CN111239988A

CN111239988A - Optical system, lens module and electronic equipment

Info

Publication number: CN111239988A
Application number: CN202010248250.2A
Authority: CN
Inventors: 刘彬彬; 李明; 邹海荣
Original assignee: OFilm Tech Co Ltd
Current assignee: Nanchang OFilm Precision Optical Products Co Ltd; OFilm Group Co Ltd
Priority date: 2020-03-31
Filing date: 2020-03-31
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: the lens comprises a first lens with positive bending force, wherein the object side surface of the first lens is a convex surface at the optical axis, and the image side surface of the first lens is a concave surface at the optical axis and the circumference; the object side surface of the second lens is a convex surface at the optical axis, and the image side surface of the second lens is a concave surface at the optical axis and the circumference; a third lens, a fourth lens, a fifth lens, and a sixth lens having a bending force; the image side surface of the seventh lens is a concave surface at the optical axis and is provided with at least one inflection point; the optical system satisfies the conditional expression: f/EPD < 1.7. According to the optical system provided by the invention, through the arrangement, the optical system has a larger light-entering aperture, so that the optical system has a larger light-entering amount, can improve the shooting effect under a dark condition, and has a better imaging effect.

Description

Optical system, lens module and electronic equipment

Technical Field

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

Background

Nowadays, with the rapid development of science and technology, the imaging quality requirements of consumers on mobile electronic products are higher and higher. At present, five-piece optical systems are relatively mature, but the resolution ratio is increasingly unable to meet the demands of consumers. Compared with the seven-piece optical system, the seven-piece optical system has obvious advantages, can obtain higher resolving power, and can be used for high-end mobile electronic products, so that the picture texture of shooting is improved, and the resolution and the definition are improved.

However, the current seven-piece optical system is still imperfect, and the shooting effect in dark light environments such as night scenes, rainy days, starry sky and the like is still unsatisfactory. Therefore, it is critical to further improve the seven-piece optical system to overcome the dark environment and achieve better shooting effect.

Disclosure of Invention

The invention aims to provide an optical system which still has a better shooting effect under the condition of dark light.

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 lens comprises a first lens with positive bending force, wherein the object side surface of the first lens is a convex surface at the optical axis, and the image side surface of the first lens is a concave surface at the optical axis and the circumference; the second lens with the bending force is characterized in that the object side surface of the second lens is a convex surface at the optical axis, and the image side surface of the second lens is a concave surface at the optical axis and the circumference; a third lens having a bending force; a fourth lens having a bending force; a fifth lens having a bending force; a sixth lens having a bending force; the image side surface of the seventh lens is a concave surface at the optical axis and is provided with at least one inflection point; the optical system satisfies the conditional expression: f/EPD < 1.7; where f is the effective focal length of the optical system and EPD is the entrance pupil diameter of the optical system. According to the optical system provided by the invention, the bending force and the surface shape of the first lens to the seventh lens are reasonably configured, and the f/EPD value is within 1.7, so that the optical system has a larger light entrance aperture, thereby having a larger light entrance amount, improving the shooting effect under a dark condition and having a better imaging effect.

In one embodiment, the optical system satisfies the conditional expression: TTL/Imgh is less than 1.7; wherein, TTL is a distance on an optical axis from an object-side surface of the first lens element to an imaging surface of the optical system, and Imgh is a half of a diagonal length of an effective photosensitive area on the imaging surface of the optical system. By satisfying that the value of TTL/Imgh is within 1.7, the optical system has the characteristic of ultra-thin, thereby realizing the miniaturization of the system.

In one embodiment, the optical system satisfies the conditional expression: f tan (hfov) >5.15 mm; wherein the HFOV is a half field angle of the optical system. By satisfying f tan (HFOV), the value of f is larger than 5.15mm, so that the optical system has the characteristic of a large image plane, and has the characteristics of high pixels and high definition.

In one embodiment, the optical system satisfies the conditional expression: 1< TTL/f < 1.5; wherein, TTL is a distance on an optical axis from an object-side surface of the first lens element to an image plane of the optical system. By meeting the condition that the value of TTL/f is between 1 and 1.5, the ratio of the total length of the control system to the focal length is less than 1.5, so that the optical system has the characteristic of miniaturization; meanwhile, the ratio is controlled to be larger than 1, so that the sensitivity of an optical system is weakened, and the processing and production of products are facilitated.

