CN112415711A

CN112415711A - Optical system, camera module and terminal equipment

Info

Publication number: CN112415711A
Application number: CN202011041797.1A
Authority: CN
Inventors: 刘彬彬; 邹海荣; 李明
Original assignee: Jiangxi Jingchao Optical Co Ltd
Current assignee: Jiangxi Jingchao Optical Co Ltd
Priority date: 2020-09-28
Filing date: 2020-09-28
Publication date: 2021-02-26

Abstract

The embodiment of the application discloses an optical system, a camera module and terminal equipment. The optical system comprises a first lens element with positive refractive power having a convex object-side surface at paraxial region and a concave image-side surface at paraxial region; a second lens element, a third lens element, a fifth lens element and a seventh lens element with negative refractive power; a fourth lens element with positive refractive power and a sixth lens element with positive refractive power; having negative refractive power; the optical system satisfies: 1< (| SAG71| + SAG72)/CT7< 1.5. The refractive power and the surface type of the first lens element to the seventh lens element and the limit (| SAG71| + SAG72)/CT7 are reasonably configured, so that the optical system can meet the requirements of high pixel, large aperture and miniaturization.

Description

Optical system, camera module and terminal equipment

Technical Field

The application belongs to the technical field of optical imaging, and particularly relates to an optical system, a camera module and terminal equipment.

Background

In recent years, with the rapid development of electronic product manufacturing technologies such as smart phones, flat panels, and video cameras and the trend of increasingly diversified user demands, the market demand for miniaturized, high-pixel imaging devices has gradually increased.

In addition to the demand for miniaturization, the size of a pixel of a photosensitive element is reduced due to the progress of semiconductor process technology, so that the demand for higher pixels can be achieved. However, it is difficult for the imaging device of the electronic device such as the mobile phone to satisfy the requirements of high pixel, large aperture and miniaturization at the same time.

Therefore, how to simultaneously achieve the miniaturization of the imaging lens, the large aperture and the high pixel imaging quality should be the research and development direction in the industry.

Disclosure of Invention

The embodiment of the application provides an optical system, a camera module and terminal equipment, and the optical system meets the requirements of high pixel, large aperture and miniaturization.

In a first aspect, an optical system includes a plurality of lenses, each of the plurality of lenses includes a first lens element with positive refractive power arranged in order from an object side (the object side refers to a side on which light is incident) to an image side (the image side refers to a side on which light is emitted), an object side surface of the first lens element is convex at a paraxial region, and an image side surface of the first lens element is concave at the paraxial region; a second lens element with negative refractive power having a convex object-side surface and a concave image-side surface; a third lens element with negative refractive power; a fourth lens element with positive refractive power; the image side surface of the fourth lens element is convex at a paraxial region; a fifth lens element with negative refractive power; a sixth lens element with positive refractive power having a convex object-side surface at a paraxial region and a convex image-side surface at a paraxial region; a seventh lens element with negative refractive power having a convex object-side surface at a paraxial region and a concave image-side surface at a paraxial region; the optical system satisfies the following conditional expression: 1< (| SAG71| + SAG72)/CT7<1.5, SAG71 is the maximum distance on the optical axis from the off-axis point in the effective diameter of the object side surface of the seventh lens to the on-axis vertex of the object side surface of the seventh lens, SAG72 is the maximum distance on the optical axis from the off-axis point in the effective diameter of the image side surface of the seventh lens to the on-axis vertex of the image side surface of the seventh lens, and CT7 is the thickness of the seventh lens on the optical axis.

The refractive power is the focal power, and represents the ability of the optical system to deflect light, positive refractive power represents the converging effect of the lens on the light beam, and negative refractive power represents the diverging effect of the lens on the light beam. When the lens has no refractive power, that is, when the focal power is zero, the lens is plane refraction, and at this time, the axially parallel light beams are still axially parallel light beams after being refracted, and the refraction phenomenon does not occur.

The refractive power of the first lens element to the seventh lens element and the surface shapes and limitations (| SAG71| + SAG72)/CT7 of the first lens element, the second lens element, the fourth lens element, the sixth lens element and the seventh lens element in the optical system are reasonably configured, so that the optical system can meet the requirements of high pixel, large aperture and miniaturization.

Specifically, the refractive power and thickness of the seventh lens element in the vertical direction can be reasonably controlled by limiting the range (| SAG71| + SAG72)/CT7, so as to avoid the seventh lens element from being too thin and too thick, reduce the incident angle of light rays on the imaging plane, and reduce the sensitivity of the optical system. In addition, the seventh lens element has a plurality of inflection points, which is beneficial to correcting distortion and curvature of field generated by the first lens element to the sixth lens element, so that the refractive power configuration close to the image plane is more uniform.

In one embodiment, the object-side surface or the image-side surface of at least one of the lenses is aspheric, which is beneficial to correcting aberration of the optical system and improving imaging quality of the optical system.

In one embodiment, the optical system satisfies the conditional expression: f1 is more than 0mm, and f1 is the focal length of the first lens. The first lens has positive refractive power and has a converging effect on light beams, and large-angle light rays enter the first lens by limiting the value of f1, and the light rays can be better converged.

In one embodiment, the optical system satisfies the conditional expression: V2-V1| >30, V2 is the Abbe number of the second lens, V1 is the Abbe number of the first lens, and the reference wavelength of the Abbe number is 587.6 nm. By defining the value of | V2-V1|, correction of chromatic aberration is facilitated, providing imaging quality.

