CN114089510A

CN114089510A - Optical lens

Info

Publication number: CN114089510A
Application number: CN202210069335.3A
Authority: CN
Inventors: 王义龙; 徐宇轩; 曾昊杰
Original assignee: Jiangxi Lianyi Optics Co Ltd
Current assignee: Jiangxi Lianyi Optics Co Ltd
Priority date: 2022-01-21
Filing date: 2022-01-21
Publication date: 2022-02-25
Anticipated expiration: 2042-01-21
Also published as: CN114089510B

Abstract

The invention discloses an optical lens, which comprises eight lenses in total, and the eight lenses sequentially comprise the following components from an object side to an imaging surface along an optical axis: the image side surface of the first lens is a concave surface; the image side surface of the second lens is a concave surface; a diaphragm; the image side surface of the third lens is a convex surface; a fourth lens having a focal power, wherein the object-side surface of the fourth lens is convex, and the image-side surface of the fourth lens is concave; the object side surface and the image side surface of the fifth lens are convex surfaces; a sixth lens element with negative refractive power having a convex object-side surface and a concave image-side surface; the object side surface and the image side surface of the seventh lens are convex surfaces; 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 optical total length TTL of the optical lens and the real image height IH corresponding to half of the maximum field angle satisfy that: 7.0 < TTL/IH < 14.0. Through this application, realize that optical lens includes big light ring, advantage that the imaging quality is high at least.

Description

Optical lens

Technical Field

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

Background

With the increasing development of security monitoring systems, the requirements on security lenses are higher and higher, and the requirements are mainly embodied in higher image quality, larger view field and larger light transmission aperture. A larger aperture means a larger amount of incoming light, so that the lens can be clearly monitored also in a dark place, that is, an optical lens having a large aperture can be applied to a more complicated monitoring environment. Therefore, it is necessary to develop an optical lens with a large aperture and high imaging quality to meet the requirement of security monitoring.

Disclosure of Invention

In view of the above, an object of the present invention is to provide an optical lens having at least advantages of a large aperture and high imaging quality.

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 optical lens sequentially comprises the following components from an object side to an imaging surface:

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

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

a diaphragm;

the image side surface of the third lens is a convex surface;

a fourth lens having a focal power, wherein the object-side surface of the fourth lens is convex, and the image-side surface of the fourth lens is concave;

the object side surface and the image side surface of the fifth lens are convex surfaces;

a sixth lens element with negative refractive power having a convex object-side surface and a concave image-side surface;

the object side surface and the image side surface of the seventh lens are convex surfaces;

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 optical total length TTL of the optical lens and the real image height IH corresponding to half of the maximum field angle satisfy that: 7.0 < TTL/IH < 14.0.

Preferably, the effective focal length f of the optical lens satisfies: f is more than 3.0mm and less than 6.0 mm.

Preferably, the real image height IH corresponding to half of the maximum field angle of the optical lens satisfies: IH is more than 2.5mm and less than 5.0 mm.

Preferably, the aperture value FNO of the optical lens is less than or equal to 1.0.

Preferably, the effective focal length f of the optical lens and the focal length f1 of the first lens satisfy: -3.5 < f1/f < -1.5.

Preferably, the effective focal length f of the optical lens and the focal length f4 of the fourth lens satisfy: | f4/f | < 55.0.

Preferably, the effective focal length f of the optical lens and the focal length f8 of the eighth lens satisfy: | f8/f | < 45.0.

Preferably, a combined focal length f12 of the first lens to the second lens and a combined focal length f38 of the third lens to the eighth lens of the optical lens satisfy: -1.2 < f12/f38 < -0.5.

Preferably, the total optical length TTL of the optical lens and the total lens thickness sum Σ TP having all optical powers satisfy: 0.6 < sigma TP/TTL < 0.8.

Preferably, the total optical length TTL of the optical lens and the effective focal length f of the optical lens satisfy: TTL/f is more than 6.0 and less than 12.0.

Compared with the prior art, the invention has the beneficial effects that: through the combination of the lens shape and the focal power between each lens of reasonable collocation, the effect of the clear formation of image of big light ring has been realized, has big light ring and the high advantage of formation of image quality, and it has good suitability in security protection control field, can effectively promote the effect of control.

