CN111142240A

CN111142240A - Optical system, lens module and electronic equipment

Info

Publication number: CN111142240A
Application number: CN202010133603.4A
Authority: CN
Inventors: 党绪文; 刘彬彬; 李明; 邹海荣
Original assignee: OFilm Tech Co Ltd
Current assignee: Nanchang OFilm Precision Optical Products Co Ltd; OFilm Group Co Ltd
Priority date: 2020-02-28
Filing date: 2020-02-28
Publication date: 2020-05-12

Abstract

The invention provides an optical system, a lens module and an electronic device, wherein the optical system sequentially comprises from an object side to an image side along an optical axis direction: the first lens element with positive refractive power has a convex object-side surface and a concave image-side surface in a paraxial region; a second lens; a third lens element with positive refractive power having a convex object-side surface; a fourth lens; the object side surface and the image side surface of the near-circumference area of the fifth lens are convex surfaces; a sixth lens; the seventh lens element with negative refractive power has a convex object-side surface in a paraxial region thereof and a concave image-side surface in the paraxial region thereof; and at least one of the object side surface and the image side surface of the fifth lens and the seventh lens is provided with at least one inflection point. Through the arrangement, the distortion, astigmatism and spherical aberration generated by the front lens group are balanced, and the resolution power is favorably improved; meanwhile, multiple inflection points are arranged, so that the bending degree of the lens is convenient to reduce, the axial thickness of the lens is reduced, and the size reduction is facilitated.

Description

Optical system, lens module and electronic equipment

Technical Field

The invention belongs to the field of optical imaging, and particularly relates to an optical system, a lens module with the optical system and electronic equipment with the optical system.

Background

With the development of science and technology and the popularization of smart phones and smart electronic devices, devices with diversified camera shooting functions are widely favored by people. The optical system is a main core component of the equipment with diversified image pickup functions, the resolution of the optical system directly affects the image pickup effect of the equipment, and the size of the optical system determines the size of the equipment.

In the conventional seven-piece optical system, since the number of lenses is large, it is difficult to control the axial thickness of the lens group within an appropriate range. Therefore, reducing the axial thickness of the optical system is an important issue in current research on ensuring a high resolution of the seven-piece optical system.

Disclosure of Invention

It is an object of the present invention to provide an optical system that solves the above problems.

In order to realize the purpose of the invention, the invention provides the following technical scheme:

in a first aspect, the present invention provides an optical system including, in order from an object side to an image side in an optical axis direction: the first lens element with positive refractive power has a convex object-side surface in a paraxial region and a concave image-side surface in a near-circumferential region; a second lens element with refractive power; the third lens element with positive refractive power has convex object-side surfaces in a paraxial region and a near-circumferential region; a fourth lens element with refractive power; the fifth lens element with refractive power has convex object-side and image-side surfaces in a near-circumferential region, both the object-side and image-side surfaces of the fifth lens element are aspheric, and at least one of the object-side and image-side surfaces of the fifth lens element is provided with at least one inflection point; a sixth lens element with refractive power; the seventh lens element with negative refractive power has a convex object-side surface in a paraxial region thereof, a concave image-side surface in a paraxial region thereof, and both the object-side surface and the image-side surface of the fifth lens element are aspheric. The fifth lens element and the seventh lens element are provided with a plurality of inflection points, which is beneficial to correcting distortion and curvature of field generated by the front lens element, so that the refractive power close to the imaging surface is uniformly configured, and the sensitivity of the optical system is reduced. The refractive power and the surface type of each lens element of the first lens element to the seventh lens element are reasonably configured to balance the distortion, astigmatism and spherical aberration generated by the front lens element group, and especially to compensate the distortion of a large field of view greatly, so that the aberration and the resolving power of each field of view are well balanced, and the resolving power of the optical system is favorably improved; meanwhile, multiple inflection points are arranged, so that the bending degree of the lens is convenient to reduce, the axial thickness of the lens is reduced, and the size of the optical system is favorably reduced.

In one embodiment, the second lens element with negative refractive power has a convex object-side surface in a paraxial region thereof and a concave image-side surface in a paraxial region and a near peripheral region thereof; the object side surface of the fourth lens in the paraxial region is a concave surface, and the image side surface of the fourth lens in the paraxial region is a convex surface; the object side surface of the near-circumference area of the sixth lens is a concave surface, the image side surface of the near-circumference area of the sixth lens is a convex surface, both the object side surface and the image side surface of the sixth lens are aspheric surfaces, and at least one of the object side surface and the image side surface of the sixth lens is provided with at least one inflection point. By optimally configuring the refractive power and the surface type of the second lens, the fourth lens and the sixth lens, the distortion, the astigmatism and the spherical aberration generated by the front lens group are convenient to balance, the compensation degree of the optical system for the distortion of a large field of view is improved, and the resolving power of the optical system is further improved; meanwhile, the inflection point is additionally arranged, so that the bending degree of the lens is further reduced, the axial thickness of the lens is reduced, and the size of the optical system is further reduced.

In one embodiment, the first lens is a glass lens, and both an object-side surface and an image-side surface of the first lens are aspheric, and the first lens satisfies the following conditional expression: n12 > 1.7; wherein n12 is the refractive index of the first lens for light with the wavelength of 546 nm. The first lens is made of glass materials, so that the refractive index of the first lens is high, the refractive power of the first lens is easy to distribute, the thickness of the first lens is reduced, the integral compactness is improved, and the deformation of the assembled optical lens system is small in high and low temperature environments and the imaging performance is more stable due to the characteristics of glass; the value of n12 is reasonably set, so that the first lens has high refractive power, spherical aberration and chromatic aberration can be well balanced, the aberration balance of the rear lens is facilitated, meanwhile, the incident ray angle with a large field angle can be rapidly reduced, and the tolerance sensitivity of the system is reduced.

