CN114460723B

CN114460723B - Optical system, camera module and electronic equipment

Info

Publication number: CN114460723B
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: 2023-06-06
Anticipated expiration: 2042-03-21
Also published as: CN114460723A

Abstract

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

Description

Optical system, camera module and electronic equipment

Technical Field

The present invention relates to the field of photography imaging technology, 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, tablet computers, and the like) are rapidly spreading. Among these, a larger viewing angle, higher portability, and a stronger night shooting capability are the current mainstream design directions. However, the above characteristics have a conflict with each other, and it is difficult to achieve a compromise. How to increase the aperture size of a wide-angle optical system while maintaining miniaturization has become a problem to be solved.

Disclosure of Invention

The present invention aims to solve at least one of the technical problems existing in the prior art. Therefore, the first aspect of the present application proposes an optical system, which can effectively solve the problem of how to achieve a wide-angle design while achieving both miniaturization and large aperture.

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

In the optical system, the first lens has negative refractive power, is favorable for absorbing light rays with large angles, compresses the light ray trend of each view field, expands the view angle of the optical system, and is favorable for wide-angle design of the optical system. The object side surface of the first lens element is concave near the optical axis, which is beneficial to enhancing the negative refractive power of the first lens element and further providing a reasonable light incidence angle for the introduction of marginal light. The second lens has positive refractive power, is favorable for shrinking large-angle light rays introduced by the first lens, reasonably utilizes the position and the size of a diaphragm, avoids overlarge vignetting, ensures that an image surface has enough light entering quantity, is convex near an optical axis, and is concave near the optical axis, and is favorable for gently shrinking light beams; the third lens element with positive refractive power has a certain symmetrical relationship with the second lens element, so as to reduce the introduction of aberration such as distortion and curvature of field, and the image side surface has convex surfaces at the optical axis and circumference to facilitate the diffusion of light to the image side; the fourth lens element with refractive power has a concave surface profile at the circumference of the object-side surface, so that the fourth lens element can be matched with the surface profile of the image-side surface of the third lens element, the incidence angle of the principal ray of light on the object-side surface of the fourth lens element can be reduced, the relative illuminance can be improved, and the off-axis aberration can be reduced; the fifth lens element with refractive power can effectively correct the aberration generated by the light passing through the object lens element (i.e., the first lens element to the fourth lens element), and reduce the correction pressure of the rear lens element (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, which is favorable for dispersing the light angle of the fifth lens, correcting distortion, astigmatism and field curvature, and further meeting the requirements of low aberration and high image quality. The seventh lens is convex at the circumference, so that the incident angle of the light on the image surface can be kept in a reasonable range, and the chip matching angle requirement is met.

In one embodiment, the optical system satisfies the relationship: 2.8 < Fno < TTL/IMGH < 3.7; IMGH is half of the image height corresponding to the maximum field angle of the optical system, fno is the f-number of the optical system, and TTL is the distance between the object side surface of the first lens and the imaging surface of the optical system on the optical axis, i.e. the total length of the optical system. TTL/IMGH reflects the light and thin characteristics of the optical system, and FNO reflects the relative light incoming amount of the system; the condition generally reflects the improvement of the light incoming amount of the optical system in the light and thin process. The optical system meets the above formula, can effectively compress the size of the optical system, and ensures the ultra-thin characteristic and miniaturization requirement of the optical system; when FNo is equal to or larger than 3.7, the optical system has poor ultrathin property and larger f-number, and is insufficient for meeting the requirements of large image plane, small size and small f-number; when FNo is less than or equal to 2.8, the design difficulty is high, the surface shape is easy to twist for many times, and the surface shape of each lens is difficult to obtain complete sensitivity optimization, so that the manufacturability of the lens group is poor.

