CN114265186A

CN114265186A - Optical lens

Info

Publication number: CN114265186A
Application number: CN202210195345.1A
Authority: CN
Inventors: 王义龙; 徐宇轩
Original assignee: Jiangxi Lianyi Optics Co Ltd
Current assignee: Jiangxi Lianyi Optics Co Ltd
Priority date: 2022-03-02
Filing date: 2022-03-02
Publication date: 2022-04-01
Anticipated expiration: 2042-03-02
Also published as: CN114265186B

Abstract

The invention provides an optical lens, which comprises eight lenses in total, and the total number of the lenses is as follows from an object side to an imaging surface along an optical axis in sequence: the image side surface of the first lens is a concave surface; a second lens having a positive optical power; a diaphragm; a third lens with focal power, wherein the object side surface of the third lens is a concave surface, and the image side surface of the third lens is a convex surface; a fourth lens having a positive refractive power, an object-side surface of which is convex; a fifth lens having a negative refractive power, an image-side surface of which is concave; a sixth lens having a refractive power, an object-side surface of which is convex; a seventh lens having positive optical power; an eighth lens element having a refractive power, the object-side surface of the eighth lens element being convex, and the image-side surface of the eighth lens element being concave; the effective focal length f and the total optical length TTL of the optical lens meet the following requirements: TTL/f is more than 3.5 and less than 5.5. The optical lens has the advantages of large aperture, small distortion and high illumination, and effectively solves the problems that the existing security lens adopts a dual-band confocal technology, the imaging range of an infrared band is small, and real color information can not be shot.

Description

Optical lens

Technical Field

The invention relates to the technical field of imaging lenses, in particular to an optical lens.

Background

Along with the society increases to the attention degree of public safety field work day by day, the demand and the requirement of monitoring facility also are constantly promoting, and current security protection camera lens adopts the confocal technique of dual band to realize daytime and night's shooting usually. Because the imaging range of the infrared band is small, the real color information of shooting cannot be guaranteed, and the color distortion is serious, so how to realize day and night full color is the technical problem needing to be solved in the field of security monitoring at present.

Disclosure of Invention

In view of the above problems, the present invention provides an optical lens, which effectively solves the technical problem of serious color distortion caused by the fact that the existing security lens adopts a dual-band confocal technology, because the imaging range of the infrared band is small, and the real color information cannot be shot.

In order to achieve the purpose, the technical scheme of the invention is as follows:

the invention provides an optical lens, which comprises eight lenses in total, and the total number of the lenses is as follows from an object side to an imaging surface along an optical axis in sequence: the image side surface of the first lens is a concave surface; a second lens having a positive optical power; a diaphragm; a third lens with focal power, wherein the object side surface of the third lens is a concave surface, and the image side surface of the third lens is a convex surface; a fourth lens having a positive refractive power, an object-side surface of which is convex; a fifth lens having a negative refractive power, an image-side surface of which is concave; a sixth lens having a refractive power, an object-side surface of which is convex; a seventh lens having positive optical power; an eighth lens element having a refractive power, the object-side surface of the eighth lens element being convex, and the image-side surface of the eighth lens element being concave;

the effective focal length f and the total optical length TTL of the optical lens meet the following requirements: TTL/f is more than 3.5 and less than 5.5.

Preferably, the effective focal length f and the back focal length BFL of the optical lens satisfy; BFL/f is more than 0.3 and less than or equal to 0.35.

Preferably, the total optical length TTL of the optical lens and the real image height IH corresponding to the maximum field angle satisfy: TTL/IH is more than 3.0 and less than 4.0.

Preferably, the field angle FOV and the aperture value FNO of the optical lens satisfy: 55 DEG < FOV/FNO < 65 deg.

Preferably, the real image height IH corresponding to the maximum field angle of the optical lens satisfies the effective focal length f and the field angle FOV:

。

preferably, the effective focal length f of the optical lens, the focal length f1 of the first lens, the radius of curvature of the object side surface R1 of the first lens and the radius of curvature of the image side surface R2 of the first lens respectively satisfy: -5 < f1/f < -1.0; l (R1-R2)/(R1+ R2) | < 4.

Preferably, the effective focal length f of the optical lens and the focal length f2 of the second lens, the object-side curvature radius R3 and the image-side curvature radius R4 of the second lens respectively satisfy: 2 < f2/f < 7; l (R3-R4)/(R3+ R4) | < 0.5.

Preferably, the effective focal length f of the optical lens, the focal length f5 of the fifth lens, the object-side curvature radius R10 of the fifth lens and the curvature radius R11 of the image-side of the fifth lens respectively satisfy: -1.5 < f5/f < -0.5; 0.3 < (R10-R11)/(R10+ R11) < 1.8.

