CN111897093A

CN111897093A - Optical system, camera module and electronic equipment

Info

Publication number: CN111897093A
Application number: CN202010799376.9A
Authority: CN
Inventors: 党绪文; 刘彬彬; 杨健; 李明; 邹海荣
Original assignee: OFilm Tech Co Ltd
Current assignee: Nanchang OFilm Precision Optical Products Co Ltd; OFilm Group Co Ltd
Priority date: 2020-08-10
Filing date: 2020-08-10
Publication date: 2020-11-06

Abstract

An optical system, a camera module and an electronic device, the optical system comprises the following components in sequence from an object side to an image side: a first lens element with positive refractive power having a convex object-side surface at paraxial region, a concave image-side surface at paraxial region, and a convex peripheral surface; a second lens element with negative refractive power having a convex object-side surface and a concave image-side surface; a third lens element and a fourth lens element with refractive power; a fifth lens element with refractive power having a concave object-side surface at its circumference; at least one of the object side surface and the image side surface of the sixth lens element with refractive power is provided with at least one inflection point; the seventh lens element with negative refractive power has a convex image-side surface at its circumference, and at least one of the object-side surface and the image-side surface has an inflection point. The surface shapes and the refractive powers of the first lens, the second lens and the seventh lens are reasonably configured, and the total length of the optical system can be shorter on the premise of not sacrificing the focal length, so that the design requirements of miniaturization and clear long-range shooting are met.

Description

Optical system, camera module and electronic equipment

Technical Field

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

Background

Nowadays, with the rapid development of multi-camera electronic devices, consumers have higher and higher imaging quality requirements on the multi-camera electronic devices, and the telephoto lens is an important component for realizing telephoto imaging of the multi-camera electronic devices, and the importance of the telephoto lens is needless to say. The telephoto lens can enable an object with a far object distance to clearly image on an image surface, and a shooting effect similar to that of a near object distance is obtained, so that a space compression effect is achieved.

The current seven-piece optical system is limited by the size of multi-camera electronic equipment, and the total length of the system is too long when the total focal length is enough, or the total focal length is not ideal when the total focal length meets the requirements.

Disclosure of Invention

The invention aims to provide an optical system, a camera module and an electronic device, which can take both the focal length and the total length of the system into consideration.

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

in a first aspect, the present invention provides an optical system comprising, in order from an object side to an image side: the first lens element with positive refractive power has a convex object-side surface at a paraxial region and a convex image-side surface at a peripheral region; a second lens element with negative refractive power; the object side surface of the second lens element is convex at a paraxial region and at a circumference, and the image side surface of the second lens element is concave at a paraxial region; a third lens element with refractive power; a fourth lens element with refractive power; the fifth lens element with refractive power has a concave object-side surface at the circumference, and both the object-side surface and the image-side surface of the fifth lens element are aspheric surfaces; the sixth lens element with refractive power has an object-side surface and an image-side surface which are both aspheric, and at least one of the object-side surface and the image-side surface of the sixth lens element is provided with at least one inflection point; the seventh lens element with negative refractive power has a convex image-side surface at a circumference, both the object-side surface and the image-side surface of the seventh lens element are aspheric, and at least one of the object-side surface and the image-side surface of the seventh lens element is provided with at least one inflection point.

By reasonably configuring the surface shapes and the refractive powers of the first lens, the second lens and the seventh lens, the optical system can have a shorter total system length on the premise of not sacrificing the focal length, and the design requirements of miniaturization and clear long-range shooting are met.

In one embodiment, the optical system satisfies the conditional expression: TTL/f is more than 0.8 and less than 0.95; 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 meeting the requirement that the value of TTL/f is between 0.8 and 0.95, the optical system can obtain better space compression feeling under the long-distance shooting condition, and when the optical system is applied to a small-size electronic photosensitive chip, higher magnification (such as a 3mm chip, and a 4.3-time magnification effect can be obtained); on the other hand, the proper use of high-refractive index materials can effectively reduce the total length of the system and ensure the economical efficiency of production.

