CN111239986A

CN111239986A - Optical system, lens module and electronic equipment

Info

Publication number: CN111239986A
Application number: CN202010233722.7A
Authority: CN
Inventors: 党绪文; 刘彬彬; 李明
Original assignee: OFilm Tech Co Ltd
Current assignee: Nanchang OFilm Precision Optical Products Co Ltd; OFilm Group Co Ltd
Priority date: 2020-03-27
Filing date: 2020-03-27
Publication date: 2020-06-05

Abstract

The invention provides an optical system, a lens module and an electronic device, wherein the optical system comprises the following components in sequence from an object side to an image side along an optical axis direction: the first lens element with positive refractive power has a convex object-side surface and a concave image-side surface at 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; a fourth lens element with positive refractive power; a fifth lens element with refractive power; a sixth lens element with negative refractive power having a concave image-side surface at paraxial region and a convex image-side surface at paraxial region, wherein at least one inflection point is disposed on at least one of the object-side surface and the image-side surface of the sixth lens element; the object side surface and the image side surface of the third lens, the fourth lens and the fifth lens are aspheric surfaces. By reasonably configuring the surface shapes and the refractive powers of the first lens, the second lens, the third lens and the fourth lens, the optical system has higher imaging quality, is matched with an electronic photosensitive chip with higher pixels, and realizes miniaturization.

Description

Optical system, lens module and electronic equipment

Technical Field

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

Background

With the market requirement for high imaging quality of camera shooting, the telephoto lens comes along. At present, the physical focal length of an optical system of a conventional telephoto lens is longer, and the pixels of a supported photosensitive chip are lower, so that the market demand is difficult to meet.

Therefore, it is necessary to further improve the imaging quality of the optical system of the telephoto lens, and to adapt to the electronic photosensitive chip with higher pixels, and on this basis, the physical length of the optical system should be reduced as much as possible to achieve miniaturization of the telephoto lens.

Disclosure of Invention

The invention aims to provide an optical system, a lens module and an electronic device, which have higher imaging quality, can be adapted to an electronic photosensitive chip with higher pixels and can meet the requirement of 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 direction, comprising: the first lens element with positive refractive power has a convex object-side surface and a concave image-side surface at a paraxial region thereof; a second lens element with refractive power having a convex object-side surface and a concave image-side surface; the third lens element with refractive power has an object-side surface and an image-side surface which are both aspheric; the fourth lens element with positive refractive power has an object-side surface and an image-side surface which are both aspheric; the fifth lens element with refractive power has an object-side surface and an image-side surface which are both aspheric; the sixth lens element with negative refractive power has a concave image-side surface at a paraxial region thereof, and a convex image-side surface at a paraxial region thereof, and at least one inflection point is disposed on at least one of an object-side surface and an image-side surface of the sixth lens element. Through the reasonable configuration of the surface type and the refractive power of each lens element of the first lens element to the sixth lens element, the optical system can have higher imaging quality, is suitable for an electronic photosensitive chip with higher pixels, and can meet the requirement of miniaturization.

In one embodiment, the optical system satisfies the conditional expression: f 43/ImgH is more than or equal to 45.5 and less than 61.0; wherein f is the effective focal length of the optical system, and ImgH is the effective imaging area diagonal length of the optical system on the imaging surface. Through the value of reasonable setting f 43/ImgH, can make this application optical system has better long focus ability, can adapt the electron sensitization chip of bigger size and higher pixel, better let remote object obtain the effect of forming images closely.

In one embodiment, the optical system satisfies the conditional expression: TTL/f is more than or equal to 0.89 and less than 1.0; 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. Through reasonable setting of the TTL/f value, the optical system can provide a higher effective focal length in a certain range, the physical length TTL of the optical system is reduced, and the optical system can be implanted into portable equipment more easily.

In one embodiment, the optical system satisfies the conditional expression: 5.5 degree/mm < FOV/f < 8.2 degree/mm; wherein FOV is a diagonal field angle of the optical system, and f is an effective focal length of the optical system. By reasonably setting the value of FOV/f, the optical system can obtain a larger field angle FOV under a certain effective focal length, so that the imaging range of a long-distance object by a long focus is enlarged.

