CN114460723A

CN114460723A - Optical system, camera module and electronic equipment

Info

Publication number: CN114460723A
Application number: CN202210277923.6A
Authority: CN
Inventors: 党绪文; 刘彬彬; 李明
Original assignee: Jiangxi Jingchao Optical Co Ltd
Current assignee: Jiangxi Jingchao Optical Co Ltd
Priority date: 2022-03-21
Filing date: 2022-03-21
Publication date: 2022-05-10
Anticipated expiration: 2042-03-21
Also published as: CN114460723B

Abstract

The invention discloses an optical system, a camera module and electronic equipment. The optical system includes: a first lens element with negative refractive power having a concave object-side surface at paraxial region; a second lens element with positive refractive power having a convex object-side surface and a concave image-side surface at paraxial region, respectively; a third lens element with positive refractive power having a convex image-side surface at paraxial region and a convex image-side surface at peripheral region; a fourth lens element with refractive power having a concave object-side surface at a circumference, a concave object-side surface at a paraxial region of the sixth lens element, a convex image-side surface at a paraxial region of the sixth lens element, a concave object-side surface at a circumference, and a convex image-side surface at a circumference; the optical system satisfies the relationship: 2.9 < Fno TTL/IMGH < 3.7. According to the optical system provided by the embodiment of the invention, the wide-angle design can be realized, and meanwhile, the good imaging quality is considered.

Description

Optical system, camera module and electronic equipment

Technical Field

The present invention relates to the field of photography imaging technologies, and in particular, to an optical system, a camera module, and an electronic device.

Background

In recent years, various lens-mounted mobile electronic devices (including various portable information terminals such as digital cameras, smart phones, notebook computers, and tablet computers) have been rapidly spreading. Among them, larger viewing angle, higher portability and stronger night-shooting capability are the mainstream design direction at present. However, the above characteristics conflict with each other, and it is difficult to achieve compatibility. How to increase the aperture size of a wide-angle optical system and keep miniaturization is a problem to be solved.

Disclosure of Invention

The present invention is directed to solving at least one of the problems of the prior art. Therefore, the present application provides an optical system that can effectively solve the problem of both miniaturization and large aperture while achieving a wide-angle design.

The optical system according to an embodiment of the first aspect of the present application includes: a first lens element with negative refractive power having a concave object-side surface at paraxial region; a second lens element with positive refractive power having a convex object-side surface and a concave image-side surface; a third lens element with positive refractive power having a convex image-side surface at paraxial region and a convex image-side surface at peripheral region; a fourth lens element with refractive power, an object-side surface of the fourth lens element being concave at a circumference; a fifth lens element with refractive power; a sixth lens element with refractive power having a concave object-side surface at a paraxial region and a convex image-side surface at a paraxial region; the seventh lens element with refractive power has a concave object-side surface at a circumference and a convex image-side surface at the circumference.

In the optical system, the first lens has negative refractive power, which is beneficial to absorbing large-angle light rays, compressing the light ray trend of each field of view, expanding the field angle of the optical system and being beneficial to the wide-angle design of the optical system. The object side surface of the first lens is a concave surface near the optical axis, which is beneficial to enhancing the negative refractive power of the first lens and further provides a reasonable light ray incidence angle for the introduction of marginal light rays. The second lens has positive refractive power, is beneficial to shrinking large-angle light rays introduced by the first lens, avoids overlarge vignetting by reasonably utilizing the position and the size of the diaphragm, and ensures that an image plane has enough light inlet quantity; the third lens element with positive refractive power has a certain symmetrical relationship with the second lens element, so that introduction of phase difference such as distortion and field curvature is reduced, and the image side surface is convex at the optical axis and the circumference, which is beneficial to light diffusion to the image; the fourth lens with refractive power is matched with a surface type design that the object side surface is concave at the circumference, so that the fourth lens can be matched with the surface type of the image side surface of the third lens, the incident angle of a main ray of the light on the object side surface of the fourth lens can be reduced, the relative illumination is improved, and the off-axis aberration is reduced; the fifth lens element with refractive power can effectively correct aberration generated when light passes through the object lens elements (i.e., the first lens element to the fourth lens element), and reduce the correction pressure of the rear lens elements (i.e., the sixth lens element and the seventh lens element). The image side surface of the sixth lens is a convex surface near the optical axis, so that the light angle of the fifth lens can be dispersed, the distortion, the astigmatism and the field curvature can be corrected, and the requirements of low aberration and high image quality can be met. The circumference of the image side surface of the seventh lens is a convex surface, so that the incident angle of light on the image surface can be kept in a reasonable range, and the requirement of a chip matching angle is met.

In one embodiment, the optical system satisfies the relationship: 2.8 < Fno TTL/IMGH < 3.7; the IMGH is half of an image height corresponding to a maximum field angle of the optical system, the Fno is an f-number of the optical system, and the TTL is a distance from an object-side surface of the first lens to an imaging surface of the optical system on an optical axis, that is, a total length of the optical system. TTL/IMGH reflects the light and thin characteristic of the optical system, and Fno reflects the relative light incoming amount of the system; the conditional expression generally reflects the improvement of the light entering amount of the optical system in the process of thinning. The size of the optical system can be effectively reduced, and the ultra-thin characteristic and miniaturization requirement of the optical system are ensured; when Fno × TTL/IMGH is more than or equal to 3.7, the ultrathin characteristic of the optical system is poor, and the diaphragm number is large, so that the requirements of large image surface, small size and small diaphragm number cannot be met; when Fno TTL/IMGH is less than or equal to 2.8, the design difficulty is high, the surface type is easy to distort for multiple times, and the surface type of each lens is difficult to obtain complete desensitization optimization, so that the lens set has poor manufacturability.

In one embodiment, the optical system satisfies the relationship: 0.0604< CT5/TTL < 0.12; CT5 is the thickness of the fifth lens element on the optical axis, i.e. the thickness of the fifth lens element, and TTL is the distance from the object-side surface of the first lens element to the image plane of the optical system on the optical axis, i.e. the total length of the optical system. The ratio of the thickness of the fifth lens to the total optical length is kept in a reasonable range by constraining the thickness of the fifth lens, so that the focal power of the fifth lens is approximately constrained due to the simple surface type of the fifth lens, the fifth lens with larger focal power in an optical system keeps proper focal power, and the focal power is reasonably dispersed into other lenses, so that the condition that the fifth lens is too thick and too thick is avoided, and the molding efficiency and the yield are influenced; in addition, the thinned fifth lens can also avoid multiple reflection ghost images of the image side surface and the object side surface of the fifth lens, and the imaging definition of the wide-angle optical system is improved.

