CN114815167A

CN114815167A - Optical system, camera module and electronic equipment

Info

Publication number: CN114815167A
Application number: CN202210587094.1A
Authority: CN
Inventors: 杨健; 华露
Original assignee: Jiangxi Jingchao Optical Co Ltd
Current assignee: Jiangxi Jingchao Optical Co Ltd
Priority date: 2022-05-27
Filing date: 2022-05-27
Publication date: 2022-07-29
Anticipated expiration: 2042-05-27
Also published as: CN114815167B

Abstract

An optical system, a camera module and an electronic device, the optical system sequentially comprises from an object side to an image side along an optical axis: the first lens element, the fifth lens element and the seventh lens element with refractive power have negative refractive power, and the fourth lens element and the sixth lens element with positive refractive power have positive refractive power, wherein an object-side surface of the first lens element, an image-side surface of the second lens element, an image-side surface of the third lens element, an object-side surface of the fifth lens element and an image-side surface of the seventh lens element are concave at a paraxial region, and the object-side surface of the first lens element, the object-side surface of the second lens element, the object-side surface of the third lens element, the object-side surface and the image-side surface of the fourth lens element, the image-side surface of the sixth lens element and the object-side surface of the seventh lens element are convex at a paraxial region. By reasonably designing the surface shape and the refractive power of each lens of the optical system, the optical system is favorable for meeting the characteristics of larger field angle, large aperture, small distortion and miniaturization.

Description

Optical system, camera module and electronic equipment

Technical Field

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

Background

In recent years, with the rise of portable electronic products having a photographing function, there has been a demand for higher quality and diversity of lens imaging, such as a larger angle of view, smaller image distortion, and a sufficient amount of light entering even in a dark environment. However, the improvement of the imaging quality usually means that the structure of the optical system is more complicated, which eventually leads to the increase of the size and the overall length of the lens, and is difficult to be applied to the light and thin electronic products.

Therefore, how to optimize the imaging quality and satisfy the requirements of large aperture, small distortion and miniaturization on the premise of ensuring that the optical system has a larger field angle becomes one of the problems to be solved in the industry.

Disclosure of Invention

The invention aims to provide an optical system, a camera module and electronic equipment, which solve the problems that the optical system in the prior art needs to meet the requirements of large aperture, small distortion and miniaturization on the premise of having a larger field angle.

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, comprising seven lens elements with refractive power along an optical axis, in order from an object side to an image side: the first lens element with negative refractive power has a concave object-side surface at an optical axis and a convex image-side surface at a paraxial region; a second lens element with 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 refractive power having a convex object-side surface at a paraxial region and a concave image-side surface at a paraxial region; a fourth lens element with positive refractive power having convex object-side and image-side surfaces at paraxial region; a fifth lens element with negative refractive power having a concave object-side surface at paraxial region; a sixth lens element with positive refractive power having a convex image-side surface at a paraxial region; a seventh lens element with negative refractive power having a convex object-side surface at a paraxial region and a concave image-side surface at a paraxial region; the object side surface and the image side surface of the sixth lens and the seventh lens respectively comprise at least one point of inflexion.

The optical system satisfies the relation: 110 deg < FOV <121 deg, and/or 1.6< f/EPD < 2.1; wherein FOV is the maximum field angle of the optical system, f is the focal length of the optical system, and EPD is the entrance pupil diameter of the optical system.

The first lens element with negative refractive power can increase the incident angle of light and enlarge the field angle of the optical system, the object-side surface of the first lens element is concave at the paraxial region, and the image-side surface of the first lens element is convex at the paraxial region, thereby enhancing the negative refractive power of the first lens element, preventing the object-side surface of the first lens element from being excessively curved, and reducing spherical aberration and chromatic aberration; the second lens element with refractive power has a convex object-side surface at a paraxial region and a concave image-side surface at a paraxial region, so that marginal light deflection is facilitated, workload of subsequent lens elements can be reduced, deflection angles of light on the lens elements are uniform, and aberration of marginal field of view is effectively corrected; the object-side surface of the third lens element is convex at the paraxial region thereof, and the image-side surface of the third lens element is concave at the paraxial region thereof, so that a reasonable incident angle can be provided for marginal rays; the fourth lens element with positive refractive power has convex object-side and image-side surfaces at paraxial region, which is favorable for reducing chief ray incidence angle of light on the surface of the fourth lens element and improving transmissivity; the fifth lens element with negative refractive power has a concave object-side surface at paraxial region, so that spherical aberration, coma aberration and distortion can be corrected; the sixth lens element with positive refractive power has a convex image-side surface at a paraxial region, which is beneficial for shortening the total length of the optical system and correcting aberration; the seventh lens element with negative refractive power has a convex object-side surface at a paraxial region and a concave image-side surface at a paraxial region, so that the aberration, astigmatism and field curvature can be corrected, and the requirements for low aberration and high image quality can be met. Therefore, satisfying the above surface shape is advantageous for the optical system to achieve the effects of a large angle of view, a large aperture, miniaturization, and small distortion.

Through making optical system satisfy above-mentioned relational expression, be favorable to optical system to satisfy the effect of big angle of vision, optical system possesses great aperture and higher light flux volume, and then increases optical system imaging effect under dim environment, simultaneously, still is favorable to reducing the aberration of marginal field of vision, guarantees that marginal field of vision has sufficient relative luminance, avoids appearing the vignetting.

