CN112180555A

CN112180555A - Optical system, lens module and electronic equipment

Info

Publication number: CN112180555A
Application number: CN202011129665.4A
Authority: CN
Inventors: 李明; 邹海荣
Original assignee: Jiangxi Jingchao Optical Co Ltd
Current assignee: Jiangxi Jingchao Optical Co Ltd
Priority date: 2020-10-20
Filing date: 2020-10-20
Publication date: 2021-01-05

Abstract

The invention provides an optical system, a lens module and an electronic device. The optical system includes, in order from an object side to an image side in an optical axis direction: the first lens element with positive refractive power has a convex object-side surface and a concave image-side surface; the second lens element with negative refractive power has a convex object-side surface and a concave image-side surface; a third lens element with refractive power; a fourth lens element with refractive power; the fifth lens element with negative refractive power has a concave image-side surface at the paraxial region thereof, and at least one inflection point is formed on the object-side surface or the image-side surface of the fifth lens element; the optical system satisfies the conditional expression: ET2/CT2< 2; wherein ET2 is the edge thickness of the second lens and CT2 is the center thickness of the second lens. The invention solves the technical problem that the five-piece lens cannot meet the requirements of high pixels and high resolution.

Description

Optical system, lens module and electronic equipment

Technical Field

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

Background

Nowadays, with the rapid development of science and technology, the imaging quality of mobile electronic products is more and more required by consumers. At present, imaging lenses of five lenses are mature, but the pixels are small, and the resolution ratio is increasingly unable to meet the market demand, so obtaining lenses with higher pixels and higher resolution is gradually a goal pursued by consumers. More lenses are typically used to increase the pixel requirements, but the greater the number of lenses, the more complex and relatively costly the manufacturing process. The existing five-piece lens cannot meet the requirements of high pixels and high resolution. Therefore, improving the pixel and resolution ratio based on the design of the five-piece optical system becomes a key factor for improving the shooting quality of the current camera.

Disclosure of Invention

An object of the present application is to provide an optical system, a lens module and an electronic device, which are used to solve the above technical problems. The invention provides an optical system, comprising in order from an object side to an image side along an optical axis: the first lens element with positive refractive power has a convex object-side surface and a concave image-side surface; the second lens element with negative refractive power has a convex object-side surface and a concave image-side surface; a third lens element with refractive power; a fourth lens element with refractive power; the fifth lens element with negative refractive power has a concave image-side surface at the paraxial region thereof, and at least one inflection point is formed on the object-side surface or the image-side surface of the fifth lens element; the optical system satisfies the conditional expression: ET2/CT2< 2; wherein ET2 is the edge thickness of the second lens and CT2 is the center thickness of the second lens. By reasonably configuring the surface shapes and the refractive powers of the first lens element to the fifth lens element, the five-piece optical system can meet the requirements of high pixel and good image quality. When the optical system meets the conditional expression, the ratio of the edge thickness of the second lens to the center thickness of the second lens can be reasonably controlled in a certain range, and the processing and production of the second lens are facilitated.

In certain embodiments, the optical system satisfies the conditional expression: f tan (hfov) >4.1 mm; wherein f is a focal length of the optical system, and the HFOV is a half field angle of the optical system. When the optical system satisfies the above conditional expressions, the optical system can be made to have a characteristic of a large image plane, thereby making the optical system have high pixels and high definition.

In certain embodiments, 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 imaging surface of the optical system, and f is a focal length of the optical system. When the optical system meets the condition formula, the ratio of the total length to the focal length of the optical system can be reasonably controlled to be smaller than a certain range, so that the system has the characteristic of miniaturization, and meanwhile, the ratio of the total length to the focal length of the optical system is controlled to be larger than a certain range, so that the sensitivity of the optical system can be weakened, and the processing and production of products are facilitated.

