CN116679425A

CN116679425A - Fixed focus lens

Info

Publication number: CN116679425A
Application number: CN202210167116.9A
Authority: CN
Inventors: 景姣; 张磊; 李泽民; 何剑炜
Original assignee: Dongguan Yutong Optical Technology Co Ltd
Current assignee: Dongguan Yutong Optical Technology Co Ltd
Priority date: 2022-02-23
Filing date: 2022-02-23
Publication date: 2023-09-01
Also published as: WO2023160277A1

Abstract

The embodiment of the invention discloses a fixed focus lens, which comprises a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an eighth lens and a ninth lens which are sequentially arranged from an object plane to an image plane along an optical axis; the first lens, the second lens, the sixth lens and the eighth lens are all negative focal power lenses, and the fourth lens, the fifth lens, the seventh lens and the ninth lens are all positive focal power lenses; the focal power of the fixed focus lens is phi, the focal power of the first lens is phi 1, the focal power of the second lens is phi 2, the focal power of the third lens is phi 3, the focal power of the fourth lens is phi 4, the focal power of the fifth lens is phi 5, the focal power of the sixth lens is phi 6, the focal power of the seventh lens is phi 7, the focal power of the eighth lens is phi 8, the focal power of the ninth lens is phi 9, -0.554< phi 1/phi < -0.391; -0.675< 2/phi < -0.355; -0.176< Φ3/Φ <0.362;0.366< phi 4/phi <0.61;0.208< phi 5/phi <0.464; -0.535< Φ6/Φ < -0.209;0.288< phi 7/phi <0.55; -0.476< Φ8/Φ < -0.18;0.34< phi 9/phi <0.532. The method and the device can meet the requirements of ultra-large light quantity, imaging quality and monitoring under the condition of low illumination.

Description

Fixed focus lens

Technical Field

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

Background

At present, the security monitoring field generally adopts an infrared light supplementing mode to achieve the imaging purpose at night and under low-light conditions, but the infrared light supplementing mode has a small imaging range and serious color distortion. In order to achieve better night imaging, there is an increasing demand for low-light cameras. At present, most of common high-image-quality large-aperture lenses in the market are F1.4, less lenses reach the large aperture of F1.2, and are usually matched with a sensor of 1/2.7, the target surface is smaller, and few lenses reach the ultra-large aperture of F1.0 and the high-image-quality lens with the large target surface. Based on the market status, it is necessary to develop a large-target-surface ultra-large aperture 4K lens so as to have a better imaging effect at night.

Disclosure of Invention

The embodiment of the invention aims to provide a fixed focus lens, which meets the requirements of ultra-large light flux, improves imaging quality and realizes monitoring under the condition of low illumination.

In order to achieve the above object, an embodiment of the present invention provides a fixed focus lens, including: a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an eighth lens and a ninth lens which are sequentially arranged from an object plane to an image plane along an optical axis;

The first lens, the second lens, the sixth lens and the eighth lens are all negative focal power lenses, and the fourth lens, the fifth lens, the seventh lens and the ninth lens are all positive focal power lenses;

the focal power of the fixed focus lens is phi 1, the focal power of the first lens is phi 2, the focal power of the third lens is phi 3, the focal power of the fourth lens is phi 4, the focal power of the fifth lens is phi 5, the focal power of the sixth lens is phi 6, the focal power of the seventh lens is phi 7, the focal power of the eighth lens is phi 8, the focal power of the ninth lens is phi 9,

-0.554<Ф1/Ф<-0.391；-0.675<Ф2/Ф<-0.355；-0.176<Ф3/Ф<0.362；0.366<Ф4/Ф<0.61；0.208<Ф5/Ф<0.464；-0.535<Ф6/Ф<-0.209；0.288<Ф7/Ф<0.55；-0.476<Ф8/Ф<-0.18；0.34<Ф9/Ф<0.532。

optionally, the second lens, the third lens, the fifth lens, the sixth lens, the seventh lens, the eighth lens and the ninth lens are all plastic aspheric lenses, and the fourth lens is a glass spherical lens.

Optionally, a surface of the lens adjacent to the object plane side is an object plane surface, and a surface of the lens adjacent to the image plane side is an image plane surface;

the object side surface of the first lens is raised towards the object plane, and the image side surface of the first lens is raised towards the object plane; the object side surface of the second lens is convex towards the image plane, and the image side surface of the second lens is convex towards the object plane; the object side surface of the third lens is raised towards the object plane, and the image side surface of the third lens is raised towards the object plane; the object side surface of the fourth lens is convex towards the object plane, and the image side surface of the fourth lens is convex towards the image plane; the object side surface of the sixth lens is convex towards the image plane, and the image side surface of the sixth lens is convex towards the object plane; the object side surface of the seventh lens is convex towards the object plane, and the image side surface of the seventh lens is convex towards the image plane; the object side surface of the eighth lens is convex towards the image plane, and the image side surface of the eighth lens is convex towards the image plane.

Optionally, the refractive index of the first lens is n1, and the abbe number is v1; the refractive index of the second lens is n2, and the Abbe number is v2; the refractive index of the third lens is n3, and the Abbe number is v3; the refractive index of the fourth lens is n4, and the Abbe number is v4; the refractive index of the fifth lens is n5, and the Abbe number is v5; the refractive index of the sixth lens is n6, and the Abbe number is v6; the refractive index of the seventh lens is n7, and the Abbe number is v7; the refractive index of the eighth lens is n8, and the Abbe number is v8; the refractive index of the ninth lens is n9, and the Abbe number is v9;

1.47<n1<1.96，38<v1<69；1.47<n2<1.55，49<v2<57.1；1.60<n3<1.68，19.1<v3<30.4；1.55<n4<2.005，20<v4<75；1.47<n5<1.55，50<v5<61；1.60<n6<1.68，19.1<v6<30.4；1.47<n7<1.55，49<v7<57.1；1.60<n8<1.68，18.9<v8<30.4；1.47<n9<1.55，50.1<v9<61。

optionally, the distance from the optical axis center of the image surface of the ninth lens to the image surface is BFL, and the distance from the optical axis center of the object surface of the first lens to the image surface is TTL, where: TTL/BFL <8.

Optionally, the second lens and the third lens, the sixth lens and the seventh lens, and the seventh lens and the eighth lens are supported by a spacer or bonded by glue.

Optionally, F is less than or equal to 1.0.