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 θ distortion of an optical lens in embodiment 1 of the present invention;

fig. 4 is a graph showing axial aberration of the optical lens in embodiment 1 of the present invention;

FIG. 5 is a vertical axis chromatic aberration diagram of an optical lens in embodiment 1 of the present invention;

fig. 6 is a schematic structural diagram of an optical lens system according to embodiment 2 of the present invention;

FIG. 7 is a graph of curvature of field of an optical lens in embodiment 2 of the present invention;

FIG. 8 is a graph showing the F-Tan θ distortion of the optical lens in embodiment 2 of the present invention;

FIG. 9 is a graph showing axial aberrations of an optical lens system according to embodiment 2 of the present invention;

FIG. 10 is a vertical axis chromatic aberration diagram of an optical lens in embodiment 2 of the present invention;

fig. 11 is a schematic structural diagram of an optical lens system according to embodiment 3 of the present invention;

FIG. 12 is a graph showing curvature of field of an optical lens in embodiment 3 of the present invention;

FIG. 13 is a graph showing F-Tan θ distortion of an optical lens in embodiment 3 of the present invention;

FIG. 14 is a graph showing axial aberrations of an optical lens according to embodiment 3 of the present invention;

FIG. 15 is a vertical axis chromatic aberration diagram of an optical lens in embodiment 3 of the present invention;

fig. 16 is a schematic structural diagram of an optical lens system according to embodiment 4 of the present invention;

FIG. 17 is a graph of curvature of field of an optical lens in embodiment 4 of the present invention;

FIG. 18 is a graph showing the F-Tan θ distortion of the optical lens in embodiment 4 of the present invention;

FIG. 19 is a graph showing axial aberrations of an optical lens system according to embodiment 4 of the present invention;

fig. 20 is a vertical axis chromatic aberration diagram of the optical lens in embodiment 4 of the present invention.

Description of the main element symbols:

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.

The image side surface of the first lens is a concave surface; the first lens is integrally set to be in a meniscus shape, more light rays can be collected as far as possible to enter a rear optical system, the light flux amount is increased, a basic guarantee is provided for a large aperture of the optical lens, and the requirement for high illumination is met. In addition, the first lens can use a material with high Abbe number, for example, the Abbe number of the first lens meets Vd2 ≥ 55, which is beneficial to reducing chromatic aberration generated by the first lens and improving imaging quality of the optical lens.

The image side surface of the second lens is a concave surface; the image side surface of the second lens is a concave surface, so that the deflection angle of light rays is smooth, collected light rays can smoothly enter the rear optical system after being collected, and the miniaturization of the rear end of the lens is facilitated. In addition, the second lens can use high-refractive index materials, for example, the refractive index of the second lens meets Nd2 ≧ 1.66, which is beneficial for reducing the aperture and thickness of the lens and improving the imaging quality.

A diaphragm; the optical lens is beneficial to converging light rays entering the optical lens and reducing the aperture of the optical lens.

The image side surface of the third lens is a convex surface; the third lens is a positive lens with a convex image side surface, so that light rays can be converged, diffused light rays can smoothly enter a rear optical system after being collected, and miniaturization of the optical lens is facilitated.

The fourth lens has focal power, and the object side surface of the fourth lens is a convex surface, and the image side surface of the fourth lens is a concave surface; the fourth lens is a meniscus lens with the convex surface facing the object side, and can compensate spherical aberration introduced by the front-end optical system.

A fifth lens element having a positive refractive power, the object-side surface and the image-side surface of the fifth lens element being convex; the fifth lens is a biconvex lens, which is beneficial to correcting astigmatism and field curvature while converging light rays, thereby improving the resolution quality.

A sixth lens element with negative refractive power having a convex object-side surface and a concave image-side surface; the sixth lens is set to have negative focal power, so that light rays can be further adjusted, and chromatic aberration brought by a front optical system can be corrected.

A seventh lens element with positive optical power, wherein both the object-side surface and the image-side surface of the seventh lens element are convex; the seventh lens is set to have positive focal power, so that the divergent light rays can be converged to a rear optical system, the optical path of the peripheral light rays reaching an imaging surface can be shortened, and the resolution quality is improved.

The eighth lens has focal power, and the object side surface of the eighth lens is a convex surface, and the image side surface of the eighth lens is a concave surface; the surface of the eighth lens is set to be gentle, so that astigmatism and curvature of field can be corrected favorably, and the resolving power of the optical lens is improved.

In some embodiments, the fourth lens has a negative optical power; the fourth lens is set to have negative focal power, and chromatic aberration of the optical lens can be suppressed.

In some embodiments, the fourth lens has a positive optical power; the fourth lens is set to be positive focal power, so that light rays can be converged, and the requirement of miniaturization of the optical lens is met.

In some embodiments, the eighth lens has a negative optical power; the eighth lens is provided with negative focal power, and chromatic aberration of the optical lens can be suppressed.

In some embodiments, the eighth lens has a positive optical power; the eighth lens is set to positive focal power, so that light collected by the seventh lens can be further converged, and the optical lens is more suitable for being used in a weak light environment.