In one embodiment, the optical system satisfies the conditional expression: 0.38mm^-1＜Fno/(ImgH*2)＜0.45mm^-1(ii) a Fno is the diaphragm number of the optical system, and ImgH is half of the diagonal length of an effective photosensitive area on an imaging surface of the optical system. It is understood that ImgH determines the size of the electronic photosensitive chip, and the larger ImgH, the larger the maximum electronic photosensitive chip size that can be supported. By satisfying the Fno/(ImgH 2) value of 0.38mm^-1And 0.45mm^-1Meanwhile, the optical system can support an electronic photosensitive chip with high pixels; simultaneously, provide great f-number, optical system can obtain higher light incident quantity for optical system can acquire the depth of field effect of preferred easily when long focus is shot, cooperates the magnification effect about 2 times simultaneously, and reasonable refractive power and lens structure set up, and especially adapted shooting feature effect.

In one embodiment, the optical system satisfies the conditional expression: 24 < (| R52| + | R61|)/CT56 < 250; wherein R52 is a radius of curvature of the image-side surface of the fifth lens element at the optical axis, R61 is a radius of curvature of the object-side surface of the sixth lens element at the optical axis, 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 at the optical axis. The numerical value of (| R52| + | R61|)/CT56 is between 24 and 250, the curvature radius of the image side surface of the fifth lens and the curvature radius of the object side surface of the sixth lens have obvious change, so that adaptive change on the surface type is caused, the change can compress the calibers of the external field rays at the edges of the fifth lens and the sixth lens, so that the rays can be guided to exit at a small angle, the incidence angle of the imaging surface of the rays is reduced, an optical system is more easily matched with an electronic photosensitive chip, tolerance sensitivity is reduced, and the performance of the edge field of view is improved;

in one embodiment, the optical system satisfies the conditional expression: 0.2 < CT4/CT45 < 2.3; wherein CT4 is the thickness of the fourth lens element on the optical axis, and 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. By meeting the requirement that the value of CT4/CT45 is between 0.2 and 2.3, the reasonable change of the distance between the fourth lens and the fifth lens is matched with the change of the surface shape of the fourth lens and the fifth lens, the centralized distribution conditions of other aberrations such as spherical aberration, coma aberration and the like of the system can be dispersed, and the performance fluctuation caused by tolerance is reduced; moreover, the thickness and the refractive power of the lens are reasonably configured, which is beneficial to improving the resolving power

In one embodiment, the optical system satisfies the conditional expression: i SAG 71I/CT 7 is less than 3.3; the SAG71 is the rise of the object side optical effective diameter edge of the seventh lens, and the CT7 is the thickness of the seventh lens on the optical axis. The seventh lens is U-shaped by meeting the condition that the value of SAG 71/CT 7 is below 3.3 and the rise of the object side surface of the seventh lens is changed, so that on the premise of keeping uniform thickness, the seventh lens provides support for accurate and small-angle incidence of light to an imaging surface from the front lens group; and the refractive power and the thickness are reasonably configured, so that the aberration introduced by the seventh lens element is small, and the optical system is favorable for controlling the whole aberration within a reasonable range.

In one embodiment, the optical system satisfies the conditional expression: f12/R21 is less than 0.54; wherein f12 is a combined effective focal length of the first and second lenses, and R21 is a radius of curvature of an object-side surface of the second lens at an optical axis. By meeting the condition that the value of f12/R21 is less than 0.54, the aperture of light in an optical system is rapidly compressed by the second lens in cooperation with the change of the focal length and the curvature of the first lens, and the further control of the rear lens on the light is facilitated; and the larger effective combined focal length of the first lens and the second lens is beneficial to the improvement of the effective focal length of the optical system.

In one embodiment, the optical system satisfies the conditional expression: 3.5mm^-1＜(IND4+IND6)/(ET45+ET56)＜16.5mm^-1(ii) a Wherein IND4 is the refractive index of the material of the fourth lens to the d-line, IND6 is the refractive index of the material of the sixth lens to the d-line, ET45 is the axial distance between the edge of the fourth lens optical effective diameter and the edge of the fifth lens optical effective diameter, and ET56 is the axial distance between the edge of the fifth lens optical effective diameter and the edge of the sixth lens optical effective diameter. Specifically, the d-line indicates a ray having a wavelength of 587.5618 nm. The value of (IND4+ IND6)/(ET45+ ET56) is 3.5mm^-1And 16.5mm^-1In between, the overall length can be further compressed, which is helpful for controlling aberration and improving performance; meanwhile, the flexible distribution and the surface shape change of the fourth lens, the fifth lens and the sixth lens increase the flexibility of the optical system and can meet the structural matching of different design targets; and reasonable refractive power configuration is favorable for improving the imaging quality of the optical system.