In one embodiment, the optical system satisfies the conditional expression: 0.5< | R5/R6| < 1.5; wherein R5 is a radius of curvature of an object-side surface of the third lens at an optical axis, and R6 is a radius of curvature of an image-side surface of the third lens at the optical axis. By satisfying the value of | R5/R6| between 0.5 and 0.6, the processing and the forming of the third lens are facilitated, and the sensitivity of the optical system on the third lens can be effectively reduced.

In one embodiment, the optical system satisfies the conditional expression: 0.5< TTH2/CT3< 1.5; wherein TTH2 is an air space distance on an optical axis from the second lens to the third lens, and CT3 is a thickness of the third lens on the optical axis. By meeting the requirement that the value of TTH2/CT3 is between 0.5 and 1.5, the sensitivity of an optical system field area is effectively reduced, and the processing and production of products are facilitated.

In one embodiment, the optical system satisfies the conditional expression: l f1/f5 l < 2; wherein f1 is the effective focal length of the first lens, and f5 is the effective focal length of the fifth lens. By satisfying that the value of | f1/f5| is within 2, the distribution of the optical effective focal lengths of the first lens and the fifth lens is reasonably controlled, and the position chromatic aberration of the optical system is effectively corrected.

In one embodiment, the optical system satisfies the conditional expression: 0.2< ET2/CT2< 1.3; wherein ET2 is the thickness of the edge of the optically effective area of the second lens, and CT2 is the thickness of the second lens on the optical axis. By meeting the requirement that the value of ET2/CT2 is between 0.2 and 1.3, the ratio of the edge thickness of the second lens to the middle thickness of the second lens is controlled to be in a proper range, and the processing and production of the second lens are facilitated.

In one embodiment, the optical system satisfies the conditional expression: TTL/f1 is less than or equal to 1.5; wherein TTL is an axial distance from an object-side surface of the first lens element to an image plane of the optical system, and f1 is an effective focal length of the first lens element. Through satisfying TTL/f 1's value within 1.5, the diopter of reasonable control first lens avoids the excessive increase of first lens bending power, guarantees the optical system total length of relative shortness.

In one embodiment, the optical system satisfies the conditional expression: EPD/R1< 1.5; wherein R1 is a radius of curvature of an object-side surface of the first lens at an optical axis. By meeting the condition that the value of EPD/R1 is within 1.5, the rationality of deflection of the incident light of the system on the first lens is effectively ensured.

In one embodiment, the optical system satisfies the conditional expression: sd61/sd52 is less than or equal to 1.3; wherein sd61 is the clear aperture of the object-side surface of the sixth lens at the maximum field angle; sd52 is the clear aperture of the image-side surface of the fifth lens at maximum field angle. By meeting the condition that the value of sd61/sd52 is within 1.3, the aberration on the fifth lens and the sixth lens structure is effectively reduced, the light of the edge field of view is smoother, and the processing and production stability of products are facilitated.

In a second aspect, the present invention further provides a lens module, which includes a lens barrel, a photosensitive element and the optical system 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 lens module, the lens module has a larger light entrance aperture, so that the lens module has a larger light entrance amount, can improve the shooting effect under dark conditions, and has a better imaging effect.

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. By adding the lens module provided by the invention into the electronic equipment, the optical system has a larger light entrance aperture, so that the optical system has a larger light entrance amount, the shooting effect of the electronic equipment under a dark condition can be improved, and the electronic equipment has a better imaging effect.

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;

FIG. 8a is a schematic structural diagram of an optical system of an eighth embodiment;

FIG. 8b is a longitudinal spherical aberration curve, an astigmatism curve and a distortion curve of the eighth embodiment;

FIG. 9a is a schematic structural diagram of an optical system of a ninth embodiment;

FIG. 9b is a longitudinal spherical aberration curve, an astigmatism curve and a distortion curve of the ninth embodiment;

FIG. 10a is a schematic structural view of an optical system of the tenth embodiment;

fig. 10b is a longitudinal spherical aberration curve, an astigmatism curve, and a distortion curve of the tenth 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 lens module provided by the embodiment of the invention, wherein the lens module is arranged in the shell. The electronic device can be a smart phone, a Personal Digital Assistant (PDA), a tablet computer, a smart watch, an unmanned aerial vehicle, an electronic book reader, a vehicle event data recorder, a wearable device and the like. By adding the lens module provided by the invention into the electronic equipment, the optical system has a larger light entrance aperture, so that the optical system has a larger light entrance amount, the shooting effect of the electronic equipment under a dark condition can be improved, and the electronic equipment has a better imaging effect.