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 imaging surface of the optical system on the optical axis, i.e., the total length of the optical system. The ratio of the middle thickness of the fifth lens to the total optical length is kept in a reasonable range by restraining the middle thickness of the fifth lens, and the optical power of the fifth lens is almost restrained because of the simplicity of the fifth lens surface, so that the optical power of the fifth lens with larger optical power in an optical system is kept to be proper, and the optical power is reasonably dispersed into other lenses, so that the situation that the middle thickness of the fifth lens is too thick and the molding efficiency and the yield are influenced is avoided; in addition, the thinned fifth lens can 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 half of the maximum effective aperture of the image-side surface of the fifth lens element, SD62 is half of the maximum effective aperture of the image-side surface of the sixth lens element, SD72 is 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 half effective diameter of the fifth lens to the seventh lens and the middle thickness of the fifth lens to the seventh lens are restrained, the ratio of the maximum effective diameter to the middle thickness is controlled in a reasonable range, the thickness characteristics of the fifth lens to the seventh lens are guaranteed, and the reasonable processability of the lens is guaranteed. When (SD 52+SD62+SD 72)/(CT 5+CT6+CT 7) is more than or equal to 4.4, the effective caliber of the lens is larger, and the thickness of the lens is smaller, so that the whole lens is thinner, the injection molding is not facilitated, and the processing precision of the lens is reduced; when (SD 52+SD62+SD 72)/(CT 5+CT6+CT 7) is less than or equal to 2.5, the effective caliber of the lens is smaller, and the middle thickness of the lens is larger, so that the whole lens is thicker, and the miniaturization design of the optical system is not facilitated.

In one embodiment, the optical system satisfies the relationship: 2.5 < |f12/f| < 8.8; f12 is a combined focal length of the first lens and the second lens, and f is a focal length of the optical system. By regulating and controlling the combined focal length of the first lens and the second lens, the introduction of aberration can be effectively reduced, the aspheric surface and focal power change are utilized to rapidly shrink and converge light rays, paraxial light rays are refracted at a low deflection angle, and the introduction of spherical aberration is reduced; by adjusting the f12 focal power, the marginal light enters the optical system as far as possible, and the enough diffraction limit and the enough performance guarantee of the marginal field of view are maintained.

In one embodiment, the optical system satisfies the relationship: f3456/f is more than 0.8 and less than 10; and f3456 is the combined focal length of the third lens, the fourth lens, the fifth lens and the sixth lens, and f is the focal length of the optical system. The third lens, the fourth lens, the fifth lens and the sixth lens bear more reasonable positive focal power, which can help to control the volume of the lens, improve the space utilization rate of the lens and ensure that the light and thin requirements of the system are 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 the combined focal length, facilitate smooth transmission of large-angle incident light, and the aberration of the edge view field can be controlled in a reasonable range, so that the method has great help to the comprehensive image quality of the edge view field.

In one embodiment, the optical system satisfies the relationship: 1.83 < (CT5+CT6)/CT 2 < 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. The rationality of the thicknesses of the fifth lens and the sixth lens is guaranteed by restraining CT5, CT6 and CT2, space is provided for the structure and molding rationality of the non-effective diameter of the lens, and the feasibility of lightening and thinning is guaranteed. When (CT 5+CT6)/CT 2 is more than or equal to 4.1, the fifth lens and the sixth lens in the optical system have enough medium thickness of lenses, but the total optical length of the high-lens-number system is difficult to reduce, and the system is not favorable for lightening and thinning. When (CT 5+CT6)/CT 2 is less than or equal to 1.83, the thickness of the lens is insufficient, so that great barriers are brought to the assembly process and the lens forming process, and the product yield is affected.

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 at the optical axis, and R62 is a radius of curvature of the image-side surface of the sixth lens element at the optical axis. The combined focal length of the fifth lens and the sixth lens can be limited in a reasonable range by adjusting the object-side surface curvature radius of the fifth lens and the image-side surface curvature radius of the sixth lens, so that enough focal power is ensured, meanwhile, the fifth lens and the sixth lens better share the total focal power, the fifth lens and the sixth lens present more reasonable surface-shaped trend, and the stray light risk is reduced; the method has the advantages that good deflection effect and aberration correction capability on the light rays of the inner field and the outer field are fully realized, so that the aberration of the whole field can be well balanced, and good resolution can be obtained in the whole field by matching with an integral seven-piece scheme.

In one embodiment, the optical system satisfies the relationship: CT1/BF is more than 0.18 and less than 0.32; CT1 is the thickness of the first lens element on the optical axis, and BF is the minimum axial distance from the image-side surface of the seventh lens element to the image-side surface along the optical axis. By guaranteeing the thickness of the first lens and the distance between the seventh lens and the image surface, the first lens in the optical system matched with seven lenses has reasonable thickness ratio, reduces the forming difficulty and the processing surface type error of the first lens, is beneficial to the regulation and control of optical distortion in actual production and improves the performance; reasonable BF, avoids the optical system from being too close to the electronic photosensitive chip, and influences the feasibility and yield of module assembly, and improves the matching performance of different chip schemes.