In one embodiment, the optical system satisfies the conditional expression: f/EPD is more than or equal to 1.35 and less than or equal to 2; where f is the effective focal length of the optical system and EPD is the entrance pupil diameter of the optical system. By reasonably setting the value of the f/EPD, the optical system has sufficient light incoming quantity, so that a dark corner of the electronic photosensitive element is avoided, and the shooting effect in a dark environment is further improved; in addition, the size of the Airy spots can be reduced by increasing the diaphragm number, the resolution limit inversely proportional to the size of the Airy spots can be further increased, and the requirement of high-pixel design can be met by reasonably configuring the resolution of the lens.

In one embodiment, the optical system satisfies the conditional expression: 0.6 < TTL/(ImgH 2) < 0.8; wherein, TTL is a distance on an optical axis from an object-side surface of the first lens element to an image plane of the optical system, and ImgH is a half of a diagonal length of an effective photosensitive area of the optical system. It can be understood that ImgH determines the size of the electronic photosensitive element, and the larger ImgH is, the larger the size of the maximum electronic photosensitive element that can be supported is, and ImgH is greater than or equal to 3.4mm, which can meet the requirements of high pixel and high image quality of most mobile phone lenses; the smaller the TTL is, the better the whole length compression effect of the optical system is, and the more compact the lens structure is. The value of TTL/(ImgH x 2) is reasonably set, and the optical system can realize miniaturization and lightness and thinness under the condition of meeting high pixel and high imaging quality.

In one embodiment, the optical system satisfies the conditional expression: 1.6 < (| SAG71| + CT7+ SAG72)/CT7 < 3.3; wherein SAG71 is the maximum sagittal height of the object side surface of the seventh lens, CT7 is the thickness of the seventh lens on the optical axis, and SAG72 is the maximum sagittal height of the image side surface of the seventh lens. By reasonably setting the value of (| SAG71| + CT7+ SAG72)/CT7, the refractive power and thickness of the lens in the direction perpendicular to the optical axis can be reasonably controlled, the lens is prevented from being too thin and too thick, the molding difficulty of the lens is reduced, and the manufacturing of an optical system is facilitated.

In one embodiment, the optical system satisfies the conditional expression: n12/R12 is more than 0.2 and less than or equal to 0.4; wherein n12 is a refractive index of the first lens for light with a wavelength of 546nm, and R12 is a curvature radius of an image side surface of the first lens at an optical axis. By reasonably setting the value of n12/R12, the higher refractive index is convenient for the first lens to reduce the physical size, and is beneficial to the design of a light and thin lens; meanwhile, the aberration is prevented from increasing due to over-concentration of the refractive power.

In one embodiment, the optical system satisfies the conditional expression: (ET1+ ET2+ ET3)/(CT1+ CT2+ CT3) < 1; wherein ET1 is a thickness of an optically effective area edge of the first lens element, ET2 is a thickness of an optically effective area edge of the second lens element, ET3 is a thickness of an optically effective area edge of the third lens element, CT1 is a thickness of the first lens element on an optical axis, CT2 is a thickness of the second lens element on the optical axis, and CT3 is a thickness of the third lens element on the optical axis. By reasonably setting the value of (ET1+ ET2+ ET3)/(CT1+ CT2+ CT3), the sizes and refractive powers of the first lens, the second lens and the third lens are optimized, and the spherical aberration generated by the front lens group can be avoided being too large, so that the overall resolving power of the optical lens is improved, and the sensitivity of the lens group is reduced.

In one embodiment, the optical system satisfies the conditional expression: | f45/f3| is more than or equal to 1.75 and less than 41; wherein f45 is the combined effective focal length of the fourth lens and the fifth lens, and f3 is the effective focal length of the third lens. It can be understood that the object plane side of the fourth lens element is concave, which provides a good refractive power distribution in the direction perpendicular to the optical axis. By reasonably setting the value of | f45/f3|, the field curvature and distortion caused by overlarge light deflection angle are reduced, so that the image quality is improved, and the assembly sensitivity of the optical system is reduced.

In one embodiment, the optical system satisfies the conditional expression: i f 6/R61I < 22; wherein f6 is an effective focal length of the sixth lens, and R61 is a radius of curvature of an object-side surface of the sixth lens at an optical axis. By reasonably setting the value of | f6/R61|, the thinness and thinness of the sixth lens can be kept, the thickness of the optical system can be reduced, and the image quality can be improved.

In one embodiment, the optical system satisfies the conditional expression: FOV is more than or equal to 70 degrees and less than or equal to 85 degrees; wherein the FOV is the maximum field angle of the optical system in the diagonal direction. Through the arrangement, the maximum shooting range exceeding 70 degrees is provided under the condition of less f-number, so that the advantage of less f-number is fully utilized, the light incoming quantity of the electronic photosensitive element in unit area is enhanced, and the capturing capability of low-frequency details of an object is improved; the matching of less f-number and large field angle can reduce the depth of field of the object to be shot and more highlight the main body, thereby improving the image quality.

In one embodiment, the optical system satisfies the conditional expression: f13/f is more than 0.8 and less than 1.1; wherein f13 is a combined effective focal length of the first lens, the second lens, and the third lens, and f is an effective focal length of the optical system. The value of f13/f is reasonably set, so that the refractive power of the first lens, the second lens and the third lens is optimally configured, the size of the head of the lens can be reduced, the deflection angle of incident light with a large visual field is reduced, and the sensitivity of the system is reduced.

