CN114002820A

CN114002820A - Optical system, lens module and electronic equipment

Info

Publication number: CN114002820A
Application number: CN202111453084.0A
Authority: CN
Inventors: 王国贵; 杨健; 李明
Original assignee: Jiangxi Jingchao Optical Co Ltd
Current assignee: Jiangxi Jingchao Optical Co Ltd
Priority date: 2021-11-30
Filing date: 2021-11-30
Publication date: 2022-02-01

Abstract

An optical system, a lens module and an electronic device, the optical system sequentially comprises from an object side to an image side along an optical axis direction: a first lens element with positive refractive power having a convex object-side surface at a paraxial region and a concave image-side surface at a paraxial region; a second lens element with refractive power having a concave object-side surface at a paraxial region and a convex 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; the optical system satisfies the relation: f123/f23 is more than or equal to 0.05 and less than or equal to 0.3; wherein f123 is a combined focal length of the first lens, the second lens, and the third lens, and f23 is a combined focal length of the second lens and the third lens. By reasonably designing the surface shape and the refractive power of each lens of the optical system, the lens has the characteristics of high pixel, high resolution and shorter total lens length.

Description

Optical system, lens module and electronic equipment

Technical Field

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

Background

With the rapid update and iteration of portable electronic products such as smart phones, consumers have more and more demands on camera functions. At present, most electronic equipment adopts an ultrathin low-cost lens, the size of the lens is usually longer, the lens is difficult to be carried on a light and thin electronic product, and the imaging quality is also in urgent need of improvement. Therefore, how to design an imaging lens having high definition and high resolution while maintaining miniaturization has become one of the important points of interest in the industry.

Disclosure of Invention

The object of the present invention is to provide an optical system having high definition, high resolution and miniaturization.

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, in order from an object side to an image side along an optical axis, comprising: a first lens element with positive refractive power having a convex object-side surface at a paraxial region and a concave image-side surface at a paraxial region; a second lens element with refractive power having a concave object-side surface at a paraxial region and a convex 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; the optical system satisfies the relation: f123/f23 is more than or equal to 0.05 and less than or equal to 0.3; wherein f123 is a combined focal length of the first lens, the second lens, and the third lens, and f23 is a combined focal length of the second lens and the third lens.

The first lens element with positive refractive power has a convex object-side surface at paraxial region and a concave image-side surface at paraxial region. The first lens element with positive refractive power has a convex object-side surface at paraxial region, so that light can be converged, thereby shortening the total length of the optical system and providing the optical system with a reasonable incident angle of light, thereby providing the optical system with a wide angle. The object side surface of the second lens is concave at a position near the optical axis, so that the light rays are diverged, and the marginal light rays from the first lens have smaller exit angles. The image side surface of the second lens and the object side surface of the third lens are both convex surfaces, so that the refractive power of the first lens is enhanced, large-angle light can enter the optical system, the image side surface of the third lens is concave at a paraxial region, the optical system has a larger back focus adjusting position, and the optical system can be better matched with a photosensitive element. By reasonably configuring the refractive power, the surface shape and the arrangement and combination sequence of the first lens to the third lens, the total length of the optical system can be compressed, thereby meeting the miniaturization requirement of the lens. When the combination relation is satisfied, the refractive power contributions of the second lens element and the third lens element are reasonably configured, so that the first lens element is favorable for better converging light rays incident from an object space, the field range of the optical system is improved, the total length of the optical system is shortened, and the first lens element is prevented from generating overlarge aberration, so that the optical system has good imaging quality. When the ratio is higher than the upper limit of the relation satisfied by the optical system, the refractive powers of the second lens element and the third lens element are weak, and the refractive power of the first lens element is too strong, which results in too large turning angle of the incident light beam, so that the optical system is not prone to generate strong astigmatism and chromatic aberration, and is not favorable for the high-resolution imaging characteristic of the optical system. When the ratio is lower than the lower limit of the relation satisfied by the optical system, the refractive powers of the second lens element and the third lens element are strong, and the refractive power of the first lens element is too weak, which is not favorable for compressing the optical system, thereby being not favorable for realizing the requirement of miniaturization.