In one embodiment, the optical system satisfies the conditional expression: BF/CT67 is more than 0.3 and less than 1.2; BF is the minimum axial distance from the image side surface of the seventh lens to an imaging surface; CT67 is the distance between the image-side surface of the sixth lens element and the object-side surface of the seventh lens element on the optical axis. The value of BF/CT67 is between 0.3 and 1.2, so that the back focus of the optical system is kept about 0.7mm, and the optical system and the electronic photosensitive chip can be ensured to have good matching performance; and the distance between the sixth lens and the seventh lens is reasonable, which is beneficial to controlling aberration and improving resolving power.

In a second aspect, the present invention further provides an image capturing module, which includes a lens barrel, a photosensitive element and the optical system according to any one of the embodiments of the first aspect, wherein the first to seventh 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 camera module, the camera module can give consideration to both the focal length and the total length of the system, and the imaging quality of long-focus telephoto is better while the camera module is miniaturized.

In a third aspect, the present invention further provides an electronic device, where the electronic device includes a housing and the camera module of the second aspect, and the camera module is disposed in the housing. By adding the camera module provided by the invention into the electronic equipment, the electronic equipment can meet the light and thin design and has an ideal focal length so as to be convenient for the electronic equipment to carry out clear long-range shooting.

Drawings

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Detailed Description

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

The embodiment of the invention provides electronic equipment, which comprises a shell and a camera module provided by the embodiment of the invention, wherein the camera module is arranged in the shell. The electronic device can be a smart phone, a Personal Digital Assistant (PDA), a tablet computer, a smart watch, an unmanned aerial vehicle, an electronic book reader, a vehicle event data recorder, a wearable device and the like. By adding the camera module provided by the invention into the electronic equipment, the electronic equipment can meet the light and thin design and has an ideal focal length so as to be convenient for the electronic equipment to carry out clear long-range shooting.

The embodiment of the invention also provides a camera module, which comprises a lens barrel, a photosensitive element and the optical system, wherein the first lens to the seventh lens of the optical system are arranged in the lens barrel, and the photosensitive element is arranged at the image side of the optical system and is used for converting light rays of an object which passes through the first lens to the seventh lens and is incident on the photosensitive element into an electric signal of an image. The photosensitive element may be a Complementary Metal Oxide Semiconductor (CMOS) or a Charge-coupled Device (CCD). The camera module can be an independent lens of a digital camera and also can be an imaging module integrated on electronic equipment such as a smart phone. By adding the optical system provided by the invention into the camera module, the camera module can give consideration to both the focal length and the total length of the system, and the imaging quality of long-focus telephoto is better while the camera module is miniaturized.

The present invention provides an optical system, which includes, in order from an object side to an image side, a first lens element, a second lens element, a third lens element, a fourth lens element, a fifth lens element, a sixth lens element and a seventh lens element.

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

a second lens element with negative refractive power; the object side surface of the second lens element is convex at a paraxial region and at a circumference, and the image side surface of the second lens element is concave at a paraxial region;

a third lens element with refractive power;

a fourth lens element with refractive power;

the fifth lens element with refractive power has a concave object-side surface at the circumference, and both the object-side surface and the image-side surface of the fifth lens element are aspheric surfaces;

the sixth lens element with refractive power has an object-side surface and an image-side surface which are both aspheric, and at least one of the object-side surface and the image-side surface of the sixth lens element is provided with at least one inflection point;

the seventh lens element with negative refractive power has a convex image-side surface at a circumference, both the object-side surface and the image-side surface of the seventh lens element are aspheric, and at least one of the object-side surface and the image-side surface of the seventh lens element is provided with at least one inflection point.