In one embodiment, the optical system satisfies the relationship: 2.5 < (SD52+ SD62+ SD72)/(CT5+ CT6+ CT7) < 4.4; SD52 is a half of the maximum effective aperture of the image-side surface of the fifth lens element, SD62 is a half of the maximum effective aperture of the image-side surface of the sixth lens element, SD72 is a half of the maximum effective aperture of the image-side surface of the seventh lens element, CT5 is the thickness of the fifth lens element on the optical axis, CT6 is the thickness of the sixth lens element on the optical axis, and CT7 is the thickness of the seventh lens element on the optical axis. The ratio of the maximum effective caliber to the middle thickness is controlled in a reasonable range by restraining the semi-effective diameters of the fifth lens to the seventh lens and the middle thicknesses of the fifth lens to the seventh lens, so that the thickness characteristics of the fifth lens to the seventh lens are guaranteed, and the lenses have reasonable processability. When (SD52+ SD62+ SD72)/(CT5+ CT6+ CT7) is more than or equal to 4.4, the effective aperture of the lens is larger, and the middle thickness of the lens is smaller, so that the whole lens is thinner and not beneficial to injection molding, and the processing precision of the lens is reduced; when (SD52+ SD62+ SD72)/(CT5+ CT6+ CT7) is less than or equal to 2.5, the effective aperture of the lens is smaller, and the middle thickness of the lens is larger, so that the whole lens is thicker, which is not beneficial to the miniaturization design of an optical system.

In one embodiment, the optical system satisfies the relationship: 2.5 < | f12/f | < 8.8; f12 is the combined focal length of the first lens and the second lens, and f is the focal length of the optical system. The introduction of aberration can be effectively reduced by regulating and controlling the combined focal length of the first lens and the second lens, the rays are quickly contracted and converged by utilizing the aspheric surface and the focal power change, the paraxial rays are refracted at a low deflection angle, and the introduction of spherical aberration is reduced; by adjusting the f12 power, the marginal light can enter the optical system as much as possible, and the sufficient diffraction limit and performance guarantee of the marginal field of view are kept.

In one embodiment, the optical system satisfies the relationship: f3456/f is more than 0.8 and less than 10; f3456 is a combined focal length of the third lens, the fourth lens, the fifth lens and the sixth lens, and f is a focal length of the optical system. The third lens, the fourth lens, the fifth lens and the sixth lens bear reasonable positive focal power, so that the volume of the lens can be controlled, the space utilization rate of the lens is improved, and the requirement of lightening and thinning the system is met; meanwhile, the third lens, the fourth lens, the fifth lens and the sixth lens are positioned in the center of the optical system, play an important role in light deflection, reasonably keep a combined focal length, contribute to smooth transmission of large-angle incident light, and control the aberration of the edge field within a reasonable range, thereby greatly helping the comprehensive image quality of the edge field.

In one embodiment, the optical system satisfies the relationship: 1.83 < (CT5+ CT6)/CT2 < 4.1; CT5 is the thickness of the fifth lens element on the optical axis, CT6 is the thickness of the sixth lens element on the optical axis, and CT2 is the thickness of the second lens element on the optical axis. Through restricting CT5, CT6, CT2, guarantee the rationality of thickness in fifth lens and the sixth lens, for the structure of the non-effective diameter of lens and shaping rationality provide the space, guarantee the feasibility of frivolousization. When (CT5+ CT6)/CT2 is not less than 4.1, the thickness of the fifth lens and the sixth lens in the optical system is enough, but the optical total length of the high-count system is difficult to be reduced, which is not beneficial to the light and thin of the system. When (CT5+ CT6)/CT2 is less than or equal to 1.83, the thickness of the lens is insufficient, which brings great obstacles to the assembly process and the lens forming process and influences the product yield.

In one embodiment, the optical system satisfies the relationship: 0.1 < | f56/(R52-R62) | < 3.3; f56 is a combined focal length of the fifth lens element and the sixth lens element, R52 is a radius of curvature of the image-side surface of the fifth lens element, and R62 is a radius of curvature of the image-side surface of the sixth lens element. By adjusting the curvature radius of the object side surface of the fifth lens and the curvature radius of the image side surface of the sixth lens, the combined focal length of the fifth lens and the sixth lens can be restricted within a reasonable range, sufficient focal power is guaranteed, meanwhile, the fifth lens and the sixth lens better share the total focal power, the fifth lens and the sixth lens present a more reasonable surface type trend, and the risk of stray light is reduced; the light of the inner and outer fields of view has good deflection effect and aberration correction capability, so that the aberration of the full field of view can be well balanced, and the full field of view can obtain good resolution by matching with an integral seven-piece scheme.

In one embodiment, the optical system satisfies the relationship: CT1/BF < 0.18 < 0.32; CT1 is the thickness of the first lens element along the optical axis, and BF is the minimum axial distance from the image-side surface of the seventh lens element to the image plane along the optical axis. The distance between the middle thickness of the first lens and the distance between the seventh lens and the image plane is guaranteed, so that the first lens in the optical system matched with the seven lenses has a reasonable thickness ratio, the forming difficulty and the machined surface type error of the first lens are reduced, the regulation and control of optical distortion in actual production are facilitated, and the performance is improved; reasonable BF prevents the optical system from being too close to the electronic photosensitive chip, so that the assembly feasibility and yield of the module are not influenced, and the matching performance of different chip schemes is improved.

The image pickup module according to the embodiment of the second aspect of the present application includes an image sensor and the optical system described in any one of the above, where the image sensor is disposed on the image side of the optical system. Through adopting above-mentioned optical system, the module of making a video recording can possess good formation of image quality when keeping miniaturized design.

According to the electronic equipment of the third aspect of the present application, the electronic equipment comprises a fixing member and the camera module, and the camera module is arranged on the fixing member. The camera module can provide good camera quality for the electronic equipment, and simultaneously keeps smaller occupied volume, thereby reducing the obstruction caused by the miniaturization design of the electronic equipment.