In one embodiment, the optical system satisfies the relationship: 1.1< TTL/f < 1.5; 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, i.e., a total length, and f is an effective focal length of the optical system. By enabling the optical system to satisfy the relational expression, the effective focal length and the total length of the optical system are reasonably configured, so that the optical lens can be miniaturized, and meanwhile, light can be better converged on an imaging surface. When TTL/f is more than 1.1, the optical length of the lens group is not too short, so that the sensitivity of the optical system is well adjusted, and light rays are converged on an imaging surface. When TTL/f is less than 1.5, the length of the optical system is not too long, so that the angle of light rays entering an imaging surface is not too large, and reasonable imaging of light rays at the edge of the imaging surface of the optical system on a photosensitive surface is facilitated. Thereby improving the resolution and imaging clarity of the optical lens.

In one embodiment, the optical system satisfies the relationship: 8< | f3/R32| < 62; wherein f3 is a focal length of the third lens, and R32 is a radius of curvature of an image side surface of the third lens at an optical axis. The image side surface of the third lens is a concave surface, so that the optical system can better balance the surface shape configuration of the object side surfaces of the first lens and the second lens, and the total effective focal length of the lens group can be prolonged. When the ratio is higher than the upper limit of the relational expression, the absolute value of the curvature radius of the image side surface of the third lens at the optical axis is smaller, the curvature of the lens at the paraxial position is increased, the surface shape sensitivity of the system is increased steeply, and poor molding can be generated for lens injection molding, so that the manufacturing yield is influenced.

In one embodiment, the optical system satisfies the relationship: v1+ v2+ v3> 160; wherein v1 is the abbe number of the first lens, v2 is the abbe number of the second lens, and v3 is the abbe number of the third lens. By enabling the optical system to satisfy the relational expression, the first lens, the second lens and the third lens are made of materials with high Abbe numbers, on one hand, the density difference between the lenses and air can be increased, aberration can be better corrected, resolution can be better improved, on the other hand, manufacturability of the process is increased, and the optical system can guarantee imaging quality in a limited air gap. When the ratio is lower than the lower limit of the relational expression, the abbe number of the lens is too low, the chromatic dispersion of the optical system is too large, and the imaging definition of the optical system is reduced.

In one embodiment, the optical system satisfies the relationship: 0< | R31/f3| < 0.12; wherein R31 is a radius of curvature of an object-side surface of the third lens at an optical axis, and f3 is an effective focal length of the third lens. The object-side surface of the third lens element is concave and has negative refractive power. The third lens is matched with the second lens to lengthen the focal length of the optical system. When the ratio is higher than the upper limit of the relation, the absolute value of the curvature radius of the object-side surface of the third lens at the optical axis is larger, and the curvature of the lens at the position near the optical axis is larger, so that the surface shape of the second lens is curved therewith, the light deflection angle is larger, and a reflected ghost image is easy to generate, thereby influencing the actual shooting picture.

In one embodiment, the optical system satisfies the relationship: -114< (R31+ R32)/(R31-R32) < 477.1; wherein R31 is a radius of curvature of an object-side surface of the third lens at an optical axis, and R32 is a radius of curvature of an image-side surface of the third lens at the optical axis. The third lens is provided with a convex object side surface and a concave image side surface, wherein the convex object side surface is arranged at the lower beam axis, and the concave image side surface is arranged at the lower beam axis, so that the surface type of the third lens cannot be too flat or too curved, the curvature radius and the surface shape of the third lens at the optical axis are controlled within a reasonable range, the optical path difference of the optical system can effectively balance the light of the central view field and the light of the edge view field, the optical path difference of the central view field and the optical path difference of the edge view field are prevented from being too large, the light of the central view field and the light of the edge view field can be converged to the vicinity of the same plane, and the correction of the field curvature is realized. In addition, the center of the third lens can be prevented from being too thin and too thick compared with the edge when the relation is met, so that the precision requirement of production and processing is met, and the forming yield is guaranteed.

