WO2023109685A1 - Prime lens - Google Patents

Abstract

A prime lens, comprising a first lens (110), a second lens (120), a third lens (130), a fourth lens (140) and a fifth lens (150) sequentially arranged from an object plane to an image plane along an optical axis, wherein the first lens (110) has a negative focal power, the second lens (120) has a negative focal power, the third lens (130) has a positive focal power, the fourth lens (140) has a negative focal power, and the fifth lens (150) has a positive focal power; the fourth lens (140) and the fifth lens (150) form a cemented lens group (10); and the focal power of each lens satisfies: -0.7 < F1/F0 < -0.5, -1.4 < F2/F0 < -1.2, 0.91 < F3/F0 < 0.94, -2.0 < F4/F0 < -1.75, 2.3 < F5/F0 < 2.5 and 3.3 < F/F0 < 3.45.

Description

fixed focus lens

This application claims the priority of the Chinese patent application with application number 202123149779.8 filed with China Patent Office on December 15, 2021, the entire content of the above application is incorporated by reference in this application.

technical field

The embodiments of the present application relate to the technical field of optical devices, for example, to a fixed-focus lens.

Background technique

With the development of technology, in order to expand the field of vision and reduce blind spots in traffic driving, the application scenarios of optical lenses with different performances are increased, and the requirements for lenses are getting higher and higher. Lenses not only need to be small, but also need to maintain good sharpness at various temperatures to improve safety.

At present, most of the wide-angle lenses on the market adopt a 6-element structure in order to achieve mega-pixel resolution, and the 6-element system has a high cost due to the large number of lenses.

Contents of the invention

The present application provides a fixed-focus lens.

An embodiment of the present application provides a fixed-focus lens, including a first lens, a second lens, a third lens, a fourth lens, and a fifth lens arranged in sequence along the optical axis from the object plane to the image plane;

The first lens has negative power, the second lens has negative power, the third lens has positive power, the fourth lens has negative power, and the fifth lens has positive power focus;

The fourth lens and the fifth lens form a cemented lens group;

The optical power of the first lens is F1, the optical power of the second lens is F2, the optical power of the third lens is F3, and the optical power of the fourth lens is F4. The focal power of the fifth lens is F5, the focal power of the fixed-focus lens is F, and the focal power of the cemented lens group is F0, wherein:

-0.7<F1/F0<-0.5, -1.4<F2/F0<-1.2, 0.91<F3/F0<0.94, -2.0<F4/F0<-1.75, 2.3<F5/F0<2.5, 3.3<F/ F0<3.45.

Description of drawings

FIG. 1 is a schematic structural diagram of a fixed-focus lens provided in Embodiment 1 of the present application;

FIG. 2 is an MTF curve diagram of the fixed-focus lens provided in Embodiment 1 of the present application;

FIG. 3 is a 550nm distortion curve diagram of the fixed-focus lens provided in Embodiment 1 of the present application;

FIG. 4 is a high-temperature defocus curve diagram of the fixed-focus lens provided in Embodiment 1 of the present application;

FIG. 5 is a low-temperature defocus curve diagram of the fixed-focus lens provided in Embodiment 1 of the present application;

FIG. 6 is a schematic structural diagram of a fixed-focus lens provided in Embodiment 2 of the present application;

FIG. 7 is an MTF curve diagram of the fixed-focus lens provided in Embodiment 2 of the present application;

FIG. 8 is a 550nm distortion curve diagram of the fixed-focus lens provided in Embodiment 2 of the present application;

FIG. 9 is a high-temperature defocus curve diagram of the fixed-focus lens provided in Embodiment 2 of the present application;

FIG. 10 is a low-temperature defocus curve of the fixed-focus lens provided in Embodiment 2 of the present application.

Detailed ways

The application will be described below in conjunction with the accompanying drawings and embodiments.