In one embodiment, the optical system satisfies the relationship: 4mm < SD11/tan (hfov) <4.5 mm; wherein SD11 is a half of the maximum effective aperture of the object-side surface of the first lens, HFOV is a half of the maximum angle of view of the optical system, and tan (HFOV) is a tangent value of the half angle of view of the optical system. By enabling the optical system to satisfy the relational expression, the ratio of half of the maximum effective aperture of the object-side surface of the first lens to the tangent value of the half field angle of the optical system is reasonably configured, the aperture of the first lens is effectively reduced, the size and occupied volume of the optical system are further reduced, the requirement of miniaturization of the optical system is met, and meanwhile, the optical system further has a larger field angle and increases the shooting range. Exceeding the upper limit of the relational expression, on the premise of having the same field angle, the aperture of the first lens is too large, and the aperture of the first lens becomes a main factor restricting the whole volume of the optical system, which is not favorable for meeting the requirement of miniaturization of the optical system, and is also unfavorable for the structural arrangement of each lens in the optical system, and increases the risk of ghost image.

In one embodiment, the optical system satisfies the relationship: 0.9< f123/f1< 1.5; wherein f123 is a combined focal length of the first lens, the second lens, and the third lens, and f1 is a focal length of the first lens. By enabling the optical system to satisfy the relational expression, the refractive powers of the first lens element, the second lens element and the third lens element are favorably and reasonably distributed, so that sufficient negative refractive power is provided for the optical system, the characteristics of large field angle and small distortion of the optical system are realized, meanwhile, the total length of the optical system is favorably shortened, the processability of each lens element is improved, and the molding difficulty of the lens elements is reduced.

In one embodiment, the optical system satisfies the relationship: 1.5< f45/f < 2.5; wherein f45 is a combined focal length of the fourth lens and the fifth lens, and f is a focal length of the optical system. By enabling the optical system to satisfy the relational expression, the refractive power of the fourth lens and the refractive power of the fifth lens are favorably and reasonably distributed, the total length of the fourth lens and the total length of the fifth lens are further shortened, the aberration generated by the lenses in front of and behind the fourth lens and the fifth lens is balanced, the characteristics of large aperture, large field angle and high imaging quality are realized, meanwhile, the deflection angle of marginal field rays is favorably reduced, the sensitivity is reduced, the aberration balance is promoted, and the imaging quality is improved.

In one embodiment, the optical system satisfies the relationship: 1< R32/R41< 2.8; wherein R32 is a curvature radius of an image side surface of the third lens at an optical axis, and R41 is a curvature radius of an object side surface of the fourth lens at the optical axis. By making the optical system satisfy the above relational expression, it is advantageous that the image-side surface of the third lens element and the object-side surface of the fourth lens element have sufficient degrees of freedom in bending, and aberrations such as astigmatism and curvature of field of the optical system are corrected more favorably. Below the lower limit of the relational expression, the object side surface of the third lens is too curved, which is not beneficial to the processing and molding of the lens; beyond the upper limit of the relation, the curvature of the object-side surface of the third lens is insufficient, which is disadvantageous for aberration correction.

In one embodiment, the optical system satisfies the relationship: 1.5< R51/R42< 3; wherein R51 is a curvature radius of an object side surface of the fifth lens element at an optical axis, and R42 is a curvature radius of an image side surface of the fourth lens element at the optical axis. By enabling the optical system to satisfy the relational expression, the ratio of the curvature radius of the object side surface of the fifth lens at the optical axis to the curvature radius of the image side surface of the fourth lens at the optical axis is favorably and reasonably configured, so that the marginal field light obtains a reasonable deflection angle, the aberration of the optical system is favorably corrected, the imaging quality is improved, and meanwhile, the machinability of the fourth lens and the fifth lens can be ensured. Below the lower limit of the relational expression, the object side surface of the fifth lens is too curved, which is not beneficial to the processing and molding of the lens; exceeding the upper limit of the relational expression, the curvature of the object-side surface of the fifth lens is insufficient, which is disadvantageous for correction of aberration.

In one embodiment, the optical system satisfies the relationship: 1< CT14/(SD11-SD41) < 1.1; the CT14 is a distance on an optical axis from an object-side surface of the first lens element to an object-side surface of the fourth lens element, the SD11 is a half of a maximum effective aperture of the object-side surface of the first lens element, and the SD41 is a half of a maximum effective aperture of the object-side surface of the fourth lens element. By enabling the optical system to satisfy the relational expression, the distance between the object side surface of the first lens and the object side surface of the fourth lens on the optical axis and the ratio of the difference value between half of the maximum effective aperture of the object side surface of the first lens and half of the maximum effective aperture of the object side surface of the fourth lens are favorably and reasonably constrained, and then the first lens and the fourth lens have reasonable section difference, so that the overlarge deflection angle of light is avoided, the risk of ghost image stray light is reduced, meanwhile, the optical system is favorably ensured to obtain a larger field angle on the premise of having a larger incident aperture, the processing manufacturability of the optical system is ensured, and the assembly difficulty of the optical system is reduced. Below the lower limit of the relational expression, the segment difference between the first lens and the fourth lens is too large, which easily causes the too large deflection angle of light, increases the risks of stray light and ghost images, and also increases the assembly difficulty of each lens in the optical system; exceeding the relational upper limit is detrimental to increasing the entrance pupil diameter and the field angle.