According to a second aspect of the present application, an image capturing module includes an image sensor and any one of the above optical systems, where the image sensor is disposed on an image side of the optical system. By adopting the optical system, the camera module can have good imaging quality while keeping a miniaturized design.

According to the electronic equipment of the embodiment of the third aspect of the application, the electronic equipment comprises the fixing piece and the camera shooting module, wherein the camera shooting module is arranged on the fixing piece. The camera module can provide good camera quality for the electronic equipment and keep small occupied volume, so that the obstruction to the miniaturization design of the electronic equipment can be reduced.

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 astigmatic 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 astigmatic 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 astigmatic diagram, and a distortion diagram of an optical system in a third embodiment;

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

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

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

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

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

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

fig. 13 is a schematic structural view 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 diagram of a camera module according to an embodiment of the present disclosure;

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

Detailed Description

Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to like or similar elements or elements having like or similar functions throughout. The embodiments described below by referring to the drawings are illustrative and intended to explain the present invention and should not be construed as limiting the invention.

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

Referring to fig. 1, an embodiment of the present application provides an optical system 10 having a seven-lens design, wherein 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. The lenses 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 element L1 has an object-side surface S1 and an image-side surface S2, the second lens element L2 has an object-side surface S3 and an image-side surface S4, the third lens element L3 has an object-side surface S5 and an image-side surface S6, the fourth lens element L4 has an object-side surface S7 and an image-side surface S8, the fifth lens element L5 has an object-side surface S9 and an image-side surface S10, the sixth lens element L6 has an object-side surface S11 and an image-side surface S12, and the seventh lens element L7 has an object-side surface S13 and an image-side surface S14. Meanwhile, the optical system 10 further has an imaging surface S17, the imaging surface S17 is located at the image side of the seventh lens L7, and the light emitted from the on-axis object point at the corresponding object distance can be imaged on the imaging surface S17 after being adjusted by each lens of the optical system 10.

In general, 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 to an image sensor having a rectangular photosurface, and the imaging surface S17 of the optical system 10 coincides with the rectangular photosurface of the image sensor. At this time, the effective pixel area on the imaging surface S17 of the optical system 10 has a horizontal direction, a vertical direction, and a diagonal direction, and in this application, the maximum field angle of the optical system 10 may be understood as the maximum field angle of the diagonal direction of the optical system 10, and ImgH may be understood as half the length of the effective pixel area 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 element 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 convex and concave at the paraxial region 101, respectively; the image-side surface S6 of the third lens element L3 is convex at the paraxial region 101, and the image-side surface S6 is convex at the peripheral region; the object side surface 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 describing that the lens surface has a certain profile at the optical axis 101, i.e. that the lens surface has such a profile in the vicinity of the optical axis 101; when describing that the lens surface has a certain profile at the circumference, i.e. the lens surface has such profile radially and near the circumference.

In the optical system 10, the first lens element L1 has negative refractive power, which is helpful for absorbing light rays with a large angle, compressing the light ray trend 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 concave object-side surface S1 of the first lens element L1 at the optical axis 101 is beneficial to enhancing the negative refractive power of the first lens element L1, and further provides a reasonable incident angle for the introduction of marginal rays. The second lens element L2 with positive refractive power has the advantages of being beneficial to shrinking the large-angle light rays introduced by the first lens element L1, reasonably utilizing the position and the size of the stop STO, avoiding excessive vignetting, ensuring that the image surface has enough light entering quantity, enabling the object side surface S3 of the second lens element L2 to be convex near the optical axis 101, enabling the image side surface S4 of the second lens element L2 to be concave near the optical axis 101, and being beneficial to gently shrinking the light beams; the third lens element L3 with positive refractive power has a certain symmetrical relationship with the second lens element L2, so as to reduce the introduction of aberration such as distortion and curvature of field, and the image-side surface S6 is convex at the optical axis 101 and the circumference thereof to facilitate the diffusion of light rays to the image space; the fourth lens element L4 with refractive power has a concave surface at the circumference of the object-side surface S7, so that the fourth lens element L4 can be matched with the surface of the image-side surface S6 of the third lens element L3, the incidence angle of the principal ray of the light on the object-side surface S7 of the fourth lens element L4 can be reduced, the relative illuminance can be improved, and the off-axis aberration can be reduced; 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-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 beneficial to dispersing the light angle of the fifth lens element L5, correcting distortion, astigmatism and field curvature, and further meeting the requirements of low aberration and high image quality. The seventh lens element L7 has a convex image side S14 at the circumference, so that the incident angle of the light beam on the image plane can be kept within a reasonable range, and the chip matching angle requirement can be 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 between the object side surface S1 of the first lens L1 and the imaging surface 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 characteristics of the optical system, and FNO reflects the relative light incoming amount of the system; the condition generally reflects the improvement of the light incoming amount of the optical system 10 in the light and thin process. For the wide-angle lens, the size of the optical system 10 can be effectively compressed by satisfying the above formula, and the ultra-thin characteristic and the miniaturization requirement of the optical system 10 are ensured; when FNo is equal to or larger than 3.7, the optical system 10 has poor ultrathin property and larger f-number, and is insufficient for meeting the requirements of large image plane, small size and small f-number; when FNo is less than or equal to 2.8, the design difficulty is high, the surface shape is easy to twist for many times, and the surface shape of each lens is difficult to obtain complete sensitivity optimization, so that the manufacturability of the lens group is poor.