Optionally, the second lens, the third lens, the fifth lens, the sixth lens, the seventh lens, the eighth lens and the ninth lens are plastic aspherical lenses, and the aspherical surface shape equation Z satisfies:

Wherein Z is the height vector of the aspheric surface at the position with the height y along the optical axis direction, and the distance vector is higher from the vertex of the aspheric surface; c=1/R, R representing the paraxial radius of curvature of the mirror; k is a conic coefficient; A. b, C, D, E, F is a higher order aspheric coefficient, where Z, R and y are each in mm.

According to the fixed focus lens provided by the embodiment of the invention, the balance of the incidence angle of the front and rear groups of lenses of the fixed focus lens is ensured by reasonably setting the number of lenses in the fixed focus lens and the relative relation between the focal power of each lens, the sensitivity of the lens is reduced, the production possibility is improved, the fixed focus lens is ensured to have higher resolution, the ultra-large light quantity is met, the imaging quality is improved, and the monitoring requirement under the low-illumination condition is met.

Drawings

Other features, objects and advantages of the present invention will become more apparent upon reading of the detailed description of non-limiting embodiments, made with reference to the accompanying drawings in which:

fig. 1 is a schematic structural diagram of a fixed focus lens according to a first embodiment of the present invention;

fig. 2 is a spherical aberration diagram of a fixed focus lens according to a first embodiment of the present invention;

fig. 3 is a field curvature distortion diagram of a fixed focus lens according to a first embodiment of the present invention;

Fig. 4 is a schematic structural diagram of a fixed-focus lens according to a second embodiment of the present invention;

fig. 5 is a spherical aberration chart of a fixed focus lens according to a second embodiment of the present invention;

fig. 6 is a field curvature distortion diagram of a fixed focus lens according to a second embodiment of the present invention;

fig. 7 is a schematic structural diagram of a fixed focus lens according to a third embodiment of the present invention;

fig. 8 is a spherical aberration diagram of a fixed focus lens according to a third embodiment of the present invention;

fig. 9 is a field curvature distortion diagram of a fixed focus lens according to a third embodiment of the present invention;

fig. 10 is a schematic structural diagram of a fixed focus lens according to a fourth embodiment of the present invention;

fig. 11 is a spherical aberration chart of a fixed focus lens according to a fourth embodiment of the present invention;

fig. 12 is a field curvature distortion diagram of a fixed focus lens according to a fourth embodiment of the present invention.

Detailed Description

In order to further describe the technical means and effects adopted by the embodiments of the present invention to achieve the preset purposes, the technical solutions in the embodiments of the present invention are clearly and completely described below with reference to the accompanying drawings and the preferred embodiments.

In the following detailed description of the embodiments of the present invention, the schematic drawings showing the structure of the device are not partially enlarged to general scale for the convenience of description, and are merely examples, which should not limit the scope of the present invention. In addition, the three-dimensional dimensions of length, width and height should be included in the actual fabrication.

Example 1

Fig. 1 is a schematic structural diagram of a fixed focus lens according to a first embodiment of the present invention. As shown in fig. 1, the fixed focus lens includes: a first lens 101, a second lens 102, a third lens 103, a fourth lens 104, a fifth lens 105, a sixth lens 106, a seventh lens 107, an eighth lens 108, and a ninth lens 109, which are arranged in order from an object plane to an image plane along an optical axis; the first lens 101, the second lens 102, the sixth lens 106, and the eighth lens 108 are negative power lenses, and the fourth lens 104, the fifth lens 105, the seventh lens 107, and the ninth lens 109 are positive power lenses; the focal length of the fixed focus lens is phi, the focal length of the first lens 101 is phi 1, the focal length of the second lens 102 is phi 2, the focal length of the third lens 103 is phi 3, the focal length of the fourth lens 104 is phi 4, the focal length of the fifth lens 105 is phi 5, the focal length of the sixth lens 106 is phi 6, the focal length of the seventh lens 107 is phi 7, the focal length of the eighth lens 108 is phi 8, the focal length of the ninth lens 109 is phi 9, -0.554< phi 1/phi < -0.391; -0.675< 2/phi < -0.355; -0.176< Φ3/Φ <0.362;0.366< phi 4/phi <0.61;0.208< phi 5/phi <0.464; -0.535< Φ6/Φ < -0.209;0.288< phi 7/phi <0.55; -0.476< Φ8/Φ < -0.18;0.34< phi 9/phi <0.532.

Illustratively, the optical power is equal to the difference between the image side beam convergence and the object side beam convergence, which characterizes the ability of the optical system to deflect light. The greater the absolute value of the optical power, the greater the ability to bend the light, the smaller the absolute value of the optical power, and the weaker the ability to bend the light. When the focal power is positive, the refraction of the light rays is convergent; when the optical power is negative, the refraction of the light is divergent. The optical power may be suitable for characterizing a refractive surface of a lens (i.e. a surface of a lens), for characterizing a lens, or for characterizing a system of lenses together (i.e. a lens group). In the fixed focus lens provided in the present embodiment, each lens may be fixed in one barrel (not shown in fig. 1), the first lens 101, the second lens 102, the sixth lens 106, and the eighth lens 108 are all negative power lenses, the fourth lens 104, the fifth lens 105, the seventh lens 107, and the ninth lens 109 are all positive power lenses, and the first lens 101 and the second lens 102 are provided as negative power lenses for controlling an incident angle of an optical system, facilitating a large angle of view and correcting curvature of field; the third lens 103 may be of negative power, also for controlling the angle of incidence of the optical system, the third lens 103 may also be of positive power for focusing the preceding light beam, and the fourth lens 104 and the fifth lens 105 may be of positive power for focusing the preceding light beam as well; the fifth lens 105 is a positive power lens, the sixth lens 106 is a negative power lens, the seventh lens 107 is a positive power lens, the eighth lens 108 is a negative power lens, the ninth lens 109 is a positive power lens, and the fifth lens 105, the sixth lens 106, the seventh lens 107, the eighth lens 108, and the ninth lens 109 are used for correcting off-axis aberrations including field curvature, coma, astigmatism, and the like. The whole lens ensures the approximate proportion distribution of the focal power of the optical system, and ensures the balance of the incident angles of the front group of lenses and the rear group of lenses so as to reduce the sensitivity of the lens, improve the possibility of production and ensure that the lens does not run out at high and low temperatures.

Further, the focal power of the fixed focus lens is Φ, the focal power of the first lens 101 is Φ1, the focal power of the second lens 102 is Φ2, the focal power of the third lens 103 is Φ3, the focal power of the fourth lens 104 is Φ4, the focal power of the fifth lens 105 is Φ5, the focal power of the sixth lens 106 is Φ6, the focal power of the seventh lens 107 is Φ7, the focal power of the eighth lens 108 is Φ8, the focal power of the ninth lens 109 is Φ9, -0.554< Φ1/Φ < -0.391; -0.675< 2/phi < -0.355; -0.176< Φ3/Φ <0.362;0.366< phi 4/phi <0.61;0.208< phi 5/phi <0.464; -0.535< Φ6/Φ < -0.209;0.288< phi 7/phi <0.55; -0.476< Φ8/Φ < -0.18;0.34< phi 9/phi <0.532. The focal power among the lenses in the fixed focus lens is reasonably set, so that the adjustment of light rays is ensured, and the imaging effect is further ensured.