In some embodiments, the edge region of the object side surface of the sixth lens may have at least one inflection point. The surface type arrangement of the sixth lens is beneficial to smoothing the trend of front light and improving the resolution quality.

In some embodiments, the total optical length TTL of the optical lens and the real image height IH corresponding to half of the maximum field angle satisfy: 7.0 < TTL/IH < 14.0. Satisfying the above range is advantageous for achieving compactness and miniaturization of the optical lens while also making the optical lens have high pixel performance.

In some embodiments, the effective focal length f of the optical lens satisfies: f is more than 3.0mm and less than 6.0 mm. Satisfying above-mentioned scope, help promoting the ability that the camera lens highlights the main part and shoot the scenery of distance.

In some embodiments, the true image height IH corresponding to half of the maximum field angle satisfies: IH is more than 2.5mm and less than 5.0 mm. The optical lens system meets the range, is favorable for realizing the imaging effect of a large image plane of the system, further has higher optical performance, and realizes the matching of the optical lens and the sensors with different specifications.

In some embodiments, the aperture value FNO of the optical lens is ≦ 1.0. Satisfying the above range, the optical lens can be ensured to have a characteristic of a large aperture.

In some embodiments, the effective focal length f of the optical lens and the focal length f1 of the first lens satisfy: -3.5 < f1/f < -1.5. Satisfying above-mentioned scope, being favorable to the proportional relation of the effective focal length of rational distribution first lens's focus and optical lens, can making first lens have great negative focal power, the angle when reducing light and getting into the diaphragm is favorable to reducing the correction burden of follow-up lens to the aberration.

In some embodiments, the effective focal length f of the optical lens and the focal length f4 of the fourth lens satisfy: | f4/f | < 55.0. Satisfying the above range is beneficial to reasonably distributing the proportional relation between the focal length of the fourth lens and the effective focal length of the optical lens, so that the optical lens has better imaging quality and lower sensitivity.

In some embodiments, the effective focal length f of the optical lens and the focal length f8 of the eighth lens satisfy: | f8/f | < 45.0. The range is satisfied, and the proportional relation between the focal length of the eighth lens and the effective focal length of the optical lens is favorably and reasonably distributed, so that the optical lens has better imaging quality and lower sensitivity.

In some embodiments, the combined focal length f12 of the first to second lenses and the combined focal length f38 of the third to eighth lenses of the optical lens satisfy: -1.2 < f12/f38 < -0.5. The optical power of the lens can be reasonably distributed, so that the aberration generated by the front two lenses and the aberration generated by the rear six lenses are better balanced, good imaging quality is obtained, and the effect of high resolving power is realized.

In some embodiments, the total optical length TTL of the optical lens and the sum Σ TP of all lens thicknesses having optical powers satisfy: 0.6 < sigma TP/TTL < 0.8. The method meets the conditions, is beneficial to controlling the total length of the system, and further realizes miniaturization.

In some embodiments, the total optical length TTL of the optical lens and the effective focal length f of the optical lens satisfy: TTL/f is more than 6.0 and less than 12.0. The method meets the conditions, is favorable for realizing the compression transformation of the object image space, ensures that the shot portrait is presented on the chip as much as possible, is favorable for realizing the effect of presenting the main body and blurring the background, and is more favorable for highlighting the detailed morphological characteristics of the shot main body.

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 B, C, D, E, F, G, H are the coefficients of the fourth order, the sixth order, the eighth order, the tenth order, the twelfth order, the fourteenth order and the 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: a first lens L1, a second lens L2, a diaphragm S5, 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 element L2 has negative power, and has a convex object-side surface S3 and a concave image-side surface S4;

diaphragm S5;

the third lens L3 has positive power, and both the object-side surface S6 and the image-side surface S7 are convex;

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

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

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

the seventh lens L7 has positive power, and both the object-side surface S14 and the image-side surface S15 are convex;

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

Table 1 shows the parameters related to each lens of the optical lens provided in this embodiment.

TABLE 1-1

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

Tables 1 to 2

In the present embodiment, a field curvature graph, an F-Tan θ distortion 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, and fig. 5.

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 +/-0.1 millimeter, which indicates that the field curvature of the optical lens is better corrected.

Fig. 3 shows an F-Tan θ distortion curve of example 1, which represents F-Tan θ distortion of light rays of different wavelengths at different image heights on an image forming plane, the horizontal axis represents F-Tan θ distortion (unit: percentage), and the vertical axis represents half field angle (unit: °). As can be seen from the figure, the optical distortion at different image heights on the image plane is controlled within ± 2%, which indicates that the distortion of the optical lens is well corrected.