Furthermore, in some embodiments, the optical system 10 also satisfies at least one of the following relationships, and may possess the corresponding technical effects when either relationship is satisfied:

The optical system 10 also satisfies the relational condition: 0.0604< CT5/TTL <0.12; 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 TTL is the distance between the object side surface S1 of the first lens element L1 and the imaging surface S17 of the optical system 10 on the optical axis, i.e., the total length of the optical system 10. The ratio of the thickness of the fifth lens L5 to the total optical length is kept in a reasonable range by restraining the thickness of the fifth lens L5, and the surface shape of the fifth lens L5 is simple, so that the focal power of the fifth lens L5 is almost restrained, the proper focal power of the fifth lens L5 with larger focal power in the optical system 10 is kept, the focal power is reasonably dispersed into other lenses, and the situation that the thickness of the fifth lens L5 is too thick is avoided, and the molding efficiency and the yield are influenced; in addition, the thinned fifth lens element L5 can avoid multiple reflection ghost images of the image side surface S10 and the object side surface S9 of the fifth lens element L5, thereby improving the imaging resolution of the optical system 10.

2.5 < (Sd52+Sd62+Sd72)/(Ct5+Ct6+Ct7) < 4.4; SD52 is half of the maximum effective aperture of the image-side surface S10 of the fifth lens element L5, SD62 is half of the maximum effective aperture of the image-side surface S12 of the sixth lens element L6, SD72 is half of the maximum effective aperture of the image-side surface S14 of the seventh lens element L7, CT5 is the thickness of the fifth lens element L5 on the optical axis 101, CT6 is the thickness of the sixth lens element L6 on the optical axis 101, and CT7 is the thickness of the seventh lens element L7 on the optical axis 101. The maximum effective caliber of the fifth lens L5 to the maximum effective caliber of the seventh lens L7 are restrained, the medium thickness of the fifth lens L5 to the seventh lens L7 is controlled in a reasonable range, the thickness characteristic of the fifth sixth lens is ensured, and the reasonable processability of the lens is ensured. When (SD 52+SD62+SD 72)/(CT 5+CT6+CT 7) is more than or equal to 4.4, the effective caliber of the lens is larger, the middle thickness of the lens is smaller, the whole lens is thinner, the injection molding is not facilitated, the processing precision of the lens is reduced, and when (SD 52+SD62+SD 72)/(CT 5+CT6+CT 7) is less than or equal to 2.5, the effective caliber of the lens is smaller, the middle thickness of the lens is larger, the whole lens is thicker, and the miniaturization design of an optical system is not facilitated.

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

F3456/f is more than 0.8 and less than 10; f3456 is a combined focal length of the third lens L3, the fourth lens L4, the fifth lens L5, and the sixth lens L6, and f is an optical system focal length. The third lens L3, the fourth lens L4, the fifth lens L5 and the sixth lens L6 bear more reasonable positive focal power, can help to control the volume of the lens, improve the space utilization rate of the lens and ensure that the light and thin requirements of a system are met; meanwhile, the third lens L3, the fourth lens L4, the fifth lens L5 and the sixth lens L6 are positioned at the center of the optical system 10, play an important role in light deflection, reasonably keep the combined focal length, facilitate smooth transmission of large-angle incident light, and the aberration of the edge view field can be controlled in a reasonable range, so that the method has great help to the comprehensive image quality of the edge view field.