In one embodiment, the optical system satisfies the conditional expression: 0.5mm^-1<(n1+n2)/f<1mm^-1N1 is the refractive index of the first lens, n2 is the refractive index of the second lens, the reference wavelength of the refractive index is 587.6nm, and f is the focal length of the optical system. By reasonably configuring the refractive power of the first lens element and the second lens element, the chromatic aberration and the spherical aberration can be minimized, the image quality can be improved, the light-collecting capability of the optical system can be enhanced by reasonably distributing the focal power, and the size of the optical system can be favorably reduced.

In one embodiment, the optical system satisfies the conditional expression: f23 < 0mm, f23 is the combined focal length of the second lens and the third lens. By limiting the value of f23, the aberration correction is facilitated, the effective convergence of marginal rays is facilitated, the compact structure of the optical system can be ensured, the size is effectively compressed, and the characteristics of wide angle and miniaturization are realized.

In one embodiment, the optical system satisfies the conditional expression: 0< (CT1+ CT2+ CT3)/TTL <0.5, where CT1 is the thickness of the first lens element on the optical axis, CT2 is the thickness of the second lens element on the optical axis, CT3 is the thickness of the third lens element on the optical axis, and TTL is the distance from the object-side surface of the first lens element to the image plane in the optical system on the optical axis. By limiting the range of (CT1+ CT2+ CT3)/TTL, the thicknesses of the first lens, the second lens and the third lens are configured reasonably, which is beneficial to reducing the sensitivity of the optical system and simultaneously beneficial to miniaturization of the optical system.

In one embodiment, the optical system satisfies the conditional expression: (| f2| + | f3|)/| R71| >50, f2 is the focal length of the second lens, f3 is the focal length of the third lens, and R71 is the radius of curvature of the object-side surface of the seventh lens at the optical axis. By limiting the range of (| f2| + | f3|)/| R71 |), the refractive powers of the second lens and the third lens are reasonably configured, so that the comprehensive spherical aberration, chromatic aberration and distortion of the first lens, the second lens and the third lens are reduced to reasonable positions, and the design difficulty of the fourth lens, the fifth lens, the sixth lens and the seventh lens is reduced; meanwhile, the light receiving capacity of the system can be enhanced and the performance of the optical system can be improved through reasonable distribution of the curvature radius of the seventh lens.

In one embodiment, the optical system satisfies the conditional expression: (f1+ | f2| + | f3|)/f >40, f1 is the focal length of the first lens, f2 is the focal length of the second lens, f3 is the focal length of the third lens, and f is the focal length of the optical system. The sizes and the refractive powers of the first lens, the second lens and the third lens are reasonably configured, so that the first lens, the second lens and the third lens can be prevented from generating large spherical aberration, the integral resolving power of the optical system is improved, meanwhile, the size compression of the first lens, the second lens and the third lens is facilitated, and the small-size optical system is facilitated to be formed.

In one embodiment, the optical system satisfies the conditional expression: r62/f < -1, R62 is the radius of curvature of the image side surface of the sixth lens at the optical axis, and f is the focal length of the optical system. By reasonably limiting the value of R62/f, the surface type complexity of the sixth lens can be reduced, the field curvature and distortion can be inhibited, the forming difficulty is reduced, the integral image quality is improved, the back focal length of the system can be effectively controlled, and the total length of the system is prevented from being too long.

In one embodiment, the optical system satisfies the conditional expression: i f6| + | f7| <20mm, f6 is the focal length of the sixth lens, and f7 is the focal length of the seventh lens. By reasonably configuring the sizes and refractive powers of the sixth lens element and the seventh lens element and limiting the value of | f6| + | f7|, the spherical aberration generated by the first lens element to the fifth lens element can be balanced, the overall resolving power of the optical system can be improved, the configuration of the refractive powers of the sixth lens element and the seventh lens element of the optical system can be controlled, the aberration around the optical system can be corrected, and meanwhile, the size compression is facilitated, and a small-sized optical system can be formed.

In one embodiment, the optical system satisfies the conditional expression: 0< R72/f <1, R72 is a radius of curvature of an image-side surface of the seventh lens element at a paraxial region, and f is a focal length of the optical system. By reasonably limiting the value of R72/f, the surface type complexity of the seventh lens can be reduced, the field curvature and distortion can be inhibited, the forming difficulty is reduced, the integral image quality is improved, the back focal length of the system can be effectively controlled, and the total length of the system is prevented from being too long.

In one embodiment, the optical system satisfies the conditional expression: 0< Yc72/SD72<0.5, Yc72 is the vertical distance from the off-axis vertex (the vertex is the point where the tangent is made and the tangent is perpendicular to the optical axis) on the image side surface of the seventh lens to the optical axis, and SD72 is the maximum effective aperture of the image side surface of the seventh lens in the vertical axis direction. By limiting the range of Yc72/SD72, the refractive power and thickness of the seventh lens element in the vertical direction can be reasonably controlled, the seventh lens element is prevented from being too thin and too thick, the incident angle of light on an image plane is reduced, and the sensitivity of the optical system is reduced. In addition, the seventh lens element has a plurality of inflection points, which is beneficial to correcting distortion and curvature of field generated by the first lens element to the sixth lens element, so that the refractive power configuration close to the image plane is more uniform.

In one embodiment, the optical system satisfies the conditional expression: 0.6< TTL/(ImgH × 2) <0.8, where TTL is an axial distance from an object-side surface of the first lens element to an image plane in the optical system, and ImgH is an image height corresponding to a maximum field angle of the optical system. And limiting the value of TTL/(ImgH x 2) within a small range, and realizing the characteristic of miniaturization of the optical system through reasonable structural layout.