Preferably, the effective focal length f of the optical lens, the focal length f7 of the seventh lens, the object-side curvature radius R14 of the seventh lens and the curvature radius R15 of the image-side of the seventh lens satisfy: f7/f is more than 1.0 and less than 2.5; l (R14-R15)/(R14+ R15) | < 1.0.

Preferably, the effective focal length f of the optical lens, the focal length f8 of the eighth lens, the object-side curvature radius R16 of the eighth lens and the curvature radius R17 of the image-side of the eighth lens satisfy: i f8/f < 80; 0 < (R16-R17)/(R16+ R17) < 0.5.

Compared with the prior art, the invention has the beneficial effects that: the optical lens of this application makes it have big light ring, little distortion and the advantage of high illuminance simultaneously through the lens shape and the focal power combination between each lens of reasonable collocation, effectively solves current security protection camera lens and adopts the confocal technique of dual band less because of infrared band imageable range, and can't guarantee to shoot true color information, and leads to the technical problem that the color distortion is serious.

Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.

Drawings

The above and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:

fig. 1 is a schematic structural diagram of an optical lens system according to embodiment 1 of the present invention;

fig. 2 is a field curvature graph of the optical lens in embodiment 1 of the present invention;

FIG. 3 is a graph showing F-Tan (theta) distortion curves of an optical lens in embodiment 1 of the present invention;

fig. 4 is a graph showing a relative illuminance curve of the optical lens in embodiment 1 of the present invention;

FIG. 5 is a graph showing axial aberrations of an optical lens system according to embodiment 1 of the present invention;

FIG. 6 is a vertical axis chromatic aberration diagram of an optical lens in embodiment 1 of the present invention;

fig. 7 is a schematic structural diagram of an optical lens system according to embodiment 2 of the present invention;

FIG. 8 is a graph of curvature of field of an optical lens in embodiment 2 of the present invention;

FIG. 9 is a graph showing F-Tan (theta) distortion curves of an optical lens in embodiment 2 of the present invention;

fig. 10 is a graph showing a relative illuminance curve of the optical lens in embodiment 2 of the present invention;

fig. 11 is a graph showing axial aberration of the optical lens in embodiment 2 of the present invention;

FIG. 12 is a vertical axis chromatic aberration diagram of an optical lens in embodiment 2 of the present invention;

fig. 13 is a schematic structural diagram of an optical lens system according to embodiment 3 of the present invention;

FIG. 14 is a graph of curvature of field of an optical lens in embodiment 3 of the present invention;

FIG. 15 is a graph showing F-Tan (theta) distortion curves of an optical lens in embodiment 3 of the present invention;

fig. 16 is a graph showing the relative illuminance of the optical lens in embodiment 3 of the present invention;

fig. 17 is a graph showing axial aberration of the optical lens in embodiment 3 of the present invention;

FIG. 18 is a vertical axis chromatic aberration diagram of an optical lens in embodiment 3 of the present invention;

fig. 19 is a schematic structural diagram of an optical lens system according to embodiment 4 of the present invention;

FIG. 20 is a graph showing curvature of field of an optical lens in embodiment 4 of the present invention;

FIG. 21 is a graph showing F-Tan (theta) distortion curves of an optical lens in embodiment 4 of the present invention;

fig. 22 is a graph showing the relative illuminance of the optical lens in embodiment 4 of the present invention;

FIG. 23 is a graph showing axial aberrations of an optical lens according to embodiment 4 of the present invention;

fig. 24 is a vertical axis chromatic aberration diagram of the optical lens in embodiment 4 of the present invention.

The following detailed description will further illustrate the invention in conjunction with the above-described figures.

Detailed Description

For a better understanding of the present application, various aspects of the present application will be described in more detail with reference to the accompanying drawings. It should be understood that the detailed description is merely illustrative of embodiments of the application and does not limit the scope of the application in any way. Like reference numerals refer to like elements throughout the specification. The expression "and/or" includes any and all combinations of one or more of the associated listed items.

It should be noted that in this specification, the expressions first, second, third, etc. are used only to distinguish one feature from another, and do not represent any limitation on the features. Thus, the first lens discussed below may also be referred to as the second lens or the third lens without departing from the teachings of the present invention.

In the drawings, the thickness, size, and shape of the lens have been slightly exaggerated for convenience of explanation. In particular, the shapes of the spherical or aspherical surfaces shown in the drawings are shown by way of example. That is, the shape of the spherical surface or the aspherical surface is not limited to the shape of the spherical surface or the aspherical surface shown in the drawings. The figures are purely diagrammatic and not drawn to scale.