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

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

FIG. 2 includes a longitudinal spherical aberration diagram, an astigmatism diagram and a distortion diagram of the optical system in the first embodiment;

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

FIG. 4 includes a longitudinal spherical aberration diagram, an astigmatism diagram and a distortion diagram of the optical system in the second embodiment;

fig. 5 is a schematic structural diagram of an optical system according to a third embodiment of the present application;

FIG. 6 includes a longitudinal spherical aberration diagram, an astigmatism diagram and a distortion diagram of the optical system in the third embodiment;

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

FIG. 8 includes a longitudinal spherical aberration diagram, an astigmatism diagram and a distortion diagram of the optical system in the fourth embodiment;

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

FIG. 10 includes a longitudinal spherical aberration diagram, an astigmatism diagram and a distortion diagram of the optical system in the fifth embodiment;

fig. 11 is a schematic structural diagram of an optical system according to a sixth embodiment of the present application;

FIG. 12 includes a longitudinal spherical aberration diagram, an astigmatism diagram and a distortion diagram of the optical system in the sixth embodiment;

fig. 13 is a schematic structural diagram of an optical system according to a seventh embodiment of the present application;

FIG. 14 includes a longitudinal spherical aberration diagram, an astigmatism diagram and a distortion diagram of the optical system in the seventh embodiment;

fig. 15 is a schematic view of a camera module according to an embodiment of the present application;

fig. 16 is a schematic structural diagram of an image capturing apparatus according to an embodiment of the present application.

Detailed Description

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention.

An optical system 10 according to one embodiment of the present invention will be described below with reference to the drawings.

Referring to fig. 1, an embodiment of the present application provides an optical system 10 with a seven-lens design, where the optical system 10 includes a first lens element L1 with negative refractive power, a second lens element L2 with positive refractive power, a third lens element L3 with positive refractive power, a fourth lens element L4 with refractive power, a fifth lens element L5 with refractive power, a sixth lens element L6 with refractive power, and a seventh lens element L7 with refractive power. Each lens in the optical system 10 should be coaxially disposed, and each lens can be mounted in a lens barrel to form an imaging lens.

The first lens L1 has an object side surface S1 and an image side surface S2, the second lens L2 has an object side surface S3 and an image side surface S4, the third lens L3 has an object side surface S5 and an image side surface S6, the fourth lens L4 has an object side surface S7 and an image side surface S8, the fifth lens L5 has an object side surface S9 and an image side surface S10, the sixth lens L6 has an object side surface S11 and an image side surface S12, and the seventh lens L7 has an object side surface S13 and an image side surface S14. Meanwhile, the optical system 10 further has an image plane S17, the image plane S17 is located on the image side of the seventh lens element L7, and light rays emitted from an on-axis object point at a corresponding object distance can be adjusted by the lenses of the optical system 10 to be imaged on the image plane S17.

Generally, the imaging surface S17 of the optical system 10 coincides with the photosensitive surface of the image sensor. It should be noted that in some embodiments, the optical system 10 may be matched with an image sensor having a rectangular photosensitive surface, and the imaging surface S17 of the optical system 10 coincides with the rectangular photosensitive surface of the image sensor. At this time, the effective pixel region on the imaging surface S17 of the optical system 10 has a horizontal direction, a vertical direction, and a diagonal direction, and the maximum angle of view of the optical system 10 in the present application can be understood as the maximum angle of view of the optical system 10 in the diagonal direction, and ImgH can be understood as half the length of the effective pixel region on the imaging surface S17 of the optical system 10 in the diagonal direction. In the embodiment of the present application, the object-side surface S1 of the first lens L1 is concave at the paraxial region 101; the object side surface S3 and the image side surface S4 of the second lens L2 are respectively convex and concave at the position close to the optical axis 101; the image-side surface S6 of the third lens element L3 is convex near the optical axis 101, and the image-side surface S6 is convex at the circumference; the object side S7 of the fourth lens L4 is concave at the circumference; the object-side surface S11 of the sixth lens element L6 is concave at the paraxial region 101, and the image-side surface is convex at the paraxial region 101; the object-side surface S13 of the seventh lens element L7 is concave at the circumference, and the image-side surface is convex at the circumference. When it is described that the lens surface has a certain surface type at the optical axis 101, that is, the lens surface has the surface type in the vicinity of the optical axis 101; when it is described that the lens surface has a certain profile at the circumference, i.e. the lens surface has such a profile in the radial direction and close to the circumference.

In the optical system 10, the first lens element L1 has negative refractive power, which is helpful for absorbing large-angle light rays, compressing the light ray direction of each field of view, expanding the field angle of the present invention, and facilitating the wide-angle design of the optical system 10. The object-side surface S1 of the first lens element L1 is concave at the optical axis 101, which is favorable for enhancing the negative refractive power of the first lens element L1, and further provides a reasonable light incident angle for the introduction of marginal light rays. The second lens element L2 with positive refractive power helps to shrink the large-angle light introduced by the first lens element L1, and reasonably utilizes the position and size of the stop STO to avoid excessive vignetting and ensure that the image plane has sufficient light-entering amount, the object side surface S3 of the second lens element L2 is convex near the optical axis 101, and the image side surface S4 of the second lens element L2 is concave near the optical axis 101, so as to help to gently shrink the light beam; the third lens element L3 with positive refractive power has a symmetrical relationship with the second lens element L2, so that aberration such as distortion and curvature of field can be reduced, and the image-side surface S6 is convex at the optical axis 101 and at the circumference, which helps light to spread to the image; the fourth lens element L4 with refractive power, in combination with the surface design that the object side surface S7 is concave at the circumference, enables the fourth lens element L4 to match the surface shape of the image side surface S6 of the third lens element L3, and reduces the incident angle of the chief ray of the light on the object side surface S7 of the fourth lens element L4, thereby improving the relative illumination and reducing the off-axis aberration; the fifth lens element L5 with refractive power can effectively correct the aberration generated by the light passing through the object lens element (i.e., the first lens element L1 to the fourth lens element L4), and reduce the correction pressure of the rear lens element (i.e., the sixth lens element L6 and the seventh lens element L7). The image-side surface S12 of the sixth lens element L6 is convex at the optical axis 101, which is favorable for dispersing the light angle of the fifth lens element L5 and correcting the distortion, astigmatism and field curvature, thereby meeting the requirements of low aberration and high image quality. The image side surface S14 of the seventh lens L7 is convex at the circumference, so that the incident angle of light rays on the image surface can be kept in a reasonable range, and the requirement of a chip matching angle is met.