In one embodiment, the optical system satisfies the relationship: -35< SAG62/SAG71< -2; SAG62 is the rise of the sixth lens from the effective aperture of the image side surface, i.e. the distance from the intersection point of the image side surface of the sixth lens and the optical axis to the maximum effective aperture of the image side surface of the sixth lens in the optical axis direction, and SAG71 is the rise of the seventh lens from the effective aperture of the object side surface, i.e. the distance from the intersection point of the object side surface of the seventh lens and the optical axis to the maximum effective aperture of the object side surface of the seventh lens in the optical axis direction. By enabling the optical system to satisfy the relational expression, the shapes of the image side surface of the sixth lens and the object side surface of the seventh lens are favorably and reasonably controlled, the surfaces of the lenses of the sixth lens and the seventh lens are prevented from being too curved, the forming difficulty of the lenses is increased, meanwhile, the aberration is favorably corrected, and the deflection angle of marginal rays is controlled within a reasonable range. Below the lower limit of the relational expression, the curvature difference between the image-side surface of the sixth lens and the object-side surface of the seventh lens is large, which is not favorable for the image-side surface of the sixth lens and the object-side surface of the seventh lens to cooperate and correct aberration; beyond the upper limit of the relation, the object side surface of the seventh lens is over-bent, which is not beneficial to the processing and molding of the seventh lens.

In one embodiment, the optical system satisfies the relationship: 0.5< (SAG61-SAG52)/CT56< 1; SAG61 is the rise of the effective aperture of the object side surface of the sixth lens, namely the distance from the intersection point of the object side surface of the sixth lens and the optical axis to the maximum effective aperture of the object side surface of the sixth lens in the optical axis direction, SAG52 is the rise of the effective aperture of the image side surface of the fifth lens, namely the distance from the intersection point of the image side surface of the fifth lens and the optical axis to the maximum effective aperture of the image side surface of the fifth lens in the optical axis direction, and CT56 is the distance from the image side surface of the fifth lens to the object side surface of the sixth lens in the optical axis direction. By enabling the optical system to meet the relational expression, the rise of the object side surface of the sixth lens and the rise of the image side surface of the fifth lens are favorably controlled, the shapes of the image side surface of the sixth lens and the object side surface of the seventh lens are reasonably controlled, the processing manufacturability of the fifth lens and the sixth lens is ensured, meanwhile, the edge field light rays are favorably provided with small deflection angles, and the edge field of an imaging surface is ensured to have enough relative brightness.

In one embodiment, the optical system satisfies the relationship: 8< (R21+ R12)/CT12< 62; wherein R21 is a radius of curvature of the object-side surface of the second lens element on the optical axis, R12 is a radius of curvature of the image-side surface of the first lens element on the optical axis, and CT12 is a distance from the image-side surface of the first lens element to the object-side surface of the second lens element on the optical axis. By enabling the optical system to satisfy the relational expression, the ratio of the curvature radius of the object side surface of the second lens at the optical axis and the curvature radius of the image side surface of the first lens at the optical axis to the distance from the image side surface of the first lens to the object side surface of the second lens on the optical axis is reasonably configured, light can smoothly transit from the first lens to the second lens, the optical system can obtain a larger field angle, and meanwhile, the reasonable distance between the first lens and the second lens can not only reduce the risk of parasitic ghost image, but also reduce the assembling difficulty of the lens.

In one embodiment, the optical system satisfies the relationship: 4.4< TTL/CT67< 4.8; wherein, TTL is an axial distance from an object-side surface of the first lens element to an image plane, and CT67 is an axial distance from an object-side surface of the sixth lens element to an object-side surface of the seventh lens element. By enabling the optical system to satisfy the above relational expression, the ratio of the distance from the object side surface of the first lens to the imaging surface on the optical axis to the distance from the object side surface of the sixth lens to the object side surface of the seventh lens on the optical axis is reasonably configured, the total length of the optical system is reduced, the miniaturization characteristic of the optical system is realized, and meanwhile, the uniform distribution of the quality of the lens is facilitated, and the stability of the lens is improved.

In a second aspect, the present invention further provides a camera module, which includes a photosensitive chip and the optical system according to any one of the embodiments of the first aspect, wherein the photosensitive chip is disposed on an image side of the optical system. The light sensing surface of the light sensing chip is positioned on the imaging surface of the optical system, and light rays which penetrate through the lens and enter an object on the light sensing surface can be converted into electric signals of images. The photosensitive chip may be a Complementary Metal Oxide Semiconductor (CMOS) or a Charge-coupled Device (CCD). The camera module can be an imaging module integrated on the electronic equipment and can also be an independent lens. By adding the optical system provided by the invention into the camera module, the camera module has the characteristics of larger field angle, large aperture, small distortion and miniaturization by reasonably designing the surface shape and the refractive power of each lens in the optical system.

In a third aspect, the present invention further provides an electronic device, which includes a housing and the camera module set in the second aspect, where the camera module set is disposed in the housing. The electronic device includes but is not limited to a smart phone, a computer, a smart watch, and the like. By adding the camera module provided by the invention into the electronic equipment, the electronic equipment has the characteristics of larger field angle, large aperture, small distortion and miniaturization.

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

FIG. 2 is a partial schematic view of the optical system shown in FIG. 1;

fig. 3 shows a longitudinal spherical aberration curve, an astigmatism curve and a distortion curve of the first embodiment;

FIG. 4 is a schematic structural view of an optical system of a second embodiment;

FIG. 5 shows a longitudinal spherical aberration curve, an astigmatism curve and a distortion curve of the second embodiment;

fig. 6 is a schematic structural view of an optical system of a third embodiment;

fig. 7 shows a longitudinal spherical aberration curve, an astigmatism curve and a distortion curve of the third embodiment;

fig. 8 is a schematic structural view of an optical system of a fourth embodiment;

fig. 9 shows a longitudinal spherical aberration curve, an astigmatism curve and a distortion curve of the fourth embodiment;

fig. 10 is a schematic configuration diagram of an optical system of the fifth embodiment;

fig. 11 shows a longitudinal spherical aberration curve, an astigmatism curve, and a distortion curve of the fifth 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.