Herein, the paraxial region refers to a region near the optical axis. If the lens surface is convex and the convex position is not defined, it means that the lens surface is convex at least in the paraxial region; if the lens surface is concave and the concave position is not defined, it means that the lens surface is concave at least in the paraxial region. The surface of each lens closest to the object is called the object side surface of the lens, and the surface of each lens closest to the imaging surface is called the image side surface of the lens.

It will be further understood that the terms "comprises," "comprising," "has," "having," "includes" and/or "including," when used in this specification, specify the presence of stated features, elements, and/or components, but do not preclude the presence or addition of one or more other features, elements, components, and/or groups thereof. Moreover, when a statement such as "at least one of" appears after a list of listed features, the entirety of the listed features is modified rather than modifying individual elements in the list. Furthermore, when describing embodiments of the present application, the use of "may" mean "one or more embodiments of the present application. Also, the term "exemplary" is intended to refer to an example or illustration.

Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present application will be described in detail below with reference to the embodiments with reference to the attached drawings.

An optical lens according to an embodiment of the present application includes, in order from an object side to an image side: the lens comprises a first lens, a second lens, a diaphragm, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens and an eighth lens.

In some embodiments, the first lens has a negative optical power and the first lens has a biconcave or a convexly concave type. The first lens adopts the optical power and the surface type arrangement, which is beneficial to collecting more light rays to enter a rear optical system as much as possible.

In some embodiments, the second lens has a positive optical power and the second lens has a meniscus or convex-concave shape. The second lens is arranged by adopting the focal power, so that the defocusing problem under high-temperature and low-temperature environments can be corrected, and meanwhile, the spherical aberration of the marginal field of view can be corrected.

In some embodiments, the third lens has a positive or negative optical power and the third lens has a meniscus type. The third lens adopts the surface type arrangement, which is beneficial to collecting more light rays as much as possible to enter a rear optical system.

In some embodiments, the fourth lens has a positive optical power, and the fourth lens has a biconvex type or a convex-concave type. The fourth lens adopts the focal power arrangement, which is beneficial to converging light rays so that the diverging light rays can smoothly enter a rear optical system after being converged.

In some embodiments, the fifth lens has a negative optical power, and the fifth lens has a biconcave or a convexly concave type. The fifth lens adopts the focal power arrangement, which is beneficial to converging light rays so that the diverging light rays can smoothly enter a rear optical system after being converged.

In some embodiments, the sixth lens has a positive or negative optical power, and the sixth lens has a biconvex or a convex-concave type.

In some embodiments, the seventh lens has a positive optical power, and the seventh lens has a convex concave type or a concave convex type. The seventh lens adopts the focal power arrangement, which is beneficial to converging light rays so that the diverging light rays can smoothly enter a rear optical system after being converged.

In some embodiments, the eighth lens has a positive or negative optical power, the eighth lens has a convex-concave type, and both the object-side surface and the image-side surface of the eighth lens have at least one inflection point. The eighth lens adopts the surface type arrangement, which is beneficial to correcting the distortion of the optical lens, and simultaneously realizes the control of the emergent angle of the light rays, thereby improving the relative illumination of the optical system.

In some embodiments, a stop for limiting the light beam is disposed between the second lens and the third lens. When the diaphragm is arranged between the second lens and the third lens, the light rays entering the optical system are favorably converged, and the caliber of the rear end of the optical lens is reduced.

In some embodiments, the effective focal length f of the optical lens and the total optical length TTL and the back focal length BFL satisfy: TTL/f is more than 3.5 and less than 5.5, BFL/f is more than 0.3 and less than or equal to 0.35. Satisfying the above range, being favorable to obtaining bigger optics back focal, thus making the camera lens possess telecentric effect, also being favorable to reducing the sensitivity of optical lens simultaneously, and shortening the total length of the camera lens, realizing the miniaturization of the camera lens.

In some embodiments, the total optical length TTL of the optical lens and the real image height IH corresponding to the maximum field angle satisfy: TTL/IH is more than 3.0 and less than 4.0. The optical lens meets the range, is beneficial to miniaturization of the optical lens, and has the characteristics of small volume and large imaging surface.

In some embodiments, the field angle FOV and the aperture value FNO of the optical lens satisfy: 55 DEG < FOV/FNO < 65 deg. The range is satisfied, and the effect of large aperture is realized by the optical lens.

In some embodiments, the real image height IH corresponding to the maximum field angle of the optical lens satisfies the effective focal length f and the field angle FOV:

the optical lens meets the range, is favorable for reducing the distortion of the optical lens, has a larger field angle and better imaging quality.