The embodiment of the invention also provides a lens 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 the light rays of objects which pass through the first lens to the seventh lens and are incident on the photosensitive element into electric signals of images. The photosensitive element may be a Complementary Metal Oxide Semiconductor (CMOS) or a Charge-coupled Device (CCD). The lens module can be an independent lens of a digital camera, and can also be an imaging module integrated on electronic equipment such as a smart phone. By adding the optical system provided by the invention into the lens module, the lens module has a larger light entrance aperture, so that the lens module has a larger light entrance amount, can improve the shooting effect under dark conditions, and has a better imaging effect.

An embodiment of the present invention provides an optical system, which includes, in order from an object side to an image side: the lens comprises a first lens with positive bending force, wherein the object side surface of the first lens is a convex surface at the optical axis, and the image side surface of the first lens is a concave surface at the optical axis and the circumference; the second lens with the bending force is characterized in that the object side surface of the second lens is a convex surface at the optical axis, and the image side surface close to the second lens is a concave surface at the optical axis and the circumference; a third lens having a bending force; a fourth lens having a bending force; a fifth lens having a bending force; a sixth lens having a bending force; the image side surface of the seventh lens is a concave surface at the optical axis and is provided with at least one inflection point; the optical system satisfies the conditional expression: f/EPD < 1.7; where f is the effective focal length of the optical system and EPD is the entrance pupil diameter of the optical system. According to the optical system provided by the invention, the bending force and the surface shape of the first lens to the seventh lens are reasonably configured, and the f/EPD value is within 1.7, so that the optical system has a larger light entrance aperture, thereby having a larger light entrance amount, improving the shooting effect under a dark condition and having a better imaging effect. Specifically, the f/EPD value can be 1.7, 1.4, 1.1, 0.7, 0.5, 0.1, etc.

In one embodiment, the optical system satisfies the conditional expression: TTL/Imgh is less than 1.7; wherein, TTL is the distance on the optical axis from the object-side surface of the first lens element to the imaging surface of the optical system, and Imgh is half the length of the diagonal line of the effective photosensitive area on the imaging surface of the optical system. By satisfying that the value of TTL/Imgh is within 1.7, the optical system has the characteristic of ultra-thin, thereby realizing the miniaturization of the system. Specifically, the value of TTL/Imgh can be 1.7, 1.5, 1.2, 1.0, 0.5, 0.3, 0.1, and the like.

In one embodiment, the optical system satisfies the conditional expression: f tan (hfov) >5.15 mm; the HFOV is a half field angle of the optical system. By satisfying f tan (HFOV), the value of f is larger than 5.15mm, so that the optical system has the characteristic of a large image plane, and has the characteristics of high pixels and high definition. f tan (hfov) may take on values of 5.15mm, 5.18mm, 5.2mm, 5.5mm, 6mm, 8mm, 10mm, and the like.

In one embodiment, the optical system satisfies the conditional expression: 1< TTL/f < 1.5; wherein, TTL is a distance on the optical axis from the object-side surface of the first lens element to the image plane of the optical system. By meeting the condition that the value of TTL/f is between 1 and 1.5, the ratio of the total length of the control system to the focal length is less than 1.5, so that the optical system has the characteristic of miniaturization; meanwhile, the ratio is controlled to be larger than 1, so that the sensitivity of an optical system is weakened, and the processing and production of products are facilitated. Specifically, the value of TTL/f can be 1, 1.1, 1.2, 1.3, 1.4, 1.5, and the like.

In one embodiment, the optical system satisfies the conditional expression: 0.5< | R5/R6| < 1.5; wherein R5 is a radius of curvature of the object-side surface of the third lens element at the optical axis, and R6 is a radius of curvature of the image-side surface of the third lens element at the optical axis. By satisfying the value of | R5/R6| between 0.5 and 0.6, the processing and the forming of the third lens are facilitated, and the sensitivity of the optical system on the third lens can be effectively reduced. Specifically, | R5/R6| may take values of 0.5, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, and the like.

In one embodiment, the optical system satisfies the conditional expression: 0.5< TTH2/CT3< 1.5; the TTH2 is an air separation distance between the second lens and the third lens on the optical axis, and the CT3 is a thickness of the third lens on the optical axis. By meeting the requirement that the value of TTH2/CT3 is between 0.5 and 1.5, the sensitivity of an optical system field area is effectively reduced, and the processing and production of products are facilitated. Specifically, TTH2/CT3 can be 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, and the like.