Embodiment one

Fig. 1 is a schematic structural view of a fixed-focus lens provided in Embodiment 1 of the present application. As shown in Fig. 1 , the fixed-focus lens provided in Embodiment 1 of the present application includes first Lens 110, second lens 120, third lens 130, fourth lens 140 and fifth lens 150, the first lens 110 has negative optical power, the second lens 120 has negative optical power, and the third lens 130 has positive optical power Degree, the fourth lens 140 has a negative refractive power, the fifth lens 150 has a positive refractive power; the fourth lens 140 and the fifth lens 150 form a cemented lens group 10; the refractive power of the first lens 110 is F1, and the second lens 120 has a power of F2, the third lens 130 has a power of F3, the fourth lens 140 has a power of F4, the fifth lens 150 has a power of F5, and the fixed-focus lens has a power of F , the focal power of the cemented lens group 10 is F0, wherein, -0.7<F1/F0<-0.5, -1.4<F2/F0<-1.2, 0.91<F3/F0<0.94, -2.0<F4/F0<- 1.75, 2.3<F5/F0<2.5, 3.3<F/F0<3.45.

Among them, the focal power is equal to the difference between the image beam convergence degree and the object beam convergence degree, which represents the ability of the optical system to deflect light. The greater the absolute value of the focal power, the stronger the ability to bend light, and the smaller the absolute value of the focal power, the weaker the ability to bend light. When the focal power is positive, the refraction of light is converging; when the focal power is negative, the refraction of light is divergent. Optical power can be applied to characterize a certain refraction surface of a lens (that is, a surface of the lens), can be applied to characterize a certain lens, and can also be used to characterize a system formed by multiple lenses (that is, a lens group).

In the fixed-focus lens provided in this embodiment, each lens can be fixed in a lens barrel (not shown in FIG. 1 ), the first lens 110 is set as a negative focal power lens, and the second lens 120 is a negative focal power lens. power lens, the third lens 130 is a positive power lens, the fourth lens 140 is a negative power lens, and the fifth lens 150 is a positive power lens. Sharing the focal power of the system is beneficial to correct the tolerance of the system structure, so as to reduce the sensitivity of the lens and improve the possibility of production.

In one embodiment, referring to FIG. 1 , the fourth lens 140 and the fifth lens 150 form a cemented lens group 10 , so that the air space between the fourth lens 140 and the fifth lens 150 can be effectively reduced, thereby reducing The total length of the small lens. In addition, the cemented lens group 10 can minimize chromatic aberration or eliminate chromatic aberration, so that various aberrations of the fixed-focus lens can be fully corrected, and on the premise of a compact structure, the resolution can be improved, optical performance such as distortion can be optimized, and the Reduce light loss caused by reflection between lenses and increase illumination, thereby improving image quality and enhancing the clarity of lens imaging. In addition, the use of the cemented lens group 10 can also reduce the assembly parts between the two lenses, simplify the assembly procedure in the lens manufacturing process, reduce the cost, and reduce the tilt/eccentricity of the lens unit due to the assembly process. Tolerance sensitivity.

Wherein, the fourth lens 140 and the fifth lens 150 can form the cemented lens group 10 in a direct bearing manner, or can form the cemented lens group 10 in a manner of indirect bearing through a spacer ring or a Mylar sheet. Not limited.

In one embodiment, the refractive power F1 of the first lens 110, the refractive power F2 of the second lens 120, the refractive power F3 of the third lens 130, the refractive power F4 of the fourth lens 140, and the refractive power of the fifth lens 140 are set. The focal power F5 of 150, the focal power F of the fixed-focus lens and the focal power F0 of the cemented lens group 10 meet: -0.7<F1/F0<-0.5, -1.4<F2/F0<-1.2, 0.91<F3 /F0<0.94, -2.0<F4/F0<-1.75, 2.3<F5/F0<2.5, 3.3<F/F0<3.45, to reasonably set the first lens 110, the second lens 120, the third lens 130, the The focal power ratio relationship between the quadruple lens 140 and the fifth lens 150 can better correct visible light aberrations and ensure that the fixed-focus lens can achieve higher definition.