In some embodiments, the effective focal length f of the optical lens and the focal length f1 of the first lens, the object side radius of curvature R1 of the first lens, and the image side radius of curvature R2 of the first lens satisfy: -5 < f1/f < -1.0, | (R1-R2)/(R1+ R2) | < 4. Satisfy above-mentioned scope, can make first lens have less negative focal power, be favorable to reducing spherical aberration and coma that first lens self produced, improve the imaging quality.

In some embodiments, the effective focal length f of the optical lens and the focal length f2 of the second lens, the object-side radius of curvature R3 of the second lens, and the image-side radius of curvature R4 of the second lens satisfy: 2 < f2/f < 7, | (R3-R4)/(R3+ R4) | < 0.5. Satisfy above-mentioned scope, can make the second lens have less positive focal power, be favorable to reducing spherical aberration and coma that second lens self produced, improve the imaging quality.

In some embodiments, the effective focal length f of the optical lens and the focal length f3 of the third lens, the object-side radius of curvature R5 of the third lens, and the image-side radius of curvature R6 of the third lens satisfy: i f3/f < 25, | (R5-R6)/(R5+ R6) | < 1. The range is satisfied, the spherical aberration and the coma aberration generated by the third lens are reduced, and the imaging quality is improved.

In some embodiments, the effective focal length f of the optical lens and the focal length f4 of the fourth lens, the object side curvature radius R8 and the image side curvature radius R9 of the fourth lens satisfy: 1.2 < f4/f < 2.4, -2 < (R8-R9)/(R8+ R9) < -0.8. The fourth lens has smaller positive focal power, thereby being beneficial to balancing various aberrations of the optical lens and improving the imaging quality.

In some embodiments, the effective focal length f of the optical lens and the focal length f5 of the fifth lens, the object-side radius of curvature R10 of the fifth lens, and the image-side radius of curvature R11 of the fifth lens satisfy: -1.5 < f5/f < -0.5, 0.3 < (R10-R11)/(R10+ R11) < 1.8. The fifth lens has smaller negative focal power, so that the spherical aberration, the coma aberration and the astigmatism of the optical lens can be balanced, and the imaging quality is improved.

In some embodiments, the effective focal length f of the optical lens and the focal length f6 of the sixth lens, the object-side radius of curvature R12 of the sixth lens, and the image-side radius of curvature R13 of the sixth lens satisfy: i f6/f < 500, | (R12-R13)/(R12+ R13) | < 3.0. Satisfying the above range is beneficial to balancing various aberrations of the optical lens.

In some embodiments, the effective focal length f of the optical lens and the focal length f7 of the seventh lens, the object side radius of curvature R14 of the seventh lens, and the image side radius of curvature R15 of the seventh lens satisfy: f7/f is more than 1.0 and less than 2.5, | (R14-R15)/(R14+ R15) | is less than 1.0. The seventh lens has smaller positive focal power, thereby being beneficial to balancing various aberrations of the optical lens and improving the imaging quality.

In some embodiments, the effective focal length f of the optical lens and the focal length f8 of the eighth lens, the object-side radius of curvature R16 of the eighth lens, and the image-side radius of curvature R17 of the eighth lens satisfy: i f8/f I < 80, 0 < (R16-R17)/(R16+ R17) < 0.5. The range is satisfied, various aberrations of the optical lens are balanced, and the imaging quality is improved.

In order to make the system have better optical performance, a plurality of aspheric lenses are adopted in the lens, and the surface shapes of the aspheric surfaces of the optical lens satisfy the following equation:

；

wherein z is the distance between the curved surface and the vertex of the curved surface in the optical axis direction, h is the distance between the optical axis and the curved surface, c is the curvature of the vertex of the curved surface, K is the coefficient of the quadric surface, and A, B, C, D, E, F, G, H are the coefficients of the second-order, fourth-order, sixth-order, eighth-order, tenth-order, twelfth-order, fourteenth-order, and sixteenth-order curved surfaces, respectively.

The invention is further illustrated below in the following examples. In various embodiments, the thickness, the curvature radius, and the material selection of each lens in the optical lens are different, and the specific differences can be referred to in the parameter tables of the various embodiments. The following examples are only preferred embodiments of the present invention, but the embodiments of the present invention are not limited only by the following examples, and any other changes, substitutions, combinations or simplifications which do not depart from the innovative points of the present invention should be construed as being equivalent substitutions and shall be included within the scope of the present invention.