In one embodiment, the optical system satisfies the conditional expression: l f1/f5 l < 2; wherein f1 is the effective focal length of the first lens, and f5 is the effective focal length of the fifth lens. By satisfying that the value of | f1/f5| is within 2, the distribution of the optical effective focal lengths of the first lens and the fifth lens is reasonably controlled, and the position chromatic aberration of the optical system is effectively corrected. Specifically, | f1/f5| can take the values of 0.1, 0.4, 0.7, 1, 1.4, 1.8, 2 and the like

In one embodiment, the optical system satisfies the conditional expression: 0.2< ET2/CT2<1.3, wherein ET2 is the thickness of the edge of the optically effective area of the second lens, and CT2 is the thickness of the second lens on the optical axis. By meeting the requirement that the value of ET2/CT2 is between 0.2 and 1.3, the ratio of the edge thickness of the second lens to the middle thickness of the second lens is controlled to be in a proper range, and the processing and production of the second lens are facilitated. Specifically, ET2/CT2 can be 0.2, 0.5, 0.7, 1, 1.1, 1.3, and the like.

In one embodiment, the optical system satisfies the conditional expression: TTL/f1 is less than or equal to 1.5; wherein, TTL is an axial distance from an object-side surface of the first lens element to an image plane of the optical system, and f1 is an effective focal length of the first lens element. Through satisfying TTL/f 1's value within 1.5, the diopter of reasonable control first lens avoids the excessive increase of first lens bending power, guarantees the optical system total length of relative shortness. Specifically, TTL/f1 can be 1.5, 1.2, 1, 0.8, 0.5, 0.3, 0.1, and the like.

In one embodiment, the optical system satisfies the conditional expression: EPD/R1< 1.5; where R1 is the radius of curvature of the object-side surface of the first lens at the optical axis. By meeting the condition that the value of EPD/R1 is within 1.5, the rationality of deflection of the incident light of the system on the first lens is effectively ensured. Specifically, the EPD/R1 may take on values of 1.5, 1.2, 1, 0.8, 0.5, 0.3, 0.1, and the like.

In one embodiment, the optical system satisfies the conditional expression: sd61/sd52 is not more than 1.3, wherein sd61 is the clear aperture of the object side surface of the sixth lens at the maximum field angle; sd52 is the clear aperture of the image-side surface of the fifth lens at maximum field angle. By meeting the condition that the value of sd61/sd52 is within 1.3, the aberration on the fifth lens and the sixth lens structure is effectively reduced, the light of the edge field of view is smoother, and the processing and production stability of products are facilitated. Specifically, sd61/sd52 can take on values of 1.2, 1, 0.8, 0.5, 0.3, 0.1, and the like.

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 L1 with positive bending force, the object side S1 of the first lens L1 being convex at the optical axis and at the circumference; the image-side surface S2 of the first lens L1 is concave both at the optical axis and at the circumference;

a second lens L2 having a negative bending force, the object-side surface S3 of the second lens L2 being convex at the optical axis and at the circumference; the image-side surface S4 of the second lens L2 is concave both at the optical axis and at the circumference;

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

a fourth lens L4 having a negative bending force, the object side S7 of the fourth lens L4 being concave at both the optical axis and the circumference; the image-side surface S8 of the fourth lens element L4 is concave at the optical axis and convex at the circumference;

a fifth lens L5 having a positive refractive power, the object side S9 of the fifth lens L5 being concave at both the optical axis and the circumference; the image-side surface S10 of the fifth lens element L5 is convex on both the optical axis and the circumference.

The sixth lens element L6 with positive refractive power has an object-side surface S11 of the sixth lens element L6 being convex at the optical axis and concave at the circumference; the image-side surface S12 of the sixth lens element L6 is concave along the optical axis and convex along the circumference.

A seventh lens element L7 with negative refractive power, the object-side surface S13 of the seventh lens element L7 being convex at the optical axis and concave at the circumference; the image-side surface S14 of the seventh lens element L7 is concave along the optical axis and convex along the circumference.

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

Further, the optical system includes a stop STO, an infrared cut filter L8, and an image forming surface S17. The stop STO is provided on the 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 other lenses. The infrared cut filter L8 is disposed on the image side of the seventh lens L7, and includes an object side surface S15 and an image side surface S16, and the infrared cut filter L8 is configured to filter out infrared light, so that the light entering the image plane S17 is visible light, and the wavelength of the visible light is 380nm-780 nm. The infrared cut-off filter L8 is made of glass and can be coated with a film. The image formation surface S17 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 555nm, and the units of the Y radius, thickness, and focal length are millimeters (mm).