In one embodiment, the optical system satisfies the relationship: EPD/ImgH is more than or equal to 0.16 and less than 0.21; the EPD is the diameter of an entrance pupil of the optical system, and the ImgH is half of the image height corresponding to the maximum field angle of the optical system. Through making optical system satisfy above-mentioned relational expression, alright make optical system have reasonable light ring size, increase whole optical system's light flux volume to make the more clear bright of formation of image effect, increase optical system's resolution ratio.

In one embodiment, the optical system satisfies the relationship: 0.70< CT2/CT3< 1.10; wherein CT2 is the thickness of the second lens element on the optical axis, and CT3 is the thickness of the third lens element on the optical axis. By enabling the optical system to meet the relational expression, the thickness and the surface shape of the lens can be reasonably controlled, so that the bending directions of the second lens and the third lens at the circumference are consistent, the surface shapes are close, the two lenses are matched more closely, and the assembly requirement of structural arrangement is met. The thickness of the lens can be uniformly configured, so that the sensitivity is reduced, and the optical distortion of the external field of view of the system can be further corrected.

In one embodiment, the optical system satisfies the relationship: the | < DIST | > is less than or equal to 2.5 percent; where DIST is the maximum value of the optical distortion of the system. By enabling the optical system to satisfy the relational expression, the optical distortion of the optical system is small, the reduction degree of a real shot picture is increased, the surface shape, curvature and refractive power of the lens are optimized, and the miniaturization design of the optical system is facilitated.

In a second aspect, the present invention further provides a lens module, which includes a lens barrel, a photosensitive element and the optical system of any one of the embodiments of the first aspect, wherein the focusing assembly and the first to third lenses of the optical system are mounted in the lens barrel, and the photosensitive element is disposed on an image side of the optical system. By adding the optical system provided by the invention into the lens module, the lens module has the characteristics of high definition, high resolution 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 lens module set in any one of the embodiments of the second aspect, wherein the lens module set is disposed in the housing. By adding the lens module provided by the invention into the electronic equipment, the electronic equipment has the characteristics of clear imaging 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. 1a is a schematic structural diagram of an optical system of a first embodiment;

FIG. 1b shows the longitudinal spherical aberration curve, astigmatism curve and distortion curve of FIG. 1 a;

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

FIG. 2b shows the longitudinal spherical aberration curve, astigmatism curve and distortion curve of FIG. 2 a;

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

FIG. 3b shows the longitudinal spherical aberration curve, astigmatism curve and distortion curve of FIG. 3 a;

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

FIG. 4b shows the longitudinal spherical aberration, astigmatism and distortion curves of FIG. 4 a;

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

fig. 5b shows the longitudinal spherical aberration curve, astigmatism curve and distortion curve of fig. 5 a.

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 provides an optical system, comprising in order from an object side to an image side along an optical axis: the first lens element with positive refractive power has a convex object-side surface at paraxial region and a concave image-side surface at paraxial region. The object side surface of the first lens is convex at the circumference, and the image side surface of the first lens is concave at the circumference. The second lens element with refractive power has a concave object-side surface at a paraxial region and a convex image-side surface at a paraxial region. The object side surface of the second lens is a concave surface at the circumference, and the image side surface of the second lens is a convex surface at the circumference. The third 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. The third lens element has a concave object-side surface at the circumference and a convex image-side surface at the circumference. The optical system satisfies the relation: f123/f23 is more than or equal to 0.05 and less than or equal to 0.3. Where f123 is a combined focal length of the first lens, the second lens, and the third lens, and f23 is a combined focal length of the second lens and the third lens.