1.83 < (CT5+CT6)/CT 2 < 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, CT6 is the thickness of the sixth lens L6 on the optical axis 101, i.e., the thickness of the sixth lens L6, and CT2 is the thickness of the second lens L2 on the optical axis 101, i.e., the thickness of the second lens L2. By restraining CT5, CT6 and CT2, the rationality of the thickness of the fifth lens L5 and the sixth lens L6 is guaranteed, space is provided for the structure of the non-effective diameter of the lens and the rationality of molding, and the feasibility of lightening and thinning is guaranteed. When (CT5+CT6)/CT2 is not less than 4.1, the fifth lens L5 and the sixth lens L6 in the optical system 10 have enough intermediate thickness, but the total optical length of the high-lens-count system is difficult to be reduced, which is unfavorable for the thinning of the system. When (CT 5+CT6)/CT 2 is less than or equal to 1.83, the thickness of the lens is insufficient, so that great barriers are brought to the assembly process and the lens forming process, and the product yield is affected.

0.1 < |f56/(R52-R62) | < 3.3; f56 is a combined focal length of the fifth lens element L5 and the sixth lens element L6, R52 is a radius of curvature of the image-side surface S10 of the fifth lens element L5 at the optical axis 101, and R62 is a radius of curvature of the image-side surface S12 of the sixth lens element L6 at the optical axis 101. The combined focal length of the fifth lens element L5 and the sixth lens element L6 can be limited in a reasonable range by adjusting the radius of curvature of the object side surface S9 of the fifth lens element L5 and the radius of curvature of the image side surface S12 of the sixth lens element L6, so that enough focal power is ensured, meanwhile, the overall focal power is better shared by the fifth lens element L5 and the sixth lens element L6, the fifth lens element L5 and the sixth lens element L6 are in a reasonable plane shape, and the stray light risk is reduced; the method has the advantages that good deflection effect and aberration correction capability on the light rays of the inner field and the outer field are fully realized, so that the aberration of the whole field can be well balanced, and good resolution can be obtained in the whole field by matching with an integral seven-piece scheme.

CT1/BF is more than 0.18 and less than 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 imaging surface S17 along the optical axis direction. By guaranteeing the thickness of the first lens L1 and the distance between the seventh lens L7 and the image plane, the first lens L1 in the optical system 10 matched with seven lenses has reasonable thickness ratio, the forming difficulty and the processing surface type error of the first lens L1 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 10 from being too close to the electronic photosensitive chip, and influences the feasibility and yield of module assembly, thereby improving the matching performance of different chip schemes.

The reference wavelength of the focal length in each relational expression condition is 587nm, the focal length at least refers to the value of the corresponding lens at the optical axis 101, and the refractive power of the lens at least refers to the situation at the optical axis 101. The above relational conditions and the technical effects thereof are directed to the optical system 10 having the lens design described above. If the lens design (lens number, refractive power configuration, surface configuration, etc.) of the optical system 10 cannot be ensured, it is difficult to ensure that the optical system 10 still has the technical effects when satisfying these relationships, and even the imaging performance may be significantly degraded.

In some embodiments, at least one lens of the optical system 10 has an aspherical surface profile, i.e., when at least one side surface (object side or image side) of the lens is aspherical, the lens may be said to have an aspherical surface profile. In one embodiment, both the object side and the image side of each lens can be designed to be aspheric. The aspheric design can help the optical system 10 to more effectively eliminate aberrations and improve 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 of manufacturing the lens and reduce the manufacturing cost. In some embodiments, to achieve the desired combination of manufacturing cost, manufacturing difficulty, imaging quality, assembly difficulty, etc., the design of each lens surface in the optical system 10 may be composed of a combination of aspheric and spherical surface types.

The surface type calculation of the aspherical surface can refer to an aspherical surface formula:

wherein Z is the distance from the corresponding point on the aspheric surface to the tangential 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 refractive index of the aspheric surface at the optical axis 101, k is the conic coefficient, and Ai is the higher order term coefficient corresponding to the i-th order higher order term in the aspheric surface formula.

It should further be noted that when a certain lens surface is aspherical, the lens surface may have a point of inflection, in which case a change in the type of surface will occur in the radial direction, e.g. one lens surface is convex at the optical axis 101 and concave at the circumference. Specifically, in some embodiments, at least one buckling point is disposed in each of the object side surface S13 and the image side surface S14 of the seventh lens element L7, and the surface-type designs of the object side surface S13 and the image side surface S14 of the seventh lens element L7 at the optical axis 101 are combined, so that good correction of field curvature and distortion aberration of the fringe field in the large-viewing angle system can be achieved, 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, the material of at least one lens in the optical system 10 is Glass (GL). The lens with plastic material can reduce the production cost of the optical system 10, while the lens with glass material can withstand 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, i.e. a combination of glass lenses and plastic lenses may be used, but the specific configuration relationship may be determined according to practical requirements, which is not meant to be exhaustive.