TABLE 1a

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

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

wherein x is the maximum rise of the distance from the vertex of the aspheric surface when the aspheric surface is at the position with the height of h along the optical axis direction; c is the paraxial curvature of the aspheric surface, c being 1/R (i.e., paraxial curvature c is the inverse of radius R of Y in table 1a above); k is a conic coefficient; ai is the correction coefficient of the i-th order of the aspherical surface. Table 1b shows the high-order coefficient A4, A6, A8, A10, A12, A14, A16, A18 and A20 that can be used for each of the aspherical mirrors S1-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 555nm, 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 sixth lens element L6 with negative refractive power has an object-side surface S11 of the sixth lens element L6 being convex at the optical axis and concave at the circumference; the image-side surface S12 of the sixth lens element L6 is concave along the optical axis and convex along the circumference.

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

Table 2a shows a table of characteristics of the optical system of the present embodiment in which data is obtained using light having a wavelength of 555nm, and the units of the Y radius, thickness, and focal length are 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 555 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:

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 555nm, and the units of the Y radius, thickness, and focal length are 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 555 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:

a fourth lens L4 with positive refractive power, the object side S7 of the fourth lens L4 being concave at both the optical axis and the circumference; the image-side surface S8 of the fourth lens element L4 is convex on the optical axis and on the circumference;

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 555nm, and the units of the Y radius, thickness, and focal length are 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 555 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:

a fourth lens L4 having a negative bending force, the object side S7 of the fourth lens L4 being concave at both the optical axis and the circumference; the image-side surface S8 of the fourth lens element L4 is convex on the optical axis and on the circumference;

a fifth lens L5 having a negative bending force, the object side S9 of the fifth lens L5 being concave at both the optical axis and the circumference; the image-side surface S10 of the fifth lens element L5 is convex at the optical axis and concave at the circumference.

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 555nm, and the units of the Y radius, thickness, and focal length are 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 555 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:

a third lens L3 having a negative bending force, the object side S5 of the third lens L3 being concave at both the optical axis and the circumference; the image-side surface S6 of the third lens element L3 is convex on the optical axis and on the circumference;

a fifth lens element L5 with positive refractive power, the object-side surface S9 of the fifth lens element L5 being convex at the optical axis and concave at the circumference; the image-side surface S10 of the fifth lens element L5 is convex on both the optical axis and the circumference.

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 555nm, and the units of the Y radius, thickness, and focal length are 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 555 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:

a second lens L2 with positive bending force, the object side S3 of the second lens L2 being convex at the optical axis and at the circumference; the image-side surface S4 of the second lens L2 is concave both at the optical axis and at the circumference;

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 555nm, and the units of the Y radius, thickness, and focal length are 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 555 nm. As can be seen from fig. 7b, the optical system according to the seventh embodiment can achieve good image quality.

Eighth embodiment

Referring to fig. 8a and 8b, the optical system of the present embodiment, in order from an object side to an image side along an optical axis direction, includes:

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

Table 8a shows a table of characteristics of the optical system of the present embodiment in which data is obtained using light having a wavelength of 555nm, and the units of the Y radius, thickness, and focal length are millimeters (mm).

TABLE 8a

Table 8b shows the high-order term coefficients that can be used for each aspherical mirror surface in the eighth embodiment, wherein each aspherical mirror surface type can be defined by the formula given in the first embodiment.

TABLE 8b

Fig. 8b shows a longitudinal spherical aberration curve, an astigmatism curve, and a distortion curve of the optical system of the eighth embodiment. The reference wavelength of the light of the astigmatism curve and the distortion curve is 555 nm. As can be seen from fig. 8b, the optical system according to the eighth embodiment can achieve good imaging quality.

Ninth embodiment

Referring to fig. 9a and 9b, the optical system of the present embodiment, in order from an object side to an image side along an optical axis, includes:

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

Table 9a shows a table of characteristics of the optical system of the present embodiment in which data is obtained using light having a wavelength of 555nm, and the units of the Y radius, thickness, and focal length are millimeters (mm).

TABLE 9a

Table 9b shows the high-order term coefficients that can be used for each aspherical mirror surface in the ninth embodiment, wherein each aspherical mirror surface type can be defined by the formula given in the first embodiment.