In the examples of the present application, 2.8 < Fno TTL/IMGH < 3.7; IMGH is half of the image height corresponding to the maximum field angle of the optical system 10, Fno is the f-number of the optical system 10, and TTL is the distance from the object-side surface S1 of the first lens element L1 to the image plane S17 of the optical system 10 on the optical axis, i.e., the total length of the optical system 10. TTL/IMGH reflects the light and thin characteristic of the optical system, and Fno reflects the relative light incoming amount of the system; this conditional expression generally reflects the improvement of the light-entering amount in the process of thinning the optical system 10. The wide-angle lens meets the above formula, can effectively compress the size of the optical system 10, and ensures the ultrathin characteristic and miniaturization requirements of the optical system 10; when Fno × TTL/IMGH is greater than or equal to 3.7, the optical system 10 has poor ultrathin characteristics and large f-number, which is not enough to meet the requirements of large image plane, small size and small f-number; when Fno TTL/IMGH is less than or equal to 2.8, the design difficulty is high, the surface type is easy to distort for multiple times, and the surface type of each lens is difficult to obtain complete desensitization optimization, so that the lens set has poor manufacturability.

Furthermore, in some embodiments, the optical system 10 also satisfies at least one of the following relationships, and can have a corresponding technical effect when either relationship is satisfied:

the optical system 10 also satisfies the relational condition: 0.0604< CT5/TTL < 0.12; the CT5 is the thickness of the fifth lens element L5 on the optical axis 101, i.e., the thickness of the fifth lens element L5, and the TTL is the distance from the object-side surface S1 of the first lens element L1 to the image plane S17 of the optical system 10 on the optical axis, i.e., the total length of the optical system 10. By restricting the middle thickness of the fifth lens L5, the ratio of the middle thickness of the fifth lens L5 to the total optical length is kept in a reasonable range, and because the surface type of the fifth lens L5 is simple, the focal power of the fifth lens L5 is almost restricted, the fifth lens L5 which bears larger focal power in the optical system 10 keeps proper focal power, and the focal power is reasonably dispersed into other lenses, so that the situation that the middle thickness and the over thickness of the fifth lens L5 are caused, and the molding efficiency and the yield are influenced is avoided; in addition, the thinned fifth lens L5 can also avoid multiple reflection ghost images of the image side surface S10 and the object side surface S9 of the fifth lens L5, thereby improving the imaging definition of the optical system 10.

2.5 < (SD52+ SD62+ SD72)/(CT5+ CT6+ CT7) < 4.4; SD52 is half of the maximum effective diameter of the image-side surface S10 of the fifth lens L5, SD62 is half of the maximum effective diameter of the image-side surface S12 of the sixth lens L6, SD72 is half of the maximum effective diameter of the image-side surface S14 of the seventh lens L7, CT5 is the thickness of the fifth lens L5 on the optical axis 101, CT6 is the thickness of the sixth lens L6 on the optical axis 101, and CT7 is the thickness of the seventh lens L7 on the optical axis 101. By restricting the maximum effective calibers of the fifth lens L5 to the seventh lens L7 and the thicknesses of the fifth lens L5 to the seventh lens L7, the ratio of the maximum effective calibers to the thicknesses of the fifth lens L5 and the seventh lens L7 is controlled in a reasonable range, the thickness characteristic of the fifth lens and the sixth lens L is guaranteed, and the lenses are guaranteed to have reasonable processability. When (SD52+ SD62+ SD72)/(CT5+ CT6+ CT7) ≥ 4.4, the effective aperture of the lens is larger, the thickness of the lens is smaller, which makes the lens thinner as a whole, which is not beneficial to injection molding, thereby reducing the processing precision of the lens, when (SD52+ SD62+ SD72)/(CT5+ CT6+ CT7) ≤ 2.5, the effective aperture of the lens is smaller, the thickness of the lens is larger, which makes the lens thicker as a whole, which is not beneficial to the miniaturization design of the optical system.

2.5 < | f12/f | < 8.8; f12 is the combined focal length of the first lens L1 and the second lens L2, and f is the focal length of the optical system 10. The introduction of aberration can be effectively reduced by regulating and controlling the combined focal length of the first lens L1 and the second lens L2, the introduction of spherical aberration is reduced by rapidly contracting and converging light rays by utilizing the aspheric surface and the focal power change and refracting paraxial light rays at a low deflection angle; by adjusting the f12 power, the marginal light can enter the optical system 10 as much as possible, and the sufficient diffraction limit and performance guarantee of the marginal field of view can be maintained.

F3456/f is more than 0.8 and less than 10; f3456 is the combined focal length of the third lens L3, the fourth lens L4, the fifth lens L5 and the sixth lens L6, and f is the optical system focal length. The third lens L3, the fourth lens L4, the fifth lens L5 and the sixth lens L6 bear reasonable positive focal power, so that the volume of the lens can be controlled, the space utilization rate of the lens is improved, and the requirement of lightening and thinning the system is met; meanwhile, the third lens L3, the fourth lens L4, the fifth lens L5 and the sixth lens L6 are located in the center of the optical system 10, play an important role in light deflection, reasonably maintain the combined focal length, contribute to smooth transmission of large-angle incident light, and control the aberration of the edge field within a reasonable range, thereby greatly contributing to the comprehensive image quality of the edge field.

1.83 < (CT5+ CT6)/CT2 < 4.1; CT5 is the thickness of the fifth lens L5 on the optical axis 101, i.e., the thickness of the fifth lens L5 is medium, CT6 is the thickness of the sixth lens L6 on the optical axis 101, i.e., the thickness of the sixth lens L6 is medium, and CT2 is the thickness of the second lens L2 on the optical axis 101, i.e., the thickness of the second lens L2 is medium. Through restricting CT5, CT6, CT2, guarantee the rationality of thickness in fifth lens L5, sixth lens L6, for the structure of the non-effective diameter of lens and shaping rationality provide the space, guarantee the feasibility of frivolousization. When (CT5+ CT6)/CT2 is greater than or equal to 4.1, the fifth lens L5 and the sixth lens L6 in the optical system 10 have sufficient thickness, but it is difficult to reduce the total optical length of the high-count system, which is not favorable for making the system thinner. When (CT5+ CT6)/CT2 is less than or equal to 1.83, the thickness of the lens is insufficient, which brings great obstacles to the assembly process and the lens forming process and influences the product yield.