In a second aspect, the present invention further provides a lens module, which includes a lens barrel, an electronic photosensitive element and the optical system according to any one of the embodiments of the first aspect, wherein the first lens to the seventh lens of the optical system are mounted in the lens barrel, and the electronic photosensitive element is disposed on an image side of the optical system. The first lens to the seventh lens of the optical system are arranged in the lens module, so that the aberration and the resolving power of each field are well balanced, the resolving power of the lens module is favorably improved, and the size of the lens module is favorably reduced.

In a third aspect, the present invention further provides an electronic device, where the electronic device includes a housing and the lens module of the second aspect, and the lens module is disposed in the housing. Through set up the lens module of the second aspect in electronic equipment, let the aberration and the resolving power of each field obtain good balance, be favorable to promoting electronic equipment's resolving power, help reducing electronic equipment's size.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.

FIG. 1a is a schematic structural diagram of an optical system of a first embodiment;

FIG. 1b is a longitudinal spherical aberration curve, an astigmatism curve and a distortion curve of the first embodiment;

FIG. 2a is a schematic structural diagram of an optical system of a second embodiment;

FIG. 2b is a longitudinal spherical aberration curve, an astigmatism curve and a distortion curve of the second embodiment;

FIG. 3a is a schematic structural diagram of an optical system of a third embodiment;

FIG. 3b is a longitudinal spherical aberration curve, an astigmatism curve and a distortion curve of the third embodiment;

FIG. 4a is a schematic structural diagram of an optical system of a fourth embodiment;

FIG. 4b is a longitudinal spherical aberration curve, an astigmatism curve and a distortion curve of the fourth embodiment;

FIG. 5a is a schematic structural diagram of an optical system of a fifth embodiment;

FIG. 5b is a longitudinal spherical aberration curve, an astigmatism curve and a distortion curve of the fifth embodiment;

FIG. 6a is a schematic structural diagram of an optical system of a sixth embodiment;

fig. 6b is a longitudinal spherical aberration curve, an astigmatism curve and a distortion curve of the sixth embodiment.

FIG. 7a is a schematic structural diagram of an optical system of a seventh embodiment;

fig. 7b is a longitudinal spherical aberration curve, an astigmatism curve and a distortion curve of the seventh embodiment.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.

The invention also provides a lens module which comprises a lens barrel, an electronic photosensitive element and the optical system provided by the embodiment of the invention, wherein the first lens to the seventh lens of the optical system are arranged in the lens barrel, and the electronic photosensitive element is arranged at the image side of the optical system and is used for converting light rays of objects which pass through the first lens to the seventh lens and are incident on the electronic photosensitive element into electric signals of images. The electron sensitive element may be a Complementary Metal Oxide Semiconductor (CMOS) or a Charge-coupled Device (CCD). The lens module can be an independent lens of a digital camera, and can also be an imaging module integrated on electronic equipment such as a smart phone. By installing the first lens to the seventh lens of the optical system provided by the embodiment of the invention in the lens module, the aberration and the resolving power of each field are well balanced, the resolving power of the lens module is favorably improved, and the size of the lens module is favorably reduced.

The invention also provides electronic equipment which comprises a shell and the lens module provided by the embodiment of the invention, wherein the lens module is arranged in the shell. The electronic device can be a smart phone, a Personal Digital Assistant (PDA), a tablet computer, a smart watch, an unmanned aerial vehicle, an electronic book reader, a vehicle event data recorder, a wearable device and the like. By arranging the lens module in the electronic equipment, the aberration and the resolving power of each field of view are well balanced, the resolving power of the electronic equipment is favorably improved, and the size of the electronic equipment is favorably reduced.

The invention provides an optical system which sequentially comprises a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens and a seventh lens from an object side to an image side along an optical axis direction. In the first to seventh lenses, any two adjacent lenses may have an air space therebetween.

Specifically, the specific form and structure of the seven lenses are as follows:

the first lens element with positive refractive power has a convex object-side surface in a paraxial region and a concave image-side surface in a near-circumferential region;

a second lens element with refractive power;

the third lens element with positive refractive power has convex object-side surfaces in a paraxial region and a near-circumferential region;

a fourth lens element with refractive power;

the fifth lens element with refractive power has convex object-side and image-side surfaces in a near-circumferential region, both the object-side and image-side surfaces of the fifth lens element are aspheric, and at least one of the object-side and image-side surfaces of the fifth lens element is provided with at least one inflection point;

a sixth lens element with refractive power;

the seventh lens element with negative refractive power has a convex object-side surface in a paraxial region thereof, a concave image-side surface in a paraxial region thereof, and both the object-side surface and the image-side surface of the fifth lens element are aspheric.

Specifically, the optical system further includes a diaphragm, and the diaphragm may be disposed at any position between the first lens and the seventh lens, such as on the first lens.

It can be understood that the fifth lens element and the seventh lens element are provided with a plurality of inflection points, which is beneficial to correcting distortion and curvature of field generated by the front lens element, so that the refractive power configuration near the image plane is more uniform, and the sensitivity of the optical system is reduced. The refractive power and the surface type of each lens element of the first lens element to the seventh lens element are reasonably configured to balance the distortion, astigmatism and spherical aberration generated by the front lens element group, and especially to compensate the distortion of a large field of view greatly, so that the aberration and the resolving power of each field of view are well balanced, and the resolving power of the optical system is favorably improved; meanwhile, multiple inflection points are arranged, so that the bending degree of the lens is convenient to reduce, the axial thickness of the lens is reduced, and the size of the optical system is favorably reduced.