Example 1

Referring to fig. 1, a schematic structural diagram of an optical lens system according to embodiment 1 of the present invention is shown, the optical lens system sequentially includes, from an object side to an image plane along an optical axis: the lens system comprises a first lens L1, a second lens L2, a diaphragm, a third lens L3, a fourth lens L4, a fifth lens L5, a sixth lens L6, a seventh lens L7, an eighth lens L8 and a filter G1.

The first lens L1 has negative power, and both the object-side surface S1 and the image-side surface S2 are concave;

the second lens L2 has positive power, and has a convex object-side surface S3 and a concave image-side surface S4;

a diaphragm;

the third lens element L3 has positive power, and has a concave object-side surface S6 and a convex image-side surface S7;

the fourth lens L4 has positive power, and both the object-side surface S8 and the image-side surface S9 are convex;

the fifth lens element L5 has negative power, and has a convex object-side surface S10 and a concave image-side surface S11;

the sixth lens element L6 has positive power, and has a convex object-side surface S12 and a concave image-side surface S13;

the seventh lens element L7 has a positive focal length, and has a convex object-side surface S14 and a concave image-side surface S15;

the eighth lens element L8 has a positive focal length, and has a convex object-side surface S16 and a concave image-side surface S17.

The relevant parameters of each lens in the optical lens in example 1 are shown in table 1-1.

TABLE 1-1

The surface shape parameters of the aspherical lens of the optical lens in example 1 are shown in table 1-2.

Tables 1 to 2

In the present embodiment, a field curvature graph, a F-tan (theta) distortion graph, a relative illuminance graph, an axial aberration graph, and a vertical axis chromatic aberration graph of the optical lens are respectively shown in fig. 2, fig. 3, fig. 4, fig. 5, and fig. 6.

Fig. 2 shows a field curvature curve of example 1, which shows the degree of curvature of light rays of different wavelengths on a meridional image plane and a sagittal image plane, with the horizontal axis representing the amount of displacement (unit: mm) and the vertical axis representing the half field angle (unit: °). As can be seen from the figure, the field curvature of the meridional image plane and the sagittal image plane is controlled within +/-0.15 mm, which indicates that the field curvature of the optical lens is better corrected.

FIG. 3 shows F-Tan (theta) distortion curves of example 1, in which F-Tan (theta) distortion of a light ray of a center wavelength at different image heights on an image forming plane is shown, the horizontal axis shows F-Tan (theta) distortion (unit:%), and the vertical axis shows a half field angle (unit:%). As can be seen from the figure, the F-Tan (theta) distortion of the optical lens is controlled within +/-3% at the maximum half field angle, which indicates that the F-Tan (theta) distortion of the optical lens is better corrected.

Fig. 4 shows a relative illuminance curve of example 1, which represents relative illuminance values at different angles of field of view on the imaging plane, with the horizontal axis representing the half field angle (unit: °) and the vertical axis representing the relative illuminance value (unit:%). As can be seen from the figure, the relative contrast value of the optical lens is still greater than 50% at the maximum half field angle, which indicates that the relative contrast of the optical lens is high.

Fig. 5 shows an axial aberration curve of example 1, which represents the aberration on the optical axis at the imaging plane for each wavelength, with the horizontal axis representing the axial aberration value (unit: mm) and the vertical axis representing the normalized pupil radius. As can be seen from the figure, the offset of the axial aberration is controlled within ± 0.02mm, which indicates that the optical lens can effectively correct the axial aberration.

Fig. 6 shows a vertical axis chromatic aberration curve of example 1, which shows chromatic aberration at different image heights on an image forming plane for each wavelength with respect to a center wavelength (0.55 μm), the horizontal axis shows a vertical axis chromatic aberration value (unit: μm) for each wavelength with respect to the center wavelength, and the vertical axis shows a normalized angle of view. As can be seen from the figure, the vertical axis chromatic aberration of the longest wavelength and the shortest wavelength is controlled within +/-1 μm, which shows that the optical lens can effectively correct the chromatic aberration of the marginal field of view and the secondary spectrum of the whole image plane.

Example 2

Referring to fig. 7, a schematic structural diagram of an optical lens system according to embodiment 2 of the present invention is shown, the optical lens system sequentially includes, from an object side to an image plane along an optical axis: the lens system comprises a first lens L1, a second lens L2, a diaphragm, a third lens L3, a fourth lens L4, a fifth lens L5, a sixth lens L6, a seventh lens L7, an eighth lens L8 and a filter G1.

a diaphragm;

the sixth lens element L6 has negative power, and has a convex object-side surface S12 and a concave image-side surface S13;

the eighth lens element L8 has a negative focal length, and has a convex object-side surface S16 and a concave image-side surface S17.