0.1 < | f56/(R52-R62) | < 3.3; f56 is the combined focal length of the fifth lens element L5 and the sixth lens element L6, R52 is the radius of curvature of the image-side surface S10 of the fifth lens element L5 on the optical axis 101, and R62 is the radius of curvature of the image-side surface S12 of the sixth lens element L6 on the optical axis 101. By adjusting the curvature radius of the object side surface S9 of the fifth lens L5 and the curvature radius of the image side surface S12 of the sixth lens L6, the combined focal length of the fifth lens L5 and the sixth lens L6 can be restricted within a reasonable range, sufficient focal power is guaranteed, meanwhile, the fifth lens L5 and the sixth lens L6 share the total focal power better, the fifth lens L5 and the sixth lens L6 present reasonable surface type trends, and the stray light risk is reduced; the light of the inner and outer fields of view is fully realized to have good deflection effect and aberration correction capability, so that the aberration of the full field of view can be well balanced, and the full field of view can obtain good resolving power by matching with the integral seven-piece scheme.

CT1/BF < 0.18 < 0.32; CT1 is the thickness of the first lens L1 on the optical axis 101, i.e., the middle thickness of the first lens L1, and BF is the minimum axial distance from the image side surface S14 of the seventh lens L7 to the image plane S17 along the optical axis. By ensuring the thickness of the first lens L1 and the distance from the seventh lens L7 to the image plane, the first lens L1 in the seven-piece optical system 10 has a reasonable thickness ratio, the forming difficulty and the processing surface type error of the first lens L1 are reduced, the optical distortion in actual production can be favorably regulated and controlled, and the performance is improved; reasonable BF prevents the optical system 10 from being too close to the electronic photosensitive chip, thereby avoiding influencing the assembly feasibility and yield of the module, and improving the matching performance of different chip schemes.

The numerical value of the focal length in the above relation is 587nm, the focal length is at least the value of the corresponding lens at the optical axis 101, and the refractive power of the lens is at least the value at the optical axis 101. And the above relationship conditions and the technical effects thereof are directed to the optical system 10 having the above lens design. When the lens design (the number of lenses, the refractive power arrangement, the surface type arrangement, etc.) of the optical system 10 cannot be ensured, it is difficult to ensure that the optical system 10 can still have the corresponding technical effect when the relational expressions are satisfied, and even the imaging performance may be significantly reduced.

In some embodiments, at least one lens of optical system 10 has an aspheric surface, which may be referred to as having an aspheric surface when at least one of the lens' surfaces (object-side or image-side) is aspheric. In one embodiment, both the object-side surface and the image-side surface of each lens can be designed to be aspheric. The aspheric design can help the optical system 10 to eliminate aberration more effectively, improving imaging quality. In some embodiments, at least one lens in the optical system 10 may also have a spherical surface shape, and the design of the spherical surface shape may reduce the difficulty and cost of manufacturing the lens. In some embodiments, the design of each lens surface in the optical system 10 may be configured by aspheric and spherical surface types for consideration of manufacturing cost, manufacturing difficulty, imaging quality, assembly difficulty, etc.

The surface shape of the aspheric surface can be calculated by referring to an aspheric surface formula:

wherein Z is the distance from the corresponding point on the aspheric surface to the tangent plane of the surface at the optical axis 101, r is the distance from the corresponding point on the aspheric surface to the optical axis 101, c is the curvature of the aspheric surface at the optical axis 101, k is the conic coefficient, and Ai is the high-order term coefficient corresponding to the ith-order high-order term in the aspheric surface type formula.

It should also be noted that when a lens surface is aspheric, the lens surface may have points of inflection where the surface will change in type radially, e.g., one lens surface is convex at the optical axis 101 and concave near the circumference. Specifically, in some embodiments, at least one inflection point is disposed on each of the object-side surface S13 and the image-side surface S14 of the seventh lens L7, and at this time, the object-side surface S13 and the image-side surface S14 of the seventh lens L7 are designed to be in a planar shape at the optical axis 101, so that the field-inflection and distortion aberrations of the fringe field in the wide-angle system can be well corrected, and the imaging quality is improved.

In some embodiments, at least one lens of the optical system 10 is made of Plastic (PC), which may be polycarbonate, gum, or the like. In some embodiments, at least one lens of the optical system 10 is made of Glass (GL). The lens made of plastic can reduce the production cost of the optical system 10, and the lens made of glass can endure higher or lower temperature and has excellent optical effect and better stability. In some embodiments, lenses of different materials may be disposed in the optical system 10, that is, a design combining a glass lens and a plastic lens may be adopted, but the specific configuration relationship may be determined according to practical requirements and is not exhaustive here.

In some embodiments, the optical system 10 further includes an aperture stop STO, which may also be a field stop, for controlling the light incident amount and the depth of field of the optical system 10, and achieving good interception of the ineffective light to improve the imaging quality of the optical system 10, and the aperture stop STO may be disposed between the object side of the optical system 10 and the object side surface S1 of the first lens L1. It is understood that in other embodiments, the stop STO may be disposed between two adjacent lenses, for example, between the second lens L2 and the third lens L3, and the arrangement is adjusted according to the actual situation, which is not limited in this embodiment. The aperture stop STO may also be formed by a holder that holds the lens.

The optical system 10 of the present application is illustrated by the following more specific examples:

first embodiment

Referring to fig. 1, in the first embodiment, the optical system 10 includes, in order from the object side to the image side along the optical axis 101, the first lens element L1 with negative refractive power, the second lens element L2 with positive refractive power, the stop STO, the third lens element L3 with positive refractive power, the fourth lens element L4 with negative refractive power, the fifth lens element L5 with positive refractive power, the sixth lens element L6 with positive refractive power, and the seventh lens element L7 with negative refractive power. The respective lens surface types of the optical system 10 are as follows:

the object-side surface S1 of the first lens element L1 is concave at the optical axis 101, and the image-side surface S2 is concave at the optical axis 101; the object side S1 is convex at the circumference, and the image side S2 is concave at the circumference.

The object-side surface S3 of the second lens element L2 is convex at the optical axis 101, and the image-side surface S4 is concave at the optical axis 101; object side S3 is convex at the circumference, and image side S4 is concave at the circumference.

The object-side surface S5 of the third lens element L3 is convex at the optical axis 101, and the image-side surface S6 is convex at the optical axis 101; the object side S5 is convex at the circumference, and the image side S6 is convex at the circumference.

The object-side surface S7 of the fourth lens element L4 is concave at the optical axis 101, and the image-side surface S8 is concave at the optical axis 101; object side S7 is concave at the circumference, and image side S8 is convex at the circumference.