In one embodiment, the optical system satisfies the conditional expression: 38 ° < HFOV <45 °, HFOV being half the maximum field angle of the optical system. By limiting the range of the HFOV, wide-angle shooting of the optical system is facilitated.

In one embodiment, the optical system satisfies the conditional expression 0.75< DL/TTL <1, where DL is a distance on an optical axis from an object-side surface of the first lens element to an image-side surface of the seventh lens element, and TTL is a distance on an optical axis from the object-side surface of the first lens element to an image-side surface of the first lens element in the optical system. By limiting the value of DL/TTL, the distance between the seventh lens and the imaging surface is increased on the basis of realizing miniaturization, and the reasonable structural layout of an optical system is facilitated.

In one embodiment, the optical system satisfies the conditional expression: 1.0< TTL/f <1.4, wherein TTL is the distance between the object side surface of the first lens and an imaging surface in the optical system on the optical axis, and f is the focal length of the optical system. By properly configuring the range of TTL/f, the optical system can be made to have a lower height, making it easy to install into a portable device. Due to the aspheric surface, the TTL is larger than the focal length f, and meanwhile, under the condition of realizing wide-angle shooting, the aberration such as chromatic aberration, spherical aberration, distortion and the like can be balanced, so that the optical system has good imaging quality.

In one embodiment, the optical system satisfies the conditional expression: FNO is more than 1.5 and less than 2.0, and the FNO is the f-number of the optical system. The optical system is characterized by a large aperture by defining the value of FNO.

In a second aspect, the present application provides a camera module, including a photosensitive element and the optical system of any one of the foregoing embodiments, where the photosensitive element is located on an image side of the optical system.

In a third aspect, the present application provides a terminal device, including the camera module.

By reasonably configuring the refractive power of the first lens element to the seventh lens element and the surface shapes and limitations (| SAG71| + SAG72)/CT7 of the first lens element, the second lens element, the fourth lens element, the sixth lens element and the seventh lens element in the optical system, the optical system can simultaneously meet the requirements of high pixel, large aperture and miniaturization.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments or the background art of the present application, the drawings required to be used in the embodiments or the background art of the present application will be described below.

Fig. 1 is a schematic structural diagram of an optical system provided in a first embodiment of the present application;

fig. 2 is a longitudinal spherical aberration curve, an astigmatism curve, and a distortion curve of the optical system of the first embodiment;

FIG. 3 is a schematic diagram of an optical system according to a second embodiment of the present application;

FIG. 4 is a longitudinal spherical aberration curve, an astigmatism curve, and a distortion curve of the optical system of the second embodiment;

FIG. 5 is a schematic diagram of an optical system provided in a third embodiment of the present application;

fig. 6 is a longitudinal spherical aberration curve, an astigmatism curve, and a distortion curve of the optical system of the third embodiment;

FIG. 7 is a schematic diagram of an optical system according to a fourth embodiment of the present application;

fig. 8 is a longitudinal spherical aberration curve, an astigmatism curve, and a distortion curve of the optical system of the fourth embodiment;

fig. 9 is a schematic structural diagram of an optical system provided in a fifth embodiment of the present application;

fig. 10 is a longitudinal spherical aberration curve, an astigmatism curve, and a distortion curve of the optical system of the fifth embodiment;

fig. 11 is a schematic diagram of an optical system applied in a terminal device.

Detailed Description

The embodiments of the present application will be described below with reference to the drawings.

An optical system provided by the present application includes seven lenses, which are, in order from an object side to an image side, a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens and a seventh lens.

Specifically, the surface shapes and refractive powers of the seven lenses are as follows:

the first lens element with positive refractive power has a convex object-side surface at paraxial region and a concave image-side surface at paraxial region; the second lens element with negative refractive power has a convex object-side surface at paraxial region and a concave image-side surface at paraxial region; the third lens element with negative refractive power; the fourth lens element with positive refractive power; the image side surface of the fourth lens element is convex at a paraxial region; the fifth lens element with negative refractive power; the sixth lens element with positive refractive power has a convex object-side surface at a paraxial region thereof and a convex image-side surface at a paraxial region thereof; the seventh lens element with negative refractive power has a convex object-side surface at a paraxial region and a concave image-side surface at a paraxial region.

The optical system satisfies the following conditional expression: 1< (| SAG71| + SAG72)/CT7<1.5, SAG71 is the maximum distance on the optical axis from the off-axis point in the effective diameter of the object side surface of the seventh lens to the on-axis vertex of the object side surface of the seventh lens, SAG72 is the maximum distance on the optical axis from the off-axis point in the effective diameter of the image side surface of the seventh lens to the on-axis vertex of the image side surface of the seventh lens, and CT7 is the thickness of the seventh lens on the optical axis.

In one embodiment, the optical system satisfies the conditional expression: 0.5mm^-1<(n1+n2)/f<1mm^-1N1 is the firstThe refractive index of the lens, n2 is the refractive index of the second lens, the reference wavelength of the refractive index is 587.6nm, and f is the focal length of the optical system. By reasonably configuring the refractive power of the first lens element and the second lens element, the chromatic aberration and the spherical aberration can be minimized, the image quality can be improved, the light-collecting capability of the optical system can be enhanced by reasonably distributing the focal power, and the size of the optical system can be favorably reduced.

In one embodiment, the optical system satisfies the conditional expression: 0< Yc72/SD72<0.5, Yc72 is a vertical distance from an off-axis vertex on the image-side surface of the seventh lens to the optical axis, and SD72 is a maximum effective aperture of the image-side surface of the seventh lens in a vertical axis direction. By limiting the range of Yc72/SD72, the refractive power and thickness of the seventh lens element in the vertical direction can be reasonably controlled, the seventh lens element is prevented from being too thin and too thick, the incident angle of light on an image plane is reduced, and the sensitivity of the optical system is reduced. In addition, the seventh lens element has a plurality of inflection points, which is beneficial to correcting distortion and curvature of field generated by the first lens element to the sixth lens element, so that the refractive power configuration close to the image plane is more uniform.

