Nd	Abbe number Vd
					1	14.206	2.600	1.54	55.7
2	5.035	4.899
					3	-7.248	3.340	1.64	23.4
4	-15.333	2.976
					5	28.661	4.720	1.85	23.8
6	-28.661	4.500
					7(STO)	Infinity	-0.527
8	80.000	3.730	1.54	55.7
					9	-25.858	0.120
10	31.501	4.430	1.62	63.4
					11	-11.816	1.000	1.85	23.8
12	15.707	5.795	1.59	68.6
					13	-15.707	0.118
14	-23.403	3.375	1.64	23.4
					15	-17.000	0.120
16	9.786	3.300	1.54	55.7
					17	9.663	6.301
18	Infinity	0.800	1.52	64.2
					19	Infinity	0.200
Image plane	Infinity	-

TABLE 8

The aspheric coefficients of the aspheric lenses of the prime lens of the present embodiment include the fourth-order aspheric coefficient A of the surface₄Sixth order aspherical surface coefficient A₆Eighth order aspheric surface coefficient A₈Ten-order aspheric surface coefficient A₁₀Twelve-order aspheric surface coefficient A₁₂Fourteen-order aspheric surface coefficient A₁₄And the conic constant K values, as shown in table 9 below.

TABLE 9

As shown in fig. 4, and by combining the relevant parameters and data in tables 1, 8, and 9, the fixed-focus lens of the present embodiment has an F1.0 super large aperture, realizes large target surface and low light level imaging, can realize dual-purpose use for day and night without infrared, and has no virtual focus in a temperature range of-40 ℃ to 80 ℃. The use of the cemented lens can effectively correct chromatic aberration and aberration of imaging. Also, the sensitivity of the assembly tolerance of the entire optical system is low. On the basis, the high resolution of 500 ten thousand pixels is realized. Meanwhile, the prime lens realizes low cost, miniaturization and light weight.

Example 5

Referring to fig. 5, in the present embodiment, a stop STO is disposed between the third lens L3 and the fourth lens L4.

The parameters of each lens of the fixed focus lens of the present embodiment include a curvature radius R value, a thickness d, a refractive index Nd of a material, and an abbe number Vd, and S1 to S19 represent each surface of each lens, a cemented lens, a stop STO, and a parallel plate CG in the fixed focus lens, as shown in table 10 below.

Number of noodles	Radius of curvature R value	Thickness d	Refractive index Nd	Abbe number Vd
					1	15.102	2.600	1.54	55.7
2	5.096	4.899
					3	-7.319	3.340	1.64	23.4
4	-15.369	2.976
					5	28.756	4.720	1.85	23.8
6	-28.756	4.500
					7(STO)	Infinity	-0.527
8	80.000	3.730	1.54	55.7
					9	-24.668	0.120
10	32.433	4.430	1.62	63.4
					11	-11.989	1.000	1.85	23.8
12	15.426	5.795	1.59	68.6
					13	-15.426	0.118
14	-23.214	3.375	1.64	23.4
					15	-17.034	0.120
16	9.840	3.300	1.54	55.7
					17	9.695	6.229
18	Infinity	0.800	1.52	64.2
					19	Infinity	0.200
Image plane	Infinity	-

Watch 10

The aspheric coefficients of the aspheric lenses of the prime lens of the present embodiment include the fourth-order aspheric coefficient A of the surface₄Sixth order aspherical surface coefficient A₆Eighth order aspheric surface coefficient A₈Ten-order aspheric surface coefficient A₁₀Twelve-order aspheric surface coefficient A₁₂Fourteen-order aspheric surface coefficient A₁₄And the conic constant K values, as shown in table 11 below.

TABLE 11

As shown in fig. 5, and by combining the relevant parameters and data in table 1, table 10, and table 11, it can be seen that the fixed-focus lens of the present embodiment has an F1.0 super-large aperture, realizes large target surface and low-light level imaging, can realize dual-purpose day and night without infrared, and has no virtual focus in the temperature range of-40 ℃ to 80 ℃. The use of the cemented lens can effectively correct chromatic aberration and aberration of imaging. Also, the sensitivity of the assembly tolerance of the entire optical system is low. On the basis, the high resolution of 500 ten thousand pixels is realized. Meanwhile, the prime lens realizes low cost, miniaturization and light weight.

The above description is only one embodiment of the present invention, and is not intended to limit the present invention, and it is apparent to those skilled in the art that various modifications and variations can be made in the present invention. 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. A prime lens, comprising: a first lens (L1) and a second lens (L2) which are arranged in order in the direction from the object side to the image side along the optical axis and have negative powers; a third lens (L3), a fourth lens (L4), and a fifth lens (L5) all of which have positive optical power; a sixth lens (L6) having negative optical power; a seventh lens (L7) having positive optical power; an eighth lens (L8); and a ninth lens (L9) having a positive refractive power, characterized by further comprising: a Stop (STO) located between the third lens (L3) and the fourth lens (L4) or on an object-side surface of the fourth lens (L4),

the power of the eighth lens (L8) is positive.

2. The prime lens according to claim 1, wherein in a direction from an object side to an image side along an optical axis,

the first lens (L1) and the ninth lens (L9) are both convex-concave lenses;

the second lens (L2) is a concave-convex lens;

the third lens (L3), the fourth lens (L4), the fifth lens (L5), and the seventh lens (L7) are all convex lenses;

the sixth lens is a concave-concave lens;

the eighth lens is concave-convex in shape at the paraxial region.

3. The prime lens according to claim 1, wherein the first lens (L1), the second lens (L2), the fourth lens (L4), the eighth lens (L8), and the ninth lens (L9) are each an aspherical lens;

the third lens (L3), the fifth lens (L5), the sixth lens (L6), and the seventh lens (L7) are all spherical lenses.

4. The prime lens according to claim 1, wherein the first lens (L1), the second lens (L2), the fourth lens (L4), the eighth lens (L8), and the ninth lens (L9) are all plastic lenses;

the third lens (L3), the fifth lens (L5), the sixth lens (L6), and the seventh lens (L7) are all glass lenses.

5. The prime lens according to claim 1, wherein the fifth lens (L5), the sixth lens (L6), and the seventh lens (L7) are cemented to constitute a cemented lens.

6. The prime lens according to claim 5, wherein the focal length (F567) of the cemented lens and the focal length (F) of the prime lens satisfy the relation: F567/F is more than or equal to 5.2 and less than or equal to 7.6.

7. The prime lens according to claim 5, wherein the focal length (F567) of the cemented lens and the center thickness (db1) of the cemented lens satisfy the relation: db1/F567 is more than or equal to 0.2 and less than or equal to 0.3.

8. The fixed focus lens as claimed in any one of claims 1 to 7, wherein a total optical length (TTL) of the fixed focus lens and a focal length (F) of the fixed focus lens satisfy the relation: TTL/F is more than or equal to 6.5 and less than or equal to 7.3.

9. Fixed focus lens according to any of claims 1 to 7, wherein the optical Back Focus (BFL) of the fixed focus lens and the focal length (F) of the fixed focus lens satisfy the relation: BFL/F is more than or equal to 0.9 and less than or equal to 1.1.

10. The prime lens according to any one of claims 1 to 7, wherein the focal length (F1) of the first lens (L1) and the focal length (F4) of the fourth lens (L4) satisfy the relation: F4/F1 is less than or equal to-2.4 and less than or equal to-2.