The object-side surface S9 of the fifth lens element L5 is convex at the optical axis 101, and the image-side surface S10 is convex at the optical axis 101; object side S9 is concave at the circumference, and image side S10 is convex at the circumference.

The object-side surface S11 of the sixth lens element L6 is concave at the optical axis 101, and the image-side surface S12 is convex at the optical axis 101; object side S11 is concave at the circumference, and image side S12 is convex at the circumference.

The object-side surface S13 of the seventh lens element L7 is convex at the optical axis 101, and the image-side surface S14 is concave at the optical axis 101; object side S13 is concave at the circumference, and image side S14 is convex at the circumference.

In the first embodiment, the lens surfaces of the first lens L1 to the seventh lens L7 are aspheric, and the material of each of the first lens L1 to the seventh lens L7 is Plastic (PC). The optical system 10 further includes a filter 110, the filter 110 can be a part of the optical system 10 or can be removed from the optical system 10, but when the filter 110 is removed, the total optical length TTL of the optical system 10 remains unchanged; in the embodiment, the optical filter 110 is an infrared cut-off filter, and the infrared cut-off filter is disposed between the image side surface S14 of the seventh lens L7 and the imaging surface S17 of the optical system 10, so as to filter out light rays in invisible wave bands such as infrared light, and only allow visible light to pass through, so as to obtain a better image effect; it is understood that the filter 110 can also filter out light in other bands, such as visible light, and only let infrared light pass through, and the optical system 10 can be used as an infrared optical lens, that is, the optical system 10 can also image and obtain better image effect in a dark environment and other special application scenes.

The lens parameters of the optical system 10 in the first embodiment are shown in table 1 below. The elements of the optical system 10 lying from the object side to the image side are arranged in the order from top to bottom in table 1, the diaphragm representing the aperture stop STO. The radius Y in table 1 is the radius of curvature of the corresponding surface of the lens at the optical axis 101. In table 1, the surface with the surface number S1 represents the object-side surface of the first lens L1, the surface with the surface number S2 represents the image-side surface of the first lens L1, and so on. The absolute value of the first value of the lens in the "thickness" parameter list is the thickness of the lens on the optical axis 101, and the absolute value of the second value is the distance from the image-side surface of the lens to the next optical surface (the object-side surface or stop surface of the next lens) on the optical axis 101, wherein the stop thickness parameter represents the distance from the stop surface to the object-side surface of the adjacent lens on the image side on the optical axis 101. In the table, the reference wavelengths of the refractive index and abbe number of each lens are 587nm, the reference wavelength of the focal length is 587nm, and the numerical units of the Y radius, thickness, and focal length are all millimeters (mm). The parameter data and the lens profile structure used for the relational calculation in the following embodiments are based on the data in the lens parameter table in the corresponding embodiment.

TABLE 1

As can be seen from table 1, the focal length f of the optical system 10 in the first embodiment is 2.47mm, the f-number FNO is 1.86, the total optical length TTL is 7.33mm, the total optical length TTL in the following embodiments is the sum of the thickness values corresponding to the surface numbers S1 to S17, and the maximum field angle FOV of the optical system 10 is 121.07 °, which indicates that the optical system 10 in this embodiment has a large field angle.

Table 2 below presents the aspherical coefficients of the corresponding lens surfaces in table 1, where K is a conic coefficient and Ai is a coefficient corresponding to the i-th order higher-order term in the aspherical surface type formula.

TABLE 2

Fig. 2 includes a longitudinal spherical aberration diagram, an astigmatism diagram, and a distortion diagram of the optical system 10 in the first embodiment. Wherein the reference wavelength of the astigmatism diagram and the distortion diagram is 587 nm. Longitudinal Spherical Aberration diagrams (Longitudinal Spherical Aberration) show the deviation of the converging focus of light rays of different wavelengths through the lens. The ordinate of the longitudinal spherical aberration diagram represents Normalized Pupil coordinates (Normalized Pupil coordmator) from the Pupil center to the Pupil edge, and the abscissa represents the distance (in mm) of the imaging plane S17 from the intersection point of the light ray and the optical axis. It can be known from the longitudinal spherical aberration diagram that the convergent focus deviation degrees of the light rays with the wavelengths in the first embodiment tend to be consistent, the maximum focus deviation of the reference wavelengths is controlled within ± 0.02mm, and for a large aperture system, the diffuse spots or the color halos in the imaging picture are effectively suppressed. FIG. 2 also includes an astigmatism plot of the Field curvature (effective Field curvatures) of optical system 10, where the S curve represents the sagittal Field curvature at 587nm and the T curve represents the meridional Field curvature at 587 nm. As can be seen from the figure, the field curvature of the optical system 10 is small, the maximum field curvature is controlled within ± 0.05mm, and for a large aperture system, the degree of curvature of image plane is effectively suppressed, and the sagittal field curvature and the meridional field curvature under each field of view tend to be consistent, and the astigmatism of each field of view is better controlled, so that it can be seen that the center to the edge of the field of view of the optical system 10 have clear imaging. Further, it is understood from the distortion map that the degree of distortion of the optical system 10 having a large aperture characteristic is also well controlled.

Second embodiment

Referring to fig. 3, in the second embodiment, the optical system 10 includes, in order from the object side to the image side along the optical axis 101, the first lens element L1 with negative refractive power, the second lens element L2 with positive refractive power, the stop STO, the third lens element L3 with positive refractive power, the fourth lens element L4 with negative refractive power, the fifth lens element L5 with positive refractive power, the sixth lens element L6 with positive refractive power, and the seventh lens element L7 with negative refractive power. In the second embodiment of the present invention,

The object-side surface S3 of the second lens element L2 is convex at the optical axis 101, and the image-side surface S4 is concave at the optical axis 101; the object side S3 is convex at the circumference, and the image side S4 is concave at the circumference.

The object-side surface S7 of the fourth lens element L4 is convex at the optical axis 101, and the image-side surface S8 is concave at the optical axis 101; object side S7 is concave at the circumference, like side S8.

The object-side surface S9 of the fifth lens element L5 is convex at the optical axis 101, and the image-side surface S10 is convex at the optical axis 101; the object side S9 is convex at the circumference, and the image side S10 is convex at the circumference.

The lens parameters of the optical system 10 in this embodiment are given in tables 3 and 4, wherein the definitions of the names and parameters of the elements can be obtained from the first embodiment, which is not described herein.