In one embodiment, the second lens element with negative refractive power has a convex object-side surface in a paraxial region thereof and a concave image-side surface in a paraxial region and a near peripheral region thereof; the object side surface of the paraxial region of the fourth lens is a concave surface, and the image side surface of the paraxial region of the fourth lens is a convex surface; the object side surface of the near-circumference area of the sixth lens is a concave surface, the image side surface of the near-circumference area of the sixth lens is a convex surface, both the object side surface and the image side surface of the sixth lens are aspheric surfaces, and at least one of the object side surface and the image side surface of the sixth lens is provided with at least one inflection point. Specifically, a plurality of inflection points may be provided on the first lens, the second lens, the third lens, and the fourth lens. By optimally configuring the refractive power and the surface type of the second lens, the fourth lens and the sixth lens, the distortion, the astigmatism and the spherical aberration generated by the front lens group are convenient to balance, the compensation degree of the optical system for the distortion of a large field of view is improved, and the resolving power of the optical system is further improved; meanwhile, the inflection point is additionally arranged, so that the bending degree of the lens is further reduced, the axial thickness of the lens is reduced, and the size of the optical system is further reduced.

In one embodiment, the first lens element is a glass lens element, and both an object-side surface and an image-side surface of the first lens element are aspheric, and the first lens element satisfies the following conditional expression: n12 > 1.7; where n12 is the refractive index of the first lens for light with a wavelength of 546 nm. Specifically, the second lens to the seventh lens are preferably made of a plastic material, and may be made of a resin such as polymethyl methacrylate, acryl diglycol carbonate, or acryl diglycol carbonate. The value of n12 can be 1.7, 1.9, 2.5, 3.5, 5, etc. It can be understood that the 1G6P aspheric optical system formed by the first lens made of glass and the second to seventh lenses made of plastic can give consideration to both the light and thin characteristics and the high resolution, and the application scenarios are more diversified. The glass provides a higher refractive index than a plastic shell, the first lens is made of glass materials, so that the refractive power of the first lens is easy to distribute, the thickness of the first lens is reduced, the overall compactness is improved, and due to the characteristics of the glass, the deformation of the assembled optical lens system in high and low temperature environments is small, and the imaging performance is more stable; the value of n12 is reasonably set, so that the first lens has high refractive power, spherical aberration and chromatic aberration can be well balanced, the aberration balance of the rear lens is facilitated, meanwhile, the incident ray angle with a large field angle can be rapidly reduced, and the tolerance sensitivity of the system is reduced.

In one embodiment, the optical system satisfies the conditional expression: f/EPD is more than or equal to 1.35 and less than or equal to 2; where f is the effective focal length of the optical system and EPD is the entrance pupil diameter of the optical system. Specifically, the value of f/EPD may be 1.35, 1.4, 1.45, 1.5, 1.55, 1.6, 1.7, 1.8, 1.9, 2.0, and the like. By reasonably setting the value of the f/EPD, the optical system has sufficient light incoming quantity, so that a dark corner of the electronic photosensitive element is avoided, and the shooting effect in a dark environment is further improved; in addition, the size of the Airy spots can be reduced by increasing the diaphragm number, the resolution limit inversely proportional to the size of the Airy spots can be further increased, and the requirement of high-pixel design can be met by reasonably configuring the resolution of the lens.

In one embodiment, the optical system satisfies the conditional expression: 0.6 < TTL/(ImgH 2) < 0.8; wherein, TTL is a distance on an optical axis from an object side surface of the first lens element to an image plane of the optical system, and ImgH is a half of a diagonal length of an effective photosensitive area of the optical system. Specifically, TTL/(ImgH × 2) may have values of 0.6, 0.65, 0.68, 0.7, 0.72, 0.75, 0.8, and the like. It can be understood that ImgH determines the size of the electronic photosensitive element, and the larger ImgH is, the larger the size of the maximum electronic photosensitive element that can be supported is, and ImgH is greater than or equal to 3.4mm, which can meet the requirements of high pixel and high image quality of most mobile phone lenses; the smaller the TTL is, the better the whole length compression effect of the optical system is, and the more compact the lens structure is. The value of TTL/(ImgH x 2) is reasonably set, and the optical system can realize miniaturization and lightness and thinness under the condition of meeting high pixel and high imaging quality.

In one embodiment, the optical system satisfies the conditional expression: 1.6 < (| SAG71| + CT7+ SAG72)/CT7 < 3.3; the SAG71 is the maximum saggital height of the object side surface of the seventh lens, the CT7 is the thickness of the seventh lens on the optical axis, and the SAG72 is the maximum saggital height of the image side surface of the seventh lens. Specifically, (| SAG71| + CT7+ SAG72)/CT7 may have values of 1.6, 1.8, 2.0, 2.2, 2.4, 2.6, 2.8, 3, 3.3, and the like. By reasonably setting the value of (| SAG71| + CT7+ SAG72)/CT7, the refractive power and thickness of the lens in the direction perpendicular to the optical axis can be reasonably controlled, the lens is prevented from being too thin and too thick, the molding difficulty of the lens is reduced, and the manufacturing of an optical system is facilitated.

In one embodiment, the optical system satisfies the conditional expression: n12/R12 is more than 0.2 and less than or equal to 0.4; wherein n12 is a refractive index of the first lens for light with a wavelength of 546nm, and R12 is a curvature radius of an image side surface of the first lens at an optical axis. Specifically, the values of n12/R12 can be 0.2, 0.25, 0.3, 0.35, 0.4, and the like. By reasonably setting the value of n12/R12, the higher refractive index is convenient for the first lens to reduce the physical size, and is beneficial to the design of a light and thin lens; meanwhile, the aberration is prevented from increasing due to over-concentration of the refractive power.