In a first aspect, the present invention provides an optical system, comprising seven lens elements with refractive power along an optical axis, in order from an object side to an image side: the first lens element with negative refractive power has a concave object-side surface at an optical axis and a convex image-side surface at a paraxial region; a second lens element with refractive power having a convex object-side surface and a concave image-side surface; a third lens element with refractive power having a convex object-side surface and a concave image-side surface; the fourth lens element with positive refractive power has a convex object-side surface and a convex image-side surface at paraxial region; a fifth lens element with negative refractive power having a concave object-side surface at paraxial region; the sixth lens element with positive refractive power has a convex image-side surface at paraxial region; a seventh lens element with negative refractive power having a convex object-side surface and a concave image-side surface; the object side surface and the image side surface of the sixth lens and the seventh lens respectively comprise at least one point of inflection.

The optical system satisfies the relation: 110 deg < FOV <121 deg, and/or 1.6< f/EPD < 2.1; where FOV is the maximum field angle of the optical system, f is the focal length of the optical system, and EPD is the entrance pupil diameter of the optical system.

The first lens element with negative refractive power can increase the incident angle of light and enlarge the field angle of the optical system, the object-side surface of the first lens element is concave at the paraxial region, and the image-side surface of the first lens element is convex at the paraxial region, thereby enhancing the negative refractive power of the first lens element, preventing the object-side surface of the first lens element from being excessively curved, and reducing spherical aberration and chromatic aberration; the second lens element with refractive power has a convex object-side surface at a paraxial region and a concave image-side surface at a paraxial region, so that marginal light deflection is facilitated, workload of subsequent lens elements can be reduced, deflection angles of light on the lens elements are uniform, and aberration of marginal field of view is effectively corrected; the object side surface of the third lens is convex at a paraxial region, and the image side surface of the third lens is concave at a paraxial region, so that a reasonable incident angle can be provided for marginal rays; the fourth lens element with positive refractive power has convex object-side and image-side surfaces at paraxial region, which is favorable for reducing chief ray incidence angle of light on the surface of the fourth lens element and improving transmissivity; the fifth lens element with negative refractive power has a concave object-side surface at a paraxial region, thereby facilitating correction of spherical aberration, coma aberration and distortion; the sixth lens element with positive refractive power has a convex image-side surface at a paraxial region, which is beneficial for shortening the total length of the optical system and correcting aberration; the seventh lens element with negative refractive power has a convex object-side surface at a paraxial region and a concave image-side surface at a paraxial region, so that the aberration, astigmatism and field curvature can be corrected, and the requirements for low aberration and high image quality can be met. Therefore, satisfying the above surface shape is advantageous for the optical system to achieve the effects of a large angle of view, a large aperture, miniaturization, and small distortion.

Through making optical system satisfy above-mentioned relational expression, be favorable to optical system to satisfy the effect of big angle of vision, optical system possesses great aperture and higher light flux, and then increases optical system imaging under dim environment, simultaneously, still is favorable to reducing the aberration of marginal field of vision, guarantees that marginal field of vision has sufficient relative brightness, avoids appearing the vignetting.

In one embodiment, the optical system satisfies the relationship: 4mm < SD11/tan (hfov) <4.5 mm; where SD11 is half of the maximum effective aperture of the object-side surface of the first lens, HFOV is half of the maximum angle of view of the optical system, and tan (HFOV) is the tangent of the half angle of view of the optical system. By enabling the optical system to satisfy the relational expression, the ratio of half of the maximum effective aperture of the object-side surface of the first lens to the tangent value of the half field angle of the optical system is reasonably configured, the aperture of the first lens is effectively reduced, the size and occupied volume of the optical system are further reduced, the requirement of miniaturization of the optical system is met, and meanwhile, the optical system further has a larger field angle and increases the shooting range. Exceeding the upper limit of the relational expression, on the premise of having the same field angle, the aperture of the first lens is too large, and the aperture of the first lens becomes a main factor restricting the whole volume of the optical system, which is not favorable for meeting the requirement of miniaturization of the optical system, and is also unfavorable for the structural arrangement of each lens in the optical system, and increases the risk of ghost image.

In one embodiment, the optical system satisfies the relationship: 0.9< f123/f1< 1.5; where f123 is a combined focal length of the first lens, the second lens, and the third lens, and f1 is a focal length of the first lens. By enabling the optical system to satisfy the relational expression, the refractive powers of the first lens element, the second lens element and the third lens element are favorably and reasonably distributed, so that sufficient negative refractive power is provided for the optical system, the characteristics of large field angle and small distortion of the optical system are realized, meanwhile, the total length of the optical system is favorably shortened, the processability of each lens element is improved, and the molding difficulty of the lens elements is reduced.

In one embodiment, the optical system satisfies the relationship: 1.5< f45/f < 2.5; where f45 is the combined focal length of the fourth lens and the fifth lens, and f is the focal length of the optical system. By enabling the optical system to satisfy the relational expression, the refractive power of the fourth lens and the refractive power of the fifth lens are favorably and reasonably distributed, the total length of the fourth lens and the total length of the fifth lens are further shortened, the aberration generated by the lenses in front of and behind the fourth lens and the fifth lens is balanced, the characteristics of large aperture, large field angle and high imaging quality are realized, meanwhile, the deflection angle of marginal field rays is favorably reduced, the sensitivity is reduced, the aberration balance is promoted, and the imaging quality is improved.