In one embodiment, the optical system satisfies the conditional expression: 1.9 < (| R32| + | R42|)/f is less than or equal to 13.44; wherein R32 is a curvature radius of the image-side surface of the third lens at the optical axis, R42 is a curvature radius of the image-side surface of the fourth lens at the optical axis, and f is an effective focal length of the optical system. By reasonably setting the value (| R32| + | R42|)/f, the distortion and coma generated by most of the front lenses can be counteracted, and simultaneously, the introduction of larger spherical aberration and vertical axis chromatic aberration can be effectively avoided, thereby being beneficial to the reasonable distribution of the primary aberration on each lens and reducing tolerance sensitivity.

In one embodiment, the optical system satisfies the conditional expression: R51/CT56 is more than or equal to 3.3 and less than 28.7; wherein R51 is a curvature radius of an object-side surface of the fifth lens element on an optical axis, and CT56 is an axial distance between an image-side surface of the fifth lens element and an object-side surface of the sixth lens element. By reasonably setting the value of R51/CT56, the difficulty in molding and assembling the optical system can be effectively reduced.

In one embodiment, the optical system satisfies the conditional expression: 1.2 < (CT1+ CT2+ CT3)/BF < 2.1; wherein CT1 is a thickness of the first lens element, CT2 is a thickness of the second lens element, CT3 is a thickness of the third lens element, and BF is a distance from an image-side surface of the sixth lens element to an image plane along an optical axis. By reasonably setting the value of (CT1+ CT2+ CT3)/BF, the aberrations generated by the first lens, the second lens and the third lens are smaller, so that the difficulty of balancing the aberrations of the optical system is reduced.

In one embodiment, the optical system satisfies the conditional expression: 1.0 < SAG61/CT6 < 2.9; SAG61 is the axial distance between the intersection point of the object side surface of the sixth lens and the optical axis and the farthest point of the sixth lens from the imaging surface along the optical axis, and CT6 is the thickness of the sixth lens on the optical axis. Through the value of reasonable setting SAG61/CT6, provide good angle of deflection for the deflection of light at the lens edge, avoided arousing the aberration of difficult correction because of the deflection is too big, still can reduce the lens shaping degree of difficulty simultaneously, and then promote the production yield.

In one embodiment, the optical system satisfies the conditional expression:

19 < (| f3| + f4+ | f5|)/(CT34+ CT45+ CT56) < 103; wherein f3 is the effective focal length of the third lens element, f4 is the effective focal length of the fourth lens element, f5 is the effective focal length of the fifth lens element, CT34 is the distance between the image-side surface of the third lens element and the object-side surface of the fourth lens element on the optical axis, CT45 is the distance between the image-side surface of the fourth lens element and the object-side surface of the fifth lens element on the optical axis, and CT56 is the distance between the image-side surface of the fifth lens element and the object-side surface of the sixth lens element on the optical axis. By reasonably setting the value of (| f3| + f4+ | f5|)/(CT34+ CT45+ CT56), the spherical aberration, chromatic aberration and the like generated by the front lens group can be effectively balanced, and the whole image quality is improved.

In one embodiment, the optical system satisfies the conditional expression: TTL/FNO is more than 2.7mm and less than 3.1 mm; 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 FNO is an f-number of the optical system. By reasonably setting the TTL/FNO value, the optical system can have a large aperture effect, and the detail effect of the shot object of the optical system under long-focus shooting can be improved to a certain extent.

In a second aspect, the present invention further provides a lens module, which includes a lens barrel and the optical system in any one of the embodiments of the first aspect, wherein the first lens to the sixth lens of the optical system are mounted in the lens barrel, and the electronic photosensitive chip is disposed at an image side of the optical system and is configured to convert light rays of an object, which pass through the first lens to the sixth lens and are incident on the electronic photosensitive chip, into an electrical signal of an image. Through install this optical system's first lens to sixth lens in the camera lens module, make this application the camera lens module has higher formation of image quality, and the higher pixel's of suitability electron sensitization chip, simultaneously the camera lens module overall length is less, realizes the miniaturization.