According to the fixed focus lens provided by the embodiment of the invention, the balance of the incidence angles of the front group lens and the rear group lens of the fixed focus lens is ensured by reasonably setting the number of lenses in the fixed focus lens and the relative relation between the focal power of each lens, the sensitivity of the lens is reduced, the production possibility is improved, the fixed focus lens is ensured to have higher resolution, the imaging quality is improved, and the monitoring requirement under the low-illumination condition is met.

As a possible embodiment, the first lens 101, the second lens 102, the third lens 103, the fifth lens 105, the sixth lens 106, the seventh lens 107, the eighth lens 108 and the ninth lens 109 are all plastic aspherical lenses, and the fourth lens 104 is a glass spherical lens.

As another possible embodiment, the second lens 102, the third lens 103, the fifth lens 105, the sixth lens 106, the seventh lens 107, the eighth lens 108 and the ninth lens 109 are all plastic aspherical lenses, and the first lens 101 and the fourth lens 104 are glass spherical lenses.

Wherein the aspherical lens functions to correct all higher order aberrations. The plastic aspheric lens can be made of various plastics known to those skilled in the art, and the glass spherical lens can be made of various types of glass known to those skilled in the art. Because the cost of the lens made of plastic is far lower than that of the lens made of glass, the lens for fixing the focus provided by the embodiment of the invention adopts a mode of mixing and matching the glass lens and the plastic lens, so that the cost of the lens for fixing the focus can be effectively controlled while the optical performance of the lens for fixing the focus is ensured. And because the two materials have the mutual compensation function, the fixed focus lens can be ensured to be normally used under the high-low temperature environment.

Optionally, the surface of the lens adjacent to the object plane is an object plane surface, and the surface of the lens adjacent to the image plane is an image plane surface; the object side surface of the first lens 101 protrudes toward the object plane, and the image side surface of the first lens 101 protrudes toward the object plane; the object side surface of the second lens 102 protrudes towards the image plane, and the image side surface of the second lens 102 protrudes towards the object plane; the object side surface of the third lens 103 protrudes towards the object plane, and the image side surface of the third lens 103 protrudes towards the object plane; the object side surface of the fourth lens 104 protrudes towards the object plane, and the image side surface of the fourth lens 104 protrudes towards the image plane; the object side surface of the sixth lens 106 protrudes towards the image plane, and the image side surface of the sixth lens 106 protrudes towards the object plane; the object side surface of the seventh lens 107 protrudes toward the object plane, and the image side surface of the seventh lens 107 protrudes toward the image plane; the object-side surface of the eighth lens 108 protrudes toward the image plane, and the image-side surface of the eighth lens 108 protrudes toward the image plane.

Illustratively, as shown in fig. 1, the object-side surface of the fifth lens 105 protrudes toward the object plane, and the image-side surface of the fifth lens 105 protrudes toward the image plane; the object side surface of the ninth lens 109 is convex toward the object plane, and the image side surface of the ninth lens 109 is convex toward the image plane. The ninth lens 109 may further be a meniscus lens in which an object side surface of the ninth lens 109 protrudes toward the object plane and an image side surface of the ninth lens 109 protrudes toward the object plane. Through the face type that rationally sets up each lens, when guaranteeing that the focal power of each lens satisfies the focal power requirement in the above-mentioned embodiment, still can guarantee whole fixed focus camera lens compact structure, fixed focus camera lens integrated level is high.

Alternatively, the refractive index of the first lens 101 is n1, and the abbe number is v1; the refractive index of the second lens 102 is n2, and the abbe number is v2; the refractive index of the third lens 103 is n3, and the abbe number is v3; the refractive index of the fourth lens 104 is n4, and the abbe number is v4; the refractive index of the fifth lens 105 is n5, and the abbe number is v5; the refractive index of the sixth lens 106 is n6, and the abbe number is v6; the refractive index of the seventh lens 107 is n7, and the abbe number is v7; the refractive index of the eighth lens 108 is n8, and the abbe number is v8; the refractive index of the ninth lens 109 is n9, and the abbe number is v9;1.47< n1<1.96, 38< v1<69;1.47< n2<1.55, 49< v2<57.1;1.60< n3<1.68, 19.1< v3<30.4;1.55< n4<2.005, 20< v4<75;1.47< n5<1.55, 50< v5<61;1.60< n6<1.68, 19.1< v6<30.4;1.47< n7<1.55, 49< v7<57.1;1.60< n8<1.68, 18.9< v8<30.4;1.47< n9<1.55, 50.1< v9<61.

Wherein, the refractive index is the ratio of the propagation speed of light in vacuum to the propagation speed of light in the medium, and is mainly used for describing the refractive power of materials to light, and the refractive indexes of different materials are different. The abbe number is an index for indicating the dispersion ability of the transparent medium, and the more serious the medium dispersion, the smaller the abbe number; conversely, the more slightly the dispersion of the medium, the greater the Abbe number. Therefore, the refractive index and the Abbe number of each lens in the fixed-focus lens are matched, so that the miniaturization design of the fixed-focus lens is facilitated; meanwhile, the method is beneficial to realizing higher pixel resolution and larger aperture. Further guaranteeing the uniformity of the incidence angle of the front lens and the rear lens, reducing the sensitivity of the lens and improving the possibility of production.

As a possible embodiment, the distance from the center of the optical axis of the image side surface of the ninth lens element 109 to the image plane is BFL, and the distance from the center of the optical axis of the object side surface of the first lens element 101 to the image plane is TTL, wherein: TTL/BFL <8.

Illustratively, the distance from the center of the optical axis of the image space surface of the ninth lens 109 to the image plane can be understood as the back focal length of the fixed-focus lens, and by reasonably setting the relationship between the back focal length of the fixed-focus lens and the total length of the fixed-focus lens, the compact structure of the whole fixed-focus lens can be ensured, and the integration level of the fixed-focus lens is high.

Optionally, the second lens 102 and the third lens 103, the sixth lens 106 and the seventh lens 107, and the seventh lens 107 and the eighth lens 108 are supported by a spacer ring or bonded by glue.