The present application is described in detail below with reference to five specific examples.

Example one

As shown in fig. 1, a straight line 11 indicates an optical axis, a side of the first lens L1 away from the second lens L2 is an object side 12, and a side of the seventh lens L7 away from the sixth lens L6 is an image side 13. In the optical system provided in this embodiment, the stop STO, the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, the sixth lens L6, the seventh lens L7, and the infrared filter element IRCF are arranged in order from the object side 12 to the image side 13.

The first lens element L1 with positive refractive power has a convex object-side surface S1 at a paraxial region and a convex peripheral region, a concave image-side surface S2 at a paraxial region, and a convex image-side surface S2 at a peripheral region.

The second lens element L2 with negative refractive power has a convex object-side surface S3 at a paraxial region and a concave peripheral region, and an aspheric image-side surface S4.

The third lens element L3 with negative refractive power is made of plastic material, and has a convex object-side surface S5 at a paraxial region, a concave object-side surface S5 at a circumference, a concave image-side surface S6 at a paraxial region, and a convex image-side surface S6 at a circumference.

The fourth lens element L4 with positive refractive power has a concave object-side surface S7 at a paraxial region, a convex object-side surface S7 at a circumference, and an aspheric image-side surface S8 at the paraxial region and the circumferential region.

The fifth lens element L5 with negative refractive power is made of plastic material, and has a convex object-side surface S9 at a paraxial region, a concave object-side surface S9 at a circumference, a concave image-side surface S10 at a paraxial region, and a convex image-side surface S10 at a circumference.

The sixth lens element L6 with positive refractive power is made of plastic material, and has a convex object-side surface S11 at a paraxial region, a concave object-side surface S11 at a circumference, and a convex image-side surface S12 at a paraxial region and a circumference.

The seventh lens element L7 with negative refractive power is made of plastic material, and has a convex object-side surface S13 at a paraxial region, a concave object-side surface S13 at a circumference, a concave image-side surface S14 at a paraxial region, and a convex image-side surface S14 at a circumference.

The stop STO may be located on the object side of the first lens L1 or between any two adjacent lenses, and the stop STO in the present embodiment is disposed on the object side of the first lens L1.

The infrared filter element IRCF is disposed behind the seventh lens L7 and includes an object side surface S15 and an image side surface S16, and is configured to filter infrared light, so that the light incident on the image plane is visible light, the wavelength of the visible light is 380nm to 780nm, and the infrared filter element IRCF is made of glass.

The image forming surface S17 is a surface on which an image is formed by the light of the subject passing through the optical system.

Table 1a shows a characteristic table of the optical system of the present embodiment, in which the radius of curvature in the present embodiment is the radius of curvature of each lens at the paraxial region.

TABLE 1a

Wherein f is a focal length of the optical system, FNO is an f-number of the optical system, FOV is a maximum field angle of the optical system, TTL is a distance on an optical axis from an object-side surface of the first lens to an image plane of the optical system, ImgH is an image height corresponding to the maximum field angle of the optical system, and DL is a distance on the optical axis from the object-side surface of the first lens to an image-side surface of the seventh lens.

Further, the combined focal length f23 of the second lens L2 and the third lens L3 is-13.0277 mm, the combined focal length f34 of the third lens L3 and the fourth lens L4 is 31.7286mm, the combined focal length f45 of the fourth lens L4 and the fifth lens L5 is 31.5062mm, the combined focal length f56 of the fifth lens L5 and the sixth lens L6 is 9.1374mm, and the combined focal length f67 of the sixth lens L6 and the seventh lens L7 is-11.1171 mm.

In this embodiment, the object-side surface or the image-side surface of at least one of the first lens L1 through the seventh lens L7 is aspheric, and the surface shape of each aspheric lens can be defined by, but is not limited to, the following aspheric formula:

wherein Z is a distance from a corresponding point on the aspherical surface to a plane tangent to the surface vertex, r is a distance from a corresponding point on the aspherical surface to the optical axis, c is a curvature of the aspherical surface vertex, k is a conic constant, and Ai is a coefficient corresponding to the i-th high-order term in the aspherical surface type formula.

Table 1b shows the high-order term coefficients a4, A6, a8, a10, a12, a14, a16, a18, and a20 that can be used for the respective aspherical mirrors S1, S2, S3, S4, S5, S6, S7, S8, S9, S10, S11, S12, S13, S14 in the first embodiment.

TABLE 1b

Fig. 2 shows a longitudinal spherical aberration curve, an astigmatism curve, and a distortion curve of the optical system of the first embodiment. The longitudinal spherical aberration curve represents the deviation of convergence focuses of light rays with different wavelengths after passing through each lens of the optical system, and the reference wavelengths of the longitudinal spherical aberration curve are 650.0000nm, 610.0000nm, 555.0000nm, 510.0000nm and 470.0000 nm; the astigmatism curves represent meridional image surface curvature and sagittal image surface curvature, wherein S represents sagittal direction, T represents meridional direction, and the reference wavelength of the astigmatism curves is 555.0000 nm; the distortion curve represents the distortion magnitude values corresponding to different angles of view, and the reference wavelength of the distortion curve is 555.0000 nm. As can be seen from fig. 2, the optical system according to the first embodiment can achieve good imaging quality.