In a third aspect, the present invention further provides an electronic device, where the electronic device includes a housing and the lens module of the second aspect, and the lens module is disposed in the housing. The lens module of the second aspect is arranged in the electronic device, so that the electronic device has high imaging quality, the overall length of the electronic device is small, and miniaturization is achieved.

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 for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious 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 derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The embodiment of the invention provides a lens module, which comprises a lens barrel, an electronic photosensitive chip and an optical system, wherein the first lens to the sixth lens of the optical system are arranged in the lens barrel, and the electronic photosensitive chip is arranged at the image side of the optical system and is used for converting light rays which pass through the first lens to the sixth lens and enter an object on the electronic photosensitive chip into an electric signal of an image. The electron sensor chip may be a Complementary Metal Oxide Semiconductor (CMOS). The lens module can be an independent lens of a digital camera, and can also be an imaging module integrated on electronic equipment such as a smart phone. Through first lens to sixth lens of installing this optical system in the camera lens module for the camera lens module that this application embodiment provided has higher formation of image quality, and the higher pixel's of suitability electron sensitization chip, and camera lens module overall length is less simultaneously, realizes the miniaturization.

The embodiment of the invention provides electronic equipment, which comprises a shell and a lens module provided by the embodiment of the invention. The lens module and the electronic photosensitive chip are arranged in the shell. The electronic device can be a smart phone, a Personal Digital Assistant (PDA), a tablet computer, a smart watch, an unmanned aerial vehicle, an electronic book reader, a vehicle event data recorder, a wearable device and the like. Through set up the lens module of the second aspect in electronic equipment for the electronic equipment that this application embodiment provided has higher formation of image quality, and electronic equipment's overall length is less simultaneously, realizes the miniaturization.

An optical system includes, in order from an object side to an image side in an optical axis direction, a first lens element, a second lens element, a third lens element, a fourth lens element, a fifth lens element and a sixth lens element. In the first to sixth lenses, any two adjacent lenses may have an air space therebetween.

Specifically, the specific shape and structure of the six lenses are as follows: the first lens element with positive refractive power has a convex object-side surface and a concave image-side surface at a paraxial region thereof; the second lens element with refractive power has a convex object-side surface at a paraxial region thereof and a concave image-side surface at a paraxial region thereof; the third lens element with refractive power has an object-side surface and an image-side surface which are both aspheric; the fourth lens element with positive refractive power has an object-side surface and an image-side surface which are both aspheric; the fifth lens element with refractive power has an object-side surface and an image-side surface which are both aspheric; the sixth lens element with negative refractive power has a concave image-side surface at a paraxial region thereof, and a convex image-side surface at a paraxial region thereof, and at least one inflection point is disposed on at least one of an object-side surface and an image-side surface of the sixth lens element. The optical system further comprises a diaphragm which can be arranged at any position between the first lens and the sixth lens, such as on the first lens.

In one embodiment, the optical system satisfies the conditional expression: f 43/ImgH is more than or equal to 45.5 and less than 61.0; wherein f is the effective focal length of the optical system, and ImgH is the diagonal length of the effective imaging area of the optical system on the imaging surface. The conditional expression is an equivalent focal length calculated by the optical system based on a full frame, generally, the equivalent focal length of the optical system is greater than 50mm, that is, the optical system has a certain telephoto capability, and when the optical system satisfies the conditional expression, it is described that a lens formed by the optical system provided by the embodiment of the present application has an amplification capability of more than 2 times compared with a 25mm imaging lens, it is described that ImgH is large, the optical system can be adapted to an electronic photosensitive chip with a larger size and a higher pixel, and meanwhile, reasonable lens size and refractive power configuration can enable a distant object to obtain a close-range imaging effect.

In one embodiment, the optical system satisfies the conditional expression: TTL/f is more than or equal to 0.89 and less than 1.0; 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. In one embodiment, f is greater than 6mm, so that the optical system has a certain amount of focusing power in combination with a sized electronic photosensitive chip. When the optical system meets the conditional expression, the optical system can provide a higher effective focal length within the range that TTL is less than 6.5mm, and the physical length TTL of the optical system is reduced, so that the optical system is easier to implant into portable equipment. It should be noted that, in the optical system, the use of the aspheric lens makes TTL smaller than the effective focal length f, which is beneficial for the optical system to balance aberrations such as chromatic aberration, spherical aberration, and distortion, thereby obtaining good imaging quality.