Wherein, the second lens 102 and the third lens 103 can be supported by a spacer ring or bonded by glue; the sixth lens 106 and the seventh lens 107 can also be supported by a spacer ring or bonded by glue; the seventh lens 107 and the eighth lens 108 may also be held by a spacer or bonded by glue. The cemented lens can be used for reducing chromatic aberration to the maximum extent or eliminating chromatic aberration, so that various aberrations of the fixed focus lens can be fully corrected, the resolution can be improved, and the optical performances such as distortion, CRA and the like can be optimized on the premise of compact structure; and the light quantity loss caused by reflection between lenses can be reduced, and the illumination is improved, so that the image quality is improved, and the imaging definition of the lens is improved. In addition, the use of the cemented lens can also reduce assembly parts between two lenses, simplify assembly procedures in the lens manufacturing process, reduce cost, and reduce tolerance sensitivity problems of lens units due to tilting/decentering and the like generated in the assembly process.

Optionally, F is less than or equal to 1.0.

The fixed focus lens provided by the embodiment of the invention can meet the larger light throughput, thereby meeting the monitoring requirement under the low-illumination condition.

With continued reference to fig. 1, optionally, the fixed focus lens further includes a diaphragm;

the diaphragm is located in the optical path between the fourth lens 104 and the fifth lens 105.

Wherein, by setting the diaphragm in the optical path between the fourth lens 104 and the fifth lens 105, the propagation direction of the light beam can be adjusted, and the incident angle of the light beam can be adjusted, which is beneficial to further improving the imaging quality.

As a possible embodiment, the radius of curvature, thickness, material and half-caliber of each lens surface in the fixed focus lens are described below.

Table 1 design values of optical parameters of fixed focus lenses

Face number	Surface type	Radius of curvature	Thickness of (L)	Nd	Vd	Semi-Diameter
							OBJ	Spherical surface	Infinity	Infinity
1	Spherical surface	78.9768	0.900	1.61	60
							2	Spherical surface	5.0072	3.389
3	Aspherical surface	-10.4570	1.550	1.535	52.8	3.9
							4	Aspherical surface	7.3031	2.108	1.67	27.2	3.9
5	Aspherical surface	15.1414	0.144			3.9
							6	Spherical surface	14.4274	5.188	1.807	45.935	6.2
STO	Spherical surface	-8.3828	0.324			6.2
							8	Aspherical surface	9.2304	1.709	1.54	60
9	Aspherical surface	10000	0.414
							10	Aspherical surface	-29.5539	1.286	1.64	22.8
11	Aspherical surface	6.9993	3.650	1.53	50
							12	Aspherical surface	-12.1314	0.467			4.05
13	Aspherical surface	-2.7588	0.888	1.66	26.36
							14	Aspherical surface	-4.4948	0.098
15	Aspherical surface	4.2928	1.867	1.54	60	3.8
							16	Aspherical surface	34.1502	3.300			3.8
17	Spherical surface	Infinity	0.700	1.52	64.2
							18	Spherical surface	Infinity	0.601

With continued reference to fig. 1, the fixed focus lens provided in the embodiment of the present invention includes a first lens 101, a second lens 102, a third lens 103, a fourth lens 104, a fifth lens 105, a sixth lens 106, a seventh lens 107, an eighth lens 108, and a ninth lens 109, which are sequentially arranged from an object plane to an image plane along an optical axis. Table 1 shows the optical physical parameters such as the radius of curvature, thickness, and material of each lens in the fixed focus lens provided in the examples. Wherein the surface numbers are numbered according to the surface order of the respective lenses, for example, "1" represents the object plane surface of the first lens 101, "2" represents the image plane surface of the first lens 101, "8" represents the object plane surface of the fifth lens 105, "9" represents the image plane surface of the fifth lens 105, and so on; the radius of curvature represents the degree of curvature of the lens surface, positive values represent the curvature of the surface toward the image plane, and negative values represent the curvature of the surface toward the object plane; thickness represents the center axial distance from the current surface to the next surface, and the radius of curvature and thickness are in millimeters (mm).

Based on the above implementation, the second lens 102, the third lens 103, the fifth lens 105, the sixth lens 106, the seventh lens 107, the eighth lens 108 and the ninth lens 109 are optional plastic aspherical lenses, and the first lens 101 and the fourth lens 104 are glass spherical lenses. The fixed focus lens provided by the embodiment of the invention further comprises the diaphragm (STO), and the propagation direction of the light beam can be adjusted by additionally arranging the diaphragm, so that the imaging quality is improved. The aperture may be located in the optical path between the fifth lens 105 and the sixth lens 106, but the specific arrangement position of the aperture is not limited in the embodiment of the present invention, and by arranging the aperture at a suitable position, it is helpful to increase the relative illuminance and reduce CRA.

The aspherical surface shape equations Z of the second lens 102, the third lens 103, the fifth lens 105, the sixth lens 106, the seventh lens 107, the eighth lens 108, and the ninth lens 109 satisfy:

Table 2 details the aspherical coefficients of the lenses in this example, by way of example, in one possible implementation.

Table 2 aspherical coefficients in fixed focus lenses

Wherein, -2.194551E-03 shows that the coefficient A with the face number 3 is-2.194551 x 10 ^-3 。

The fixed focus lens of the first embodiment achieves the following technical indexes:

f number: f=1.0.

Further, fig. 2 is a spherical aberration graph of a fixed focus lens according to the first embodiment of the present invention, as shown in fig. 2, spherical aberration of the fixed focus lens at different wavelengths (0.436 μm, 0.486 μm, 0.588 μm and 0.656 μm) is within 0.05mm, and the different wavelength curves are relatively concentrated, which indicates that axial aberration of the fixed focus lens is very small, so that it can be known that the fixed focus lens according to the first embodiment of the present invention can correct aberration well.

Fig. 3 is a field curvature distortion diagram of a fixed focus lens according to a first embodiment of the present invention, as shown in fig. 3, in a left coordinate system, a horizontal coordinate represents a field curvature in mm; the vertical coordinates represent the normalized image height without units; wherein T represents meridian and S represents sagittal; as can be seen from fig. 3, the fixed focus lens provided in the first embodiment is effectively controlled in field curvature from 436nm light to 656nm light, that is, the difference between the image quality of the center and the image quality of the periphery is small during imaging; in the right coordinate system, the horizontal coordinate represents the magnitude of distortion in units of; the vertical coordinates represent the normalized image height with no units.