TABLE 3

TABLE 4

As can be seen from the aberration diagrams in fig. 4, the longitudinal spherical aberration, astigmatism, and distortion of the optical system 10 having the wide-angle characteristic are all controlled well, and the optical system 10 of this embodiment can have good imaging quality.

Third embodiment

Referring to fig. 5, in the third embodiment, the optical system 10 includes, in order from the object side to the image side along the optical axis 101, the first lens element L1 with negative refractive power, the second lens element L2 with positive refractive power, the stop STO, the third lens element L3 with positive refractive power, the fourth lens element L4 with negative refractive power, the fifth lens element L5 with positive refractive power, the sixth lens element L6 with positive refractive power, and the seventh lens element L7 with negative refractive power. In the third embodiment of the present invention,

The object-side surface S11 of the sixth lens element L6 is concave at the optical axis 101, and the image-side surface S12 is convex at the optical axis 101; the object side S11 is convex at the circumference, and the image side S12 is convex at the circumference.

The lens parameters of the optical system 10 in this embodiment are given in tables 5 and 6, wherein the definitions of the names and parameters of the elements can be obtained from the first embodiment, which is not repeated herein.

TABLE 5

TABLE 6

As can be seen from the aberration diagrams in fig. 6, the longitudinal spherical aberration, astigmatism, and distortion of the optical system 10 having the wide-angle characteristic are all controlled well, and the optical system 10 of this embodiment can have good imaging quality.

Fourth embodiment

Referring to fig. 7, in the fourth embodiment, the optical system 10 includes, in order from the object side to the image side along the optical axis 101, the first lens element L1 with negative refractive power, the second lens element L2 with positive refractive power, the stop STO, the third lens element L3 with positive refractive power, the fourth lens element L4 with negative refractive power, the fifth lens element L5 with positive refractive power, the sixth lens element L6 with positive refractive power, and the seventh lens element L7 with positive refractive power. In the fourth embodiment of the present invention, the,

the object-side surface S1 of the first lens element L1 is concave at the optical axis 101, and the image-side surface S2 is convex at the optical axis 101; the object side S1 is convex at the circumference, and the image side S2 is concave at the circumference.

The object-side surface S5 of the third lens element L3 is concave at the optical axis 101, and the image-side surface S6 is convex at the optical axis 101; object side S5 is concave at the circumference, and image side S6 is convex at the circumference.

The object-side surface S9 of the fifth lens element L5 is concave at the optical axis 101, and the image-side surface S10 is convex at the optical axis 101; the object side S9 is convex at the circumference, and the image side S10 is convex at the circumference.

The lens parameters of the optical system 10 in this embodiment are given in tables 7 and 8, wherein the definitions of the names and parameters of the elements can be obtained from the first embodiment, which is not described herein.

TABLE 7

TABLE 8

As can be seen from the aberration diagrams in fig. 8, the longitudinal spherical aberration, astigmatism, and distortion of the optical system 10 having the wide-angle characteristic are all controlled well, and the optical system 10 of this embodiment can have good imaging quality.

Fifth embodiment

Referring to fig. 9, in the fifth embodiment, the optical system 10 includes, in order from the object side to the image side along the optical axis 101, the first lens element L1 with negative refractive power, the second lens element L2 with positive refractive power, the stop STO, the third lens element L3 with positive refractive power, the fourth lens element L4 with negative refractive power, the fifth lens element L5 with positive refractive power, the sixth lens element L6 with positive refractive power, and the seventh lens element L7 with positive refractive power. In the fifth embodiment, it is preferred that,

the object-side surface S1 of the first lens element L1 is concave along the optical axis 101, and the image-side surface S2 is convex along the optical axis 101; the object side S1 is convex at the circumference, and the image side S2 is concave at the circumference.

The object-side surface S7 of the fourth lens element L4 is concave at the optical axis 101, and the image-side surface S8 is concave at the optical axis 101; object side S7 is concave at the circumference, like side S8.

The object-side surface S9 of the fifth lens element L5 is convex at the optical axis 101, and the image-side surface S10 is concave at the optical axis 101; the object side S9 is convex at the circumference, and the image side S10 is concave at the circumference.

The lens parameters of the optical system 10 in this embodiment are given in tables 9 and 10, wherein the definitions of the names and parameters of the elements can be obtained from the first embodiment, which is not repeated herein.

TABLE 9

Watch 10

As can be seen from the aberration diagrams in fig. 10, the longitudinal spherical aberration, astigmatism, and distortion of the optical system 10 having the wide-angle characteristic are all controlled well, and the optical system 10 of this embodiment can have good imaging quality.

Sixth embodiment

Referring to fig. 11, in the sixth embodiment, the optical system 10 includes, in order from the object side to the image side along the optical axis 101, the first lens element L1 with negative refractive power, the second lens element L2 with positive refractive power, the stop STO, the third lens element L3 with positive refractive power, the fourth lens element L4 with positive refractive power, the fifth lens element L5 with negative refractive power, the sixth lens element L6 with negative refractive power, and the seventh lens element L7 with positive refractive power. In the sixth embodiment, in the fifth embodiment,

The object-side surface S5 of the third lens element L3 is convex at the optical axis 101, and the image-side surface S6 is convex at the optical axis 101; object side S5 is concave at the circumference, and image side S6 is convex at the circumference.

The object-side surface S7 of the fourth lens element L4 is concave at the optical axis 101, and the image-side surface S8 is convex at the optical axis 101; object side S7 is concave at the circumference, and image side S8 is convex at the circumference.

The object-side surface S9 of the fifth lens element L5 is concave at the optical axis 101, and the image-side surface S10 is convex at the optical axis 101; object side S9 is concave at the circumference, and image side S10 is convex at the circumference.

The lens parameters of the optical system 10 in this embodiment are given in tables 11 and 12, wherein the definitions of the names and parameters of the elements can be obtained from the first embodiment, which is not described herein.

TABLE 11

TABLE 12

As can be seen from the aberration diagrams in fig. 12, the longitudinal spherical aberration, astigmatism, and distortion of the optical system 10 having the wide-angle characteristic are all controlled well, and the optical system 10 of this embodiment can have good imaging quality.

Seventh embodiment

Referring to fig. 13, in the seventh embodiment, the optical system 10 includes, in order from the object side to the image side along the optical axis 101, the first lens element L1 with negative refractive power, the second lens element L2 with positive refractive power, the stop STO, the third lens element L3 with positive refractive power, the fourth lens element L4 with positive refractive power, the fifth lens element L5 with positive refractive power, the sixth lens element L6 with negative refractive power, and the seventh lens element L7 with positive refractive power. In the seventh embodiment, the first and second embodiments,

The object-side surface S7 of the fourth lens element L4 is concave along the optical axis 101, and the image-side surface S8 is convex along the optical axis 101; object side S7 is concave at the circumference, and image side S8 is convex at the circumference.