In one embodiment, the optical system satisfies the conditional expression: 5.5 degree/mm < FOV/f < 8.2 degree/mm; wherein FOV is a diagonal field angle of the optical system, and f is an effective focal length of the optical system. When the optical system meets the above conditional expression, a larger field angle FOV can be obtained at a certain effective focal length, thereby increasing the imaging range of the telephoto on the remote object. In one embodiment, the F-number of the optical system is less than 2.21, so that the optical system has a higher light input, thereby providing better relative brightness and color control for tele photography.

In one embodiment, the optical system satisfies the conditional expression: 1.9 < (| R32| + | R42|)/f is less than or equal to 13.44; wherein, R32 is a curvature radius of the image-side surface of the third lens element on the optical axis, R42 is a curvature radius of the image-side surface of the fourth lens element on the optical axis, and f is an effective focal length of the optical system. In the optical system, the third lens element provides positive or negative refractive power, and the fourth lens element provides positive refractive power, so that the combined structure of the third lens element and the fourth lens element can counteract most of the distortion and coma generated by the front lens element. Meanwhile, when the optical system meets the conditional expression, the reasonable curvature radius can avoid introducing larger spherical aberration and vertical axis chromatic aberration, thereby being beneficial to the reasonable distribution of the primary aberration on each lens and further reducing tolerance sensitivity.

In one embodiment, the optical system satisfies the conditional expression: R51/CT56 is more than or equal to 3.3 and less than 28.7; wherein R51 is a radius of curvature of the object-side surface of the fifth lens element at a paraxial region thereof, and CT56 is a distance between the image-side surface of the fifth lens element and the object-side surface of the sixth lens element. In the optical system, the fifth lens element provides positive or negative refractive power, and the refractive power distribution of the entire lens assembly is adjusted, so as to help disperse aberration and obtain high resolution. Meanwhile, when the optical system meets the conditional expression, the proper curvature of the edge changes, and the deflection angle of each field ray at the edge is reduced; reasonable lens curvature and thickness control can effectively reduce the molding and assembling difficulty of the optical system.

In one embodiment, the optical system satisfies the conditional expression: 1.2 < (CT1+ CT2+ CT3)/BF < 2.1; wherein CT1 is the thickness of the first lens element, CT2 is the thickness of the second lens element, CT3 is the thickness of the third lens element, and BF is the closest distance from the image-side surface of the sixth lens element to the image-forming surface along the optical axis. In a specific embodiment, BF is greater than 0.75, and under the condition, the optical system and the electronic photosensitive chip can form a good matching relation, and various module components can be added and mounted more conveniently. It can be understood that when the optical system satisfies the above conditional expressions, the compact structure of the first lens, the second lens and the third lens helps to reduce TTL, and the reasonable thickness-to-distance control makes the aberration generated by the first three lenses small, thereby reducing the difficulty of balancing aberration of the optical system.

In one embodiment, the optical system satisfies the conditional expression: 1.0 < SAG61/CT6 < 2.9; SAG61 is the axial distance between the intersection point of the object-side surface of the sixth lens and the optical axis and the farthest point of the sixth lens from the imaging surface along the optical axis, and CT6 is the thickness of the sixth lens on the optical axis. Through the value of reasonable setting SAG61/CT6, provide good angle of deflection for the deflection of light at the lens edge, avoided arousing the aberration of difficult correction because of the deflection is too big, still can reduce the lens shaping degree of difficulty simultaneously, and then promote the production yield.

In one embodiment, the optical system satisfies the conditional expression:

19 < (| f3| + f4+ | f5|)/(CT34+ CT45+ CT56) < 103; wherein f3 is an effective focal length of the third lens element, f4 is an effective focal length of the fourth lens element, f5 is an effective focal length of the fifth lens element, CT34 is an axial distance between an image-side surface of the third lens element and an object-side surface of the fourth lens element, CT45 is an axial distance between an image-side surface of the fourth lens element and an object-side surface of the fifth lens element, and CT56 is an axial distance between an image-side surface of the fifth lens element and an object-side surface of the sixth lens element. By reasonably setting the value of (| f3| + f4+ | f5|)/(CT34+ CT45+ CT56), the spherical aberration, chromatic aberration and the like generated by the front lens group can be effectively balanced, and the whole image quality is improved.