In one embodiment, the optical system satisfies the relationship: 1< R32/R41< 2.8; wherein, R32 is a curvature radius of the image-side surface of the third lens element at the optical axis, and R41 is a curvature radius of the object-side surface of the fourth lens element at the optical axis. By making the optical system satisfy the above relational expression, it is advantageous that the image-side surface of the third lens element and the object-side surface of the fourth lens element have sufficient degrees of freedom in bending, and aberrations such as astigmatism and curvature of field of the optical system are corrected more favorably. Below the lower limit of the relational expression, the object side surface of the third lens is too curved, which is not beneficial to the processing and molding of the lens; beyond the upper limit of the relation, the curvature of the object-side surface of the third lens is insufficient, which is disadvantageous for aberration correction.

In one embodiment, the optical system satisfies the relationship: 1.5< R51/R42< 3; wherein, R51 is a curvature radius of an object side surface of the fifth lens element at the optical axis, and R42 is a curvature radius of an image side surface of the fourth lens element at the optical axis. By enabling the optical system to satisfy the relational expression, the ratio of the curvature radius of the object side surface of the fifth lens at the optical axis to the curvature radius of the image side surface of the fourth lens at the optical axis is reasonably configured, so that the marginal field rays can obtain a reasonable deflection angle, the aberration of the optical system can be corrected, the imaging quality can be improved, and meanwhile, the machinability of the fourth lens and the fifth lens can be ensured. Below the lower limit of the relational expression, the object side surface of the fifth lens is too curved, which is not beneficial to the processing and molding of the lens; exceeding the upper limit of the relational expression, the curvature of the object-side surface of the fifth lens is insufficient, which is disadvantageous for correction of aberration.

In one embodiment, the optical system satisfies the relationship: 1< CT14/(SD11-SD41) < 1.1; the CT14 is a distance on the optical axis from the object-side surface of the first lens element to the object-side surface of the fourth lens element, the SD11 is a half of the maximum effective aperture of the object-side surface of the first lens element, and the SD41 is a half of the maximum effective aperture of the object-side surface of the fourth lens element. By enabling the optical system to satisfy the relational expression, the distance between the object side surface of the first lens and the object side surface of the fourth lens on the optical axis and the ratio of the difference value between half of the maximum effective aperture of the object side surface of the first lens and half of the maximum effective aperture of the object side surface of the fourth lens are favorably and reasonably constrained, and then the first lens and the fourth lens have reasonable section difference, so that the overlarge deflection angle of light is avoided, the risk of ghost image stray light is reduced, meanwhile, the optical system is favorably ensured to obtain a larger field angle on the premise of having a larger incident aperture, the processing manufacturability of the optical system is ensured, and the assembly difficulty of the optical system is reduced. Below the lower limit of the relational expression, the segment difference between the first lens and the fourth lens is too large, which easily causes the too large deflection angle of light, increases the risks of stray light and ghost images, and also increases the assembly difficulty of each lens in the optical system; exceeding the relational upper limit is detrimental to increasing the entrance pupil diameter and the field angle.

In one embodiment, the optical system satisfies the relationship: -35< SAG62/SAG71< -2; SAG62 is the rise of the effective aperture of the image-side surface of the sixth lens, i.e. the distance from the intersection point of the image-side surface of the sixth lens and the optical axis to the maximum effective aperture of the image-side surface of the sixth lens in the optical axis direction, and SAG71 is the rise of the effective aperture of the object-side surface of the seventh lens, i.e. the distance from the intersection point of the object-side surface of the seventh lens and the optical axis to the maximum effective aperture of the object-side surface of the seventh lens in the optical axis direction. By enabling the optical system to satisfy the relational expression, the shapes of the image side surface of the sixth lens and the object side surface of the seventh lens are favorably and reasonably controlled, the surfaces of the lenses of the sixth lens and the seventh lens are prevented from being too curved, the forming difficulty of the lenses is increased, meanwhile, the aberration is favorably corrected, and the deflection angle of marginal rays is controlled within a reasonable range. Below the lower limit of the relational expression, the curvature difference between the image-side surface of the sixth lens and the object-side surface of the seventh lens is large, which is not favorable for the image-side surface of the sixth lens and the object-side surface of the seventh lens to cooperate and correct aberration; beyond the upper limit of the relation, the object side surface of the seventh lens is over-bent, which is not beneficial to the processing and molding of the seventh lens.

In one embodiment, the optical system satisfies the relationship: 8< (R21+ R12)/CT12< 62; wherein R21 is a radius of curvature of the object-side surface of the second lens element at the optical axis, R12 is a radius of curvature of the image-side surface of the first lens element at the optical axis, and CT12 is a distance from the image-side surface of the first lens element to the object-side surface of the second lens element at the optical axis. By enabling the optical system to satisfy the relational expression, the ratio of the curvature radius of the object side surface of the second lens at the optical axis and the curvature radius of the image side surface of the first lens at the optical axis to the distance from the image side surface of the first lens to the object side surface of the second lens on the optical axis is reasonably configured, light can smoothly transit from the first lens to the second lens, the optical system can obtain a larger field angle, and meanwhile, the reasonable distance between the first lens and the second lens can not only reduce the risk of parasitic ghost image, but also reduce the assembling difficulty of the lens.