Fig. 4 shows an axial aberration curve of example 1, which represents the aberration on the optical axis at the imaging plane, the horizontal axis represents the axial chromatic aberration value (unit: mm), and the vertical axis represents the normalized pupil radius. It can be seen from the figure that the offset of the axial chromatic aberration is controlled within ± 0.06 mm, which shows that the optical lens can effectively correct the axial chromatic aberration.

Fig. 5 shows a vertical axis chromatic aberration curve of example 1, which represents chromatic aberration at different image heights on an image formation plane for each wavelength with respect to a center wavelength (0.55 μm), the horizontal axis represents a vertical axis chromatic aberration value (unit: μm) for each wavelength with respect to the center wavelength, and the vertical axis represents 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 +/-15 microns, which shows that the optical lens can effectively correct the aberration of the marginal field and the secondary spectrum of the whole image plane.

Example 2

Referring to fig. 5, a schematic structural diagram of an optical lens according to embodiment 2 of the present invention is shown, where the optical lens according to embodiment 2 of the present invention has a structure substantially the same as that of the optical lens according to embodiment 1, except that the fourth lens element L4 has negative optical power, the object-side surface S3 of the second lens element L2 is a concave surface, the object-side surface S6 of the third lens element L3 is a concave surface, and the curvature radii and material choices of the lens elements are different, and specific relevant parameters of the lens elements are shown in table 2-1.

The parameters related to each lens of the optical lens provided in this embodiment are shown in table 2-1.

TABLE 2-1

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

Tables 2 to 2

In the present embodiment, a field curvature graph, an F-Tan θ distortion graph, an axial aberration graph, and a vertical axis chromatic aberration graph of the optical lens are respectively shown in fig. 7, fig. 8, fig. 9, and fig. 10.

Fig. 7 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 +/-0.1 millimeter, which indicates that the field curvature of the optical lens is better corrected.

Fig. 8 shows an F-Tan θ distortion curve of example 2, which represents F-Tan θ distortion of light rays of different wavelengths at different image heights on an image forming plane, the horizontal axis represents F-Tan θ distortion (unit: percentage), and the vertical axis represents half field angle (unit: °). As can be seen from the figure, the optical distortion at different image heights on the imaging surface is controlled within ± 5%, which indicates that the distortion of the optical lens is well corrected.

Fig. 9 shows an axial aberration curve of example 2, which represents the aberration on the optical axis at the imaging plane, the horizontal axis represents the axial chromatic aberration value (unit: mm), and the vertical axis represents the normalized pupil radius. It can be seen from the figure that the offset of the axial chromatic aberration is controlled within ± 0.06 mm, which shows that the optical lens can effectively correct the axial chromatic aberration.

Fig. 10 shows a vertical axis chromatic aberration curve of example 2, which shows chromatic aberration at different image heights on an image formation 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 +/-10 microns, which shows that the optical lens can effectively correct the aberration of the marginal field and the secondary spectrum of the whole image plane.

Example 3

Referring to fig. 11, a schematic structural diagram of an optical lens system according to embodiment 3 of the present invention is shown, where the optical lens system according to embodiment 3 of the present invention has a structure substantially the same as that of the optical lens system according to embodiment 1, except that an object-side surface S3 of the second lens element L2 is a concave surface, and curvature radii and material choices of the lens elements are different, and specific relevant parameters of the lens elements are shown in table 3-1.

The parameters related to each lens of the optical lens provided in this embodiment are shown in table 3-1.

TABLE 3-1

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

TABLE 3-2

In the present embodiment, a field curvature graph, an F-Tan θ distortion graph, an axial aberration graph, and a vertical axis chromatic aberration graph of the optical lens are respectively shown in fig. 12, 13, 14, and 15.

Fig. 12 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 +/-0.04 mm, which indicates that the field curvature of the optical lens is better corrected.

Fig. 13 shows an F-Tan θ distortion curve of example 3, which represents F-Tan θ distortion of light rays of different wavelengths at different image heights on an image forming plane, the horizontal axis represents F-Tan θ distortion (unit: percentage), and the vertical axis represents half field angle (unit: °). As can be seen from the figure, the optical distortion at different image heights on the imaging surface is controlled within ± 3%, which indicates that the distortion of the optical lens is well corrected.

Fig. 14 shows an axial aberration curve of example 3, which represents the aberration on the optical axis at the imaging plane, the horizontal axis represents the axial chromatic aberration value (unit: mm), and the vertical axis represents the normalized pupil radius. It can be seen from the figure that the offset of the axial chromatic aberration is controlled within ± 0.02 mm, which shows that the optical lens can effectively correct the axial chromatic aberration.