Example two

As shown in fig. 3, a straight line 11 indicates an optical axis, a side of the first lens L1 away from the second lens L2 is an object side 12, and a side of the seventh lens L7 away from the sixth lens L6 is an image side 13. In the optical system provided in this embodiment, the stop STO, the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, the sixth lens L6, the seventh lens L7, and the infrared filter element IRCF are arranged in order from the object side 12 to the image side 13.

The third lens element L3 with negative refractive power has a concave object-side surface S5 at a paraxial region and a concave peripheral region, and has a convex image-side surface S6 at a paraxial region and a convex peripheral region.

Table 2a shows a characteristic table of the optical system of the present embodiment, in which the radius of curvature in the present embodiment is the radius of curvature of each lens at the paraxial region.

TABLE 2a

Further, the combined focal length f23 of the second lens L2 and the third lens L3 is-16.4058 mm, the combined focal length f34 of the third lens L3 and the fourth lens L4 is 22.9984mm, the combined focal length f45 of the fourth lens L4 and the fifth lens L5 is 24.1886mm, the combined focal length f56 of the fifth lens L5 and the sixth lens L6 is 9.2549mm, and the combined focal length f67 of the sixth lens L6 and the seventh lens L7 is-11.4932 mm.

Table 2b shows high-order term coefficients A4, a6, A8, a10, a12, a14, a16, a18, and a20 that can be used for each aspherical mirror surface S1, S2, S3, S4, S5, S6, S7, S8, S9, S10, S11, S12, S13, and S14 in the second embodiment, wherein each aspherical mirror surface type can be defined by the formula given in the first embodiment.

TABLE 2b

Fig. 4 shows a longitudinal spherical aberration curve, an astigmatism curve, and a distortion curve of the optical system of the second embodiment. The longitudinal spherical aberration curve represents the deviation of convergence focuses of light rays with different wavelengths after passing through each lens of the optical system, and the reference wavelengths of the longitudinal spherical aberration curve are 650.0000nm, 610.0000nm, 555.0000nm, 510.0000nm and 470.0000 nm; the astigmatism curves represent meridional image surface curvature and sagittal image surface curvature, wherein S represents sagittal direction, T represents meridional direction, and the reference wavelength of the astigmatism curves is 555.0000 nm; the distortion curve represents the distortion magnitude values corresponding to different angles of view, and the reference wavelength of the distortion curve is 555.0000 nm. As can be seen from fig. 4, the optical system according to the second embodiment can achieve good imaging quality.

EXAMPLE III

As shown in fig. 5, a straight line 11 indicates an optical axis, a side of the first lens L1 away from the second lens L2 is an object side 12, and a side of the seventh lens L7 away from the sixth lens L6 is an image side 13. In the optical system provided in this embodiment, the stop STO, the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, the sixth lens L6, the seventh lens L7, and the infrared filter element IRCF are arranged in order from the object side 12 to the image side 13.

The first lens element L1 with positive refractive power has a convex object-side surface S1 at a paraxial region and a concave peripheral region, and an aspheric image-side surface S2.

The fifth lens element L5 with negative refractive power has a concave object-side surface S9 at a paraxial region and a concave peripheral region, a concave image-side surface S10 at a paraxial region, and a convex image-side surface S10 at a peripheral region, and is made of plastic material.

The seventh lens element L7 with negative refractive power has a convex object-side surface S13 at a paraxial region and a convex peripheral region, a concave image-side surface S14 at a paraxial region, and a convex image-side surface S14 at a peripheral region, and is made of plastic material.

Table 3a shows a characteristic table of the optical system of the present embodiment, in which the radius of curvature in the present embodiment is the radius of curvature of each lens at the paraxial region.

TABLE 3a

Further, the combined focal length f23 of the second lens L2 and the third lens L3 is-36.5896 mm, the combined focal length f34 of the third lens L3 and the fourth lens L4 is 21.1467mm, the combined focal length f45 of the fourth lens L4 and the fifth lens L5 is 25.0957mm, the combined focal length f56 of the fifth lens L5 and the sixth lens L6 is 8.5989mm, and the combined focal length f67 of the sixth lens L6 and the seventh lens L7 is-152.8332 mm.

Table 3b shows high-order term coefficients A4, a6, A8, a10, a12, a14, a16, a18, and a20 that can be used for each aspherical mirror surface S1, S2, S3, S4, S5, S6, S7, S8, S9, S10, S11, S12, S13, and S14 in the third embodiment, wherein each aspherical mirror surface type can be defined by the formula given in the first embodiment.

TABLE 3b

Fig. 6 shows a longitudinal spherical aberration curve, an astigmatism curve, and a distortion curve of the optical system of the third embodiment. The longitudinal spherical aberration curve represents the deviation of convergence focuses of light rays with different wavelengths after passing through each lens of the optical system, and the reference wavelengths of the longitudinal spherical aberration curve are 650.0000nm, 610.0000nm, 555.0000nm, 510.0000nm and 470.0000 nm; the astigmatism curves represent meridional image surface curvature and sagittal image surface curvature, wherein S represents sagittal direction, T represents meridional direction, and the reference wavelength of the astigmatism curves is 555.0000 nm; the distortion curve represents the distortion magnitude values corresponding to different angles of view, and the reference wavelength of the distortion curve is 555.0000 nm. As can be seen from fig. 6, the optical system according to the third embodiment can achieve good image quality.

Example four

As shown in fig. 7, a straight line 11 indicates an optical axis, a side of the first lens L1 away from the second lens L2 is an object side 12, and a side of the seventh lens L7 away from the sixth lens L6 is an image side 13. In the optical system provided in this embodiment, the stop STO, the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, the sixth lens L6, the seventh lens L7, and the infrared filter element IRCF are arranged in order from the object side 12 to the image side 13.