The relevant parameters of each lens in the optical lens in embodiment 2 are shown in table 2-1.

TABLE 2-1

The surface shape parameters of the aspherical lens of the optical lens in example 2 are shown in table 2-2.

Tables 2 to 2

In the present embodiment, a field curvature graph, a F-tan (theta) distortion graph, a relative illuminance graph, an axial aberration graph, and a vertical axis chromatic aberration graph of the optical lens are respectively shown in fig. 8, 9, 10, 11, and 12.

Fig. 8 shows a field curvature curve of example 2, which shows the degree of curvature of light rays of different wavelengths on a meridional image plane and a sagittal image plane, with the horizontal axis representing the amount of displacement (unit: mm) and the vertical axis representing the half field angle (unit: °). As can be seen from the figure, the field curvature of the meridional image plane and the sagittal image plane is controlled within +/-0.25 mm, which indicates that the field curvature of the optical lens is better corrected.

FIG. 9 shows F-Tan (theta) distortion curves of example 2, in which F-Tan (theta) distortion of a light ray of a center wavelength at different image heights on an image forming plane is shown, the horizontal axis shows F-Tan (theta) distortion (unit:%), and the vertical axis shows a half field angle (unit:%). It can be seen from the figure that the F-tan (theta) distortion of the optical lens is controlled within ± 0.5% at the maximum half field angle, which indicates that the F-tan (theta) distortion of the optical lens is better corrected.

Fig. 10 shows a relative illuminance curve of example 2, which represents relative illuminance values at different angles of field of view on the imaging plane, with the horizontal axis representing the half field angle (unit: °) and the vertical axis representing the relative illuminance value (unit:%). As can be seen from the figure, the relative contrast value of the optical lens is still greater than 50% at the maximum half field angle, which indicates that the relative contrast of the optical lens is high.

Fig. 11 shows an axial aberration curve of example 2, which represents the aberration on the optical axis at the imaging plane for each wavelength, with the horizontal axis representing the axial aberration value (unit: mm) and the vertical axis representing the normalized pupil radius. As can be seen from the figure, the offset of the axial aberration is controlled within ± 0.03mm, which indicates that the optical lens can effectively correct the axial aberration.

Fig. 12 shows a vertical axis chromatic aberration curve of example 2, which shows chromatic aberration at different image heights on an image forming plane for each wavelength with respect to a center wavelength (0.55 μm), the horizontal axis shows a vertical axis chromatic aberration value (unit: μm) for each wavelength with respect to the center wavelength, and the vertical axis shows a normalized angle of view. As can be seen from the figure, the vertical axis chromatic aberration of the longest wavelength and the shortest wavelength is controlled within +/-1.4 mu m, which shows that the optical lens can effectively correct the chromatic aberration of the marginal field of view and the secondary spectrum of the whole image plane.

Example 3

Referring to fig. 13, a schematic structural diagram of an optical lens system according to embodiment 3 of the present invention is shown, the optical lens system sequentially includes, from an object side to an image plane along an optical axis: the lens system comprises a first lens L1, a second lens L2, a diaphragm, a third lens L3, a fourth lens L4, a fifth lens L5, a sixth lens L6, a seventh lens L7, an eighth lens L8 and a filter G1.

The first lens element L1 has negative power, and has a convex object-side surface S1 and a concave image-side surface S2;

the second lens L2 has positive power, and has a concave object-side surface S3 and a convex image-side surface S4;

a diaphragm;

the fifth lens L5 has negative power, and both the object-side surface S10 and the image-side surface S11 are concave;

the sixth lens L6 has positive power, and both the object-side surface S12 and the image-side surface S13 are convex;

the seventh lens element L7 has a positive focal length, and has a concave object-side surface S14 and a convex image-side surface S15;

The relevant parameters of each lens in the optical lens in example 3 are shown in table 3-1.

TABLE 3-1

The surface shape parameters of the aspherical lens of the optical lens in example 3 are shown in table 3-2.

TABLE 3-2

In the present embodiment, a field curvature graph, a F-tan (theta) distortion graph, a relative illuminance graph, an axial aberration graph, and a vertical axis chromatic aberration graph of the optical lens are respectively shown in fig. 14, fig. 15, fig. 16, fig. 17, and fig. 18.

Fig. 14 shows a field curvature curve of example 3, which shows the degree of curvature of light rays of different wavelengths on a meridional image plane and a sagittal image plane, with the horizontal axis representing the amount of displacement (unit: mm) and the vertical axis representing the half field angle (unit: °). As can be seen from the figure, the field curvature of the meridional image plane and the sagittal image plane is controlled within +/-0.1 mm, which indicates that the field curvature of the optical lens is better corrected.