In some embodiments, the optical system 10 further includes an aperture stop STO, which may also be a field stop, where the aperture stop STO is used to control the light entering amount and the depth of field of the optical system 10, and also can achieve good interception of the non-effective light to improve the imaging quality of the optical system 10, and may be disposed between the object side of the optical system 10 and the object side S1 of the first lens L1. It will be appreciated 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 particularly 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 an object side to an image side along an optical axis 101, a first lens L1 with negative refractive power, a second lens L2 with positive refractive power, a stop STO, a third lens L3 with positive refractive power, a fourth lens L4 with negative refractive power, a fifth lens L5 with positive refractive power, a sixth lens L6 with positive refractive power, and a seventh lens L7 with negative refractive power. The lens surfaces 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 surface S1 is convex at the circumference and the image side surface 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; the object side surface S3 is convex at the circumference and the image side surface 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 surface S5 is convex at the circumference, and the image side surface 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; the object side surface S7 is concave at the circumference and the image side surface 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; the object side surface S9 is concave at the circumference and the image side surface 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; the object side surface S11 is concave at the circumference and the image side surface 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; the object side surface S13 is concave at the circumference and the image side surface S14 is convex at the circumference.

In the first embodiment, each of the first to seventh lenses L1 to L7 has an aspherical surface, and each of the first to seventh lenses L1 to L7 is made of Plastic (PC). The optical system 10 further includes a filter 110, the filter 110 being either part of the optical system 10 or removable from the optical system 10, but the total optical length TTL of the optical system 10 remains unchanged when the filter 110 is removed; in the embodiment, the 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 an invisible band, 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 optical filter 110 can also filter out light rays of other wavebands, such as visible light, and only let infrared light pass through, and the optical system 10 can be used as an infrared optical lens, i.e. the optical system 10 can also image in dim environments and other special application scenarios and can obtain better image effect.

The lens parameters of the optical system 10 in the first embodiment are presented in table 1 below. The elements from the object side to the image side of the optical system 10 are sequentially arranged in the order from top to bottom of table 1, with the aperture stop characterizing the aperture stop STO. The Y radius in table 1 is the refractive index radius 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 element L1, the surface with the surface number S2 represents the image side surface of the first lens element L1, and so on. The absolute value of the first value of the lens in the "thickness" parameter row 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 of the lens to the subsequent optical surface (the object side of the subsequent lens or the aperture plane) on the optical axis 101, wherein the thickness parameter of the aperture represents the distance from the aperture plane to the object side of the adjacent lens on the optical axis 101. The refractive index and Abbe number of each lens in the table are 587nm, the focal length is 587nm, and the Y radius, thickness and focal length are each in millimeters (mm). The parameter data and lens surface type structure used for relational computation in the following embodiments are based on the data in the lens parameter table in the corresponding embodiments.

TABLE 1

As is clear 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, the maximum field angle FOV of the optical system 10 is 121.07 °, and it is clear that the optical system 10 of 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 astigmatic and aberrational maps is 587nm. The longitudinal spherical aberration diagram (Longitudinal Spherical Aberration) shows the focus deviation of light rays with different wavelengths after passing through the lens. The ordinate of the longitudinal spherical aberration diagram represents the normalized pupil coordinates (Normalized Pupil Coordinator) from the pupil center to the pupil edge, and the abscissa represents the distance (in mm) from the imaging surface S17 to the intersection of the light ray and the optical axis. As can be seen from the longitudinal spherical aberration chart, the focus deviation degree of the light rays with each wavelength in the first embodiment tends to be consistent, the maximum focus deviation of each reference wavelength is controlled within ±0.02mm, and for a large aperture system, diffuse spots or halos in an imaging picture are effectively suppressed. Fig. 2 also includes a field curvature astigmatism diagram (Astigmatic Field Curves) of the optical system 10, where the S-curve represents the sagittal field curvature at 587nm and the T-curve represents the meridional field curvature at 587nm. 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, the image surface curvature degree is effectively suppressed for the large aperture system, the sagittal field curvature and meridional field curvature under each field tend to be consistent, and the astigmatism of each field is better controlled, so that the center to the edge of the field of the optical system 10 has clear imaging. Further, as can be seen from the distortion map, 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 an object side to an image side along an optical axis 101, a first lens L1 with negative refractive power, a second lens L2 with positive refractive power, a stop STO, a third lens L3 with positive refractive power, a fourth lens L4 with negative refractive power, a fifth lens L5 with positive refractive power, a sixth lens L6 with positive refractive power, and a seventh lens L7 with negative refractive power. In the case of the second embodiment of the present invention,