Example two

Fig. 4 is a schematic structural diagram of a fixed-focus lens according to a second embodiment of the present invention, where, as shown in fig. 4, the fixed-focus lens includes: a first lens 201, a second lens 202, a third lens 203, a fourth lens 204, a fifth lens 205, a sixth lens 206, a seventh lens 207, an eighth lens 208, and a ninth lens 209, which are arranged in order from the object plane to the image plane along the optical axis; the first lens 201, the second lens 202, the sixth lens 206, and the eighth lens 208 are negative power lenses, and the fourth lens 204, the fifth lens 205, the seventh lens 207, and the ninth lens 209 are positive power lenses; the focal length of the fixed focus lens is phi, the focal length of the first lens 201 is phi 1, the focal length of the second lens 202 is phi 2, the focal length of the third lens 203 is phi 3, the focal length of the fourth lens 204 is phi 4, the focal length of the fifth lens 205 is phi 5, the focal length of the sixth lens 206 is phi 6, the focal length of the seventh lens 207 is phi 7, the focal length of the eighth lens 208 is phi 8, and the focal length of the ninth lens 209 is phi 9, -0.554< phi 1/phi < -0.391; -0.675< 2/phi < -0.355; -0.176< Φ3/Φ <0.362;0.366< phi 4/phi <0.61;0.208< phi 5/phi <0.464; -0.535< Φ6/Φ < -0.209;0.288< phi 7/phi <0.55; -0.476< Φ8/Φ < -0.18;0.34< phi 9/phi <0.532.

The relative relation between the number of lenses in the fixed focus lens and the focal power of each lens is reasonably set, so that the fixed focus lens can meet the ultra-large light flux on the premise of smaller f-number, and the monitoring requirement under the low-illumination condition is realized; meanwhile, the imaging requirement of the fixed focus lens is met by using the resolving power in a high-low temperature environment, and the imaging capability of the lens in a night environment is guaranteed.

As a possible embodiment, the second lens 202, the third lens 203, the fifth lens 105, the sixth lens 206, the seventh lens 207, the eighth lens 208 and the ninth lens 209 are all plastic aspherical lenses, and the first lens 201 and the fourth lens 204 are glass spherical lenses. The material of the plastic aspheric lens can be various plastics known to those skilled in the art, and the material of the glass spherical lens is various types of glass known to those skilled in the art. Because the cost of the lens made of plastic is far lower than that of the lens made of glass, the lens for fixing the focus provided by the embodiment of the invention adopts a mode of mixing and matching the glass lens and the plastic lens, so that the cost of the lens for fixing the focus can be effectively controlled while the optical performance of the lens for fixing the focus is ensured.

The focal power, refractive index, and abbe number range of each lens are the same as those of the first embodiment, and will not be described here again.

Exemplary, table 3 details specific setting parameters of each lens in the fixed focus lens provided in the second embodiment of the present invention in a possible implementation manner.

Table 3 design values of optical parameters of fixed focus lenses

Face number	Surface type	Radius of curvature	Thickness of (L)	Nd	Vd	Semi-Diameter
							OBJ	Spherical surface	Infinity	Infinity
1	Spherical surface	80.7201	1.380	1.61	59.2
							2	Spherical surface	5.0508	3.750
3	Aspherical surface	-9.6306	1.485	1.54	50	4
							4	Aspherical surface	6.0798	1.778	1.66	19.7	4
5	Aspherical surface	14.1425	0.118			4
							6	Spherical surface	13.1213	4.658	1.806	45	6.2
STO	Spherical surface	-10.1691	0.349			6.2
							8	Aspherical surface	9.6688	2.027	1.535	51.8
9	Aspherical surface	-16.0419	1.416	1.64	22.9
							10	Aspherical surface	10.1589	3.581	1.535	55.33
11	Aspherical surface	-12.7295	0.525
							12	Aspherical surface	-2.9183	1.018	1.66	19
13	Aspherical surface	-4.7459	0.099			3.76
							14	Aspherical surface	4.4031	1.847	1.54	51.4	3.8
15	Aspherical surface	31.4068	3.300			3.8
							16	Spherical surface	Infinity	0.700	1.52	64.2
17	Spherical surface	Infinity	1.186

With continued reference to fig. 4, the fixed focus lens provided in the embodiment of the present invention includes a first lens 201, a second lens 202, a third lens 203, a fourth lens 204, a fifth lens 205, a sixth lens 206, a seventh lens 207, an eighth lens 208, and a ninth lens 209, which are sequentially arranged from an object plane to an image plane along an optical axis. Table 3 shows the optical physical parameters such as the radius of curvature, thickness, and material of each lens in the fixed focus lens provided in the examples. Wherein the surface numbers are numbered according to the surface order of the respective lenses, for example, "1" represents the object plane surface of the first lens 201, "2" represents the image plane surface of the first lens 201, "8" represents the object plane surface of the fifth lens 205, "9" represents the image plane surface of the fifth lens 205, and so on; the radius of curvature represents the degree of curvature of the lens surface, positive values represent the curvature of the surface toward the image plane, and negative values represent the curvature of the surface toward the object plane; thickness represents the center axial distance from the current surface to the next surface, and the radius of curvature and thickness are in millimeters (mm).

Based on the above implementation, the second lens 202, the third lens 203, the fifth lens 205, the sixth lens 206, the seventh lens 207, the eighth lens 208 and the ninth lens 209 are plastic aspherical lenses, and the first lens 201 and the fourth lens 204 are glass spherical lenses. The fixed focus lens provided by the embodiment of the invention further comprises the diaphragm (STO), and the propagation direction of the light beam can be adjusted by additionally arranging the diaphragm, so that the imaging quality is improved. The aperture may be located in the optical path between the fifth lens 205 and the sixth lens 206, but the specific arrangement position of the aperture is not limited by the embodiment of the present invention, and by arranging the aperture at a suitable position, it is helpful to increase the relative illuminance and reduce CRA.

The aspherical surface shape equations Z of the second lens 202, the third lens 203, the fifth lens 205, the sixth lens 206, the seventh lens 207, the eighth lens 208, and the ninth lens 209 satisfy:

Table 4 details the aspherical coefficients of the lenses in this example, by way of example, in one possible implementation.

Table 4 aspherical coefficients in fixed focus lenses

Wherein, -2.273994E-03 shows that the coefficient A with the face number of 3 is-2.279994 x 10 ^-3 。

The fixed focus lens of the second embodiment achieves the following technical indexes:

f number: f=1.0.

Further, fig. 5 is a spherical aberration graph of a fixed focus lens according to the second embodiment of the present invention, as shown in fig. 2, spherical aberration of the fixed focus lens at different wavelengths (0.436 μm, 0.486 μm, 0.588 μm, 0.656 μm and 0.850 μm) is within 0.05mm, and the different wavelength curves are relatively concentrated, which indicates that axial aberration of the fixed focus lens is very small, so that it is known that the fixed focus lens according to the second embodiment of the present invention can correct aberration well.