In one embodiment, the optical system satisfies the conditional expression: (ET1+ ET2+ ET3)/(CT1+ CT2+ CT3) < 1; wherein ET1 is a thickness of an edge of an optically effective area of the first lens element, ET2 is a thickness of an edge of an optically effective area of the second lens element, ET3 is a thickness of an edge of an optically effective area of the third lens element, CT1 is a thickness of the first lens element along an optical axis, CT2 is a thickness of the second lens element along the optical axis, and CT3 is a thickness of the third lens element along the optical axis. Specifically, the value of (ET1+ ET2+ ET3)/(CT1+ CT2+ CT3) may be 0.3, 0.5, 0.6, 0.65, 0.7, 0.75, 0.8, 0.9, 1, and the like. By reasonably setting the value of (ET1+ ET2+ ET3)/(CT1+ CT2+ CT3), the sizes and refractive powers of the first lens, the second lens and the third lens are optimized, and the spherical aberration generated by the front lens group can be avoided being too large, so that the overall resolving power of the optical lens is improved, and the sensitivity of the lens group is reduced.

In one embodiment, the optical system satisfies the conditional expression: | f45/f3| is more than or equal to 1.75 and less than 41; wherein f45 is the combined effective focal length of the fourth lens and the fifth lens, and f3 is the effective focal length of the third lens. Specifically, the value of | f45/f3| may be 1.75, 16, 23, 30, 37, 40, 41, and so on. It can be understood that the object plane side of the fourth lens element is concave, which provides a good refractive power distribution in the direction perpendicular to the optical axis. By reasonably setting the value of | f45/f3|, the field curvature and distortion caused by overlarge light deflection angle are reduced, so that the image quality is improved, and the assembly sensitivity of the optical system is reduced.

In one embodiment, the optical system satisfies the conditional expression: i f 6/R61I < 22; where f6 is an effective focal length of the sixth lens element, and R61 is a radius of curvature of an object-side surface of the sixth lens element at an optical axis. Specifically, the value of | f6/R61| may be 0.1, 0.5, 1, 5, 10, 15, 22, and so on. By reasonably setting the value of | f6/R61|, the thinness and thinness of the sixth lens can be kept, the thickness of the optical system can be reduced, and the image quality can be improved.

In one embodiment, the optical system satisfies the conditional expression: FOV is more than or equal to 70 degrees and less than or equal to 85 degrees; wherein the FOV is the maximum field angle of the optical system in the diagonal direction. Specifically, the value of the FOV may be 70 °, 73 °, 75 °, 78 °, 80 °, 83 °, 85 °, and the like. Through the arrangement, the maximum shooting range exceeding 70 degrees is provided under the condition of less f-number, so that the advantage of less f-number is fully utilized, the light incoming quantity of the electronic photosensitive element in unit area is enhanced, and the capturing capability of low-frequency details of an object is improved; the matching of less f-number and large field angle can reduce the depth of field of the object to be shot and more highlight the main body, thereby improving the image quality.

In one embodiment, the optical system satisfies the conditional expression: f13/f is more than 0.8 and less than 1.1; where f13 is the combined effective focal length of the first lens, the second lens and the third lens, and f is the effective focal length of the optical system. Specifically, the value of f13/f can be 0.8, 0.85, 0.9, 0.95, 1, 1.05, 1.1, etc. The value of f13/f is reasonably set, so that the refractive power of the first lens, the second lens and the third lens is optimally configured, the size of the head of the lens can be reduced, the deflection angle of incident light with a large visual field is reduced, and the sensitivity of the system is reduced.

First embodiment

Referring to fig. 1a and fig. 1b, the optical system of the present embodiment, in order from an object side to an image side along an optical axis, includes:

the first lens element L1 with positive refractive power has a convex object-side surface S1 in the paraxial region and the paraxial region of the first lens element L1; the image side surface S2 of the first lens L1 in the paraxial region is concave, and the image side surface S2 in the paraxial region is convex;

the second lens element L2 with negative refractive power has a convex object-side surface S3 in the paraxial region and the paraxial region of the second lens element L2 and a concave image-side surface S4 in the paraxial region and the peripheral region of the second lens element L2;

the third lens element L3 with positive refractive power has a convex object-side surface S5 in the paraxial region and a concave object-side surface S5 in the paraxial region of the third lens element L3; the image side surface S6 of the third lens L3 in the paraxial region and the near circumferential region is concave;

the fourth lens element L4 with positive refractive power has a concave object-side surface S7 in the paraxial region and the peripherical region of the fourth lens element L4 and a convex image-side surface S8 in the paraxial region and the peripherical region of the fourth lens element L4;

the fifth lens element L5 with positive refractive power has a convex object-side surface S9 in the paraxial region and a concave object-side surface S9 in the paraxial region of the fifth lens element L5; the image-side surface S10 of the fifth lens element L5 in the paraxial region is concave, and the image-side surface S10 in the paraxial region is convex.

The sixth lens element L6 with negative refractive power has a concave object-side surface S11 in the paraxial and peripherical regions of the sixth lens element L6; the image-side surface S12 of the sixth lens L6 in the paraxial region and the near circumferential region is convex.

The seventh lens element L7 with negative refractive power has a convex object-side surface S13 in the paraxial region and the paraxial region of the seventh lens element L7; the image-side surface S14 of the seventh lens element L7 in the paraxial region is concave, and the image-side surface S14 in the paraxial region is convex.