Fig. 15 shows a vertical axis chromatic aberration curve of example 3, which represents chromatic aberration at different image heights on an image formation plane for each wavelength with respect to a center wavelength (0.55 μm), the horizontal axis represents a vertical axis chromatic aberration value (unit: μm) for each wavelength with respect to the center wavelength, and the vertical axis represents 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 +/-4 microns, which shows that the optical lens can effectively correct the aberration of the marginal field and the secondary spectrum of the whole image plane.

Example 4

Referring to fig. 16, which shows a schematic structural diagram of an optical lens provided in embodiment 4 of the present invention, the optical lens provided in embodiment 4 of the present invention has a structure that is substantially the same as the optical lens in embodiment 1, except that the fourth lens L4 has negative refractive power, the eighth lens L8 has positive refractive power, the object-side surface S1 of the first lens L1 is concave, the object-side surface S3 of the second lens L2 is concave, the object-side surface S6 of the third lens L3 is concave, and curvature radii and material selections of the lenses are different, and specific relevant parameters of each lens are shown in table 4-1.

The parameters related to each lens of the optical lens provided in this embodiment are shown in table 4-1.

TABLE 4-1

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

TABLE 4-2

In the present embodiment, a field curvature graph, an F-Tan θ distortion graph, an axial aberration graph, and a vertical axis chromatic aberration graph of the optical lens are respectively shown in fig. 17, 18, 19, and 20.

Fig. 17 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 +/-0.06 mm, which indicates that the field curvature of the optical lens is better corrected.

Fig. 18 shows an F-Tan θ distortion curve of example 4, which represents the F-Tan θ distortion of light rays of different wavelengths at different image heights on the image forming plane, the horizontal axis represents the F-Tan θ distortion (unit: percentage), and the vertical axis represents the half field angle (unit: °). As can be seen from the figure, the optical distortion at different image heights on the imaging surface is controlled within ± 3%, which indicates that the distortion of the optical lens is well corrected.

Fig. 19 shows an axial aberration curve of example 4, which represents the aberration on the optical axis at the imaging plane, the horizontal axis represents the axial chromatic aberration value (unit: mm), and the vertical axis represents the normalized pupil radius. It can be seen from the figure that the offset of the axial chromatic aberration is controlled within ± 0.03 mm, which shows that the optical lens can effectively correct the axial chromatic aberration.

Fig. 20 shows a vertical axis chromatic aberration curve of example 4, which shows chromatic aberration at different image heights on an image formation 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 microns, which shows that the optical lens can effectively correct the aberration of the marginal field and the secondary spectrum of the whole image plane.

Please refer to table 5, which shows the optical characteristics corresponding to the optical lens provided in each of the above four embodiments, mainly including the effective focal length f, the total optical length TTL, the f-stop FNO, the field angle FOV, the real image height IH corresponding to half of the maximum field angle, the field angle FOV, and the values corresponding to each of the foregoing conditional expressions.

TABLE 5

In summary, the optical lens provided in the embodiments of the present invention adopts eight lenses, optimizes the shape of the lenses, reasonably distributes the focal power of each lens, and so on, and achieves the advantages that the optical lens at least includes a large aperture and has high imaging quality.

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;

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

a diaphragm;

the image side surface of the third lens is a convex surface;

2. An optical lens according to claim 1, characterized in that the effective focal length f of the optical lens satisfies: f is more than 3.0mm and less than 6.0 mm.

3. The optical lens according to claim 1, wherein a real image height IH corresponding to half of a maximum field angle of the optical lens satisfies: IH is more than 2.5mm and less than 5.0 mm.

4. An optical lens according to claim 1, characterized in that the aperture value FNO of the optical lens is ≦ 1.0.

5. 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 satisfy: -3.5 < f1/f < -1.5.

6. An optical lens according to claim 1, characterized in that the effective focal length f of the optical lens and the focal length f4 of the fourth lens satisfy: | f4/f | < 55.0.

7. 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 satisfy: | f8/f | < 45.0.

8. An optical lens according to claim 1, characterized in that a combined focal length f12 of the first to second lenses and a combined focal length f38 of the third to eighth lenses of the optical lens satisfy: -1.2 < f12/f38 < -0.5.

9. An optical lens according to claim 1, wherein the total optical length TTL and the sum Σ TP of all lens thicknesses having optical powers satisfy: 0.6 < sigma TP/TTL < 0.8.

10. An optical lens according to claim 1, wherein the total optical length TTL of the optical lens and the effective focal length f of the optical lens satisfy: TTL/f is more than 6.0 and less than 12.0.