In one embodiment, the optical system satisfies the relationship: 3< | SLO62/SLO71| < 4; wherein SLO62 is the maximum inclination angle of the image-side surface of the sixth lens, and SLO71 is the maximum inclination angle of the object-side surface of the seventh lens. Fig. 2 shows the maximum inclination angles of the image-side surface of the sixth lens and the object-side surface of the seventh lens, SLO62 is the maximum angle between the tangent to the image-side surface of the sixth lens and a line perpendicular to the optical axis, and SLO71 is the maximum angle between the tangent to the object-side surface of the seventh lens and a line perpendicular to the optical axis. By enabling the optical system to satisfy the relational expression, the ratio of the maximum inclination angle of the image side surface of the sixth lens to the maximum inclination angle of the object side surface of the seventh lens is favorably and reasonably configured, and the bending degrees of the image side surface of the sixth lens and the object side surface of the seventh lens are restrained so as to enable the image side surface of the sixth lens and the object side surface of the seventh lens to be matched with each other, so that the aberration generated by the first lens to the fifth lens in front of the sixth lens can be jointly corrected, and the integral aberration balance of the optical system can be realized. Below the lower limit of the relation, the ratio of the maximum inclination angle of the image-side surface of the sixth lens element to the maximum inclination angle of the object-side surface of the seventh lens element is too small to facilitate the sixth lens element and the seventh lens element to cooperate with each other to correct the aberration of the optical system; if the maximum inclination angle of the image-side surface of the sixth lens element is too large, the image-side surface of the sixth lens element is too curved, which is disadvantageous to the lens forming process and increases the sensitivity of the optical system.

In one embodiment, the optical system satisfies the relationship: 4.4< TTL/CT67< 4.8; wherein, TTL is an axial distance from an object-side surface of the first lens element to an image plane, and CT67 is an axial distance from an object-side surface of the sixth lens element to an object-side surface of the seventh lens element. By enabling the optical system to satisfy the above relational expression, the ratio of the distance from the object side surface of the first lens to the imaging surface on the optical axis to the distance from the object side surface of the sixth lens to the object side surface of the seventh lens on the optical axis is reasonably configured, the total length of the optical system is reduced, the miniaturization characteristic of the optical system is realized, meanwhile, the uniform distribution of the quality of the lens is facilitated, and the stability of the lens is improved.

First embodiment

Referring to fig. 1 and fig. 3, the optical system of the present embodiment, in order from an object side to an image side along an optical axis direction, includes:

the first lens element L1 with negative refractive power has a concave object-side surface S1 at a paraxial region and a convex image-side surface S2 at a paraxial region of the first lens element L1.

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

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

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

The fifth lens element L5 with negative refractive power has a concave object-side surface S9 at a paraxial region and a concave image-side surface S10 at a paraxial region of the fifth lens element L5.

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

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

Further, the optical system includes a stop STO, an infrared cut filter IR, and an imaging surface IMG. In this embodiment, the stop STO is provided on the object side surface side of the fourth lens of the optical system for controlling the amount of light entering. The infrared cut filter IR is disposed between the seventh lens L7 and the imaging surface IMG, and includes an object side surface S15 and an image side surface S16, and is configured to filter infrared light, so that the light incident on the imaging surface IMG is only visible light, and the wavelength of the visible light is 380nm to 780 nm. The material of the infrared cut filter IR is GLASS (GLASS), and the GLASS can be coated with a film. The first lens L1 to the seventh lens L7 are made of Plastic (Plastic). The effective pixel area of the electronic photosensitive element is positioned on the imaging surface IMG.

Table 1a shows parameters of the optical system of the present embodiment, in which the Y radius is a curvature radius of the object-side surface or the image-side surface of the corresponding surface number at the optical axis. Surface numbers S1 and S2 denote an object-side surface S1 and an image-side surface S2 of the first lens L1, respectively, that is, in the same lens, a surface with a smaller surface number is an object-side surface, and a surface with a larger surface number is an image-side surface. The first numerical value in the "thickness" parameter column of the first lens element L1 is the axial thickness of the lens element, and the second numerical value is the axial distance from the image-side surface to the rear surface of the lens element in the image-side direction. The focal length, refractive index of the material and abbe number are all obtained by using visible light with reference wavelength of 587.6nm, and the unit of Y radius, thickness and focal length is millimeter (mm).

TABLE 1a

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

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

wherein x is the distance from the corresponding point on the aspheric surface to the plane tangent to the surface vertex, h is the distance from the corresponding point on the aspheric surface to the optical axis, c is the curvature of the aspheric surface vertex, k is the conic coefficient, and Ai is the coefficient corresponding to the i-th high-order term in the aspheric surface type formula. Table 1b shows the high-order term coefficients a4, A6, A8, a10, a12, a14, a16, a18, a20, a22, a24, a26, a28, and a30 of the aspherical mirrors S1, S2, S3, S4, S5, S6, S7, S8, S9, S10, S11, S12, S13, and S14 that can be used in the first embodiment.

TABLE 1b

Fig. 3 (a) shows a longitudinal spherical aberration curve of the optical system of the first embodiment at wavelengths of 650.0000nm, 610.0000nm, 555.0000nm, 510.0000nm, 470.0000nm and 435.0000nm, in which the abscissa in the X-axis direction represents the focus shift, i.e., the distance (in mm) from the image plane to the intersection of the light rays and the optical axis, the ordinate in the Y-axis direction represents the normalized field of view, and the longitudinal spherical aberration curve represents the convergent focus shift of the light rays of different wavelengths after passing through the lenses of the optical system. As can be seen from fig. 3 (a), the convergent focus deviation degrees of the light rays with different wavelengths in the first embodiment tend to be consistent, and the diffuse speckle or the chromatic halo in the imaging picture is effectively suppressed in the optical system, which shows that the imaging quality of the optical system in the present embodiment is better.