The material of the first lens L1 is Glass (Glass), and the materials of the second lens L2 to the seventh lens L7 are all Plastic (Plastic).

Further, the optical system includes a stop STO, an infrared cut filter L8, and an image forming surface S17. The stop STO is provided on the side of the first lens L1 away from the second lens L2, and controls the amount of light entering. In other embodiments, the stop STO can be disposed between two adjacent lenses, or on other lenses. The infrared cut filter L8 is disposed on the image side of the seventh lens L7, and includes an object side surface S15 and an image side surface S16, and the infrared cut filter L8 is configured to filter out infrared light, so that the light entering the image plane S17 is visible light, and the wavelength of the visible light is 380nm-780 nm. The material of the infrared cut filter L8 is Glass (Glass), and a film may be coated on the Glass. The image formation surface S17 is an effective pixel region of the electrophotographic photosensitive member.

Table 1a shows a table of characteristics of the optical system of the present embodiment in which data is obtained using light having a wavelength of 546nm, and the units of the Y radius, thickness, and focal length are millimeters (mm).

TABLE 1a

Wherein f is an effective focal length of the optical system, FNO is an f-number of the optical system, FOV is a maximum field angle of the optical system in a diagonal direction, and 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.

In the present embodiment, the object-side surface and the image-side surface of any one of the first lens L1 through the seventh lens L7 are aspheric surfaces, and the surface shape x of each aspheric lens can be defined by, but is not limited to, the following aspheric surface formula:

wherein x is the maximum rise of the distance from the vertex of the aspheric surface when the aspheric surface is at the position with the height of h along the optical axis direction; c is the paraxial curvature of the aspheric surface, c being 1/R (i.e., paraxial curvature c is the inverse of radius R of Y in table 1a above); k is a conic coefficient; ai is the correction coefficient of the i-th order of the aspherical surface. Table 1b shows the high-order coefficient A4, A6, A8, A10, A12, A14, A16, A18 and A20 that can be used for each of the aspherical mirrors S1-S10 in the first embodiment.

TABLE 1b

Fig. 1b shows a longitudinal spherical aberration curve, an astigmatism curve and a distortion curve of the optical system of the first embodiment. The reference wavelength of the light rays of the astigmatism curve and the distortion curve is 546nm, wherein, the longitudinal spherical aberration curve represents the deviation of the convergent focus of the light rays with different wavelengths after passing through each lens of the optical system; the astigmatism curves are meridional image surface curvature and sagittal image surface curvature; the distortion curve represents the distortion magnitude values corresponding to different angles of view. As can be seen from fig. 1b, the optical system according to the first embodiment can achieve good imaging quality.

Second embodiment

Referring to fig. 2a and fig. 2b, the optical system of the present embodiment, in order from an object side to an image side along an optical axis direction, includes:

the third lens element L3 with positive refractive power has a convex object-side surface S5 in the paraxial region and the paraxial region of the third lens element L3; the image side surface S6 of the third lens L3 in the paraxial region and the near circumferential region is convex;

the fourth lens element L4 with negative refractive power has a concave object-side surface S7 in the paraxial region and the paraxial region of the fourth lens element L4, a convex image-side surface S8 in the paraxial region of the fourth lens element L4, and a concave image-side surface S8 in the paraxial region;

The sixth lens element L6 with positive refractive power has a convex object-side surface S11 in the paraxial region and a concave object-side surface S11 in the paraxial region of the sixth lens element L6; the image-side surface S12 of the sixth lens L6 in the paraxial region and the near circumferential region is convex.

The seventh lens element L7 with negative refractive power has a convex object-side surface S13 in the paraxial region and a concave object-side surface S13 in the paraxial region of the seventh lens element L7; the image-side surface S14 of the seventh lens element L7 in the paraxial region is concave, and the image-side surface S14 in the paraxial region is convex.

Other structures of the second embodiment are the same as those of the first embodiment, and reference may be made thereto.

Table 2a shows a table of characteristics of the optical system of the present embodiment in which data is obtained using light having a wavelength of 546nm, and the units of the Y radius, thickness, and focal length are millimeters (mm).

TABLE 2a

Wherein the values of the parameters in Table 2a are the same as those of the first embodiment.

Table 2b gives the coefficients of high order terms that can be used for each aspherical mirror in the second embodiment, wherein each aspherical mirror type can be defined by the formula given in the first embodiment.

TABLE 2b

Fig. 2b shows a longitudinal spherical aberration curve, an astigmatism curve and a distortion curve of the optical system of the second embodiment. Wherein the reference wavelength of the light rays of the astigmatism curve and the distortion curve is 546 nm. As can be seen from fig. 2b, the optical system according to the second embodiment can achieve good imaging quality.

Third embodiment

Referring to fig. 3a and 3b, the optical system of the present embodiment, in order from an object side to an image side along an optical axis direction, includes:

the third lens element L3 with positive refractive power has a convex object-side surface S5 in the paraxial region and a concave object-side surface S5 in the paraxial region of the third lens element L3; the image side surface S6 of the third lens L3 in the paraxial region and the near circumferential region is convex;

the fourth lens element L4 with positive refractive power has a concave object-side surface S7 in the paraxial region and the paraxial region of the fourth lens element L4, a convex image-side surface S8 in the paraxial region of the fourth lens element L4, and a concave image-side surface S8 in the paraxial region;

the fifth lens element L5 with negative refractive power has a convex object-side surface S9 in the paraxial region and a concave object-side surface S9 in the paraxial region of the fifth lens element L5; the image-side surface S10 of the fifth lens element L5 in the paraxial region is concave, and the image-side surface S10 in the paraxial region is convex.