The first lens element with positive refractive power has a convex object-side surface at paraxial region and a concave image-side surface at paraxial region. The first lens element with positive refractive power has a convex object-side surface at paraxial region, so that light can be converged, thereby shortening the total length of the optical system and providing the optical system with a reasonable incident angle of light, thereby providing the optical system with a wide angle. The object side surface of the second lens is concave at a position near the optical axis, so that the light rays are diverged, and the marginal light rays from the first lens have smaller exit angles. The image side surface of the second lens and the object side surface of the third lens are both convex surfaces, so that the refractive power of the first lens is enhanced, large-angle light can enter the optical system, the image side surface of the third lens is concave at a paraxial region, the optical system has a larger back focus adjusting position, and the optical system can be better matched with a photosensitive element. By reasonably configuring the refractive power, the surface shape and the arrangement and combination sequence of the first lens to the third lens, the total length of the optical system can be compressed, thereby meeting the requirement of miniaturization of the lens. The first lens element to the third lens element provide positive refractive power, and the lens assembly with positive refractive power focuses the optical fiber on the image side surface. The second lens element and the third lens element jointly provide negative refractive power, and the lens assembly with negative refractive power disperses light. When the combination relation is satisfied, the aberration of the optical system can be corrected, so that the resolution of the optical system is improved, and meanwhile, the light imaging distance is controlled, so that the picture can be clearer. When the ratio is higher than the upper limit of the optical system, the refractive power of the second lens element and the third lens element is weak, which hinders the increase of the focal length. When the ratio is lower than the lower limit of the relation, compression of the optical system is not facilitated, and thus the requirement for miniaturization is not facilitated.

In one embodiment, the optical system satisfies the relationship: 1.1< TTL/f < 1.5. 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 f is an effective focal length of the optical system. By enabling the optical system to satisfy the relational expression, the effective focal length and the total length of the optical system are reasonably configured, so that the optical lens can be miniaturized, and meanwhile, light can be better converged on an imaging surface. When TTL/f is more than 1.1, the optical length of the lens group is not too short, so that the sensitivity of the optical system is well adjusted, and light rays are converged on an imaging surface. When TTL/f is less than 1.5, the length of the optical system is not too long, so that the angle of light rays entering an imaging surface is not too large, and reasonable imaging of light rays at the edge of the imaging surface of the optical system on a photosensitive surface is facilitated. Thereby improving the resolution and imaging clarity of the optical lens.

In one embodiment, the optical system satisfies the relationship: 8< | f3/R32| < 62. Where f3 is the focal length of the third lens element, and R32 is the radius of curvature of the image-side surface of the third lens element at the optical axis. The image side surface of the third lens is a convex surface, so that the optical system can better balance the configuration of the surface shape of the object side surface of the first lens and the object side surface of the second lens, the total effective focal length of the lens group can be prolonged, when the ratio is higher than the upper limit of the relation, the absolute value of the curvature radius of the image side surface of the third lens at the optical axis is smaller, the curvature of the lens at the paraxial position is large, the sensitivity of the system surface shape is suddenly increased, and poor molding can be caused for the injection molding of the lens, and the manufacturing yield is influenced.

In one embodiment, the optical system satisfies the relationship: v1+ v2+ v3> 160. Wherein v1 is the abbe number of the first lens, v2 is the abbe number of the second lens, and v3 is the abbe number of the third lens. By enabling the optical system to satisfy the relational expression, the lens with high Abbe number and low refractive index can strengthen the density difference between the materials of the first lens, the second lens and the third lens and the air, so that aberration can be better corrected, and resolution can be better improved. When the ratio is higher than the upper limit of the relation, the refractive index of the material is lowered. Satisfying the above relationship also increases manufacturability of the process, allowing the optical system to ensure imaging quality in a limited air gap.

In one embodiment, the optical system satisfies the relationship: 0< | R31/f3| < 0.12. Wherein R31 is the radius of curvature of the object-side surface of the third lens at the optical axis, and f3 is the effective focal length of the third lens. The object-side surface of the third lens element is concave and has negative refractive power. The third lens is matched with the second lens to lengthen the focal length of the optical system. When the ratio is higher than the upper limit of the relation, the absolute value of the curvature radius of the object side surface of the third lens at the optical axis is larger, the curvature of the lens at the position near the optical axis is increased, meanwhile, the surface shape of the second lens is also bent along with the curvature, the deflection angle of light is increased, a reflected ghost image is easily generated, and the actual shooting picture is influenced.