Fig. 3 (b) also shows an astigmatism graph of the optical system of the first embodiment at a wavelength of 555.0000nm, in which the abscissa in the X-axis direction represents the focus shift and the ordinate in the Y-axis direction represents the image height in mm. The S curve in the astigmatism plot represents the sagittal field curvature at 555.0000nm, and the T curve represents the meridional field curvature at 555.0000 nm. As can be seen from (b) in fig. 3, the curvature of field of the optical system is small, the curvature of field and astigmatism of each field are well corrected, and the center and the edge of the field have clear images.

Fig. 3 (c) also shows a distortion curve of the optical system of the first embodiment at a wavelength of 555.0000 nm. Wherein the abscissa in the X-axis direction represents a distortion value in units, and the ordinate in the Y-axis direction represents an image height in units of mm. The distortion curve represents the distortion magnitude values corresponding to different angles of view. As can be seen from (c) of fig. 3, at a wavelength of 555.0000nm, the image distortion caused by the main beam is small, and the imaging quality of the system is excellent.

As can be seen from (a), (b), and (c) in fig. 3, the optical system of the present embodiment has small aberration, good imaging quality, and good imaging quality.

Second embodiment

Referring to fig. 4 and 5, 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 positive refractive power has a convex object-side surface S3 at a paraxial region and a concave image-side surface S4 at a paraxial region of the second lens element L2.

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

Table 2a shows parameters of the optical system of the present embodiment, in which the focal length, the refractive index of the material, and the abbe number are obtained using visible light having a reference wavelength of 587.6nm, and the units of the Y radius, the thickness, and the focal length are millimeters (mm), and other parameters have the same meanings as those of the first embodiment.

TABLE 2a

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. 5 shows a longitudinal spherical aberration curve, an astigmatism curve and a distortion curve of the optical system of the second embodiment, wherein the longitudinal spherical aberration curve represents the convergent focus deviations of light rays of different wavelengths after passing through the lenses of the optical system; the astigmatism curves represent the meridian field curvature and the sagittal field curvature; the distortion curve represents the distortion magnitude values corresponding to different angles of view. As can be seen from the aberration diagram in fig. 5, the longitudinal spherical aberration, curvature of field, and distortion of the optical system are well controlled, so that the optical system of this embodiment has good imaging quality.

Third embodiment

Referring to fig. 6 and 7, 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 negative refractive power has a convex object-side surface S5 at a paraxial region and a concave image-side surface S6 at a paraxial region of the third lens element L3.

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

Table 3a shows parameters of the optical system of the present embodiment, in which the focal length, the refractive index of the material, and the abbe number are obtained using visible light having a reference wavelength of 587.6nm, and the units of the Y radius, the thickness, and the focal length are millimeters (mm), and other parameters have the same meanings as those of the first embodiment.

TABLE 3a

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

TABLE 3b

FIG. 7 shows a longitudinal spherical aberration curve, an astigmatism curve and a distortion curve of the optical system of the third embodiment, wherein the longitudinal spherical aberration curves represent the convergent focus deviations of light rays of different wavelengths after passing through the lenses of the optical system; the astigmatism curves represent the meridian field curvature and the sagittal field curvature; the distortion curve represents the distortion magnitude values corresponding to different angles of view. As can be seen from the aberration diagrams in fig. 7, the longitudinal spherical aberration, curvature of field, and distortion of the optical system are well controlled, so that the optical system of this embodiment has good imaging quality.

Fourth embodiment

Referring to fig. 8 and 9, 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 at a paraxial region and a convex image-side surface S10 at a paraxial region of the fifth lens element L5.

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

Table 4a shows parameters of the optical system of the present embodiment, in which the focal length, the refractive index of the material, and the abbe number are obtained using visible light having a reference wavelength of 587.6nm, and the units of the Y radius, the thickness, and the focal length are millimeters (mm), and other parameters have the same meanings as those of the first embodiment.

TABLE 4a

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. 9 shows a longitudinal spherical aberration curve, an astigmatism curve and a distortion curve of the optical system of the fourth embodiment, wherein the longitudinal spherical aberration curve represents the convergent focus deviations of light rays of different wavelengths after passing through the lenses of the optical system; the astigmatism curves represent the meridian field curvature and the sagittal field curvature; the distortion curve represents the distortion magnitude values corresponding to different angles of view. As can be seen from the aberration diagrams in fig. 9, the longitudinal spherical aberration, curvature of field, and distortion of the optical system are well controlled, so that the optical system of this embodiment has good imaging quality.

Fifth embodiment

Referring to fig. 10 and 11, 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 fifth embodiment is the same as that of the first embodiment, and reference may be made thereto.

Table 5a shows parameters of the optical system of the present embodiment, in which the focal length, the refractive index of the material, and the abbe number are obtained using visible light having a reference wavelength of 587.6nm, and the units of the Y radius, the thickness, and the focal length are millimeters (mm), and other parameters have the same meanings as those of the first embodiment.

TABLE 5a

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. 11 shows a longitudinal spherical aberration curve, an astigmatism curve and a distortion curve of the optical system of the fifth embodiment, wherein the longitudinal spherical aberration curves represent the convergent focus deviations of light rays of different wavelengths after passing through the lenses of the optical system; the astigmatism curves represent the meridian field curvature and the sagittal field curvature; the distortion curve represents the distortion magnitude values corresponding to different angles of view. As can be seen from the aberration diagrams in fig. 11, the longitudinal spherical aberration, curvature of field, and distortion of the optical system are well controlled, so that the optical system of this embodiment has good imaging quality. And the distortion of the optical systems of the first to fifth embodiments is within plus or minus 2%.