The fourth lens element L4 has a convex object-side surface S7 at the optical axis 101 and a concave image-side surface S8 at the optical axis 101; the object side surface S7 is concave at the circumference, and the image side surface S8 is concave 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; the object side surface S9 is convex at the circumference, and the image side surface S10 is convex at the circumference.

The parameters of each lens of the optical system 10 in this embodiment are shown in tables 3 and 4, wherein the names and parameters of each element are defined in the first embodiment, and are not described herein.

TABLE 3 Table 3

TABLE 4 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 well controlled, 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, a first lens L1 with negative refractive power, a second lens L2 with positive refractive power, a stop STO, a third lens L3 with positive refractive power, a fourth lens L4 with negative refractive power, a fifth lens L5 with positive refractive power, a sixth lens L6 with positive refractive power, and a seventh lens L7 with negative refractive power. In the third embodiment of the present invention, in the third embodiment,

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 surface S11 is convex at the circumference, and the image side surface S12 is convex at the circumference.

The lens parameters of the optical system 10 in this embodiment are shown in tables 5 and 6, wherein the definition of the names and parameters of the elements can be obtained in the first embodiment, and the details are omitted here.

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 well controlled, 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, a first lens L1 with negative refractive power, a second lens L2 with positive refractive power, a stop STO, a third lens L3 with positive refractive power, a fourth lens L4 with negative refractive power, a fifth lens L5 with positive refractive power, a sixth lens L6 with positive refractive power, and a seventh lens L7 with positive refractive power. In the fourth embodiment, in the case of the present invention,

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 surface S1 is convex at the circumference and the image side surface 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; the object side surface S5 is concave at the circumference and the image side surface 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 surface S9 is convex at the circumference, and the image side surface 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 definition of the names and parameters of the elements can be obtained in the first embodiment, and the details are omitted here.

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 well controlled, 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, a first lens L1 with negative refractive power, a second lens L2 with positive refractive power, a stop STO, a third lens L3 with positive refractive power, a fourth lens L4 with negative refractive power, a fifth lens L5 with positive refractive power, a sixth lens L6 with positive refractive power, and a seventh lens L7 with positive refractive power. In the fifth embodiment of the present invention, in the fifth embodiment,

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; the object side surface S7 is concave at the circumference, and the image side surface S8 is concave 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 concave at the optical axis 101; the object side surface S9 is convex at the circumference and the image side surface S10 is concave at the circumference.

The lens parameters of the optical system 10 in this embodiment are given in table 9 and table 10, wherein the definition of the names and parameters of the elements can be obtained in the first embodiment, and the details are not repeated here.

TABLE 9

Table 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 well controlled, 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, a first lens L1 with negative refractive power, a second lens L2 with positive refractive power, a stop STO, a third lens L3 with positive refractive power, a fourth lens L4 with positive refractive power, a fifth lens L5 with negative refractive power, a sixth lens L6 with negative refractive power, and a seventh lens L7 with positive refractive power. In the case of the sixth embodiment of the present invention,

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 surface S5 is concave at the circumference and the image side surface S6 is convex at the circumference.

The fourth lens element L4 has a concave object-side surface S7 at the optical axis 101 and a convex image-side surface S8 at the optical axis 101; the object side surface S7 is concave at the circumference and the image side surface 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; the object side surface S9 is concave at the circumference and the image side surface S10 is convex at the circumference.

The lens parameters of the optical system 10 in this embodiment are given in table 11 and table 12, wherein the definition of the names and parameters of the elements can be obtained in the first embodiment, and the details are not repeated here.

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 well controlled, 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, a first lens L1 with negative refractive power, a second lens L2 with positive refractive power, a stop STO, a third lens L3 with positive refractive power, a fourth lens L4 with positive refractive power, a fifth lens L5 with positive refractive power, a sixth lens L6 with negative refractive power, and a seventh lens L7 with positive refractive power. In the seventh embodiment of the present invention, in the seventh embodiment,

The lens parameters of the optical system 10 in this embodiment are given in tables 13 and 14, wherein the definition of the names and parameters of the elements can be obtained in the first embodiment, and the details are omitted here.