Fig. 6 is a field curvature distortion diagram of a fixed focus lens according to a second embodiment of the present invention, as shown in fig. 6, in a left coordinate system, a horizontal coordinate represents a field curvature in mm; the vertical coordinates represent the normalized image height without units; wherein T represents meridian and S represents sagittal; as can be seen from fig. 6, the fixed focus lens provided in the second embodiment is effectively controlled in field curvature from light with a wavelength of 436nm to light with a wavelength of 850nm, that is, the difference between the image quality of the center and the image quality of the periphery is small during imaging; in the right coordinate system, the horizontal coordinate represents the magnitude of distortion in units of; the vertical coordinates represent the normalized image height with no units.

Example III

Fig. 7 is a schematic structural diagram of a fixed-focus lens according to a third embodiment of the present invention, where, as shown in fig. 7, the fixed-focus lens includes: a first lens 301, a second lens 302, a third lens 303, a fourth lens 304, a fifth lens 305, a sixth lens 306, a seventh lens 307, an eighth lens 308, and a ninth lens 309, which are arranged in order from the object plane to the image plane along the optical axis; the first lens 301, the second lens 302, the sixth lens 306, and the eighth lens 308 are negative power lenses, and the fourth lens 304, the fifth lens 305, the seventh lens 307, and the ninth lens 309 are positive power lenses; the focal length of the fixed focus lens is phi, the focal length of the first lens 301 is phi 1, the focal length of the second lens 302 is phi 2, the focal length of the third lens 303 is phi 3, the focal length of the fourth lens 304 is phi 4, the focal length of the fifth lens 305 is phi 5, the focal length of the sixth lens 306 is phi 6, the focal length of the seventh lens 307 is phi 7, the focal length of the eighth lens 308 is phi 8, the focal length of the ninth lens 309 is phi 9, -0.554< phi 1/phi < -0.391; -0.675< 2/phi < -0.355; -0.176< Φ3/Φ <0.362;0.366< phi 4/phi <0.61;0.208< phi 5/phi <0.464; -0.535< Φ6/Φ < -0.209;0.288< phi 7/phi <0.55; -0.476< Φ8/Φ < -0.18;0.34< phi 9/phi <0.532.

As a possible embodiment, the first lens 301, the second lens 302, the third lens 303, the fifth lens 305, the sixth lens 306, the seventh lens 307, the eighth lens 308 and the ninth lens 309 are all plastic aspherical lenses, and the fourth lens 304 is a glass spherical lens. The material of the plastic aspheric lens can be various plastics known to those skilled in the art, and the material of the glass spherical lens is various types of glass known to those skilled in the art. Because the cost of the lens made of plastic is far lower than that of the lens made of glass, the lens for fixing the focus provided by the embodiment of the invention adopts a mode of mixing and matching the glass lens and the plastic lens, so that the cost of the lens for fixing the focus can be effectively controlled while the optical performance of the lens for fixing the focus is ensured.

Exemplary, table 5 details specific setting parameters of each lens in the fixed focus lens provided in the third embodiment of the present invention in a possible implementation manner.

Table 5 design values of optical parameters of fixed focus lenses

Face number	Surface type	Radius of curvature	Thickness of (L)	Nd	Vd	Semi-Diameter
							OBJ	Spherical surface	Infinity	Infinity
1	Aspherical surface	90.8753	0.877	1.535	53
							2	Aspherical surface	5.1083	3.985
3	Aspherical surface	-11.3289	0.965	1.535	52.77	4.2
							4	Aspherical surface	11.4494	0.100	4.2
5	Aspherical surface	13.0219	1.989	1.64	23.24	4.2
							6	Aspherical surface	8.2737	0.175	4.02
7	Spherical surface	11.4055	4.477	2	25.53	6.2
							STO	Spherical surface	-16.3407	0.333	6.2
9	Aspherical surface	8.1952	2.063	1.535	56.84
							10	Aspherical surface	-41.7244	0.196
11	Aspherical surface	-19.1171	1.319	1.66	20.3
							12	Aspherical surface	8.3005	0.100
13	Aspherical surface	6.2967	4.039	1.535	56
							14	Aspherical surface	-11.2569	0.450
15	Aspherical surface	-2.7376	0.930	1.64	22.92	4.2
							16	Aspherical surface	-4.4027	0.098
17	Aspherical surface	4.6358	2.284	1.535	57.8	3.8
							18	Aspherical surface	-224.6197	3.300	3.8
19	Spherical surface	Infinity	0.700	1.52	64.2
							20	Spherical surface	Infinity	1.440

With continued reference to fig. 7, the fixed focus lens provided in the embodiment of the present invention includes a first lens 301, a second lens 302, a third lens 303, a fourth lens 304, a fifth lens 305, a sixth lens 306, a seventh lens 307, an eighth lens 308, and a ninth lens 309, which are sequentially arranged from an object plane to an image plane along an optical axis. Table 5 shows the optical physical parameters such as the radius of curvature, thickness, and material of each lens in the fixed focus lens provided in the examples. Wherein the surface numbers are numbered according to the surface order of the respective lenses, for example, "1" represents the object plane surface of the first lens 301, "2" represents the image plane surface of the first lens 301, "9" represents the object plane surface of the fifth lens 305, "10" represents the image plane surface of the fifth lens 305, and so on; the radius of curvature represents the degree of curvature of the lens surface, positive values represent the curvature of the surface toward the image plane, and negative values represent the curvature of the surface toward the object plane; thickness represents the center axial distance from the current surface to the next surface, and the radius of curvature and thickness are in millimeters (mm).

Based on the above implementation, the first lens 301, the second lens 302, the third lens 303, the fifth lens 305, the sixth lens 306, the seventh lens 307, the eighth lens 308 and the ninth lens 309 are plastic aspheric lenses, and the fourth lens 304 is a glass spherical lens. The fixed focus lens provided by the embodiment of the invention further comprises the diaphragm (STO), and the propagation direction of the light beam can be adjusted by additionally arranging the diaphragm, so that the imaging quality is improved. The aperture may be located in the optical path between the fifth lens 305 and the sixth lens 306, but the specific arrangement position of the aperture is not limited in the embodiment of the present invention, and by arranging the aperture at a suitable position, it is helpful to increase the relative illuminance and reduce CRA.

The aspherical surface shape equations Z of the second lens 302, the third lens 303, the fifth lens 305, the sixth lens 306, the seventh lens 307, the eighth lens 308, and the ninth lens 309 satisfy:

Table 6 details the aspherical coefficients of the lenses in this example, by way of example, in one possible implementation.