The fourth lens element L4 with positive refractive power has a convex object-side surface S7 at a paraxial region and a convex peripheral region, and has an aspheric image-side surface S8 at a paraxial region and a convex peripheral region.

The fifth lens element L5 with negative refractive power has a concave object-side surface S9 at a paraxial region and a concave peripheral region, and has a convex image-side surface S10 at a paraxial region and a convex peripheral region, and is made of plastic material.

Table 4a shows a characteristic table of the optical system of the present embodiment, in which the radius of curvature in the present embodiment is the radius of curvature of each lens at the paraxial region.

TABLE 4a

Further, the combined focal length f23 of the second lens L2 and the third lens L3 is-30.1658 mm, the combined focal length f34 of the third lens L3 and the fourth lens L4 is 17.6302mm, the combined focal length f45 of the fourth lens L4 and the fifth lens L5 is 18.1426mm, the combined focal length f56 of the fifth lens L5 and the sixth lens L6 is 8.1268mm, and the combined focal length f67 of the sixth lens L6 and the seventh lens L7 is-244.9808 mm.

Table 4b shows high-order term coefficients A4, a6, A8, a10, a12, a14, a16, a18, and a20 that can be used for each aspherical mirror surface S1, S2, S3, S4, S5, S6, S7, S8, S9, S10, S11, S12, S13, and S14 in the fourth embodiment, wherein each aspherical mirror surface type can be defined by the formula given in the first embodiment.

TABLE 4b

Number of noodles	S1	S2	S3	S4	S5	S6	S7
								K	-1.946762	-5.039056	-3.888751	-1.266274	9.730845	99.000000	-64.771018
A4	0.025175	-0.046124	-0.077520	-0.018792	0.013185	0.197091	0.197585
								A6	0.094386	-0.052766	-0.000907	-0.081239	-0.315486	-1.114911	-1.043923
A8	-0.341832	0.242378	0.119436	0.377392	1.149037	3.384806	3.080814
								A10	0.761346	-0.390268	-0.026577	-0.724435	-3.587910	-7.381096	-6.525620
A12	-1.062680	0.270728	-0.384378	0.758841	7.832948	11.108539	9.472838
								A14	0.925466	0.040752	0.782197	-0.331925	-11.297375	-11.303890	-9.152680
A16	-0.486134	-0.193541	-0.696603	-0.085012	10.043239	7.392438	5.605423
								A18	0.139966	0.113759	0.298893	0.139834	-4.928034	-2.760003	-1.944336
A20	-0.016938	-0.021804	-0.049945	-0.037148	1.018658	0.440555	0.288061
								Number of noodles	S8	S9	S10	S11	S12	S13	S14
K	40.446062	-72.844991	46.423703	-9.218948	4.187265	-10.044293	-4.682547
								A4	0.049568	0.029300	0.083022	0.231055	0.044518	-0.269155	-0.140513
A6	-0.393128	-0.343974	-0.537462	-0.435365	0.181046	0.186263	0.080071
								A8	1.064620	0.736987	0.981506	0.507870	-0.305988	-0.119907	-0.035900
A10	-2.180842	-1.114439	-1.160175	-0.466691	0.216356	0.056239	0.009707
								A12	3.043992	1.159981	0.912873	0.292349	-0.088786	-0.016414	-0.001338
A14	-2.810867	-0.833615	-0.463049	-0.117242	0.022421	0.002936	0.000046
								A16	1.654883	0.403240	0.144431	0.028525	-0.003409	-0.000316	0.000010
A18	-0.566844	-0.119575	-0.025124	-0.003804	0.000285	0.000019	-0.000001
								A20	0.086893	0.016284	0.001863	0.000212	-0.000010	0.000000	0.000000

Fig. 8 shows a longitudinal spherical aberration curve, an astigmatism curve, and a distortion curve of the optical system of the fourth embodiment. The longitudinal spherical aberration curve represents the deviation of convergence focuses of light rays with different wavelengths after passing through each lens of the optical system, and the reference wavelengths of the longitudinal spherical aberration curve are 650.0000nm, 610.0000nm, 555.0000nm, 510.0000nm and 470.0000 nm; the astigmatism curves represent meridional image surface curvature and sagittal image surface curvature, wherein S represents sagittal direction, T represents meridional direction, and the reference wavelength of the astigmatism curves is 555.0000 nm; the distortion curve represents the distortion magnitude values corresponding to different angles of view, and the reference wavelength of the distortion curve is 555.0000 nm. As can be seen from fig. 8, the optical system according to the fourth embodiment can achieve good image quality.

EXAMPLE five

As shown in fig. 9, a straight line 11 indicates an optical axis, a side of the first lens L1 away from the second lens L2 is an object side 12, and a side of the seventh lens L7 away from the sixth lens L6 is an image side 13. In the optical system provided in this embodiment, the stop STO, the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, the sixth lens L6, the seventh lens L7, and the infrared filter element IRCF are arranged in order from the object side 12 to the image side 13.

Table 5a shows a characteristic table of the optical system of the present embodiment, in which the radius of curvature in the present embodiment is the radius of curvature of each lens at the paraxial region.

TABLE 5a

Further, the combined focal length f23 of the second lens L2 and the third lens L3 is-15.1853 mm, the combined focal length f34 of the third lens L3 and the fourth lens L4 is 18.8297mm, the combined focal length f45 of the fourth lens L4 and the fifth lens L5 is 24.4426mm, the combined focal length f56 of the fifth lens L5 and the sixth lens L6 is 10.3997mm, and the combined focal length f67 of the sixth lens L6 and the seventh lens L7 is-12.1354 mm.