Specifically, the value of TTL/f may be 0.8, 0.82, 0.86, 0.88, 0.9, 0.95, and the like. In this embodiment, the maximum value of f can reach 7.42mm, and can be matched with an electronic photosensitive chip with a diagonal length of about 5mm under an effective imaging area, the equivalent focal length can reach 63.8mm, and compared with a lens with 24mm, a 2.66-time magnification shooting effect can be obtained, so that a good spatial compression sense can be obtained, and long-range shooting can be met. On the other hand, the minimum value of TTL can reach 5.75mm, and the thickness of the glass is good.

In one embodiment, the optical system satisfies the conditional expression: 0.38mm^-1＜Fno/(ImgH*2)＜0.45mm^-1(ii) a Fno is the diaphragm number of the optical system, and ImgH is half of the diagonal length of an effective photosensitive area on an imaging surface of the optical system. It is understood that ImgH determines the size of the electronic photosensitive chip, and the larger ImgH, the larger the maximum electronic photosensitive chip size that can be supported. By satisfying the Fno/(ImgH 2) value of 0.38mm^-1And 0.45mm^-1Meanwhile, the optical system can support an electronic photosensitive chip with high pixels; meanwhile, a larger f-number is provided, and the optical system can obtain a higher light incoming quantity, so that the optical system can easily obtain a better depth of field effect during long-focus shooting, and simultaneously cooperate with an amplification effect of about 2 times, andreasonable refractive power and lens structure setting are very suitable for shooting close-up effect. Specifically, Fno/(ImgH × 2) may be 0.38mm^-1、0.39mm^-1、0.4mm^-1、0.41mm^-1、0.43mm^-1And 0.45mm^-1And the like.

In one embodiment, the optical system satisfies the conditional expression: 24 < (| R52| + | R61|)/CT56 < 250; wherein R52 is a radius of curvature of the image-side surface of the fifth lens element at the optical axis, R61 is a radius of curvature of the object-side surface of the sixth lens element at the optical axis, 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 at the optical axis. The value of (| R52| + | R61|)/CT56 is between 24 and 250, the curvature radius of the image side surface of the fifth lens and the curvature radius of the object side surface of the sixth lens have obvious change, so that adaptive change on the surface type is caused, the change can compress the calibers of the external field rays at the edges of the fifth lens and the sixth lens, so that the rays can be guided to exit at a small angle, the incidence angle of the imaging surface of the rays is reduced, an optical system is enabled to be matched with an electronic photosensitive chip more easily, tolerance sensitivity is reduced, and the performance of the edge field is improved. Specifically, (| R52| + | R61|)/CT56 can take on values of 24, 46, 68, 140, 190, 220, 250, and the like.

In one embodiment, the optical system satisfies the conditional expression: 0.2 < CT4/CT45 < 2.3; wherein CT4 is the thickness of the fourth lens element on the optical axis, and 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. By meeting the requirement that the value of CT4/CT45 is between 0.2 and 2.3, the reasonable change of the distance between the fourth lens and the fifth lens is matched with the change of the surface shape of the fourth lens and the fifth lens, the centralized distribution conditions of other aberrations such as spherical aberration, coma aberration and the like of the system can be dispersed, and the performance fluctuation caused by tolerance is reduced; and the thickness and the refractive power of the lens are reasonably configured, which is beneficial to improving the resolving power. Specifically, the value of CT4/CT45 may be 0.2, 0.46, 0.81, 1.2, 1.3, 1.7, 1.9, 2.3, etc.

In one embodiment, the optical system satisfies the conditional expression: i SAG 71I/CT 7 is less than 3.3; the SAG71 is the rise of the object side optical effective diameter edge of the seventh lens, and the CT7 is the thickness of the seventh lens on the optical axis. The seventh lens is U-shaped by meeting the condition that the value of SAG 71/CT 7 is below 3.3 and the rise of the object side surface of the seventh lens is changed, so that on the premise of keeping uniform thickness, the seventh lens provides support for accurate and small-angle incidence of light to an imaging surface from the front lens group; and the refractive power and the thickness are reasonably configured, so that the aberration introduced by the seventh lens element is small, and the optical system is favorable for controlling the whole aberration within a reasonable range. Specifically, the value of i SAG71 i/CT 7 may be 0.13, 0.25, 0.7, 1.6, 2.3, 3.3, and the like.