In one embodiment, the optical system satisfies the relationship: -114< (R31+ R32)/(R31-R32) < 477.1. Wherein R31 is a radius of curvature of the object-side surface of the third lens element at the optical axis, and R32 is a radius of curvature of the image-side surface of the third lens element at the optical axis. The third lens is provided with a convex object side surface and a concave image side surface, wherein the convex object side surface is arranged at the lower beam axis, and the concave image side surface is arranged at the lower beam axis, so that the surface type of the third lens cannot be too flat or too curved, the curvature radius and the surface shape of the third lens at the optical axis are controlled within a reasonable range, the optical path difference of the optical system can effectively balance the light of the central view field and the light of the edge view field, the optical path difference of the central view field and the optical path difference of the edge view field are prevented from being too large, the light of the central view field and the light of the edge view field can be converged to the vicinity of the same plane, and the correction of the field curvature is realized. In addition, the center of the third lens can be prevented from being too thin and too thick compared with the edge when the relation is met, so that the precision requirement of production and processing is met, and the forming yield is guaranteed.

In one embodiment, the optical system satisfies the relationship: 0.16 is less than or equal to EPD/ImgH and less than 0.21. The EPD is an entrance pupil diameter of the optical system, and the ImgH is a half of an image height corresponding to a maximum field angle of the optical system. Through making optical system satisfy above-mentioned relational expression, alright make optical system have reasonable light ring size, increase whole optical system's light flux volume to make the more clear bright of formation of image effect, increase optical system's resolution ratio.

Preferably, 0.5 ≦ EPD/ImgH < 0.8. By enabling the optical system to meet the relational expression, the optical system has the characteristic of large aperture, the light transmission quantity of the whole optical system can be increased, imaging is clearer and brighter, and the portrait effect with smaller depth of field is favorably realized. More preferably, 0.5 < EPD/ImgH <0.7, and the optical system satisfies the above relation, thereby facilitating aberration correction of the first lens and the aperture band and ensuring resolution.

Preferably, | DIST | ≦ 2%, and by enabling the optical system to satisfy the above relation, the image distortion degree of the marginal field of view of the optical system is small, thereby improving the shooting experience of the user.

The present invention further provides a lens module, which includes a lens barrel, a photosensitive element and the optical system according to any of the embodiments of the first aspect, wherein the first to third lenses of the optical system are mounted in the lens barrel, and the photosensitive element is disposed on the image side of the optical system. By adding the optical system provided by the invention into the lens module, the lens module has the characteristics of high definition, high resolution 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 lens module of the second aspect, wherein the lens module is arranged in the shell. By adding the lens module provided by the invention into the electronic equipment, the electronic equipment has the characteristics of high definition, high resolution and miniaturization.

In one embodiment, the first lens L1 to the third lens L3 may be made of plastic, glass, or a glass-plastic composite material. The effective pixel area of the photosensitive element is located on the imaging plane IMG.

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 at a paraxial region and a concave image-side surface S2 at a paraxial region of the first lens element L1. The object-side surface S1 of the first lens element L1 is convex near the circumference, and the image-side surface S2 is concave near the circumference.

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

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

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 of the optical system for controlling the amount of light entering. The infrared cut filter IR is disposed between the third lens L3 and the imaging surface IMG, and includes an object side surface S7 and an image side surface S8, and is configured to filter infrared light, so that the light incident on the imaging surface IMG is visible light with a wavelength of 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 third lens L3 are all made of plastic, and the filter IR is made of glass. The effective pixel area of the photosensitive element is located on the imaging plane IMG.

Table 1a shows a table of characteristics of the optical system of the present embodiment, in which the reference wavelength of the focal length of the lens is 555nm, the reference wavelengths of the abbe number and the refractive index of the lens are 587.56nm, and the radius Y in table 1a is the radius of curvature of the object-side surface or the image-side surface at the optical axis of the corresponding surface number. 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. For any of the first to third lenses, the first value in the "thickness" parameter column of the lens is the thickness of the lens on the optical axis, the second value is the distance from the image-side surface of the lens to the rear surface of the lens in the image-side direction on the optical axis, and the filter IR is similar. The units of the Y radius, thickness and effective focal length are millimeters (mm).

TABLE 1a

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

In the present embodiment, the object-side surface and the image-side surface of the first lens L1-the third lens L3 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, and a20 that can be used for the aspherical mirrors S1 and S2 in the first embodiment.