FIG. 15 shows F-Tan (theta) distortion curves of example 3, in which F-Tan (theta) distortion at different image heights on the image plane is shown for a light ray of the center wavelength, and the horizontal axis shows F-Tan (theta) distortion (unit:%) and the vertical axis shows half field angle (unit:%). As can be seen from the figure, the F-Tan (theta) distortion of the optical lens is controlled within +/-2% at the maximum half field angle, which indicates that the F-Tan (theta) distortion of the optical lens is better corrected.

Fig. 16 shows a relative illuminance curve of example 3, which represents relative illuminance values at different angles of field of view on the imaging plane, with the horizontal axis representing the half field angle (unit: °) and the vertical axis representing the relative illuminance value (unit:%). As can be seen from the figure, the relative contrast value of the optical lens is still greater than 50% at the maximum half field angle, which indicates that the relative contrast of the optical lens is high.

Fig. 17 shows an axial aberration curve of example 3, which represents the aberration on the optical axis at the imaging plane for each wavelength, with the horizontal axis representing the axial aberration value (unit: mm) and the vertical axis representing the normalized pupil radius. As can be seen from the figure, the offset of the axial aberration is controlled within ± 0.04mm, which indicates that the optical lens can effectively correct the axial aberration.

Fig. 18 shows a vertical axis chromatic aberration curve of example 3, which shows chromatic aberration at different image heights on an image forming plane for each wavelength with respect to a center wavelength (0.55 μm), the horizontal axis shows a vertical axis chromatic aberration value (unit: μm) for each wavelength with respect to the center wavelength, and the vertical axis shows a normalized angle of view. As can be seen from the figure, the vertical axis chromatic aberration of the longest wavelength and the shortest wavelength is controlled within +/-8 mu m, which shows that the optical lens can effectively correct the chromatic aberration of the marginal field of view and the secondary spectrum of the whole image plane.

Example 4

Referring to fig. 19, a schematic structural diagram of an optical lens system according to embodiment 4 of the present invention is shown, the optical lens system sequentially includes, from an object side to an image plane along an optical axis: the lens system comprises a first lens L1, a second lens L2, a diaphragm, a third lens L3, a fourth lens L4, a fifth lens L5, a sixth lens L6, a seventh lens L7, an eighth lens L8 and a filter G1.

a diaphragm;

the third lens element L3 has negative power, and has a concave object-side surface S6 and a convex image-side surface S7;

the fourth lens element L4 has positive power, and has a convex object-side surface S8 and a concave image-side surface S9;

The relevant parameters of each lens in the optical lens in example 4 are shown in table 4-1.

TABLE 4-1

The surface shape parameters of the aspherical lens of the optical lens in example 4 are shown in table 4-2.

TABLE 4-2

In the present embodiment, a field curvature graph, a F-tan (theta) distortion graph, a relative illuminance graph, an axial aberration graph, and a vertical axis chromatic aberration graph of the optical lens are respectively shown in fig. 20, 21, 22, 23, and 24.

Fig. 20 shows a field curvature curve of example 4, which shows the degree of curvature of light rays of different wavelengths on a meridional image plane and a sagittal image plane, with the horizontal axis representing the amount of displacement (unit: mm) and the vertical axis representing the half field angle (unit: °). As can be seen from the figure, the field curvature of the meridional image plane and the sagittal image plane is controlled within +/-0.2 mm, which indicates that the field curvature of the optical lens is better corrected.

FIG. 21 shows F-Tan (theta) distortion curves of example 4, in which F-Tan (theta) distortion at different image heights on the image plane is shown for a light ray of the center wavelength, and the horizontal axis shows F-Tan (theta) distortion (unit:%) and the vertical axis shows half field angle (unit:%). As can be seen from the figure, the F-Tan (theta) distortion of the optical lens is controlled within +/-2% at the maximum half field angle, which indicates that the F-Tan (theta) distortion of the optical lens is better corrected.

Fig. 22 shows a relative illuminance curve of example 4, which represents relative illuminance values at different angles of field of view on the imaging plane, with the horizontal axis representing the half field angle (unit: °) and the vertical axis representing the relative illuminance value (unit:%). As can be seen from the figure, the relative contrast value of the optical lens is still greater than 50% at the maximum half field angle, which indicates that the relative contrast of the optical lens is high.

Fig. 23 shows an axial aberration curve of example 4, which represents the aberration on the optical axis at the imaging plane for each wavelength, with the horizontal axis representing the axial aberration value (unit: mm) and the vertical axis representing the normalized pupil radius. As can be seen from the figure, the offset of the axial aberration is controlled within ± 0.03mm, which indicates that the optical lens can effectively correct the axial aberration.