TABLE 9b

Fig. 9b shows a longitudinal spherical aberration curve, an astigmatism curve, and a distortion curve of the optical system of the ninth embodiment. The reference wavelength of the light of the astigmatism curve and the distortion curve is 555 nm. As can be seen from fig. 9b, the optical system according to the ninth embodiment can achieve good imaging quality.

Tenth embodiment

Referring to fig. 10a and 10b, the optical system of the present embodiment, in order from an object side to an image side along an optical axis direction, includes:

A sixth lens L6 having a negative bending force, the object side S11 of the sixth lens L6 being concave at both the optical axis and the circumference; the image-side surface S12 of the sixth lens element L6 is concave along the optical axis and convex along the circumference.

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

Table 10a shows a table of characteristics of the optical system of the present embodiment in which data is obtained using light having a wavelength of 555nm, and the units of the Y radius, thickness, and focal length are millimeters (mm).

TABLE 10a

Table 10b shows the high-order term coefficients that can be used for each aspherical mirror surface in the tenth embodiment, wherein each aspherical mirror surface type can be defined by the formula given in the first embodiment.

TABLE 10b

Fig. 10b shows a longitudinal spherical aberration curve, an astigmatism curve, and a distortion curve of the optical system of the tenth embodiment. The reference wavelength of the light of the astigmatism curve and the distortion curve is 555 nm. As can be seen from fig. 10b, the optical system according to the tenth embodiment can achieve good imaging quality.

Table 11 shows values of f/EPD, f tan (hfov), TTL/Imgh, TTL/f, | R5/R6|, TTH2/CT3, | f1/f5|, ET2/CT2, TTL/f1, EPD/R1, sd61/sd52 of the optical systems of the first to tenth embodiments. Wherein f tan (hfov) is in millimeters (mm).

TABLE 11

As can be seen from table 11, the optical systems provided in the embodiments of the present invention all satisfy the following conditional expressions: f/EPD <1.7, f tan (HFOV) >5.15mm, TTL/Imgh <1.7, 1< TTL/f <1.5, 0.5< | R5/R6| <1.5, 0.5< TTH2/CT3<1.5, | f1/f5| <2, 0.2< ET2/CT2<1.3, TTL/f1 ≦ 1.5, EPD/R1<1.5, and sd61/sd52 ≦ 1.3.

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

Claims

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

the lens comprises a first lens with positive bending force, wherein the object side surface of the first lens is a convex surface at the optical axis, and the image side surface of the first lens is a concave surface at the optical axis and the circumference;

the second lens with the bending force is characterized in that the object side surface of the second lens is a convex surface at the optical axis, and the image side surface of the second lens is a concave surface at the optical axis and the circumference;

a third lens having a bending force;

a fourth lens having a bending force;

a fifth lens having a bending force;

a sixth lens having a bending force;

the image side surface of the seventh lens is a concave surface at the optical axis and is provided with at least one inflection point;

the optical system satisfies the conditional expression:

f/EPD<1.7；

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

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

TTL/Imgh<1.7；

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

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

f*tan(HFOV)>5.15mm；

wherein the HFOV is a half field angle of the optical system.

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

1<TTL/f<1.5；

wherein, TTL is a distance on an optical axis from an object-side surface of the first lens element to an image plane of the optical system.

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

0.5<|R5/R6|<1.5；

wherein R5 is a radius of curvature of an object-side surface of the third lens at an optical axis, and R6 is a radius of curvature of an image-side surface of the third lens at the optical axis.

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

0.5<TTH2/CT3<1.5；

wherein TTH2 is an air space distance on an optical axis from the second lens to the third lens, and CT3 is a thickness of the third lens on the optical axis.

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

|f1/f5|<2；

wherein f1 is the effective focal length of the first lens, and f5 is the effective focal length of the fifth lens.

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

0.2<ET2/CT2<1.3；

wherein ET2 is the thickness of the edge of the optically effective area of the second lens, and CT2 is the thickness of the second lens on the optical axis.

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

TTL/f1≤1.5；

wherein TTL is an axial distance from an object-side surface of the first lens element to an image plane of the optical system, and f1 is an effective focal length of the first lens element.

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

EPD/R1<1.5；

wherein R1 is a radius of curvature of an object-side surface of the first lens at an optical axis.

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

sd61/sd52≤1.3；

wherein sd61 is the clear aperture of the object-side surface of the sixth lens at the maximum field angle; sd52 is the clear aperture of the image-side surface of the fifth lens at maximum field angle.

12. A lens module comprising a lens barrel, a photosensitive element, and the optical system according to any one of claims 1 to 11, 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.

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