TABLE 1b

Fig. 1b (a) shows a longitudinal spherical aberration curve of the optical system of the first embodiment at wavelengths of 650nm, 610nm, 555nm, 510nm and 470nm, wherein the abscissa in the X-axis direction represents the focus offset, the ordinate in the Y-axis direction represents the normalized field of view, and the longitudinal spherical aberration curve represents the convergent focus offset of light rays of different wavelengths after passing through the respective lenses of the optical system. As can be seen from fig. 1b (a), the spherical aberration value of the optical system in the first embodiment is better, which illustrates that the imaging quality of the optical system in this embodiment is better.

Fig. 1b (b) also shows a graph of astigmatism of the optical system of the first embodiment at a wavelength of 555nm, in which the abscissa in the X-axis direction represents the focus offset and the ordinate in the Y-axis direction represents the image height in mm. The astigmatism curves represent the meridional imaging plane curvature T and the sagittal imaging plane curvature S. As can be seen from fig. 1b (b), astigmatism of the optical system is well compensated.

Fig. 1b (c) also shows a distortion curve of the optical system of the first embodiment at a wavelength of 555 nm. The abscissa along the X-axis direction represents the focus offset, the ordinate along the Y-axis direction represents the image height, and the distortion curve represents the distortion magnitude values corresponding to different angles of view. As can be seen from fig. 1b (c), the distortion of the optical system is well corrected at a wavelength of 555 nm.

As can be seen from (a), (b) and (c) in fig. 1b, the optical system of the present embodiment has small aberration, good imaging quality and 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 second lens element L2 with negative refractive power has a concave object-side surface S3 at a paraxial region and a convex image-side surface S4 at a paraxial region of the second lens element L2. The object-side surface S3 of the second lens element L2 is concave at the near circumference, and the image-side surface S4 is convex at the near circumference.

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 the reference wavelength of the focal length of the lens is 555nm, the reference wavelengths of the abbe number and the refractive index of the lens are 587.56nm, and the radius Y in table 2a is the radius of curvature of the object-side surface or the image-side surface at the optical axis of the corresponding surface number. 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. For any of the first to third lenses, the first value in the "thickness" parameter column of the lens is the thickness of the lens on the optical axis, the second value is the distance from the image-side surface of the lens to the rear surface of the lens in the image-side direction on the optical axis, and the filter IR is similar. The units of the Y radius, thickness and effective focal length are millimeters (mm). The meaning of each parameter is the same as that 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. 2b 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 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 meridional imaging plane curvature and sagittal imaging plane 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. 2b, 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. 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 negative refractive power has a concave object-side surface S5 at a paraxial region and a convex image-side surface S6 at a paraxial region of the third lens element L3. The object-side surface S5 of the third lens element L3 is convex near the circumference, and the image-side surface S6 is concave near the circumference.

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 the reference wavelength of the focal length of the lens is 555nm, the reference wavelengths of the abbe number and refractive index of the lens are 587.56nm, and the radius Y in table 3a is the radius of curvature of the object-side surface or image-side surface at the optical axis of the corresponding surface number. 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. For any of the first to third lenses, the first value in the "thickness" parameter column of the lens is the thickness of the lens on the optical axis, the second value is the distance from the image-side surface of the lens to the rear surface of the lens in the image-side direction on the optical axis, and the filter IR is similar. The units of the Y radius, thickness and effective focal length are millimeters (mm). The meaning of each parameter is the same as that of the first embodiment.

TABLE 3a

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 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 meridional imaging plane curvature and sagittal imaging plane 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. 3b, 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. 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:

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 the reference wavelength of the focal length of the lens is 555nm, the reference wavelengths of the abbe number and refractive index of the lens are 587.56nm, and the radius Y in table 4a is the radius of curvature of the object-side surface or image-side surface at the optical axis of the corresponding surface number. 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. For any of the first to third lenses, the first value in the "thickness" parameter column of the lens is the thickness of the lens on the optical axis, the second value is the distance from the image-side surface of the lens to the rear surface of the lens in the image-side direction on the optical axis, and the filter IR is similar. The units of the Y radius, thickness and effective focal length are millimeters (mm). The meaning of each parameter is the same as that 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. 4b 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 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 meridional imaging plane curvature and sagittal imaging plane 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. 4b, 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. 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 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 the reference wavelength of the focal length of the lens is 555nm, the reference wavelengths of the abbe number and refractive index of the lens are 587.56nm, and the radius Y in table 5a is the radius of curvature of the object-side surface or image-side surface at the optical axis of the corresponding surface number. 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. For any of the first to third lenses, the first value in the "thickness" parameter column of the lens is the thickness of the lens on the optical axis, the second value is the distance from the image-side surface of the lens to the rear surface of the lens in the image-side direction on the optical axis, and the filter IR is similar. The units of the Y radius, thickness and effective focal length are millimeters (mm). The meaning of each parameter is the same as that 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. 5b 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 meridional imaging plane curvature and sagittal imaging plane 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. 5b, 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.