In one embodiment, the optical system satisfies the conditional expression: f12/R21 is less than 0.54; wherein f12 is a combined effective focal length of the first and second lenses, and R21 is a radius of curvature of an object-side surface of the second lens at an optical axis. By meeting the condition that the value of f12/R21 is less than 0.54, the aperture of light in an optical system is rapidly compressed by the second lens in cooperation with the change of the focal length and the curvature of the first lens, and the further control of the rear lens on the light is facilitated; and the larger effective combined focal length of the first lens and the second lens is beneficial to the improvement of the effective focal length of the optical system. Specifically, f12/R21 can be 0.15, 0.23, 0.34, 0.42, 0.49, 0.54 and the like.

In one embodiment, the optical system satisfies the conditional expression: 3.5mm^-1＜(IND4+IND6)/(ET45+ET56)＜16.5mm^-1(ii) a Wherein IND4 is the refractive index of the material of the fourth lens to the d-line, IND6 is the refractive index of the material of the sixth lens to the d-line, ET45 is the axial distance between the edge of the fourth lens optical effective diameter and the edge of the fifth lens optical effective diameter, and ET56 is the axial distance between the edge of the fifth lens optical effective diameter and the edge of the sixth lens optical effective diameter. The value of (IND4+ IND6)/(ET45+ ET56) is 3.5mm^-1And 16.5mm^-1In between, the overall length can be further compressed, which is helpful for controlling aberration and improving performance; meanwhile, the flexible distribution and the surface shape change of the fourth lens, the fifth lens and the sixth lens increase the flexibility of the optical system and can meet the structural matching of different design targets; and reasonable refractive power configuration is favorable for improving the imaging quality of the optical system. Specifically, (IND 4)The value of + IND6)/(ET45+ ET56) may be 3.5mm^-1、4.7mm^-1、6.7mm^-1、10.3mm^-1、12.3mm^-1、15.9mm^-1And 16.5mm^-1And the like. Line d refers to light having a wavelength of 587.5618 nm.

In one embodiment, the optical system satisfies the conditional expression: BF/CT67 is more than 0.3 and less than 1.2; BF is the minimum axial distance from the image side surface of the seventh lens to an imaging surface; CT67 is the distance between the image-side surface of the sixth lens element and the object-side surface of the seventh lens element on the optical axis. The value of BF/CT67 is between 0.3 and 1.2, so that the back focus of the optical system is kept about 0.7mm, and the optical system and the electronic photosensitive chip can be ensured to have good matching performance; and the distance between the sixth lens and the seventh lens is reasonable, which is beneficial to controlling aberration and improving resolving power. Specifically, the BF/CT67 value may be 0.3, 0.45, 0.63, 0.8, 0.94, 1.1, 1.2, etc.

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 paraxial region and at peripheral region of the first lens element L1; the image-side surface S2 of the first lens element L1 is concave at paraxial region and convex at peripheral region;

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

the third lens element L3 with negative refractive power has a convex object-side surface S5 at paraxial region and a concave object-side surface at periphery of the third lens element L3; the image-side surface S6 of the third lens element L3 is concave at the paraxial region and at the peripheral region;

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

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

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

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

The first lens element L1 to the seventh lens element L7 are all made of plastic.

In addition, the optical system further includes a stop STO, an infrared filter IR, and an imaging surface IMG. The stop STO is provided on the object side surface S1 of the first lens L1 for controlling the amount of light entering. In other embodiments, the stop STO can be disposed between two adjacent lenses, or on the image side surface S2 of the first lens L1 and the object side surface or the image side surface of the other lenses. The infrared filter IR is disposed on the image side of the seventh lens L7, and includes an object side surface S15 and an image side surface S16, and 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 filter IR is glass, and a film can be coated on the glass. The imaging plane IMG is an effective pixel area of the photosensitive element.

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 587.5618nm, and the units of the Y radius, thickness, and focal length are all millimeters (mm).