The sixth lens element L6 with positive refractive power has a concave object-side surface S11 in the paraxial and peripherical regions of the sixth lens element L6; the image-side surface S12 of the sixth lens L6 in the paraxial region and the near circumferential region is convex.

Other structures of the third embodiment are the same as those of the first embodiment, and reference may be made thereto.

Table 3a shows a table of characteristics of the optical system of the present embodiment in which data is obtained using light having a wavelength of 546nm, and the units of the Y radius, thickness, and focal length are millimeters (mm).

TABLE 3a

Wherein the values of the parameters in Table 3a are the same as those of the first embodiment.

Table 3b gives the coefficients of high-order terms that can be used for each aspherical mirror surface in the third embodiment, wherein each aspherical mirror surface type can be defined by the formula given in the first embodiment.

TABLE 3b

Fig. 3b shows a longitudinal spherical aberration curve, an astigmatism curve and a distortion curve of the optical system of the third embodiment. Wherein the reference wavelength of the light rays of the astigmatism curve and the distortion curve is 546 nm. As can be seen from fig. 3b, the optical system according to the third embodiment can achieve good imaging quality.

Fourth embodiment

Referring to fig. 4a and 4b, the optical system of the present embodiment, in order from an object side to an image side along an optical axis direction, includes:

the second lens element L2 with negative refractive power has a convex object-side surface S3 in the paraxial region of the second lens element L2, a concave object-side surface S3 in the paraxial region, and a concave image-side surface S4 in the paraxial and peripheral regions of the second lens element L2;

the third lens element L3 with positive refractive power has a convex object-side surface S5 in the paraxial region and a concave object-side surface S5 in the paraxial region of the third lens element L3; the image side surface S6 of the third lens L3 in the paraxial region is concave, and the image side surface S6 in the paraxial region is convex;

Other structures of the fourth embodiment are the same as those of the first embodiment, and reference may be made thereto.

Table 4a shows a table of characteristics of the optical system of the present embodiment in which data is obtained using light having a wavelength of 546nm, and the units of the Y radius, thickness, and focal length are millimeters (mm).

TABLE 4a

Wherein the values of the parameters in Table 4a are the same as those of the first embodiment.

Table 4b gives the coefficients of high-order terms that can be used for each aspherical mirror surface in the fourth embodiment, wherein each aspherical mirror surface type can be defined by the formula given in the first embodiment.

TABLE 4b

Fig. 4b shows a longitudinal spherical aberration curve, an astigmatism curve and a distortion curve of the optical system of the fourth embodiment. As can be seen from fig. 4b, the optical system according to the fourth embodiment can achieve good imaging quality.

Fifth embodiment

Referring to fig. 5a and 5b, the optical system of the present embodiment, in order from an object side to an image side along an optical axis direction, includes:

the fifth lens element L5 with negative refractive power has a concave object-side surface S9 in the paraxial and peripherical regions of the fifth lens element L5; the image-side surface S10 of the fifth lens L5 in the paraxial region and the near circumferential region is convex.

The sixth lens element L6 with positive refractive power has a convex object-side surface S11 in the paraxial region and a concave object-side surface S11 in the paraxial region of the sixth lens element L6; the image-side surface S12 of the sixth lens element L6 in the paraxial region is concave, and the image-side surface S12 in the paraxial region is convex.

The other structure of the fifth embodiment is the same as that of the first embodiment, and reference may be made thereto.

Table 5a shows a table of characteristics of the optical system of the present embodiment in which data is obtained using light having a wavelength of 546nm, and the units of the Y radius, thickness, and focal length are millimeters (mm).

TABLE 5a

Wherein the meanings of the parameters in Table 5a are the same as those of the first embodiment.

Table 5b shows the high-order term coefficients that can be used for each aspherical mirror surface in the fifth embodiment, wherein each aspherical mirror surface type can be defined by the formula given in the first embodiment.

TABLE 5b

Fig. 5b shows a longitudinal spherical aberration curve, an astigmatism curve and a distortion curve of the optical system of the fifth embodiment. Wherein the reference wavelength of the light rays of the astigmatism curve and the distortion curve is 546 nm. As can be seen from fig. 5b, the optical system according to the fifth embodiment can achieve good image quality.

Sixth embodiment

Referring to fig. 6a and 6b, the optical system of the present embodiment, in order from an object side to an image side along an optical axis direction, includes:

the third lens element L3 with positive refractive power has a convex object-side surface S5 in the paraxial region and the paraxial region of the third lens element L3; the image side surface S6 of the third lens L3 in the paraxial region is concave, and the image side surface S6 in the paraxial region is convex;

Other structures of the sixth embodiment are the same as those of the first embodiment, and reference may be made thereto.

Table 6a shows a table of characteristics of the optical system of the present embodiment in which data is obtained using light having a wavelength of 546nm, and the units of the Y radius, thickness, and focal length are millimeters (mm).

TABLE 6a

Wherein the values of the parameters in Table 6a are the same as those of the first embodiment.

Table 6b shows the high-order term coefficients that can be used for each aspherical mirror surface in the sixth embodiment, wherein each aspherical mirror surface type can be defined by the formula given in the first embodiment.

TABLE 6b

Fig. 6b shows a longitudinal spherical aberration curve, an astigmatism curve and a distortion curve of the optical system of the sixth embodiment. Wherein the reference wavelength of the light rays of the astigmatism curve and the distortion curve is 546 nm. As can be seen from fig. 6b, the optical system according to the sixth embodiment can achieve good image quality.