Table 5b shows high-order term coefficients A4, a6, A8, a10, a12, a14, a16, a18, and a20 that can be used for each aspherical mirror surface S1, S2, S3, S4, S5, S6, S7, S8, S9, S10, S11, S12, S13, and S14 in the fifth embodiment, wherein each aspherical mirror surface type can be defined by the formula given in the first embodiment.

TABLE 5b

Number of noodles	S1	S2	S3	S4	S5	S6	S7
								K	-1.915846	-3.700589	-2.588220	-1.250820	67.168094	-99.000000	-99.000000
A4	0.035690	-0.071202	-0.107434	-0.046278	-0.010057	0.193081	0.220462
								A6	0.023102	0.057315	0.079462	0.030038	-0.138076	-1.150631	-1.177774
A8	-0.089971	-0.023373	0.065563	0.103726	0.391870	3.606371	3.411264
								A10	0.207397	0.012742	-0.199675	-0.243249	-0.990386	-7.872540	-6.761098
A12	-0.293175	-0.051827	0.230593	0.302708	1.720711	11.481440	8.859194
								A14	0.255478	0.080741	-0.164282	-0.280613	-2.081043	-11.034070	-7.563974
A16	-0.134167	-0.059557	0.085731	0.210992	1.623454	6.731774	4.082286
								A18	0.038643	0.021433	-0.031237	-0.102219	-0.702133	-2.342824	-1.261846
A20	-0.004711	-0.003027	0.005611	0.023207	0.125291	0.349897	0.169207
								Number of noodles	S8	S9	S10	S11	S12	S13	S14
K	25.677174	99.000000	-43.428575	-11.459383	-1.239310	-11.239435	-4.955623
								A4	0.005216	0.028787	0.080638	0.218404	0.130750	-0.257906	-0.128621
A6	-0.131826	-0.497339	-0.500657	-0.389995	-0.035149	0.184781	0.074485
								A8	0.121249	1.263947	0.831122	0.397090	-0.066405	-0.120371	-0.033241
A10	0.147628	-2.147374	-0.872801	-0.319836	0.064578	0.055161	0.008860
								A12	-0.585946	2.500140	0.612915	0.184671	-0.029266	-0.015627	-0.001256
A14	0.723954	-1.976111	-0.284820	-0.071756	0.007773	0.002716	0.000065
								A16	-0.440568	1.008056	0.084288	0.017469	-0.001216	-0.000284	0.000005
A18	0.127778	-0.298078	-0.014383	-0.002365	0.000103	0.000017	-0.000001
								A20	-0.012339	0.038621	0.001073	0.000135	-0.000004	0.000000	0.000000

Fig. 10 shows a longitudinal spherical aberration curve, an astigmatism curve, and a distortion curve of the optical system of the fifth embodiment. The longitudinal spherical aberration curve represents the deviation of convergence focuses of light rays with different wavelengths after passing through each lens of the optical system, and the reference wavelengths of the longitudinal spherical aberration curve are 650.0000nm, 610.0000nm, 555.0000nm, 510.0000nm and 470.0000 nm; the astigmatism curves represent meridional image surface curvature and sagittal image surface curvature, wherein S represents sagittal direction, T represents meridional direction, and the reference wavelength of the astigmatism curves is 555.0000 nm; the distortion curve represents the distortion magnitude values corresponding to different angles of view, and the reference wavelength of the distortion curve is 555.0000 nm. As can be seen from fig. 10, the optical system according to the fifth embodiment can achieve good image quality.

Table 6 shows values of TTL/(ImgH × 2), HFOV, DL/TTL, TTL/f, f1, f23, R72/f, | f6| + | f7|, | V2-V1|, FNO, (n1+ n2)/f, (| f2| + | f3|)/| R71|, (f1+ | f2| + | f3|)/f, R62/f, Yc72/SD72, (CT1+ CT2+ CT3)/TTL, (| SAG71| + SAG72)/CT7 of the optical systems of the first to fifth embodiments.

TABLE 6

As can be seen from table 6, each example satisfies: 0.6<TTL/(ImgH*2)<0.8，38°<HFOV<45°，0.75<DL/TTL<1，1.0<TTL/f<1.4，f1＞0mm，f23＜0mm，0<R72/f<1，|f6|+|f7|<20mm，|V2-V1|>30，1.5＜FNO＜2.0，0.5mm^-1<(n1+n2)/f<1mm^-1，(|f2|+|f3|)/|R71|>50，(f1+|f2|+|f3|)/f>40，R62/f<-1，0<Yc72/SD72<0.5，0<(CT1+CT2+CT3)/TTL<0.5，1<(|SAG71|+SAG72)/CT7<1.5。

Referring to fig. 11, the optical system according to the present application is applied to a camera module 20 in a terminal device 30. The terminal device 30 may be a mobile phone, a tablet computer, an unmanned aerial vehicle, a computer, or the like. The photosensitive element of the camera module 20 is located on the image side of the optical system, and the camera module 20 is assembled inside the terminal device 30.

The application provides a camera module, including photosensitive element and the optical system that this application embodiment provided, photosensitive element is located optical system's image side for incidenting the light on the electron photosensitive element and convert the signal of telecommunication of image into with passing first lens to seventh lens. The electron sensor may be a Complementary Metal Oxide Semiconductor (CMOS) or a Charge-coupled Device (CCD). The optical system is installed in the camera module, so that the camera module meets the requirements of high pixel, large aperture and miniaturization.