TABLE 1a

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

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

wherein x is the maximum rise of the distance from the vertex of the aspheric surface when the aspheric surface is at the position with the height of h along the optical axis direction; c is the paraxial curvature of the aspheric surface, c being 1/R (i.e., paraxial curvature c is the inverse of radius R of Y in table 1a above); k is a conic coefficient; ai is the correction coefficient of the i-th order of the aspherical surface. Table 1b shows the high-order coefficient A4, A6, A8, A10, A12, A14, A16, A18 and A20 that can be used for each of the aspherical mirrors S1-S14 in the first embodiment.

TABLE 1b

Fig. 1b shows a longitudinal spherical aberration curve, an astigmatism curve and a distortion curve of the optical system of the first embodiment. The reference wavelength of the light rays of the astigmatism curve and the distortion curve is 587.5618nm, wherein the longitudinal spherical aberration curve represents the deviation of the convergent focus of the light rays with different wavelengths after passing through each lens of the optical system; the astigmatism curves are meridional image surface curvature and sagittal image surface curvature; the distortion curve represents the distortion magnitude values corresponding to different angles of view. As can be seen from fig. 1b, the optical system according to the first embodiment can achieve good imaging quality.

Second embodiment

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

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

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

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

The sixth lens element L6 with negative refractive power has a concave object-side surface S11 at a paraxial region and a concave object-side surface at a circumference of the sixth lens element L6; the image-side surface S12 of the sixth lens element L6 is concave at the paraxial region and convex at the peripheral region.

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

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 587.5618nm, and the units of the Y radius, thickness, and focal length are all millimeters (mm).

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. The reference wavelength of the light of the astigmatism curve and the distortion curve is 587.5618 nm. As can be seen from fig. 2b, the optical system according to the second embodiment can achieve good imaging quality.

Third embodiment

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

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

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

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

The sixth lens element L6 with negative refractive power has a concave object-side surface S11 at a paraxial region and a concave object-side surface at a circumference of the sixth lens element L6; the image-side surface S12 of the sixth lens element L6 is convex at the paraxial region and at the periphery.

The seventh lens element L7 with negative refractive power has a convex object-side surface S13 at a paraxial region and a convex object-side surface at a circumference of the seventh lens element L7; the image-side surface S14 of the seventh lens element L7 is concave at the paraxial region and convex at the 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 587.5618nm, and the units of the Y radius, thickness, and focal length are all millimeters (mm).

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. The reference wavelength of the light of the astigmatism curve and the distortion curve is 587.5618 nm. As can be seen from fig. 3b, the optical system according to the third embodiment can achieve good imaging quality.

Fourth embodiment

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

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

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

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 587.5618nm, and the units of the Y radius, thickness, and focal length are all millimeters (mm).

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. The reference wavelength of the light of the astigmatism curve and the distortion curve is 587.5618 nm. As can be seen from fig. 4b, the optical system according to the fourth embodiment can achieve good imaging quality.

Fifth embodiment

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

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

the third lens element L3 with negative refractive power has a concave object-side surface S5 at a paraxial region and a concave object-side surface at a peripheral region of the third lens element L3; the image-side surface S6 of the third lens element L3 is convex at the paraxial region and at the periphery;

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

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 587.5618nm, and the units of the Y radius, thickness, and focal length are all millimeters (mm).

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. The reference wavelength of the light of the astigmatism curve and the distortion curve is 587.5618 nm. As can be seen from fig. 5b, the optical system according to the fifth embodiment can achieve good image quality.

Sixth embodiment

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

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

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

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

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

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 587.5618nm, and the units of the Y radius, thickness, and focal length are all millimeters (mm).

TABLE 6a

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. The reference wavelength of the light of the astigmatism curve and the distortion curve is 587.5618 nm. As can be seen from fig. 6b, the optical system according to the sixth embodiment can achieve good image quality.

Seventh embodiment

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

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

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

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

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 587.5618nm, and the units of the Y radius, thickness, and focal length are all millimeters (mm).

TABLE 7a

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. The reference wavelength of the light of the astigmatism curve and the distortion curve is 587.5618 nm. As can be seen from fig. 7b, the optical system according to the seventh embodiment can achieve good image quality.