The lens parameters of the optical system 10 in this embodiment are given in tables 13 and 14, wherein the definitions of the element names and parameters can be obtained from the first embodiment, which is not described herein.

Watch 13

TABLE 14

As can be seen from the aberration diagrams in fig. 14, the longitudinal spherical aberration, astigmatism, and distortion of the optical system 10 having the wide-angle characteristic are all controlled well, and the optical system 10 of this embodiment can have good imaging quality.

Referring to table 15, table 15 summarizes ratios of the relations in the first embodiment to the seventh embodiment of the present application.

Watch 15

The optical system 10 in each of the above embodiments can maintain good imaging quality while achieving a compact design by compressing the overall length compared to a general optical system, and can also have a larger imaging range.

In the first to seventh embodiments, the introduction of aberration can be effectively reduced by the combination of the ultra-wide-angle intermediate diaphragm and the large entrance pupil diameter, and the introduction of spherical aberration is reduced by rapidly contracting and converging light rays by using the aspheric surface and the change of focal power, refracting paraxial light rays at a low deflection angle, and reducing the introduction of the focal length; the marginal field does not excessively suppress the light entering amount through vignetting block light, and the f12 power is adjusted to enable marginal light to enter an optical system as far as possible, so that the sufficient diffraction limit and performance guarantee of the marginal field are maintained.

Referring to fig. 15, an embodiment of the present application further provides a camera module 20, where the camera module 20 includes an optical system 10 and an image sensor 210, and the image sensor 210 is disposed on an image side of the optical system 10, and the two can be fixed by a bracket. The image sensor 210 may be a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor) sensor. Generally, the imaging surface S17 of the optical system 10 overlaps the photosensitive surface of the image sensor 210 when assembled. By adopting the optical system 10, the camera module 20 can have good imaging quality while maintaining a compact design.

Referring to fig. 16, some embodiments of the present application also provide an electronic device 30. The electronic device 30 includes a fixing member 310, the camera module 20 is mounted on the fixing member 310, and the fixing member 310 may be a display screen, a circuit board, a middle frame, a rear cover, or the like. The electronic device 30 may be, but is not limited to, a smart phone, a smart watch, smart glasses, an e-book reader, a tablet computer, a PDA (Personal Digital Assistant), and the like. The camera module 20 can provide good camera quality for the electronic device 30, and meanwhile, the occupied volume is kept small, so that the obstruction to the miniaturization design of the device can be reduced.

In the description of the present invention, it is to be understood that the terms "central," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," "circumferential," and the like are used in the orientations and positional relationships indicated in the drawings for convenience in describing the invention and to simplify the description, and are not intended to indicate or imply that the referenced device or element must have a particular orientation, be constructed and operated in a particular orientation, and are not to be considered limiting of the invention.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless specifically defined otherwise.

In the present invention, unless otherwise expressly stated or limited, the terms "mounted," "connected," "secured," and the like are to be construed broadly and can, for example, be fixedly connected, detachably connected, or integrally formed; the connection can be mechanical connection, electrical connection or communication; either directly or indirectly through intervening media, either internally or in any other relationship. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.

In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.

While embodiments of the invention have been shown and described, it will be understood by those of ordinary skill in the art that: various changes, modifications, substitutions and alterations can be made to the embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. An optical system, comprising:

a first lens element with negative refractive power having a concave object-side surface at paraxial region;

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

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

a fourth lens element with refractive power, an object-side surface of the fourth lens element being concave at a circumference;

a fifth lens element with refractive power;

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

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

the optical system satisfies the relationship:

2.9＜Fno*TTL/IMGH＜3.7；

the IMGH is half of an image height corresponding to a maximum field angle of the optical system, the Fno is an f-number of the optical system, and the TTL is a distance from an object side surface of the first lens to an imaging surface of the optical system on an optical axis.

2. The optical system of claim 1, wherein the optical system satisfies the relationship:

0.0604<CT5/TTL<0.12；

CT5 is the thickness of the fifth lens on the optical axis.

3. The optical system of claim 1, wherein the optical system satisfies the relationship:

2.5＜(SD52+SD62+SD72)/(CT5+CT6+CT7)＜4.4；

SD52 is a half of the maximum effective aperture of the image-side surface of the fifth lens element, SD62 is a half of the maximum effective aperture of the image-side surface of the sixth lens element, SD72 is a half of the maximum effective aperture of the image-side surface of the seventh lens element, CT5 is the thickness of the fifth lens element on the optical axis, CT6 is the thickness of the sixth lens element on the optical axis, and CT7 is the thickness of the seventh lens element on the optical axis.

4. The optical system of claim 1, wherein the optical system satisfies the relationship:

2.5＜|f12/f|＜8.8；

f12 is the combined focal length of the first lens and the second lens, and f is the focal length of the optical system.

5. The optical system of claim 1, wherein the optical system satisfies the relationship:

0.8＜f3456/f＜10；

f3456 is a combined focal length of the third lens, the fourth lens, the fifth lens and the sixth lens, and f is a focal length of the optical system.

6. The optical system of claim 1, wherein the optical system satisfies the relationship:

1.83＜(CT5+CT6)/CT2＜4.1；

CT5 is the thickness of the fifth lens element, CT6 is the thickness of the sixth lens element, and CT2 is the thickness of the second lens element.

7. The optical system of claim 1, wherein the optical system satisfies the relationship:

0.1＜|f56/(R52-R62)|＜3.3；

f56 is a combined focal length of the fifth lens element and the sixth lens element, R52 is a radius of curvature of the image-side surface of the fifth lens element, and R62 is a radius of curvature of the image-side surface of the sixth lens element.

8. The optical system of claim 1, wherein the optical system satisfies the relationship:

0.18＜CT1/BF＜0.32；

CT1 is the thickness of the first lens element along the optical axis, and BF is the minimum distance from the image-side surface of the seventh lens element to the image plane along the optical axis.

9. A camera module comprising an image sensor and the optical system of any one of claims 1 to 8, wherein the image sensor is disposed on an image side of the optical system.

10. An electronic device, comprising a fixing member and the camera module set according to claim 9, wherein the camera module set is disposed on the fixing member.