Table 6 shows values of SD11/tan (hfov), f/EPD, f123/f1, f45/f, R32/R41, R51/R42, CT14/(SD11-SD41), SAG62/SAG71, (SAG61-SAG52)/CT56, (R21+ R12)/CT12, | SLO62/SLO71| and TTL/CT67 in the optical systems of the first to fifth embodiments.

TABLE 6

As can be seen from table 6, the optical systems of the first to fifth embodiments all satisfy the following relations: 110 deg < FOV <121 deg, 4mm < SD11/tan (HFOV) <4.5mm, 1.6< f/EPD <2.1, 0.9< f123/f1<1.5, 1.5< f45/f <2.5, 1< R32/R41<2.8, 1.5< R51/R42<3, 1< CT14/(SD11-SD41) <1.1, -35< SAG62/SAG71< -2, 0.5< (SAG61-SAG52)/CT56<1, 8< (R21+ R12)/CT12<62, 3< | SLO 62/O71 | 4, and 4.4< TTL/CT < 67< 4.8.

The invention further provides a camera module, which comprises a photosensitive chip and the optical system of any one of the embodiments of the first aspect, wherein the photosensitive chip is arranged on the image side of the optical system. The light sensing surface of the light sensing chip is positioned on the imaging surface of the optical system, and light rays which penetrate through the lens and enter an object on the light sensing surface can be converted into electric signals of images. The photosensitive chip may be a Complementary Metal Oxide Semiconductor (CMOS) or a Charge-coupled Device (CCD). The camera module can be an imaging module integrated on the electronic equipment and can also be an independent lens. By adding the optical system provided by the invention into the camera module, the camera module has the characteristics of larger field angle, large aperture, small distortion and miniaturization by reasonably designing the surface shape and the refractive power of each lens in the optical system.

The invention also provides electronic equipment which comprises a shell and the camera module in the second aspect, wherein the camera module is arranged in the shell. The electronic device includes but is not limited to a smart phone, a computer, a smart watch, and the like. By adding the camera module provided by the invention into the electronic equipment, the electronic equipment has the characteristics of larger field angle, large aperture, small distortion and miniaturization.

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.

Claims

1. An optical system, comprising seven lens elements with refractive power along an optical axis, in order from an object side to an image side:

the first lens element with negative refractive power has a concave object-side surface at an optical axis and a convex image-side surface at a paraxial region;

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

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

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

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

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

the object side surface and the image side surface of the sixth lens and the seventh lens respectively comprise at least one inflection point;

the optical system satisfies the relation: 110 deg < FOV <121 deg, and/or 1.6< f/EPD < 2.1;

wherein FOV is the maximum field angle of the optical system, f is the focal length of the optical system, and EPD is the entrance pupil diameter of the optical system.

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

4mm<SD11/tan(HFOV)<4.5mm；

wherein SD11 is a half of the maximum effective aperture of the object-side surface of the first lens, HFOV is a half of the maximum angle of view of the optical system, and tan (HFOV) is a tangent value of the half angle of view of the optical system.

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

0.9<f123/f1<1.5；

wherein f123 is a combined focal length of the first lens, the second lens, and the third lens, and f1 is a focal length of the first lens.

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

1.5<f45/f<2.5；

wherein f45 is a combined focal length of the fourth lens and the fifth lens, and f is a focal length of the optical system.

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

1< R32/R41<2.8, and/or 1.5< R51/R42< 3;

wherein R32 is a radius of curvature of the image-side surface of the third lens element at the optical axis, R41 is a radius of curvature of the object-side surface of the fourth lens element at the optical axis, R51 is a radius of curvature of the object-side surface of the fifth lens element at the optical axis, and R42 is a radius of curvature of the image-side surface of the fourth lens element at the optical axis.

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

1<CT14/(SD11-SD41)<1.1；

the CT14 is a distance on an optical axis from an object-side surface of the first lens element to an object-side surface of the fourth lens element, the SD11 is a half of a maximum effective aperture of the object-side surface of the first lens element, and the SD41 is a half of a maximum effective aperture of the object-side surface of the fourth lens element.

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

-35<SAG62/SAG71<-2；

wherein SAG62 is the saggital height at the image side effective aperture of the sixth lens and SAG71 is the saggital height at the object side effective aperture of the seventh lens.

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

0.5<(SAG61-SAG52)/CT56<1；

wherein SAG61 is the saggital height of the sixth lens at the object side effective aperture, SAG52 is the saggital height of the fifth lens at the image side effective aperture, and CT56 is the distance from the image side of the fifth lens to the object side of the sixth lens on the optical axis.

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

8< (R21+ R12)/CT12<62, and/or 4.4< TTL/CT67< 4.8;

wherein R21 is a curvature radius of an object-side surface of the second lens element on an optical axis, R12 is a curvature radius of an image-side surface of the first lens element on the optical axis, CT12 is a distance between the image-side surface of the first lens element and an object-side surface of the second lens element on the optical axis, TTL is a distance between the object-side surface of the first lens element and an image plane on the optical axis, and CT67 is a distance between the object-side surface of the sixth lens element and an object-side surface of the seventh lens element on the optical axis.

10. An image pickup module comprising the optical system according to any one of claims 1 to 9 and a photosensitive chip, the photosensitive chip being located on an image side of the optical system.

11. An electronic device comprising a housing and the camera module of claim 10, wherein the camera module is disposed within the housing.