To sum up, the fixed-focus lens provided by the embodiment of the present application is an ultra-wide-angle, high-performance fixed-focus lens, which is suitable for wide-angle and athermalized application scenarios. It only uses 5 lenses, and the number of lenses is small. The fixed-focus lens has a smaller overall length, volume and weight. At the same time, by arranging the fourth lens 140 and the fifth lens 150 to be glued together, and reasonably matching the focal powers of the five lenses, under the premise of low cost, the aberration can be better corrected to achieve higher definition and smaller Optical distortion improves the overall performance of the fixed-focus lens.

As a feasible implementation manner, the first lens 110 and the third lens 130 are glass spherical lenses, and the second lens 120 , the fourth lens 140 and the fifth lens 150 are plastic aspheric lenses.

Among them, the second lens 120 , the fourth lens 140 and the fifth lens 150 are made of plastic aspheric lenses to correct high-order aberrations of the system, thereby improving the imaging quality of the system.

Moreover, since the cost of a lens made of plastic is much lower than that of a lens made of glass, the fixed-focus lens provided by this embodiment has good image quality, low cost, and light weight by setting three plastic aspheric lenses.

At the same time, the number of plastic aspheric lenses in the fixed-focus lens is less than 4, so that it can be used in conjunction with 2 glass spherical lenses. Because the two types of materials have a mutual compensation effect, the imaging quality of the system can be effectively improved, and at the same time, it can also meet the needs of fixed-focus lenses. The lens does not go out of focus when used in high and low temperature environments, ensuring that fixed-focus lenses can still be used normally in high and low temperature environments.

It should be noted that the material of the above plastic aspheric lens can be various plastics known to those skilled in the art, and the material of the glass spherical lens can be various types of glass known to those skilled in the art, which will not be described in detail in this embodiment. Not limited.

As a feasible implementation manner, the refractive index of the second lens 120 is n2, and the Abbe number is v2; the refractive index of the fourth lens 140 is n4, and the Abbe number is v4; the refractive index of the fifth lens 150 is n5, The Abbe number is v5, among which, 0.25<n2/v2<0.35, 0.6<n4/v4<0.8, 0.2<n5/v5<0.35.

Among them, the refractive index is the ratio of the propagation speed of light in vacuum to the propagation speed of light in the medium, which is mainly used to describe the refraction ability of materials for light, and different materials have different refractive indices. The Abbe number is an index used to represent the dispersion ability of a transparent medium. The more serious the dispersion of the medium, the smaller the Abbe number; conversely, the lighter the dispersion of the medium, the larger the Abbe number.

In this embodiment, by coordinating the refractive index and Abbe number of the second lens 120, the fourth lens 140 and the fifth lens 150, it is beneficial to realize the miniaturization design of the fixed-focus lens and make it have higher pixels resolution.

As a feasible implementation, the first lens 110 has a refractive index of n1, the second lens 120 has a refractive index of n2, the third lens 130 has a refractive index of n3, the fourth lens 140 has a refractive index of n4, and the fifth lens 140 has a refractive index of n4. The refractive index of the lens 150 is n5, wherein n1>1.69, 1.45<n2<1.6, n3>1.8, 1.55<n4<1.7, 1.45<n5<1.6.

Among them, by matching and setting the refractive index of each lens in the fixed-focus lens, the aberration of the fixed-focus lens can be better corrected, and the imaging quality can be improved.

As a feasible implementation, the distance from the center of the optical axis on the image side of the fifth lens 150 to the image plane is BFL, and the distance from the center of the optical axis on the object side of the first lens 110 to the image plane is TTL, where BFL/ TTL>0.16.

Wherein, the distance BFL from the center of the optical axis on the image side of the fifth lens 150 to the image plane can be understood as the back focus of the fixed-focus lens, and the distance TTL from the center of the optical axis on the object side of the first lens 110 to the image plane can be understood as the fixed focus lens. The total optical length of the focal lens. In this embodiment, the relationship between the back focus of the fixed-focus lens and the total optical length of the fixed-focus lens is reasonably set to ensure sufficient installation space for the flat filter and the imaging sensor.

As a feasible implementation manner, the maximum aperture of the first lens 110 is DIA, and the distance from the center of the optical axis on the object side of the first lens 110 to the image plane is TTL, wherein DIA/TTL<0.83.

Among them, by reasonably setting the maximum light aperture DIA of the first lens 110 and the total length TTL of the fixed-focus lens to meet DIA/TTL<0.83, while meeting the light input amount of the fixed-focus lens, avoiding the lens aperture from being too large, and ensuring that the entire fixed-focus lens is compact .

As a feasible implementation manner, as shown in FIG. 1 , the object side of the first lens 110 is convex, and the image side of the first lens 110 is concave; the object side of the third lens 130 is convex, and the image of the third lens 130 is convex. The side surface is convex; the object side of the fourth lens 140 is convex, and the image side of the fourth lens 140 is concave; the object side of the fifth lens 150 is convex, and the image side of the fifth lens 150 is convex.

Exemplarily, as shown in FIG. 1 , by reasonably setting the surface shapes of the first lens 110 , the third lens 130 , the fourth lens 140 and the fifth lens 150 , it is ensured that the optical power and focal length of each lens meet the requirements of the above-mentioned embodiments. While meeting the requirements of optical power and focal length, it can also ensure that the entire fixed-focus lens has a compact structure and a high degree of integration of the fixed-focus lens.

As a feasible implementation manner, as shown in FIG. 1 , the object side of the second lens 120 is concave, and the image side of the second lens 120 is concave.

Exemplarily, as shown in FIG. 1, by reasonably setting the surface shape of the second lens 120, it is ensured that the optical power and focal length of the second lens 120 meet the requirements of the optical power and focal length in the above-mentioned embodiments, and the entire The fixed-focus lens has a compact structure and a high degree of integration.

As a feasible implementation manner, the object side surface of the second lens 120 is a convex surface, and the image side surface of the second lens 120 is a concave surface.

Wherein, the object side surface of the second lens 120 can also be set to be a convex surface, so as to ensure that the optical power and focal length of the second lens 120 meet the requirements of the optical power and focal length in the above embodiment, and further ensure that the entire fixed-focus lens has a compact structure. The fixed focus lens is highly integrated.

As a feasible implementation manner, the fixed-focus lens provided in the embodiment of the present application further includes an aperture 160 , and the aperture 160 is located in an optical path between the third lens 130 and the fourth lens 140 .

Wherein, the propagating direction of the light beam can be adjusted by adding the diaphragm 160, which is beneficial to improve the imaging quality. The aperture 160 may be located in the optical path between the third lens 130 and the fourth lens 140 , but the embodiment of the present application does not limit the location of the aperture.

As a feasible implementation manner, as shown in FIG. 1 , the fixed-focus lens provided in the embodiment of the present application further includes a plate glass 170 , and the plate glass 170 is disposed on the side of the image side of the fifth lens 150 .

Wherein, by arranging the plate glass 170 on the image side of the fifth lens 150, the imaging sensor can be protected.

As a feasible implementation, the plate glass 170 can be set as a plate filter to filter out unwanted stray light, thereby improving the image quality of the fixed-focus lens, for example, filtering infrared light during daytime through a plate filter To improve the imaging quality of the fixed-focus lens.

Exemplarily, Table 1 illustrates the specific optical and physical parameters of each lens in the fixed-focus lens provided in Embodiment 1 of the present application in a feasible implementation manner, and the optical-physical parameters in Table 1 correspond to the fixed-focus lens shown in Figure 1 lens.

Wherein, the first lens 110 has negative refractive power, its object side is convex, and the image side is concave; the second lens 120 has negative refractive power, its object side is concave, and the image side is concave; the third lens 130 has positive Power, the object side is convex, and the image side is convex; the fourth lens 140 has negative power, the object side is convex, and the image side is concave; the fifth lens 150 has positive power, and the object side is convex, The image side is convex; the fourth lens 140 and the fifth lens 150 form a cemented lens group 10 ; the diaphragm 160 is located in the optical path between the third lens 130 and the fourth lens 140 .

Table 1 Design values of the optical physical parameters of the fixed-focus lens

Face number	surface type	radius of curvature	thickness	Nd	Vd
OBJ	STANDARD	Infinity	Infinity	the	the
S1	STANDARD	13.212	1.000	1.800	50.000
S2	STANDARD	3.043	2.039	the	the
S3	EVENASPH	-7.333	0.812	1.543	56.812
S4	EVENASPH	1.557	1.613	the	the
S5	STANDARD	5.233	2.177	1.837	24.408
S6	STANDARD	-5.233	0.050	the	the
STO	STANDARD	Infinity	0.613	the	the
S8	STANDARD	Infinity	-0.050	the	the
S9	EVENASPH	2.846	0.645	1.630	24.817
S10	EVENASPH	0.734	1.858	1.540	60.000
S11	EVENASPH	-1.937	0.254	the	the
S12	STANDARD	Infinity	0.700	1.517	64.199
S13	STANDARD	Infinity	1.411	the	the

Wherein, the surface numbers are numbered according to the surface order of each lens, for example, "S1" represents the object side of the first lens 110, "S2" represents the image side of the first lens 110, and so on; the radius of curvature represents the curvature of the lens surface Positive value means that the surface is bent to the side of the image plane, negative value means that the surface is bent to the side of the object plane, where "Infinity" means that the surface is a plane, and the radius of curvature is infinite; the thickness means the distance from the current surface to the next surface The unit of central axial distance, radius of curvature and thickness are millimeters (mm); "Nd" represents the refractive index, that is, the deflection ability of the material between the current surface and the next surface for light, and the space represents the current position is air, The refractive index is 1; "Vd" represents the Abbe number, that is, the dispersion characteristics of the material between the current surface and the next surface for light, and a blank space represents the current position is air; "STANDARD" represents a spherical surface, and "EVENASPH" represents an aspherical surface; "OBJ" stands for object plane; "STO" stands for stop.

Its aspheric conic coefficient can be limited by the following aspheric formula, but not limited to the following representation:

Among them, z is the axial sagittal height of the aspherical surface in the Z direction; r is the height of the aspheric surface; c is the curvature of the fitted sphere, which is the reciprocal of the radius of curvature in value; k is the fitting conic coefficient; A-G is the 4 of the aspheric polynomial Coefficients of order, 6th order, 8th order, 10th order, 12th order, 14th order, 16th order.

Exemplarily, Table 2 illustrates the aspheric coefficients of the lenses in the first embodiment in a feasible implementation manner.

Table 2 Design values of the aspheric coefficients of each lens in the fixed-focus lens

Wherein, -8.15E+01 means that the coefficient A of the plane number 3 is -8.15*10 ¹ , and so on.

In one embodiment, FIG. 2 is a graph of the modulation transfer function (Modulation Transfer Function, MTF) of the fixed-focus lens provided by Embodiment 1 of the present application, wherein the MTF graph can represent the comprehensive imaging quality of the fixed-focus lens, and the MTF value The higher the image, the clearer the image, as shown in Figure 2, its abscissa Spatial Frequency in cycles per mm represents the spatial frequency in cycles per mm, its ordinate Modulus of the OTF represents the OTF coefficient, and the MTF curve is at 80 line pairs/ mm, the transfer function is basically above 0.45, which can meet the required image quality requirements.

Fig. 3 is the 550nm distortion curve diagram of the fixed-focus lens provided by Embodiment 1 of the present application. As shown in Fig. 3, the horizontal coordinate represents the size of the distortion (Distortion), and the unit is % (Percent); the vertical coordinate represents the normalized image height , there is no unit; it can be seen from FIG. 3 that the distortion of the fixed-focus lens provided by this embodiment is well corrected, and the imaging distortion is small, which meets the requirement of low distortion.

Fig. 4 is a high-temperature defocus curve diagram of the fixed-focus lens provided in Embodiment 1 of the present application, and Fig. 5 is a low-temperature defocus curve diagram of the fixed-focus lens provided in Embodiment 1 of the present application, as shown in Fig. 4 and Fig. 5 . The abscissa Focus shift in Millimeters represents the focal shift (mm), and the ordinate Modulus of the OTF represents the OTF coefficient. As can be seen from Fig. 4 and Fig. 5, the fixed-focus lens provided by Embodiment 1 of the present application is under high temperature and low temperature conditions, The positions of the peak values of the defocus curve are close to the central field of view, which can reduce the influence of tolerances, especially eccentricity, on imaging quality, thereby effectively improving the yield rate and having good processability.

Embodiment two

Fig. 6 is a schematic structural view of the fixed-focus lens provided in Embodiment 2 of the present application. As shown in Fig. 6 , the fixed-focus lens provided in Embodiment 2 of the present application includes first lenses 110 arranged in sequence along the optical axis from the object plane to the image plane , the second lens 120, the third lens 130, the fourth lens 140 and the fifth lens 150, wherein the first lens 110 has a negative power, its object side is convex, and the image side is concave; the second lens 120 has a negative Refractive power, the object side is convex, and the image side is concave; the third lens 130 has positive refractive power, the object side is convex, and the image side is convex; the fourth lens 140 has negative refractive power, and the object side is convex , the image side is concave; the fifth lens 150 has positive refractive power, the object side is convex, and the image side is convex; the fourth lens 140 and the fifth lens 150 form a cemented lens group 10 .

Exemplarily, Table 3 illustrates the specific optical physical parameters of each lens in the fixed-focus lens provided in Embodiment 2 of the present application in a feasible implementation manner, and the optical physical parameters in Table 3 correspond to the fixed-focus lens shown in Figure 6 lens.

Table 3 Design values of the optical physical parameters of the fixed-focus lens

Face number	surface type	radius of curvature	thickness	Nd	Vd
OBJ	STANDARD	Infinity	Infinity	the	the
S1	STANDARD	12.007	1.000	1.942	49.997
S2	STANDARD	2.824	2.022	the	the
S3	EVENASPH	16.630	0.721	1.514	58.344
S4	EVENASPH	1.196	1.195	the	the
S5	STANDARD	6.667	2.898	1.848	23.605
S6	STANDARD	-4.196	-0.050	the	the
STO	STANDARD	Infinity	0.320	the	the
S8	EVENASPH	2.699	0.843	1.637	24.625
S9	EVENASPH	0.800	1.898	1.537	60.000
S10	EVENASPH	-1.876	0.400	the	the
S11	STANDARD	Infinity	0.700	1.517	64.199
S12	STANDARD	Infinity	1.000	the	the

Wherein, the surface numbers are numbered according to the surface order of each lens, for example, "S1" represents the object side of the first lens 110, "S2" represents the image side of the first lens 110, and so on; the radius of curvature represents the curvature of the lens surface Positive value means that the surface is bent to the side of the image plane, negative value means that the surface is bent to the side of the object plane, where "Infinity" means that the surface is a plane, and the radius of curvature is infinite; the thickness means the distance from the current surface to the next surface The unit of central axial distance, radius of curvature and thickness are millimeters (mm); "Nd" represents the refractive index, that is, the deflection ability of the material between the current surface and the next surface for light, and the space represents the current position is air, The refractive index is 1; "Vd" represents the Abbe number, that is, the dispersion characteristics of the material between the current surface and the next surface for light, and a blank space represents the current position is air; "STANDARD" represents a spherical surface, and "EVENASPH" represents an aspherical surface; "OBJ" stands for object plane; "STO" stands for stop.

Its aspheric conic coefficient can be limited by the following aspheric formula, but not limited to the following representation:

Among them, z is the axial sagittal height of the aspherical surface in the Z direction; r is the height of the aspheric surface; c is the curvature of the fitted sphere, which is the reciprocal of the radius of curvature in value; k is the fitting conic coefficient; A-G is the 4 of the aspheric polynomial Coefficients of order, 6th order, 8th order, 10th order, 12th order, 14th order, 16th order.

Exemplarily, Table 4 illustrates the aspheric coefficients of the lenses in the second embodiment in a feasible implementation manner.

Table 4 Design values of the aspheric coefficients of each lens in the fixed-focus lens

Wherein, -1.40E+02 means that the coefficient A of the plane number 3 is -1.40*10 ² , and so on.

In one embodiment, FIG. 7 is the MTF curve diagram of the fixed-focus lens provided in Embodiment 2 of the present application, wherein the MTF curve diagram can represent the comprehensive imaging quality of the fixed-focus lens. The higher the MTF value, the clearer the imaging, as shown in the figure As shown in 7, the abscissa Spatial Frequency in cycles per mm represents the spatial frequency in the unit of cycle per mm, and the ordinate Modulus of the OTF represents the OTF coefficient, and the transfer function of the MTF curve is basically above 0.4 when the MTF curve is 80 line pairs/mm , which can meet the required image quality requirements.

Fig. 8 is a 550nm distortion curve diagram of the fixed-focus lens provided in Embodiment 2 of the present application. As shown in Fig. 8, the horizontal coordinate represents the size of the distortion (Distortion), and the unit is % (Percent); the vertical coordinate represents the normalized image height , there is no unit; it can be seen from FIG. 8 that the distortion of the fixed-focus lens provided by this embodiment is well corrected, and the imaging distortion is small, which meets the requirement of low distortion.

Fig. 9 is a high-temperature defocus curve of the fixed-focus lens provided in Embodiment 2 of the present application, and Fig. 10 is a low-temperature defocus curve of the fixed-focus lens provided in Embodiment 2 of the present application, as shown in Fig. 9 and Fig. 10 . The abscissa Focus shift in Millimeters represents the focus shift (mm), and the ordinate Modulus of the OTF represents the OTF coefficient. As can be seen from Figures 9 and 10, the fixed-focus lens provided by Embodiment 2 of the present application is under high temperature and low temperature conditions. The positions of the peak values of the defocus curve are close to the central field of view, which can reduce the influence of tolerances, especially eccentricity, on imaging quality, thereby effectively improving the yield rate and having good processability.

Exemplarily, Table 5 illustrates the aspheric coefficients of the lenses in the second embodiment in a feasible implementation manner.

Table 5 Design values of the aspheric coefficients of each lens in the fixed-focus lens

Wherein, -1.40E+02 means that the coefficient A of the plane number 3 is -1.40*10 ² , and so on.

In one embodiment, FIG. 7 is the MTF curve diagram of the fixed-focus lens provided in Embodiment 2 of the present application, wherein the MTF curve diagram can represent the comprehensive imaging quality of the fixed-focus lens. The higher the MTF value, the clearer the imaging, as shown in the figure As shown in 7, the abscissa Spatial Frequency in cycles per mm represents the spatial frequency in the unit of cycle per mm, and the ordinate Modulus of the OTF represents the OTF coefficient, and the transfer function of the MTF curve is basically above 0.4 when the MTF curve is 80 line pairs/mm , which can meet the required image quality requirements.

Fig. 8 is a 550nm distortion curve diagram of the fixed-focus lens provided in Embodiment 2 of the present application. As shown in Fig. 8, the horizontal coordinate represents the size of the distortion (Distortion), and the unit is % (Percent); the vertical coordinate represents the normalized image height , there is no unit; it can be seen from FIG. 8 that the distortion of the fixed-focus lens provided by this embodiment is well corrected, and the imaging distortion is small, which meets the requirement of low distortion.

Fig. 9 is a high-temperature defocus curve of the fixed-focus lens provided in Embodiment 2 of the present application, and Fig. 10 is a low-temperature defocus curve of the fixed-focus lens provided in Embodiment 2 of the present application, as shown in Fig. 9 and Fig. 10 . The abscissa Focus shift in Millimeters represents the focus shift (mm), and the ordinate Modulus of the OTF represents the OTF coefficient. As can be seen from Figures 9 and 10, the fixed-focus lens provided by Embodiment 2 of the present application is under high temperature and low temperature conditions. The positions of the peak values of the defocus curve are close to the central field of view, which can reduce the influence of tolerances, especially eccentricity, on imaging quality, thereby effectively improving the yield rate and having good processability.

An embodiment of the present application provides a fixed-focus lens, which reduces costs while improving imaging quality.

Those skilled in the art will understand that the present application is not limited to the specific embodiments described here, and those skilled in the art can make various changes, readjustments, mutual combinations and substitutions without departing from the protection scope of the present application. Therefore, although the present application has been described through the above embodiments, the present application is not limited to the above embodiments, and can also include more other equivalent embodiments without departing from the concept of the present invention, and the scope of the present application consists of The scope of the appended claims determines.

Claims (10)

1. A fixed-focus lens, comprising a first lens (110), a second lens (120), a third lens (130), a fourth lens (140) and a fifth lens arranged in sequence along an optical axis from an object plane to an image plane (150);

   The first lens (110) has negative power, the second lens (120) has negative power, the third lens (130) has positive power, and the fourth lens (140) has negative optical power, the fifth lens (150) has positive optical power;

   The fourth lens (140) and the fifth lens (150) form a cemented lens group (10);

   The refractive power of the first lens (110) is F1, the refractive power of the second lens (120) is F2, the refractive power of the third lens (130) is F3, and the fourth lens The refractive power of (140) is F4, the refractive power of the fifth lens (150) is F5, the refractive power of the fixed focus lens is F, and the refractive power of the cemented lens group (10) is F0, where:

   -0.7<F1/F0<-0.5, -1.4<F2/F0<-1.2, 0.91<F3/F0<0.94, -2.0<F4/F0<-1.75, 2.3<F5/F0<2.5, 3.3<F/ F0<3.45.
2. The fixed-focus lens according to claim 1, wherein,

   The first lens (110) and the third lens (130) are glass spherical lenses, and the second lens (120), the fourth lens (140) and the fifth lens (150) are plastic aspheric lens.
3. The fixed-focus lens according to claim 1, wherein,

   The refractive index of the second lens (120) is n2, and the Abbe number is v2; the refractive index of the fourth lens (140) is n4, and the Abbe number is v4; the refractive index of the fifth lens (150) The rate is n5, and the Abbe number is v5, where:

   0.25<n2/v2<0.35, 0.6<n4/v4<0.8, 0.2<n5/v5<0.35.
4. The fixed-focus lens according to claim 1, wherein,

   The refractive index of the first lens (110) is n1, the refractive index of the second lens (120) is n2, the refractive index of the third lens (130) is n3, and the fourth lens (140) The refractive index of n4, the refractive index of the fifth lens (150) n5, wherein:

   n1>1.69, 1.45<n2<1.6, n3>1.8, 1.55<n4<1.7, 1.45<n5<1.6.
5. The fixed-focus lens according to claim 1, wherein,

   The distance from the center of the optical axis of the image side of the fifth lens (150) to the image plane is BFL, and the distance from the center of the optical axis of the object side of the first lens (110) to the image plane is TTL, wherein BFL/ TTL>0.16.
6. The fixed-focus lens according to claim 1, wherein,

   The maximum aperture of the first lens (110) is DIA, and the distance from the center of the optical axis on the object side of the first lens (110) to the image plane is TTL, wherein DIA/TTL<0.83.
7. The fixed-focus lens according to claim 1, wherein,

   The object side of the first lens (110) is a convex surface, and the image side of the first lens (110) is a concave surface;

   The object side of the third lens (130) is convex, and the image side of the third lens (130) is convex;

   The object side of the fourth lens (140) is convex, and the image side of the fourth lens (140) is concave;

   The object side of the fifth lens (150) is convex, and the image side of the fifth lens (150) is convex.
8. The fixed-focus lens according to claim 7, wherein,

   The object side of the second lens (120) is concave, and the image side of the second lens (120) is concave.
9. The fixed-focus lens according to claim 7, wherein,

   The object side of the second lens (120) is convex, and the image side of the second lens (120) is concave.
10. The fixed-focus lens according to claim 1, further comprising an aperture (160);

    The diaphragm (160) is located in an optical path between the third lens (130) and the fourth lens (140).

Images