Table 6 aspherical coefficients in fixed focus lenses

Wherein, -2.811354E-05 represents that the coefficient A with the face number 1 is-2.811354 x 10 ^-5 。

The fixed focus lens of the third embodiment achieves the following technical indexes:

f number: f=1.0.

Further, fig. 8 is a spherical aberration graph of a fixed focus lens according to the third embodiment of the present invention, as shown in fig. 8, spherical aberration of the fixed focus lens at different wavelengths (0.436 μm, 0.486 μm, 0.588 μm and 0.656 μm) is within 0.05mm, and the different wavelength curves are relatively concentrated, which indicates that axial aberration of the fixed focus lens is very small, so that it is known that the fixed focus lens according to the third embodiment of the present invention can correct aberration better.

Fig. 9 is a field curvature distortion diagram of a fixed focus lens according to a third embodiment of the present invention, where, as shown in fig. 9, in a left coordinate system, a horizontal coordinate represents a field curvature in mm; the vertical coordinates represent the normalized image height without units; wherein T represents meridian and S represents sagittal; as can be seen from fig. 9, the fixed focus lens provided in the third embodiment is effectively controlled in field curvature from 436nm light to 656nm light, that is, the difference between the image quality of the center and the image quality of the periphery is small during imaging; in the right coordinate system, the horizontal coordinate represents the magnitude of distortion in units of; the vertical coordinates represent the normalized image height with no units.

Example IV

Fig. 10 is a schematic structural diagram of a fixed-focus lens according to a fourth embodiment of the present invention, where, as shown in fig. 10, the fixed-focus lens includes: a first lens 401, a second lens 402, a third lens 403, a fourth lens 404, a fifth lens 405, a sixth lens 406, a seventh lens 407, an eighth lens 408, and a ninth lens 409, which are arranged in order from the object plane to the image plane along the optical axis; the first lens 401, the second lens 402, the sixth lens 406, and the eighth lens 408 are negative power lenses, and the fourth lens 404, the fifth lens 405, the seventh lens 407, and the ninth lens 409 are positive power lenses; the focal length of the fixed focus lens is phi, the focal length of the first lens 401 is phi 1, the focal length of the second lens 402 is phi 2, the focal length of the third lens 403 is phi 3, the focal length of the fourth lens 404 is phi 4, the focal length of the fifth lens 405 is phi 5, the focal length of the sixth lens 406 is phi 6, the focal length of the seventh lens 407 is phi 7, the focal length of the eighth lens 408 is phi 8, the focal length of the ninth lens 409 is phi 9, -0.554< phi 1/phi < -0.391; -0.675< 2/phi < -0.355; -0.176< Φ3/Φ <0.362;0.366< phi 4/phi <0.61;0.208< phi 5/phi <0.464; -0.535< Φ6/Φ < -0.209;0.288< phi 7/phi <0.55; -0.476< Φ8/Φ < -0.18;0.34< phi 9/phi <0.532.

As a possible embodiment, the second lens 402, the third lens 403, the fifth lens 405, the sixth lens 406, the seventh lens 407, the eighth lens 408, and the ninth lens 409 are plastic aspherical lenses, and the first lens 401 and the fourth lens 404 are glass spherical lenses. The material of the plastic aspheric lens can be various plastics known to those skilled in the art, and the material of the glass spherical lens is various types of glass known to those skilled in the art. Because the cost of the lens made of plastic is far lower than that of the lens made of glass, the lens for fixing the focus provided by the embodiment of the invention adopts a mode of mixing and matching the glass lens and the plastic lens, so that the cost of the lens for fixing the focus can be effectively controlled while the optical performance of the lens for fixing the focus is ensured.

Exemplary, table 7 details specific setting parameters of each lens in the fixed focus lens provided in the fourth embodiment of the present invention in a possible implementation manner.

Table 7 design values of optical parameters of fixed focus lens

Face number	Surface type	Radius of curvature	Thickness of (L)	Nd	Vd	Semi-Diameter
							OBJ	Spherical surface	Infinity	Infinity
1	Spherical surface	40.1814	1.499	1.82	48.1
							2	Spherical surface	5.4168	2.964
3	Aspherical surface	-9.8208	1.526	1.535	53	4
							4	Aspherical surface	6.2305	0.097			4.2
5	Aspherical surface	5.9632	2.072	1.66	21.5	4.2
							6	Aspherical surface	13.6693	0.222			4.2
7	Spherical surface	13.3159	4.526	1.648	70	6.2
							STO	Spherical surface	-11.5901	0.594			6.2
9	Aspherical surface	7.6845	3.427	1.535	56.4
							10	Aspherical surface	-13.3480	0.534
11	Aspherical surface	-37.4255	0.882	1.64	23.4
							12	Aspherical surface	14.4222	3.169	1.535	56.09
13	Aspherical surface	-11.8680	0.853
							14	Aspherical surface	-2.1710	0.953	1.66	20.1
15	Aspherical surface	-3.9463	0.113			4.171
							16	Aspherical surface	4.2404	1.775	1.535	57.4	3.8
17	Aspherical surface	895.9781	3.300			3.8
							18	Spherical surface	Infinity	0.700	1.52	64.2
19	Spherical surface	Infinity	0.603

With continued reference to fig. 10, the fixed focus lens provided in the embodiment of the present invention includes a first lens 401, a second lens 402, a third lens 403, a fourth lens 404, a fifth lens 405, a sixth lens 406, a seventh lens 407, an eighth lens 408, and a ninth lens 409, which are sequentially arranged from an object plane to an image plane along an optical axis. Table 7 shows the optical physical parameters such as the radius of curvature, thickness, and material of each lens in the fixed focus lens provided in the examples. Wherein the surface numbers are numbered according to the surface order of the respective lenses, for example, "1" represents the object plane surface of the first lens 401, "2" represents the image plane surface of the first lens 401, "9" represents the object plane surface of the fifth lens 405, "10" represents the image plane surface of the fifth lens 405, and so on; the radius of curvature represents the degree of curvature of the lens surface, positive values represent the curvature of the surface toward the image plane, and negative values represent the curvature of the surface toward the object plane; thickness represents the center axial distance from the current surface to the next surface, and the radius of curvature and thickness are in millimeters (mm).

Based on the above implementation, the second lens 402, the third lens 403, the fifth lens 405, the sixth lens 406, the seventh lens 407, the eighth lens 408 and the ninth lens 409 are plastic aspherical lenses, and the first lens 401 and the fourth lens 404 are glass spherical lenses. The fixed focus lens provided by the embodiment of the invention further comprises the diaphragm (STO), and the propagation direction of the light beam can be adjusted by additionally arranging the diaphragm, so that the imaging quality is improved. A diaphragm may be located in the optical path between the fifth lens 405 and the sixth lens 406, but the specific arrangement position of the diaphragm is not limited in the embodiment of the present invention, and by arranging the diaphragm at a suitable position, it is helpful to increase the relative illuminance and reduce CRA.