In one embodiment, the optical system satisfies the conditional expression: TTL/FNO is more than 2.7mm and less than 3.1 mm; wherein, TTL is the distance on the optical axis from the object side surface of the first lens to the imaging surface of the optical system, and FNO is the f-number of the optical system. Through reasonable setting of TTL/FNO value, the optical system can have a large aperture effect, and the detailed effect of the object shot by the optical system under long-focus shooting can be improved to a certain extent.

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:

a first lens element L1 with positive refractive power having a convex surface near the optical axis and near the circumference of the object-side surface S1 of the first lens element L1, a concave surface near the optical axis of the image-side surface S2 of the first lens element L1, and a convex surface near the circumference of the image-side surface S2;

a second lens element L2 with positive refractive power, the second lens element L2 having a convex surface at a paraxial region of the object-side surface S3, a concave surface at a paraxial region of the object-side surface S3, and a concave surface at a paraxial region and a near circumferential region of the image-side surface S4 of the second lens element L2;

a third lens element L3 with negative dioptric power, the third lens element L3 having a convex surface near the optical axis and near the circumference of the object-side surface S5, and the third lens element L3 having a concave surface near the optical axis and near the circumference of the image-side surface S6;

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

a fifth lens element L5 with positive refractive power, the fifth lens element L5 having a concave surface near the optical axis and near the circumference of the object-side surface S9; the fifth lens element L5 has a convex image-side surface S10 at a paraxial region thereof and a concave image-side surface S10 at a peripheral region thereof.

A sixth lens element L6 with negative refractive power having a convex object-side surface S11 at a paraxial region and a concave object-side surface S11 at a paraxial region of the sixth lens element L6; the sixth lens element L6 has a concave image-side surface S12 at a paraxial region thereof and a convex image-side surface S12 at a paraxial region thereof.

The first lens element L1 to the sixth lens element L6 are all made of Plastic (Plastic).

Further, the optical system includes a stop STO, an infrared filter L7, and an image forming surface S15. The stop STO is provided on the side of the first lens L1 away from the second lens L2, and controls the amount of light entering. In other embodiments, the stop STO can be disposed between two adjacent lenses, or on other lenses. The infrared filter L7 is disposed on the image side of the sixth lens L6, and includes an object side surface S13 and an image side surface S14, and the infrared filter L7 is configured to filter infrared light, so that the light entering the image plane S15 is visible light, and the wavelength of the visible light is 380nm-780 nm. The infrared filter L7 is made of Glass (Glass), and may be coated on the Glass. The imaging surface S15 is an effective pixel area of the electronic photosensitive chip.

Table 1a shows a table of characteristics of the optical system of the present embodiment, in which data is obtained using light having a wavelength of 587nm, and the units of the Y radius, thickness, and focal length are millimeters (mm).

TABLE 1a

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

In the present embodiment, the object-side surface and the image-side surface of any one of the first lens L1 through the sixth lens L6 are aspheric surfaces, and the surface shape x of each aspheric lens can be defined by, but is not limited to, the following aspheric surface formula:

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

TABLE 1b

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

Second embodiment

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

a second lens element L2 with negative dioptric power, the second lens element L2 having a convex surface near the optical axis and near the circumference of the object-side surface S3, and the second lens element L2 having a concave surface near the optical axis and near the circumference of the image-side surface S4;

a fourth lens element L4 with positive refractive power having a concave object-side surface S7 of the fourth lens element L4 at a paraxial region and a convex near-circumferential region, and an image-side surface S8 of the fourth lens element L4 at a paraxial region and a convex near-circumferential region;

A sixth lens element L6 with negative dioptric power, the sixth lens element L6 having a convex surface near the optical axis and near the circumference of the object-side surface S11; the sixth lens element L6 has a concave image-side surface S12 at a paraxial region thereof and a convex image-side surface S12 at a paraxial region thereof.