Fig. 24 shows a vertical axis chromatic aberration curve of example 4, which shows chromatic aberration at different image heights on an image forming plane for each wavelength with respect to a center wavelength (0.55 μm), the horizontal axis shows a vertical axis chromatic aberration value (unit: μm) for each wavelength with respect to the center wavelength, and the vertical axis shows a normalized angle of view. As can be seen from the figure, the vertical axis chromatic aberration of the longest wavelength and the shortest wavelength is controlled within +/-6 mu m, which shows that the optical lens can effectively correct the chromatic aberration of the marginal field of view and the secondary spectrum of the whole image plane.

Please refer to table 5, which shows the optical characteristics corresponding to the above embodiments, including the effective focal length f, the total optical length TTL, the f-number FNO, the real image height IH, and the field angle FOV of the optical lens, and the values corresponding to each conditional expression in the embodiments.

TABLE 5

In summary, the optical lens of the embodiment of the invention has the advantages of large aperture, small distortion and high illumination intensity by reasonably matching the lens shape and focal power combination among the lenses, and effectively solves the technical problem of serious color distortion caused by the fact that the existing security lens adopts a two-band confocal technology because the imaging range of an infrared band is smaller and real color information cannot be shot.

The above examples are merely illustrative of several embodiments of the present invention, and the description thereof is more specific and detailed, but not to be construed as limiting the scope of the invention. It should be noted that, for those skilled in the art, various changes and modifications can be made without departing from the spirit of the invention, and these changes and modifications are all within the scope of the invention. Therefore, the protection scope of the present invention should be subject to the appended claims.

Claims

1. An optical lens system comprising eight lenses, in order from an object side to an image plane along an optical axis, comprising:

the image side surface of the first lens is a concave surface;

a second lens having a positive optical power;

a diaphragm;

a third lens with focal power, wherein the object side surface of the third lens is a concave surface, and the image side surface of the third lens is a convex surface;

a fourth lens having a positive refractive power, an object-side surface of which is convex;

a fifth lens having a negative refractive power, an image-side surface of which is concave;

a sixth lens having a refractive power, an object-side surface of which is convex;

a seventh lens having positive optical power;

an eighth lens element having a refractive power, the object-side surface of the eighth lens element being convex, and the image-side surface of the eighth lens element being concave;

2. An optical lens according to claim 1, characterized in that the effective focal length f and the back focal length BFL of the optical lens satisfy: BFL/f is more than 0.3 and less than or equal to 0.35.

3. The optical lens of claim 1, wherein the total optical length TTL of the optical lens and the real image height IH corresponding to the maximum field angle satisfy: TTL/IH is more than 3.0 and less than 4.0.

4. An optical lens according to claim 1, wherein the field angle FOV and the aperture value FNO of the optical lens satisfy: 55 DEG < FOV/FNO < 65 deg.

5. The optical lens according to claim 1, wherein the real image height IH corresponding to the maximum field angle of the optical lens satisfies the effective focal length f and the field angle FOV:

。

6. an optical lens according to claim 1, characterized in that the effective focal length f of the optical lens and the focal length f1 of the first lens, the object side curvature radius R1 and the image side curvature radius R2 of the first lens satisfy: -5.0 < f1/f < -1.0, | (R1-R2)/(R1+ R2) | < 4.

7. An optical lens according to claim 1, wherein the effective focal length f of the optical lens and the focal length f2 of the second lens, the object side curvature radius R3 and the image side curvature radius R4 of the second lens satisfy: 2 < f2/f < 7, | (R3-R4)/(R3+ R4) | < 0.5.

8. An optical lens according to claim 1, characterized in that the effective focal length f of the optical lens and the focal length f5 of the fifth lens, the object side curvature radius R10 and the image side curvature radius R11 of the fifth lens satisfy: -1.5 < f5/f < -0.5, 0.3 < (R10-R11)/(R10+ R11) < 1.8.

9. An optical lens according to claim 1, wherein the effective focal length f of the optical lens and the focal length f7 of the seventh lens, the object side curvature radius R14 and the image side curvature radius R15 of the seventh lens satisfy: f7/f is more than 1.0 and less than 2.5; l (R14-R15)/(R14+ R15) | < 1.0.

10. An optical lens according to claim 1, characterized in that the effective focal length f of the optical lens and the focal length f8 of the eighth lens, the object side curvature radius R16 and the image side curvature radius R17 of the eighth lens satisfy: i f8/f I < 80, 0 < (R16-R17)/(R16+ R17) < 0.5.