TABLE 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 well controlled, and the optical system 10 of this embodiment can have good imaging quality.

Referring to table 15, table 15 is a summary of the ratios of the relationships in the first embodiment to the seventh embodiment of the present application.

TABLE 15

The optical system 10 in the above embodiments can compress the total length to achieve a miniaturized design while maintaining good imaging quality, and can also have a large imaging range, compared to a general optical system.

In the first to seventh embodiments, the combination of the ultra-wide angle intermediate diaphragm and the large entrance pupil diameter can effectively reduce the introduction of aberration, and the aspheric surface and the focal power change are utilized to rapidly shrink the converging light, refract the paraxial light at a low deflection angle, and reduce the introduction of spherical aberration; the marginal view field can not excessively press the light quantity through vignetting and blocking light, but the f12 focal power is adjusted, so that marginal light enters the optical system as much as possible, and the sufficient diffraction limit and the performance guarantee of the marginal view field are maintained.

Referring to fig. 15, an embodiment of the present application further provides an image capturing module 20, where the image capturing 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 may be fixed by a bracket. The image sensor 210 may be a CCD sensor (Charge Coupled Device ) or a CMOS sensor (Complementary Metal Oxide Semiconductor, complementary metal oxide semiconductor). Generally, the imaging surface S17 of the optical system 10 overlaps the photosensitive surface of the image sensor 210 at the time of assembly. By adopting the optical system 10 described above, the image pickup 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, and the camera module 20 is mounted on the fixing member 310, where the fixing member 310 may be a display screen, a circuit board, a middle frame, a rear cover, and the like. The electronic device 30 may be, but is not limited to, a smart phone, a smart watch, smart glasses, an electronic book reader, a tablet computer, a PDA (Personal Digital Assistant ), etc. The camera module 20 can provide good camera quality for the electronic device 30, and simultaneously keep a small occupied volume, so that the obstruction to the miniaturized design of the device can be reduced.

In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings are merely for convenience in describing the present invention and simplifying the description, and do not indicate or imply that the device or element being referred to must have a specific orientation, be configured and operated in a specific orientation, and therefore should not be construed as limiting the present invention.

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

In the present invention, unless explicitly specified and limited otherwise, the terms "mounted," "connected," "secured," and the like are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally formed; the device can be mechanically connected, electrically connected and communicated; can be directly connected or indirectly connected through an intermediate medium, and can be communicated with the inside of two elements or the interaction relationship of the two elements. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art according to the specific circumstances.

In the description of the present specification, a description referring to terms "one embodiment," "some embodiments," "examples," "specific examples," or "some examples," etc., means 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 present invention. In this specification, schematic representations of the above terms are not necessarily directed 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, the different embodiments or examples described in this specification and the features of the different embodiments or examples may be combined and combined by those skilled in the art without contradiction.

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

Claims

1. An optical system, comprising seven lens elements with refractive power:

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

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

a fourth lens element with refractive power having a concave object-side surface 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 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；

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

IMGH is half of the image height corresponding to the maximum field angle of the optical system, fno is the f-number of the optical system, TTL is the distance between the object side surface of the first lens element and the imaging surface of the optical system on the optical axis, SD52 is half of the maximum effective caliber of the image side surface of the fifth lens element, SD62 is half of the maximum effective caliber of the image side surface of the sixth lens element, SD72 is half of the maximum effective caliber 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.

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

0.0604<CT5/TTL<0.12。

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

2.5＜|f12/f|＜8.8；

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

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

0.8＜f3456/f＜10；

and f3456 is the combined focal length of the third lens, the fourth lens, the fifth lens and the sixth 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:

1.83＜(CT5+CT6)/CT2＜4.1；

CT2 is the thickness of the second lens on the optical axis.

6. 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 at the optical axis, and R62 is a radius of curvature of the image-side surface of the sixth lens element at the optical axis.

7. 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 on the optical axis, and BF is the minimum distance between the image-side surface of the seventh lens element and the image-side surface along the optical axis.

8. An imaging module comprising an image sensor and the optical system of any one of claims 1 to 7, wherein the image sensor is disposed on an image side of the optical system.

9. An electronic device, comprising a fixing member and the camera module set according to claim 8, wherein the camera module set is disposed on the fixing member.