The application also provides a terminal device, and the terminal device comprises the camera module provided by the embodiment of the application. The terminal equipment can be a mobile phone, a tablet personal computer, an unmanned aerial vehicle, a computer and the like. The camera module is installed in the terminal equipment, so that the terminal equipment can meet the requirements of high pixel, large aperture and miniaturization.

The foregoing is a preferred embodiment of the present application, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present application, and these modifications and decorations are also regarded as the protection scope of the present application.

Claims

1. An optical system comprising a plurality of lenses, the plurality of lenses comprising, arranged in order from an object side to an image side:

a first lens element with positive refractive power having a convex object-side surface at a paraxial region and a concave image-side surface at a paraxial region;

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

a third lens element with negative refractive power;

a fourth lens element with positive refractive power; the image side surface of the fourth lens element is convex at a paraxial region;

a fifth lens element with negative refractive power;

a sixth lens element with positive refractive power having a convex object-side surface at a paraxial region and a convex image-side surface at a paraxial region;

a seventh lens element with negative refractive power having a convex object-side surface at a paraxial region and a concave image-side surface at a paraxial region;

the optical system satisfies the following conditional expression:

1<(|SAG71|+SAG72)/CT7<1.5，

SAG71 is a maximum distance on an optical axis from an off-axis point in an object-side effective diameter of the seventh lens to an on-axis vertex of an object-side surface of the seventh lens, SAG72 is a maximum distance on an optical axis from an off-axis point in an image-side effective diameter of the seventh lens to an on-axis vertex of an image-side surface of the seventh lens, and CT7 is a thickness of the seventh lens on the optical axis.

2. The optical system according to claim 1, wherein the optical system satisfies the conditional expression:

|V2-V1|>30，

v2 is the Abbe number of the second lens, V1 is the Abbe number of the first lens, and the reference wavelength of the Abbe number is 587.6 nm.

3. The optical system according to claim 1, wherein the optical system satisfies the conditional expression:

0.5mm^-1<(n1+n2)/f<1mm^-1，

n1 is a refractive index of the first lens, n2 is a refractive index of the second lens, a reference wavelength of the refractive index is 587.6nm, and f is a focal length of the optical system.

4. The optical system according to claim 1, wherein the optical system satisfies the conditional expression:

f23＜0mm，

f23 is the combined focal length of the second lens and the third lens.

5. The optical system according to claim 1, wherein the optical system satisfies the conditional expression:

0<(CT1+CT2+CT3)/TTL<0.5，

CT1 is the thickness of the first lens element, CT2 is the thickness of the second lens element, CT3 is the thickness of the third lens element, and TTL is the distance between the object-side surface of the first lens element and the image plane of the optical system.

6. The optical system according to claim 1, wherein the optical system satisfies the conditional expression:

(|f2|+|f3|)/|R71|>50，

f2 is a focal length of the second lens, f3 is a focal length of the third lens, and R71 is a radius of curvature of an object-side surface of the seventh lens at an optical axis.

7. The optical system according to claim 1, wherein the optical system satisfies the conditional expression:

(f1+|f2|+|f3|)/f>40，

f1 is a focal length of the first lens, f2 is a focal length of the second lens, f3 is a focal length of the third lens, and f is a focal length of the optical system.

8. The optical system according to claim 1, wherein the optical system satisfies the conditional expression:

R62/f<-1，

r62 is a radius of curvature of an image-side surface of the sixth lens element at an optical axis, and f is a focal length of the optical system.

9. The optical system according to claim 1, wherein the optical system satisfies the conditional expression:

|f6|+|f7|<20mm，

f6 is the focal length of the sixth lens, and f7 is the focal length of the seventh lens.

10. The optical system according to claim 1, wherein the optical system satisfies the conditional expression:

0<R72/f<1，

r72 is a radius of curvature of an image-side surface of the seventh lens element at a paraxial region, and f is a focal length of the optical system.

11. The optical system according to claim 1, wherein the optical system satisfies the conditional expression:

0<Yc72/SD72<0.5，

yc72 is a vertical distance from an off-axis vertex on the image-side surface of the seventh lens element to the optical axis, and SD72 is a maximum effective diameter of the image-side surface of the seventh lens element in a vertical axis direction.

12. The optical system according to claim 1, wherein the optical system satisfies the conditional expression:

0.6<TTL/(ImgH*2)<0.8，

TTL is a distance on an optical axis from an object-side surface of the first lens element to an image plane in the optical system, and ImgH is an image height corresponding to a maximum field angle of the optical system.

13. The optical system according to claim 1, wherein the optical system satisfies the conditional expression:

38°<HFOV<45°，

the HFOV is half of the maximum field angle of the optical system.

14. The optical system according to claim 1, wherein the optical system satisfies the conditional expression:

0.75<DL/TTL<1，

DL is a distance on an optical axis from an object-side surface of the first lens element to an image-side surface of the seventh lens element, and TTL is a distance on the optical axis from the object-side surface of the first lens element to an image plane in the optical system.

15. The optical system according to claim 1, wherein the optical system satisfies the conditional expression:

1.0<TTL/f<1.4，

TTL is a distance on an optical axis from an object-side surface of the first lens element to an image plane in the optical system, and f is a focal length of the optical system.

16. The optical system according to claim 1, wherein the optical system satisfies the conditional expression:

1.5＜FNO＜2.0，

the FNO is an f-number of the optical system.

17. A camera module comprising a photosensitive element and the optical system of any one of claims 1 to 16, wherein the photosensitive element is located on the image side of the optical system.

18. A terminal device characterized by comprising the camera module according to claim 17.