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

Table 2a shows a table of characteristics of the optical system of the present embodiment in which data is obtained using light having a wavelength of 587nm, and the units of the Y radius, thickness, and focal length are all millimeters (mm).

TABLE 2a

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

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

TABLE 2b

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

Third embodiment

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

a second lens element L2 with positive refractive power, the second lens element L2 having a convex surface near the optical axis and near the circumference of the object-side surface S3, and the second lens element L2 having a concave surface near the optical axis and near the circumference of the image-side surface S4;

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

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

Table 3a shows a table of characteristics of the optical system of the present embodiment in which data is obtained using light having a wavelength of 587nm, and the units of the Y radius, thickness, and focal length are all millimeters (mm).

TABLE 3a

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

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

TABLE 3b

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

Fourth embodiment

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

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

a third lens element L3 with negative dioptric power, the third lens element L3 having an object-side surface S5 with a concave surface at the paraxial region and at the near circumference, and the third lens element L3 having a convex surface at the paraxial region and at the near circumference of an image-side surface S6;

a fourth lens element L4 with positive refractive power having a convex surface near the optical axis and near the circumference of the object-side surface S7 of the fourth lens element L4, a concave surface near the optical axis of the image-side surface S8 of the fourth lens element L4, and a convex surface near the circumference of the image-side surface S8;

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

A sixth lens element L6 with negative dioptric power, the sixth lens element L6 having a concave surface near the optical axis and near the circumference of the object-side surface S11; the sixth lens element L6 has a concave image-side surface S12 at a paraxial region thereof and a convex image-side surface S12 at a paraxial region thereof.

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

Table 4a shows a table of characteristics of the optical system of the present embodiment in which data is obtained using light having a wavelength of 587nm, and the units of the Y radius, thickness, and focal length are all millimeters (mm).

TABLE 4a

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

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

TABLE 4b

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

Fifth embodiment

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

a third lens element L3 with positive refractive power having a convex surface near the optical axis and near the circumference of the object-side surface S5 of the third lens element L3, and a convex surface near the optical axis and near the circumference of the image-side surface S6 of the third lens element L3;

a fourth lens element L4 with positive refractive power, the fourth lens element L4 having a convex surface near the optical axis and near the circumference of the object-side surface S7, and the fourth lens element L4 having a concave surface near the optical axis and near the circumference of the image-side surface S8;

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

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

Table 5a shows a table of characteristics of the optical system of the present embodiment in which data is obtained using light having a wavelength of 587nm, and the units of the Y radius, thickness, and focal length are all millimeters (mm).

TABLE 5a

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

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

TABLE 5b

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

Sixth embodiment

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

a third lens element L3 with positive refractive power having a convex surface near the optical axis and near the circumference of the object-side surface S5 of the third lens element L3, and a concave surface near the optical axis and near the circumference of the image-side surface S6 of the third lens element L3;

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

a fifth lens element L5 with positive refractive power, the fifth lens element L5 having a concave surface near the optical axis and near the circumference of the object-side surface S9; the fifth lens element L5 has a convex surface at a paraxial region and a peripheral region of the image-side surface S10.

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

Table 6a shows a table of characteristics of the optical system of the present embodiment in which data is obtained using light having a wavelength of 587nm, and the units of the Y radius, thickness, and focal length are all millimeters (mm).

TABLE 6a

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

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

TABLE 6b

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

Seventh embodiment

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

a fifth lens element L5 with negative dioptric power, the fifth lens element L5 having a concave surface near the optical axis and near the circumference of the object-side surface S9; the fifth lens element L5 has a convex image-side surface S10 at a paraxial region thereof and a concave image-side surface S10 at a paraxial region thereof;

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

Table 7a shows a table of characteristics of the optical system of the present embodiment, in which data is obtained using light having a wavelength of 587nm, and the units of the Y radius, thickness, and focal length are all millimeters (mm).

TABLE 7a

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

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

TABLE 7b

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

Table 8 shows values of f × 43/ImgH, TTL/f, FOV/f, (| R32| + | R42|)/f, R51/CT56, (CT1+ CT2+ CT3)/BF, SAG61/CT6, (| f3| + f4+ | f5|)/(CT34+ CT45+ CT56) of the optical systems of the first to seventh embodiments.