Table 6 shows values of TTL/f, f3/R32, v1+ v2+ v3, R31/f3, (R31+ R32)/(R31-R32), EPD/ImgH, CT2/CT3, f123/f23 in the optical systems of the first to fifth embodiments.

TABLE 6

	TTL/f	f3/R32	v1+v2+v3	R31/f3
					First embodiment	1.233	61.017	167.760	0.019
Second embodiment	1.275	9.191	167.760	0.109
					Third embodiment	1.173	-14.655	167.760	-0.091
Fourth embodiment	1.178	-17.489	167.760	-0.075
					Fifth embodiment	1.310	8.983	167.760	0.112
	(R31+R32)/(R31-R32)	EPD/ImgH	CT2/CT3	f123/f23
					First embodiment	-113.909	0.199	0.993	0.229
Second embodiment	19.938	0.189	0.884	0.293
					Third embodiment	7.093	0.208	0.897	0.065
Fourth embodiment	7.578	0.207	0.716	0.050
					Fifth embodiment	477.000	0.162	0.919	0.262

As can be seen from table 6, the optical systems of the first to fifth embodiments all satisfy the following relations:

1.1< TTL/f <1.5, 8< | f3/R32| <62, v1+ v2+ v3>160, 0< | R31/f3| <0.12, -114< (R31+ R32)/(R31-R32) <477.1, 0.16 < EPD/ImgH <0.21, 0.70< CT2/CT3<1.10, 0.05 < f123/f23< 0.3.

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, in order from an object side to an image side along an optical axis:

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

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

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

the optical system satisfies the relation: f123/f23 is more than or equal to 0.05 and less than or equal to 0.3;

wherein f123 is a combined focal length of the first lens, the second lens, and the third lens, and f23 is a combined focal length of the second lens and the third lens.

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

1.1<TTL/f<1.5；

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 f is an effective focal length of the optical system.

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

8<|f3/R32|<62；

wherein f3 is an effective focal length of the third lens, and R32 is a radius of curvature of an image side surface of the third lens at an optical axis.

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

v1+v2+v3>160；

wherein v1 is the abbe number of the first lens, v2 is the abbe number of the second lens, and v3 is the abbe number of the third lens.

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

0<|R31/f3|<0.12；

wherein R31 is a radius of curvature of an object-side surface of the third lens at an optical axis, and f3 is an effective focal length of the third lens.

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

-114<(R31+R32)/(R31-R32)<477.1；

wherein R31 is a radius of curvature of an object-side surface of the third lens at an optical axis, and R32 is a radius of curvature of an image-side surface of the third lens at the optical axis.

7. The optical system of claim 1, wherein the optical system satisfies the relationship: EPD/ImgH is more than or equal to 0.16 and less than 0.21;

the EPD is the diameter of an entrance pupil of the optical system, and the ImgH is half of the image height corresponding to the maximum field angle of the optical system.

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

0.70<CT2/CT3<1.10；

wherein CT2 is the thickness of the second lens element on the optical axis, and CT3 is the thickness of the third lens element on the optical axis.

9. A lens module comprising a lens barrel, a photosensitive element, and the optical system according to any one of claims 1 to 8, wherein the first to third lenses of the optical system are mounted in the lens barrel, and the photosensitive element is disposed on the image side of the optical system.

10. An electronic apparatus, characterized in that the electronic apparatus comprises a housing and the lens module according to claim 9, the lens module being disposed in the housing.