Seventh embodiment

Referring to fig. 7a and 7b, the optical system of the present embodiment, in order from an object side to an image side along an optical axis direction, includes:

The other structure of the seventh embodiment is the same as that of the first embodiment, and reference may be made thereto.

Table 7a shows a table of characteristics of the optical system of the present embodiment in which data is obtained using light having a wavelength of 546nm, and the units of the Y radius, thickness, and focal length are millimeters (mm).

TABLE 7a

Wherein the meanings of the parameters in Table 7a are the same as those of the first embodiment.

Table 7b shows the high-order term coefficients that can be used for each aspherical mirror surface in the seventh embodiment, wherein each aspherical mirror surface type can be defined by the formula given in the first embodiment.

TABLE 7b

Fig. 7b shows a longitudinal spherical aberration curve, an astigmatism curve, and a distortion curve of the optical system of the seventh embodiment. Wherein the reference wavelength of the light rays of the astigmatism curve and the distortion curve is 546 nm. As can be seen from fig. 7b, the optical system according to the seventh embodiment can achieve good image quality.

Table 8 shows values of f/EPD, TTL/(ImgH × 2), f13/f, (| SAG71| + CT7+ SAG72)/CT7, n12/R12, (ET1+ ET2+ ET3)/(CT1+ CT2+ CT3), | f45/f3|, and | f6/R61| of the optical systems in the first to seventh embodiments.

TABLE 8

As can be seen from table 8, the optical systems of the first to seventh embodiments all satisfy the following conditional expressions: f/EPD is more than 1.35 and less than or equal to 1.75, TTL/(ImgH 2) is more than 0.6 and less than 0.8, f13/f is more than 0.8 and less than 1.1, 1.6 and less than (| SAG71| + CT7+ SAG72)/CT7 and less than 3.3, n12/R12 is more than or equal to 0.2 and less than or equal to 0.4, ET1+ ET2+ ET3)/(CT1+ CT2+ CT3) is less than or equal to 0.75, and | f45/f3| < 41 and | f6/R61| < 22 are more than or equal to 1.75.

While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

1. An optical system comprising, in order from an object side to an image side in an optical axis direction:

a second lens element with refractive power;

a fourth lens element with refractive power;

a sixth lens element with refractive power;

2. The optical system as claimed in claim 1, wherein the second lens element with negative refractive power has a convex object-side surface in a paraxial region thereof and a concave image-side surface in a paraxial and peripheral region thereof;

the object side surface of the fourth lens in the paraxial region is a concave surface, and the image side surface of the fourth lens in the paraxial region is a convex surface;

the object side surface of the near-circumference area of the sixth lens is a concave surface, the image side surface of the near-circumference area of the sixth lens is a convex surface, both the object side surface and the image side surface of the sixth lens are aspheric surfaces, and at least one of the object side surface and the image side surface of the sixth lens is provided with at least one inflection point.

3. The optical system according to claim 1 or 2, wherein the first lens is a glass lens, and both an object-side surface and an image-side surface of the first lens are aspheric, and the first lens satisfies a conditional expression:

n12＞1.7；

wherein n12 is the refractive index of the first lens for light with the wavelength of 546 nm.

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

1.35≤f/EPD≤2；

where f is the effective focal length of the optical system and EPD is the entrance pupil diameter of the optical system.

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

0.6＜TTL/(ImgH*2)＜0.8；

wherein, TTL is a distance on an optical axis from an object-side surface of the first lens element to an image plane of the optical system, and ImgH is a half of a diagonal length of an effective photosensitive area of the optical system.

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

1.6＜(|SAG71|+CT7+SAG72)/CT7＜3.3；

wherein SAG71 is the maximum sagittal height of the object side surface of the seventh lens, CT7 is the thickness of the seventh lens on the optical axis, and SAG72 is the maximum sagittal height of the image side surface of the seventh lens.

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

0.2＜n12/R12≤0.4；

wherein n12 is a refractive index of the first lens for light with a wavelength of 546nm, and R12 is a curvature radius of an image side surface of the first lens at an optical axis.

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

(ET1+ET2+ET3)/(CT1+CT2+CT3)＜1；

wherein ET1 is a thickness of an optically effective area edge of the first lens element, ET2 is a thickness of an optically effective area edge of the second lens element, ET3 is a thickness of an optically effective area edge of the third lens element, CT1 is a thickness of the first lens element on an optical axis, CT2 is a thickness of the second lens element on the optical axis, and CT3 is a thickness of the third lens element on the optical axis.

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

1.75≤|f45/f3|＜41；

wherein f45 is the combined effective focal length of the fourth lens and the fifth lens, and f3 is the effective focal length of the third lens.

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

|f6/R61|＜22；

wherein f6 is an effective focal length of the sixth lens, and R61 is a radius of curvature of an object-side surface of the sixth lens at an optical axis.

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

70°≤FOV≤85°；

wherein the FOV is the maximum field angle of the optical system in the diagonal direction.

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

0.8＜f13/f＜1.1；

wherein f13 is a combined effective focal length of the first lens, the second lens, and the third lens, and f is an effective focal length of the optical system.

13. A lens module comprising a lens barrel, an electron-sensitive element, and the optical system according to any one of claims 1 to 12, wherein the first to seventh lenses of the optical system are mounted in the lens barrel, and the electron-sensitive element is disposed on an image side of the optical system.

14. An electronic device comprising a housing and the lens module as recited in claim 13, wherein the lens module is disposed in the housing.