Table 8 shows values of TTL/f, Fno/(ImgH × 2), (| R52| + | R61|)/CT56, CT4/CT45, | SAG71|/CT7, f12/R21, (IND4+ IND6)/(ET45+ ET56), and BF/CT67 of the optical systems in the first to seventh embodiments, where Fno/(ImgH × 2) and (IND4+ IND6)/(ET45+ ET56) are in units of mm^-1。

TABLE 8

	TTL/f	Fno/(ImgH*2)	(\|R52\|+\|R61\|)/CT56	CT4/CT45
					First embodiment	0.927	0.385	169.523	0.446
Second embodiment	0.822	0.436	46.343	2.278
					Third embodiment	0.942	0.396	68.644	0.320
Fourth embodiment	0.934	0.395	24.305	0.223
					Fifth embodiment	0.896	0.390	224.267	1.255
Sixth embodiment	0.896	0.388	247.252	1.332
					Seventh embodiment	0.836	0.438	37.825	1.872
	\|SAG71\|/CT7	f12/R21	(IND4+IND6)/(ET45+ET56)	BF/CT67
					First embodiment	2.801	0.343	4.532	1.115
Second embodiment	0.545	0.237	16.387	0.507
					Third embodiment	3.233	0.427	3.747	0.675
Fourth embodiment	1.584	0.369	3.691	0.569
					Fifth embodiment	2.735	0.535	15.827	0.432
Sixth embodiment	2.323	0.535	12.232	0.341
					Seventh embodiment	0.135	0.054	9.238	1.154

As can be seen from table 8, the optical systems of the first to seventh embodiments all satisfy the conditional expressions: TTL/f is more than 0.8 and less than 0.95 and 0.38mm^-1＜Fno/(ImgH*2)＜0.45mm^-1、24＜(|R52|+|R61|)/CT56＜250、0.2＜CT4/CT45＜2.3、|SAG71|/CT7＜3.3、f12/R21＜0.54、3.5mm^-1＜(IND4+IND6)/(ET45+ET56)＜16.5mm^-1And 0.3 < BF/CT67 < 1.2.

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

Claims

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

a third lens element with refractive power;

a fourth lens element with refractive power;

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

0.8＜TTL/f＜0.95；

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 according to claim 1, wherein the optical system satisfies a conditional expression:

0.38mm^-1＜Fno/(ImgH*2)＜0.45mm^-1；

fno is the diaphragm number of the optical system, and ImgH is half of the diagonal length of an effective photosensitive area on an imaging surface of the optical system.

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

24＜(|R52|+|R61|)/CT56＜250；

wherein R52 is a radius of curvature of the image-side surface of the fifth lens element at the optical axis, R61 is a radius of curvature of the object-side surface of the sixth lens element at the optical axis, 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 at the optical axis.

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

0.2＜CT4/CT45＜2.3；

wherein CT4 is the thickness of the fourth lens element on the optical axis, and 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.

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

|SAG71|/CT7＜3.3；

the SAG71 is the rise of the object side optical effective diameter edge of the seventh lens, and the CT7 is the thickness of the seventh lens on the optical axis.

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

f12/R21＜0.54；

wherein f12 is a combined effective focal length of the first and second lenses, and R21 is a radius of curvature of an object-side surface of the second lens at an optical axis.

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

3.5mm^-1＜(IND4+IND6)/(ET45+ET56)＜16.5mm^-1；

wherein IND4 is the refractive index of the material of the fourth lens to the d-line, IND6 is the refractive index of the material of the sixth lens to the d-line, ET45 is the axial distance between the edge of the fourth lens optical effective diameter and the edge of the fifth lens optical effective diameter, and ET56 is the axial distance between the edge of the fifth lens optical effective diameter and the edge of the sixth lens optical effective diameter.

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

0.3＜BF/CT67＜1.2；

BF is the minimum axial distance from the image side surface of the seventh lens to an imaging surface; CT67 is the distance between the image-side surface of the sixth lens element and the object-side surface of the seventh lens element on the optical axis.

10. An image pickup module comprising a lens barrel, a photosensitive element, and the optical system according to any one of claims 1 to 9, wherein the first to seventh 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.

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