TABLE 8

As can be seen from table 8, each example satisfies: 45.5 < f 43/ImgH < 61.0, 0.89 < TTL/f < 1.0, 5.5 < FOV/f < 8.2, 1.9 < (| R32| + | R42|)/f < 13.44, 3.3 < R51/CT56 < 28.7, 1.2 < (CT1+ CT2+ CT3)/BF < 2.1, 1.0 < SAG61/CT6 < 2.9, 19 < (| f3| + f4+ | f5|)/(CT34+ CT45+ CT56) < 103.

The technical features of the above embodiments may be arbitrarily combined, and for the sake of brief description, all possible combinations of the technical features in the above embodiments are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

The above examples only show some embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the present invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present invention should be subject to the appended claims.

Claims

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

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

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

the third lens element with refractive power has an object-side surface and an image-side surface which are both aspheric;

the fourth lens element with positive refractive power has an object-side surface and an image-side surface which are both aspheric;

the fifth lens element with refractive power has an object-side surface and an image-side surface which are both aspheric;

the sixth lens element with negative refractive power has a concave image-side surface at a paraxial region thereof, and has a convex image-side surface at a paraxial region thereof, wherein at least one of the object-side surface and the image-side surface of the sixth lens element has at least one inflection point.

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

45.5≤f*43/ImgH＜61.0；

wherein f is the effective focal length of the optical system, and ImgH is the diagonal length of the effective imaging area of the optical system on the imaging surface.

3. The optical system according to claim 1, wherein the optical system satisfies the conditional expression:

0.89≤TTL/f＜1.0；

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.

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

5.5°/mm＜FOV/f＜8.2°/mm；

wherein FOV is a diagonal field angle of the optical system, and f is an effective focal length of the optical system.

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

1.9＜(|R32|+|R42|)/f≤13.44；

wherein R32 is a curvature radius of the image-side surface of the third lens at the optical axis, R42 is a curvature radius of the image-side surface of the fourth lens at the optical axis, and f is an effective focal length of the optical system.

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

3.3≤R51/CT56＜28.7；

wherein R51 is a curvature radius of an object-side surface of the fifth lens element on an optical axis, and CT56 is an axial distance between an image-side surface of the fifth lens element and an object-side surface of the sixth lens element.

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

1.2＜(CT1+CT2+CT3)/BF＜2.1；

wherein CT1 is a thickness of the first lens element, CT2 is a thickness of the second lens element, CT3 is a thickness of the third lens element, and BF is a distance from an image-side surface of the sixth lens element to an image plane along an optical axis.

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

1.0＜SAG61/CT6＜2.9；

SAG61 is the axial distance between the intersection point of the object side surface of the sixth lens and the optical axis and the farthest point of the sixth lens from the imaging surface along the optical axis, and CT6 is the thickness of the sixth lens on the optical axis.

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

19＜(|f3|+f4+|f5|)/(CT34+CT45+CT56)＜103；

wherein f3 is the effective focal length of the third lens element, f4 is the effective focal length of the fourth lens element, f5 is the effective focal length of the fifth lens element, CT34 is the distance between the image-side surface of the third lens element and the object-side surface of the fourth lens element on the optical axis, CT45 is the distance between the image-side surface of the fourth lens element and the object-side surface of the fifth lens element on the optical axis, and CT56 is the distance between the image-side surface of the fifth lens element and the object-side surface of the sixth lens element on the optical axis.

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

2.7mm＜TTL/FNO＜3.1mm；

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 FNO is an f-number of the optical system.

11. A lens module comprising a barrel, an electronic photosensitive chip and the optical system according to any one of claims 1 to 10, wherein the first to sixth lenses of the optical system are mounted in the barrel, and the electronic photosensitive chip is disposed on an image side of the optical system and is configured to convert light rays of an object incident on the electronic photosensitive chip through the first to sixth lenses into an electrical signal of an image.

12. An electronic device comprising a housing and the lens module as recited in claim 10, wherein the lens module is disposed in the housing.