The aspherical surface shape equations Z of the second lens 402, the third lens 403, the fifth lens 405, the sixth lens 406, the seventh lens 407, the eighth lens 408, and the ninth lens 409 satisfy:

Table 8 details the aspherical coefficients of the lenses in this example, by way of example, in one possible implementation.

Table 8 aspherical coefficients in fixed focus lenses

Wherein, -2.796474E-03 shows that the coefficient A with the face number 3 is-2.796474 x 10 ^-3 。

The fixed focus lens of the fourth embodiment achieves the following technical indexes:

f number: f=1.0.

Further, fig. 11 is a spherical aberration graph of a fixed focus lens according to the fourth embodiment of the present invention, as shown in fig. 11, spherical aberration of the fixed focus lens at different wavelengths (0.436 μm, 0.486 μm, 0.588 μm and 0.656 μm) is within 0.05mm, and the different wavelength curves are relatively concentrated, which indicates that axial aberration of the fixed focus lens is very small, so that it is known that the fixed focus lens according to the fourth embodiment of the present invention can correct aberration well.

Fig. 12 is a field curvature distortion diagram of a fixed focus lens according to a fourth embodiment of the present invention, where, as shown in fig. 12, in a left coordinate system, a horizontal coordinate represents a field curvature in mm; the vertical coordinates represent the normalized image height without units; wherein T represents meridian and S represents sagittal; as can be seen from fig. 12, the fixed focus lens provided in the fourth embodiment is effectively controlled in field curvature from 436nm light to 656nm light, that is, the difference between the image quality of the center and the image quality of the periphery is small during imaging; in the right coordinate system, the horizontal coordinate represents the magnitude of distortion in units of; the vertical coordinates represent the normalized image height with no units.

Table 9 is a summary of the parameters of the above examples, and details of the refractive power, refractive index, and abbe number of each lens in the above examples are shown in table 9.

Table 9 summary of parameters of the above examples

	Example 1	Example two	Example III	Example IV	Protection scope
						Ф1/Ф	-0.475	-0.473	-0.414	-0.531	-0.554～-0.391
Ф2/Ф	-0.536	-0.630	-0.401	-0.599	-0.675～-0.355
						Ф3/Ф	0.220	0.283	-0.099	0.285	-0.176～0.362
Ф4/Ф	0.572	0.539	0.575	0.401	0.366～0.61
						Ф5/Ф	0.244	0.363	0.324	0.427	0.208～0.464
Ф6/Ф	-0.479	-0.442	-0.489	-0.256	-0.535～-0.209
						Ф7/Ф	0.466	0.376	0.512	0.325	0.288～0.55
Ф8/Ф	-0.308	-0.285	-0.291	-0.444	-0.476～-0.18
						Ф9/Ф	0.470	0.454	0.493	0.519	0.34～0.532
n1	1.61	1.61	1.535	1.82	1.47～1.96
						n2	1.535	1.54	1.535	1.535	1.47～1.55
n3	1.67	1.66	1.64	1.66	1.6～1.68
						n4	1.807	1.806	2	1.648	1.55～2.005
n5	1.54	1.535	1.535	1.535	1.47～1.55
						n6	1.64	1.64	1.66	1.64	1.6～1.68
n7	1.53	1.535	1.535	1.535	1.47～1.55
						n8	1.66	1.66	1.64	1.66	1.6～1.68
n9	1.54	1.54	1.535	1.535	1.47～1.55
						v1	60	59.2	53	48.1	38～69
v2	52.8	50	52.77	53	49～57.1
						v3	27.2	19.7	23.24	21.5	19.1～30.4
v4	45.935	45	25.53	70	20～75
						v5	60	51.8	56.84	56.4	50～61
v6	22.8	22.9	20.3	23.4	19.1～30.4
						v7	50	55.33	56	56.09	49～57.1
v8	26.36	19	22.92	20.1	18.9～30.4
						v9	60	51.4	57.8	57.4	50.1～61
TTL/BFL	6.2	5.63	5.48	6.476	<8

Note that the above is only a preferred embodiment of the present invention and the technical principle applied. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, and that various obvious changes, rearrangements, combinations, and substitutions can be made by those skilled in the art without departing from the scope of the invention. Therefore, while the invention has been described in connection with the above embodiments, the invention is not limited to the embodiments, but may be embodied in many other equivalent forms without departing from the spirit or scope of the invention, which is set forth in the following claims.

Claims

1. A fixed focus lens, comprising: a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an eighth lens and a ninth lens which are sequentially arranged from an object plane to an image plane along an optical axis;

2. the fixed focus lens of claim 1, wherein the second lens, the third lens, the fifth lens, the sixth lens, the seventh lens, the eighth lens, and the ninth lens are all plastic aspherical lenses, and the fourth lens is a glass spherical lens.

3. The fixed focus lens of claim 1, wherein a surface of the lens adjacent to the object plane side is an object side surface, and a surface of the lens adjacent to the image plane side is an image side surface;

4. The fixed focus lens of claim 1, wherein the first lens has a refractive index n1 and an abbe number v1; the refractive index of the second lens is n2, and the Abbe number is v2; the refractive index of the third lens is n3, and the Abbe number is v3; the refractive index of the fourth lens is n4, and the Abbe number is v4; the refractive index of the fifth lens is n5, and the Abbe number is v5; the refractive index of the sixth lens is n6, and the Abbe number is v6; the refractive index of the seventh lens is n7, and the Abbe number is v7; the refractive index of the eighth lens is n8, and the Abbe number is v8; the refractive index of the ninth lens is n9, and the Abbe number is v9;

5. The fixed focus lens of claim 1, wherein the distance from the optical axis center of the image side surface of the ninth lens to the image plane is BFL, and the distance from the optical axis center of the object side surface of the first lens to the image plane is TTL, wherein: TTL/BFL <8.

6. The fixed focus lens of claim 1, wherein the second lens and the third lens, the sixth lens and the seventh lens, and the seventh lens and the eighth lens are held against each other by a spacer or bonded by glue.

7. The fixed focus lens of claim 1, wherein F satisfies f.ltoreq.1.0.

8. The fixed focus lens of claim 2, wherein the second lens, the third lens, the fifth lens, the sixth lens, the seventh lens, the eighth lens, and the ninth lens are all plastic aspherical lenses, and an aspherical surface shape equation Z satisfies: