CN112130288A

CN112130288A - Black light lens

Info

Publication number: CN112130288A
Application number: CN202011127819.6A
Authority: CN
Inventors: 姚晨; 何剑炜; 米士隆
Original assignee: Dongguan Yutong Optical Technology Co Ltd
Current assignee: Dongguan Yutong Optical Technology Co Ltd
Priority date: 2020-10-20
Filing date: 2020-10-20
Publication date: 2020-12-25

Abstract

The embodiment of the invention discloses a black light lens. The black light lens includes: the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the seventh lens and the eighth lens are sequentially arranged from an object plane to an image plane along an optical axis; the first lens has negative focal power, the second lens has negative focal power, the third lens has positive focal power, the fourth lens has positive focal power, the fifth lens has negative focal power, the sixth lens has positive focal power, the seventh lens has negative focal power, and the eighth lens has positive focal power. The black light lens provided by the invention has the advantages that the imaging quality is improved and the high-definition image quality requirement is met under the condition of ensuring high performance, small volume and low cost.

Description

Black light lens

Technical Field

The embodiment of the invention relates to the technical field of optical devices, in particular to a black light lens.

Background

With the continuous progress of science and technology, the security awareness of people is strengthened, the security monitoring industry rises rapidly, and the role of monitoring in life is more and more important. At present, a fixed focus monitoring lens is visible everywhere in life, but the conventional security monitoring and road condition monitoring lens has the following defects: most of the lens are simple in structure, the size of the target surface is small, the resolution of the acquired image is low, the shooting effect is general, and the picture value is not large. Most of the apertures of the zoom lenses on the market are small, so that the light transmission of the lenses is less, images obtained under a low-illumination scene are darker, and the image quality is difficult to guarantee. As security protection advances toward high definition and miniaturization, a lens is required to achieve higher performance and smaller size.

Disclosure of Invention

The embodiment of the invention provides a black light lens, which can improve the imaging quality and meet the requirement of high-definition image quality under the condition of ensuring high performance, small volume and low cost.

In a first aspect, an embodiment of the present invention provides a black light lens, including: the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the seventh lens and the eighth lens are sequentially arranged from an object plane to an image plane along an optical axis;

the first lens has a negative optical power, the second lens has a negative optical power, the third lens has a positive optical power, the fourth lens has a positive optical power, the fifth lens has a negative optical power, the sixth lens has a positive optical power, the seventh lens has a negative optical power, and the eighth lens has a positive optical power.

Optionally, the first lens and the fourth lens are both glass spherical lenses, and the second lens, the third lens, the fifth lens, the sixth lens, the seventh lens and the eighth lens are all plastic aspherical lenses.

Optionally, the first lens, the third lens and the fourth lens are all glass spherical lenses, and the second lens, the fifth lens, the sixth lens, the seventh lens and the eighth lens are all plastic aspheric lenses.

Optionally, the black light lens further includes a diaphragm;

the diaphragm is located in an optical path between the fifth lens and the sixth lens.

Optionally, a focal length of the first lens is f1, a focal length of the second lens is f2, a focal length of the third lens is f3, a focal length of the fourth lens is f4, a focal length of the fifth lens is f5, a focal length of the sixth lens is f6, a focal length of the seventh lens is f7, a focal length of the eighth lens is f8, and an entrance pupil diameter of the black light lens is N;

wherein | f1/N | is more than or equal to 0.5 and less than or equal to 7.5; the absolute value of f2/N is more than or equal to 1.1 and less than or equal to 8; l f3/N | > 1.3; the absolute value of f4/N is more than or equal to 1.5 and less than or equal to 8.6; the absolute value of f5/N is more than or equal to 0.6 and less than or equal to 9; the | f6/N | ≧ 0.22; the absolute value of f7/N is more than or equal to 0.18 and less than or equal to 5.5; the | f8/N | is less than or equal to 11.

Optionally, the refractive index of the first lens is n1, and the abbe number is v 1; the refractive index of the second lens is n2, and the Abbe number is v 2; the refractive index of the third lens is n3, and the Abbe number is v 3; the refractive index of the fourth lens is n4, and the Abbe number is v 4;

wherein n1 is more than or equal to 1.43; v1 is more than or equal to 39; n2 is more than or equal to 1.45 and less than or equal to 1.8; 22 is less than or equal to v2 is less than or equal to 68; n3 is more than or equal to 1.52; v3 is less than or equal to 65; n4 is more than or equal to 1.55 and less than or equal to 2.0; v4 is more than or equal to 32.

Optionally, the radius of curvature of the near object surface of the first lens is R11; the near object surface curvature radius of the second lens is R21, and the near image surface curvature radius is R22; the near object surface curvature radius of the third lens is R31, and the near image surface curvature radius is R32; the curvature radius of a near object surface of the fifth lens is R51, and the curvature radius of a near image surface of the fifth lens is R52; the curvature radius of a near object surface of the seventh lens is R71, and the curvature radius of a near image surface of the seventh lens is R72; the near-image surface curvature radius of the eighth lens is R82; the air space of the third lens and the fourth lens is TH 34;

wherein R11 is more than or equal to 8; the absolute value of R21/R22 is more than or equal to 0.6 and less than or equal to 6.8; the ratio of R31 to R32 is less than or equal to 2.5; the absolute value of R51/R52 is more than or equal to 0.23 and less than or equal to 3.6; the | R71/R72| is more than or equal to 0.02; i R82 is not less than 6; TH34 is more than or equal to 0.

Optionally, the fifth lens is a meniscus lens.

Optionally, a distance from the optical axis center of the image space surface of the eighth lens to the image plane is BFL, a distance from the optical axis center of the object space surface of the first lens to the image plane is TTL, and BFL/TTL is greater than or equal to 0.05.

Optionally, an aperture of the black light lens is F, an angle of view is FOV, an angle of incidence of image plane light is CRA, and an aperture of the plastic lens is DL; wherein F is more than or equal to 1.0 and less than or equal to 1.1; FOV is more than or equal to 95 degrees and less than or equal to 115 degrees; CRA is less than or equal to 15 degrees; DL is less than or equal to 15 mm.

According to the technical scheme provided by the embodiment of the invention, the number of the lenses in the black light lens and the relative relation of the focal power of each lens are reasonably set, so that the balance of the incident angles of the front and rear groups of lenses of the black light lens is ensured on the premise of low cost, the sensitivity of the lens is reduced, the production possibility is improved, the black light lens is ensured to have higher resolving power in an environment of-30-80 ℃, the imaging quality is improved, and the requirement of high-definition image quality is met.

Drawings

To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, a brief description will be given below of the drawings required for the embodiments or the technical solutions in the prior art, and it is obvious that the drawings in the following description, although being some specific embodiments of the present invention, can be extended and extended to other structures and drawings by those skilled in the art according to the basic concepts of the device structure, the driving method and the manufacturing method disclosed and suggested by the various embodiments of the present invention, without making sure that these should be within the scope of the claims of the present invention.

Fig. 1 is a schematic structural diagram of a black light lens according to an embodiment of the present invention;

fig. 2 is a spherical aberration curve chart of a black light lens according to an embodiment of the present invention;

fig. 3 is a light fan diagram of a black light lens according to an embodiment of the present invention;

fig. 4 is a visible light spot arrangement diagram of a black light lens according to an embodiment of the present invention;

fig. 5 is a field curvature distortion diagram of a black light lens according to an embodiment of the present invention;

fig. 6 is an MTF graph of a black light lens according to an embodiment of the present invention;

fig. 7 is a schematic structural diagram of a black light lens according to a second embodiment of the present invention;

fig. 8 is a spherical aberration curve chart of a black light lens according to a second embodiment of the present invention;

fig. 9 is a light fan diagram of a black light lens according to a second embodiment of the present invention;

fig. 10 is a visible light spot arrangement diagram of a black light lens according to a second embodiment of the present invention;

fig. 11 is a field curvature distortion diagram of a black light lens according to a second embodiment of the present invention;

fig. 12 is an MTF graph of a black light lens according to a second embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described through embodiments with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the basic idea disclosed and suggested by the embodiments of the present invention, are within the scope of the present invention.

Example one

Fig. 1 is a schematic structural diagram of a black light lens according to a first embodiment of the present invention, and as shown in fig. 1, the black light lens according to the first embodiment of the present invention includes: a first lens 110, a second lens 120, a third lens 130, a fourth lens 140, a fifth lens 150, a sixth lens 160, a seventh lens 170, and an eighth lens 180 arranged in this order from an object plane to an image plane along an optical axis; the first lens 110 has a negative power, the second lens 120 has a negative power, the third lens 130 has a positive power, the fourth lens 140 has a positive power, the fifth lens 150 has a negative power, the sixth lens 160 has a positive power, the seventh lens 170 has a negative power, and the eighth lens 180 has a positive power.

Illustratively, the optical power is equal to the difference between the image-side and object-side beam convergence, which characterizes the ability of the optical system to deflect light. The larger the absolute value of the focal power is, the stronger the bending ability to the light ray is, and the smaller the absolute value of the focal power is, the weaker the bending ability to the light ray is. When the focal power is positive, the refraction of the light is convergent; when the focal power is negative, the refraction of the light is divergent. The optical power can be suitable for representing a certain refractive surface of a lens (namely, a surface of the lens), can be suitable for representing a certain lens, and can also be suitable for representing a system (namely a lens group) formed by a plurality of lenses together. In the black light lens provided by the present embodiment, each lens can be fixed in one lens barrel (not shown in fig. 1), the first lens 110, the second lens 120, the fifth lens 150 and the seventh lens 170 are arranged as negative power lenses, the first lens 110 and the second lens 120 are used for controlling the incident angle of the light rays of the optical system, and ensuring a large field angle; the third lens 130, the fourth lens 140, the sixth lens 160 and the eighth lens 180 are positive power lenses, and the third lens 130 and the fourth lens 140 bear larger power and play a role in relieving the balance tolerance of the light incidence angle. The focal power of the whole black light lens is distributed according to a certain proportion, and the balance of the incident angles of the front and rear lens groups is ensured, so that the sensitivity of the lens is reduced, and the production possibility is improved.

Optionally, the first lens 110 and the fourth lens 140 are both glass spherical lenses, and the second lens 120, the third lens 130, the fifth lens 150, the sixth lens 160, the seventh lens 170, and the eighth lens 180 are all plastic aspherical lenses.

The aspheric lens has the function of correcting aberrations such as field curvature, astigmatism, spherical aberration, coma aberration and the like. 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 can be various types of glass known to those skilled in the art. Because the cost of the lens made of the plastic material is far lower than that of the lens made of the glass material, the black light lens provided by the embodiment of the invention has good image quality and low cost by arranging 6 plastic aspheric lenses. And because the two materials have the mutual compensation function, the black light lens can still be normally used in high and low temperature environments.

Optionally, the black light lens further includes a diaphragm 190;

a stop 190 is located in the optical path between the fifth lens 150 and the sixth lens 160.

By arranging the diaphragm 190 in the optical path between the fifth lens 150 and the sixth lens 160, 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.

Optionally, the focal length of the first lens 110 is f1, the focal length of the second lens 120 is f2, the focal length of the third lens 130 is f3, the focal length of the fourth lens 140 is f4, the focal length of the fifth lens 150 is f5, the focal length of the sixth lens 160 is f6, the focal length of the seventh lens 170 is f7, the focal length of the eighth lens 180 is f8, and the entrance pupil diameter of the black light lens is N;

The focal length of each lens is reasonably distributed, so that aberration correction is facilitated, and the black light lens is guaranteed to have higher resolving power.

Optionally, the refractive index of the first lens 110 is n1, and the abbe number is v 1; the refractive index of the second lens 120 is n2, and the abbe number is v 2; the refractive index of the third lens 130 is n3, and the Abbe number is v 3; the refractive index of the fourth lens 140 is n4, and the abbe number is v 4;

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 expressing the dispersion capability of the transparent medium, and the more severe the dispersion of the medium is, the smaller the abbe number is; conversely, the more slight the dispersion of the medium, the greater the abbe number. Therefore, the refractive index and the Abbe number of each lens in the black light lens are matched, the balance of the incident angles of the front and rear groups of lenses is ensured, the sensitivity of the lens is reduced, and the production possibility is improved.

Optionally, the radius of curvature of the near object surface of the first lens 110 is R11; the near object surface curvature radius of the second lens 120 is R21, and the near image surface curvature radius is R22; the near object surface curvature radius of the third lens 130 is R31, and the near image surface curvature radius is R32; the near object surface curvature radius of the fifth lens 150 is R51, and the near image surface curvature radius is R52; the near object surface curvature radius of the seventh lens 170 is R71, and the near image surface curvature radius is R72; the near-image-plane radius of curvature of the eighth lens 180 is R82; the air interval of the third lens 130 and the fourth lens 140 is TH 34;

Specifically, the curvature radius is in millimeters (mm), and the curvature radius R11 of the near object surface of the first lens 110 is set to satisfy that R11 is more than or equal to 8; the curvature radius of the near object surface of the second lens 120 is R21, the curvature radius of the near image surface is R22, the requirement of | R21/R22| -6.8 | -0.6 ≦ is met, the curvature radius of the near object surface of the third lens 130 is R31, the curvature radius of the near image surface is R32, and the requirement of | R31/R32| -2.5 is met; the curvature radius of a near object surface of the fifth lens 150 is R51, the curvature radius of a near image surface is R52, and | R51/R52| is more than or equal to 0.23 and less than or equal to 3.6; the curvature radius of a near object surface of the seventh lens 170 is R71, the curvature radius of a near image surface of the seventh lens is R72, and | R71/R72| ≧ 0.02, and the curvature radius of a near image surface of the eighth lens 180 is R82, and | R82| ≧ 6; the object plane and the image plane of the first lens 110, the second lens 120, the third lens 130, the fifth lens 150 and the seventh lens 170 are curved in the same direction, so that the miniaturization design of the black light lens is facilitated, and meanwhile, the imaging quality of the black light lens is facilitated to be improved by optimizing the shapes of the first lens 110, the second lens 120, the third lens 130, the fifth lens 150, the seventh lens 170 and the eighth lens 180. The image plane of the eighth lens element 180 may be a large convex surface, which plays a role in reducing the incident angle of image plane light rays of the black light lens. By reasonably restricting the total length of the air space, the structure of the lens can be more compact, and the effective focal length and the total length of the black light lens are still in a reasonable range while high image quality is realized.

Exemplarily, setting TH34 to 0 enables combining the third lens 130 and the fourth lens 140 into a cemented lens by cementing the image side surface of the third lens 130 with the object side surface of the fourth lens 140; the use of the cemented lens can effectively reduce the air space between the third lens 130 and the fourth lens 140, thereby reducing the overall lens length. In addition, the cemented lens can be used for reducing chromatic aberration or eliminating chromatic aberration to the maximum extent, so that various aberrations of the black light lens can be fully corrected, the resolution can be improved, and 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 the 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 the assembly parts between the two lenses, simplify the assembly procedure in the lens manufacturing process, reduce the cost, and reduce the tolerance sensitivity problems of the lens unit, such as inclination/decentration, and the like, generated in the assembly process.

Optionally, the fifth lens 150 is a meniscus lens.

The meniscus lens is composed of two spherical surfaces with small curvature radius and small numerical value difference, and the fifth lens 150 is a meniscus lens and can correct field curvature.

Optionally, a distance from the optical axis center of the image side surface of the eighth lens element 180 to the image plane is BFL, and a distance from the optical axis center of the object side surface of the first lens element 110 to the image plane is TTL, where BFL/TTL is greater than or equal to 0.05.

The distance BFL from the optical axis center of the image side surface of the eighth lens 180 to the image plane can be understood as the back focal of the black light lens, the distance TTL from the optical axis center of the object side surface of the first lens 110 to the image plane can be understood as the total length of the black light lens, and the relationship between the back focal of the black light lens and the total length of the black light lens is reasonably set, so that the compact structure of the whole black light lens can be ensured, and the integration level of the black light lens is high.

Optionally, the aperture of the black light lens is F, the field angle is FOV, the image plane ray incidence angle is CRA, and the aperture of the plastic lens is DL; wherein F is more than or equal to 1.0 and less than or equal to 1.1; FOV is more than or equal to 95 degrees and less than or equal to 115 degrees; CRA is less than or equal to 15 degrees; DL is less than or equal to 15 mm.

The aperture of the black light lens and the aperture of the lens can meet the requirement of large light throughput, so that the monitoring requirement under the low-illumination condition is met. Meanwhile, the black light lens is a black light lens with an ultra-large field angle, and meets the requirement of the ultra-large field angle. By limiting the incidence angle CRA of the chief ray corresponding to the maximum field angle of the black light lens on the image plane, the angle of the ray incident on the photosensitive element in the system can be effectively suppressed, so that the sensitivity of the black light lens on the photosensitive element is improved.

According to the black light lens provided by the embodiment of the invention, through reasonably distributing the focal power, the surface type, the refractive index, the Abbe number and the like of each lens, on the premise of low cost, the balance of the incident angles of the front and rear lens groups of the black light lens is ensured, the sensitivity of the lens is reduced, the black light lens is ensured to have higher resolving power, the imaging quality is improved, and the requirement of high-definition image quality is met; meanwhile, the resolution of the black light lens in an environment of-30-80 ℃ is guaranteed to meet the imaging requirement, the imaging capability of the lens in a night environment is guaranteed, and the consistency of image quality under different conditions is realized.

As a possible embodiment, the radius of curvature, thickness, material, and K-factor of each lens surface in the black light lens are explained below.

TABLE 1 design values of radius of curvature, thickness, material and K-factor of a black light lens

With reference to fig. 1, the black light lens provided by the first embodiment of the present invention includes a first lens 110, a second lens 120, a third lens 130, a fourth lens 140, a fifth lens 150, a sixth lens 160, a seventh lens 170, and an eighth lens 180, which are sequentially arranged along an optical axis from an object plane to an image plane. Table 1 shows optical physical parameters such as a curvature radius, a thickness, and a material of each lens in the black light lens provided in the embodiment. The surface numbers are numbered according to the surface sequence of the lenses, for example, "1" represents the object plane surface of the first lens 110, "2" represents the image plane surface of the first lens 110, "10" represents the object plane surface of the fifth lens 150, "11" represents the image plane surface of the fifth lens 150, and so on; the curvature radius represents the bending degree of the surface of the lens, a positive value represents that the surface is bent to the image surface side, and a negative value represents that the surface is bent to the object surface side; thickness represents the central axial distance from the current surface to the next surface, and the radius of curvature and thickness are both in millimeters (mm).

In addition to the above embodiments, optionally, the first lens 110 and the fourth lens 140 are glass spherical lenses, and the second lens 120, the third lens 130, the fifth lens 150, the sixth lens 160, the seventh lens 170, and the eighth lens 180 are plastic aspherical lenses. The black light lens provided by the first embodiment of the invention further comprises the diaphragm 190(STO), and the propagation direction of the light beam can be adjusted by additionally arranging the diaphragm 190, so that the imaging quality is improved. The stop 190 may be located in the optical path between the fifth lens 150 and the sixth lens 160, but the specific location of the stop 190 is not limited in the embodiment of the present invention, and by locating the stop at a suitable location, it is helpful to improve the relative illuminance and reduce the CRA.

The aspherical surface shape equation Z of the first lens 110, the second lens 120, the third lens 130, the fourth lens 140, the fifth lens 150, the sixth lens 160, the seventh lens 170, and the eighth lens 180 satisfies:

wherein Z is the distance rise from the vertex of the aspheric surface when the aspheric surface is at the position with the height of y along the optical axis direction; c is 1/R, R represents the paraxial radius of curvature of the mirror surface; k is the cone coefficient; A. b, C, D, E, F is a high-order aspheric coefficient, where Z, R and y are both in mm.

Illustratively, table 2 details the aspheric coefficients of the lenses of the present embodiment in one possible implementation.

TABLE 2 aspheric coefficients in black light lens

wherein-1.19E-03 indicates that the coefficient A with the face number 3 is-1.19 x 10^-3And so on.

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

Fig. 3 is a light fan diagram of a black light lens according to an embodiment of the present invention, as shown in fig. 3, imaging ranges of light rays with different wavelengths (0.486 μm, 0.588 μm, and 0.656 μm) under different angles of view of the black light lens are within 50 μm, and curves are very concentrated, so that it is ensured that aberrations of different field regions are small, that is, it is explained that the black light lens better corrects aberrations of an optical system.

Fig. 4 is a visible light spot diagram of a black-light lens according to an embodiment of the present invention, wherein the spot diagram is one of the most common evaluation methods in modern optical design. The point diagram is that after many light rays emitted by a point light source pass through an optical system, intersection points of the light rays and an image surface are not concentrated on the same point any more due to aberration, and a diffusion pattern scattered in a certain range is formed. As shown in fig. 4, in the black light lens provided in the first embodiment of the present invention, the diffusion patterns of the visible light rays (0.4861 μm, 0.5876 μm, and 0.6563 μm) with different wavelengths in each field are relatively concentrated and distributed uniformly, and the phenomenon that the diffusion patterns in a certain field are separated from each other up and down along with the wavelength does not occur, which indicates that there is no obvious purple edge. Meanwhile, the root mean square radius values (RMS radius) of the visible rays (0.4861 μm, 0.5876 μm and 0.6563 μm) with different wavelengths at each field position of the black light lens are respectively 1.906 μm, 2.677 μm, 3.855 μm, 3.694 μm, 3.166 μm, 2.717 μm and 3.595 μm, which shows that the RMS radius of each field is less than 5 μm, namely, the black light lens has lower chromatic aberration and aberration in the full field of view, the purple edge problem of visible light waveband imaging is solved, and high-resolution imaging can be realized.

Fig. 5 is a field curvature distortion diagram of a black light lens according to an embodiment of the present invention, as shown in fig. 5, in a left coordinate system, a horizontal coordinate represents a size of the field curvature, and the unit is mm; the vertical coordinate represents the normalized image height, with no units; wherein T represents meridian and S represents arc loss; as can be seen from fig. 5, the black light lens provided in this embodiment is effectively controlled in curvature of field from 486nm to 656nm, i.e. when imaging, the difference between the image quality at the center and the image quality at the periphery is small; in the right-hand coordinate system, the horizontal coordinate represents the magnitude of distortion in units; the vertical coordinate represents the normalized image height, with no units; as can be seen from fig. 5, the distortion of the black-light lens provided by this embodiment is better corrected, the imaging distortion is smaller, and the requirement of low distortion is met.

Fig. 6 is an MTF graph of a black-light lens according to a first embodiment of the present invention, as shown in fig. 6, where the MTF graph shows a faithful reproduction of a lens contrast, a vertical axis shows a quality of the contrast, and a horizontal axis shows a distance from an imaging center. The 160 line pairs/mm time transfer function in the MTF curve is basically more than 0.2, and the 4K image quality requirement can be met.

In conclusion, the black light lens provided by the embodiment has the advantages of an ultra-large field angle, high image quality and small volume, the design adopts an 8-piece structure, the 4K image quality requirement is met under the condition of low cost, and the use requirement under the environment of minus 30-80 ℃ can be met by adopting a glass-plastic mixed structure.

Example two

Fig. 7 is a schematic structural diagram of a black light lens according to a second embodiment of the present invention, and as shown in fig. 7, the black light lens according to the second embodiment of the present invention includes: a first lens 210, a second lens 220, a third lens 230, a fourth lens 240, a fifth lens 250, a sixth lens 260, a seventh lens 270, and an eighth lens 280 arranged in this order from an object plane to an image plane along an optical axis; the first lens 210 has a negative power, the second lens 220 has a negative power, the third lens 230 has a positive power, the fourth lens 240 has a positive power, the fifth lens 250 has a negative power, the sixth lens 260 has a positive power, the seventh lens 270 has a negative power, and the eighth lens 280 has a positive power.

Optionally, the first lens 210, the third lens 230, and the fourth lens 240 are all glass spherical lenses, and the second lens 220, the fifth lens 250, the sixth lens 260, the seventh lens 270, and the eighth lens 280 are all plastic aspheric lenses.

Among them, the aspherical lens plays a role of correcting all high-order aberrations. 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 can be various types of glass known to those skilled in the art, which are neither described nor limited in the embodiments of the present invention. Since the cost of the lens made of plastic is much lower than that of the lens made of glass, the black light lens provided by the second embodiment of the invention has good image quality and low cost by arranging 5 plastic aspheric lenses. And because the two materials have the mutual compensation function, the black light lens can still be normally used in high and low temperature environments.

The focal power, focal length, refractive index, abbe number, and stop position of the black-light lens are the same as those in the first embodiment, and are not described herein again.

Table 3 details specific setting parameters of each lens in the black light lens provided in the second embodiment of the present invention, in another possible implementation manner, where the black light lens in table 3 corresponds to the black light lens described in fig. 7.

TABLE 3 design values of radius of curvature, thickness, material and K-factor of the black light lens

With reference to fig. 7, the black light lens provided by the second embodiment of the present invention includes a first lens 210, a second lens 220, a third lens 230, a fourth lens 240, a fifth lens 250, a sixth lens 260, a seventh lens 270, and an eighth lens 280, which are sequentially arranged from an object plane to an image plane along an optical axis. Table 3 shows optical physical parameters such as a curvature radius, a thickness, and a material of each lens in the black light lens provided in the embodiment. Wherein, the surface numbers are numbered according to the surface sequence of the lenses, for example, "1" represents the object surface of the first lens 210, "2" represents the image surface of the first lens 210, "10" represents the object surface of the fifth lens 250, "11" represents the image surface of the fifth lens 250, and so on; the curvature radius represents the bending degree of the surface of the lens, a positive value represents that the surface is bent to the image surface side, and a negative value represents that the surface is bent to the object surface side; thickness represents the central axial distance from the current surface to the next surface, and the radius of curvature and thickness are both in millimeters (mm).

On the basis of the above embodiment, optionally, the first lens 210, the third lens 230, and the fourth lens 240 are all glass spherical lenses, and the second lens 220, the fifth lens 250, the sixth lens 260, the seventh lens 270, and the eighth lens 280 are all plastic aspherical lenses. The black light lens provided by the second embodiment of the invention further comprises the diaphragm 290(STO), and the propagation direction of the light beam can be adjusted by additionally arranging the diaphragm 290, so that the imaging quality is improved. The stop 290 may be located in the optical path between the fifth lens 250 and the sixth lens 260, but the specific arrangement position of the stop 290 is not limited in the embodiment of the present invention, and by arranging the stop at a proper position, it is helpful to improve the relative illuminance and reduce the CRA.

The aspherical surface shape equation Z of the first lens 210, the second lens 220, the third lens 230, the fourth lens 240, the fifth lens 250, the sixth lens 260, the seventh lens 270, and the eighth lens 280 satisfies:

Illustratively, table 4 details the aspheric coefficients of the lenses of the present embodiment in one possible implementation.

TABLE 4 aspheric coefficients in black-light lens

wherein-1.37E-03 indicates that the coefficient A with the face number of 3 is-1.37 x 10^-3And so on.

Further, fig. 8 is a spherical aberration curve diagram of the black light lens according to the second embodiment of the present invention, as shown in fig. 8, spherical aberrations of the black light lens at different wavelengths (0.486 μm, 0.588 μm, and 0.656 μm) are all within 0.05mm, and different wavelength curves are relatively concentrated, which indicates that axial aberrations of the black light lens are small, so that it can be known that the black light lens according to the second embodiment of the present invention can correct aberrations well.

Fig. 9 is a light fan diagram of a black light lens according to a second embodiment of the present invention, as shown in fig. 9, imaging ranges of light rays with different wavelengths (0.486 μm, 0.588 μm, and 0.656 μm) under different field angles of the black light lens are within 50 μm, and curves are very concentrated, so that it is ensured that aberrations of different field areas are small, that is, it is explained that the black light lens better corrects aberrations of an optical system.

Fig. 10 is a visible light spot diagram of a black-light lens according to a second embodiment of the present invention, wherein the spot diagram is one of the most common evaluation methods in modern optical design. The point diagram is that after many light rays emitted by a point light source pass through an optical system, intersection points of the light rays and an image surface are not concentrated on the same point any more due to aberration, and a diffusion pattern scattered in a certain range is formed. As shown in fig. 4, in the black light lens provided in the second embodiment of the present invention, the diffusion patterns of the visible light rays (0.4861 μm, 0.5876 μm, and 0.6563 μm) with different wavelengths in each field are relatively concentrated and distributed uniformly, and the phenomenon that the diffusion patterns in a certain field are separated from each other up and down along with the wavelength does not occur, which indicates that there is no obvious purple edge. Meanwhile, the root mean square radius values (RMS radius) of the visible rays (0.4861 μm, 0.5876 μm and 0.6563 μm) with different wavelengths at each field position of the black light lens are respectively 1.843 μm, 1.484 μm, 2.260 μm, 3.108 μm, 3.144 μm, 3.108 μm and 2.983 μm, which shows that the RMS radius of each field is less than 5 μm, namely that the black light lens has lower chromatic aberration and aberration in a full field, solves the purple edge problem of visible light waveband imaging, and can realize high-resolution imaging.

Fig. 11 is a field curvature distortion diagram of a black light lens according to a second embodiment of the present invention, as shown in fig. 11, in a left coordinate system, a horizontal coordinate represents a size of the field curvature, and the unit is mm; the vertical coordinate represents the normalized image height, with no units; wherein T represents meridian and S represents arc loss; as can be seen from fig. 5, the black light lens provided by this embodiment is effectively controlled in curvature of field from 486nm to 656nm, i.e. when imaging, the difference between the image quality at the center and the image quality at the periphery is small; in the right-hand coordinate system, the horizontal coordinate represents the magnitude of distortion in units; the vertical coordinate represents the normalized image height, with no units; as can be seen from fig. 11, the distortion of the black-light lens provided by this embodiment is better corrected, the imaging distortion is smaller, and the requirement of low distortion is met.

Fig. 12 is an MTF graph of a black-light lens according to a second embodiment of the present invention, where as shown in fig. 12, the MTF graph shows a faithful reproduction of a lens contrast, a vertical axis shows a quality of the contrast, and a horizontal axis shows a distance from an imaging center. The 160 line pairs/mm time transfer function in the MTF curve is basically more than 0.2, and the 4K image quality requirement can be met.

It is to be noted that the foregoing is only illustrative of the preferred embodiments of the present invention and the technical principles employed. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, but is capable of various obvious modifications, rearrangements, combinations and substitutions as will now become apparent to those skilled in the art without departing from the scope of the invention. Therefore, although the present invention has been described in greater detail by the above embodiments, the present invention is not limited to the above embodiments, and may include other equivalent embodiments without departing from the spirit of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A black light lens, comprising: the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the seventh lens and the eighth lens are sequentially arranged from an object plane to an image plane along an optical axis;

2. The black light lens according to claim 1, wherein the first lens and the fourth lens are each a glass spherical lens, and the second lens, the third lens, the fifth lens, the sixth lens, the seventh lens and the eighth lens are each a plastic aspherical lens.

3. The black light lens according to claim 1, wherein the first lens, the third lens and the fourth lens are all glass spherical lenses, and the second lens, the fifth lens, the sixth lens, the seventh lens and the eighth lens are all plastic aspherical lenses.

4. A black light lens according to claim 2 or 3, further comprising a diaphragm;

5. The black light lens of claim 1, wherein the first lens has a focal length of f1, the second lens has a focal length of f2, the third lens has a focal length of f3, the fourth lens has a focal length of f4, the fifth lens has a focal length of f5, the sixth lens has a focal length of f6, the seventh lens has a focal length of f7, the eighth lens has a focal length of f8, and the black light lens has an entrance pupil diameter of N;

6. The black light lens according to claim 1, wherein the first lens has a refractive index of n1, an abbe number of v 1; the refractive index of the second lens is n2, and the Abbe number is v 2; the refractive index of the third lens is n3, and the Abbe number is v 3; the refractive index of the fourth lens is n4, and the Abbe number is v 4;

7. The black light lens according to claim 1, wherein the first lens has a radius of curvature of the near object plane of R11; the near object surface curvature radius of the second lens is R21, and the near image surface curvature radius is R22; the near object surface curvature radius of the third lens is R31, and the near image surface curvature radius is R32; the curvature radius of a near object surface of the fifth lens is R51, and the curvature radius of a near image surface of the fifth lens is R52; the curvature radius of a near object surface of the seventh lens is R71, and the curvature radius of a near image surface of the seventh lens is R72; the near-image surface curvature radius of the eighth lens is R82; the air space of the third lens and the fourth lens is TH 34;

8. The black light lens of claim 1, wherein the fifth lens is a meniscus lens.

9. The black light lens according to claim 1, wherein a distance from an optical axis center of the image side surface of the eighth lens element to the image plane is BFL, and a distance from an optical axis center of the object side surface of the first lens element to the image plane is TTL, wherein BFL/TTL is greater than or equal to 0.05.

10. The black-light lens according to claim 1, wherein the aperture of the black-light lens is F, the field angle is FOV, the image plane ray incidence angle is CRA, and the aperture of the plastic lens is DL;

wherein F is more than or equal to 1.0 and less than or equal to 1.1;

95°≤FOV≤115°；

CRA≤15°；

DL≤15mm。