In certain embodiments, the optical system satisfies the conditional expression: l R5/R6 l < 15; wherein, R5 is the radius of curvature of the object-side surface of the third lens element at the optical axis, and R6 is the radius of curvature of the image-side surface of the third lens element at the optical axis. When the optical system meets the conditional expression, the object side curvature radius and the image side curvature radius of the third lens can be reasonably controlled within a certain range, 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 certain embodiments, the optical system satisfies the conditional expression: l f1/f < 1.5; wherein f1 is the focal length of the first lens, and f is the focal length of the optical system. When the optical system meets the conditional expression, the ratio of the focal length of the first lens to the focal length of the optical system can be reasonably controlled, and the chromatic aberration of the position of the optical system can be effectively corrected.

In certain embodiments, the optical system satisfies the conditional expression: f/EPD <2.0, where f is the focal length of the optical system and EPD is the entrance pupil diameter of the optical system. When the optical system meets the conditional expression, the optical system has the characteristic of large aperture, so that the optical system has larger light incoming quantity, and the shooting effect under dark conditions is improved.

In certain embodiments, the optical system satisfies the conditional expression: (L41p1-L41p2) - (L32p1-L32p2) <0.4mm, wherein L32p1 represents the maximum perpendicular distance from the optical axis of the intersection of the fringe field of view with the image-side surface of the third lens, L32p2 represents the minimum perpendicular distance from the optical axis of the intersection of the fringe field of view with the image-side surface of the third lens, L41p1 represents the maximum perpendicular distance from the optical axis of the intersection of the fringe field of view with the object-side surface of the fourth lens, and L41p2 represents the minimum perpendicular distance from the optical axis of the intersection of the fringe field of view with the object-side surface of the fourth lens, the fringe field of view being a light beam incident and converging to the farthest point from the optical axis of the imaging surface of the optical imaging system. When the optical system meets the condition formula, the difference value between the light aperture of the object side surface of the fourth lens and the light aperture of the image side surface of the third lens can be reasonably controlled in a certain range, the structural offset of the third lens and the fourth lens can be effectively reduced, the marginal field light is smoother, and the processing and production stability of products are easy.

In certain embodiments, the optical system satisfies the conditional expression: r5 > 27, where R5 is the radius of curvature of the third lens object-side surface at the optical axis. When the optical system meets the conditional expression, the curvature radius of the object side surface of the third lens can be reasonably controlled within a certain range, and the imaging quality is favorably improved.

The invention provides a lens module, which comprises a lens barrel, an electronic photosensitive element and the optical system, wherein the first lens to the fifth lens of the optical system are arranged in the lens barrel, and the electronic photosensitive element is arranged at the image side of the optical system and is used for converting light rays of objects which pass through the first lens to the fifth lens and are incident on the electronic photosensitive element into electric signals of images. By installing the first lens to the fifth lens of the optical system in the lens module and reasonably configuring the surface shapes and the refractive powers of the lenses of the first lens to the fifth lens, the five-piece type optical system can meet the requirements of high pixels and high resolution.

The invention provides electronic equipment which comprises a shell and the lens module, wherein the lens module is arranged in the shell. According to the lens module, the electronic equipment can meet the requirements of high pixels and high resolution by arranging the lens module in the electronic equipment.

In summary, the invention provides a five-piece large-image-surface and large-aperture optical system, which can enable the optical system to obtain high pixels and high resolution, and enable the optical system to have better imaging effect; the optical system has the characteristic of large aperture, has larger light inlet amount compared with a camera lens, can improve the dim light shooting condition, can meet the requirement of high-definition image shooting, is also suitable for shooting in dim light environments such as night scenes, rainy days, starry sky and the like, and has 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 for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

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

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

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

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

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

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

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

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

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

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

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

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

fig. 7 is a schematic view of an optical system and an optical path provided in an embodiment of the present application.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The embodiment of the application provides a lens module, which comprises a lens barrel, an electronic photosensitive element and an optical system provided by the embodiment of the invention, wherein first lenses to fifth lenses of the optical system are arranged in the lens barrel, and the electronic photosensitive element is arranged at the image side of the optical system and is used for converting light rays of objects which pass through the first lenses to the fifth lenses and are incident on the electronic photosensitive element into electric signals of images. The electron sensor 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 installing the first lens to the fifth lens of the optical system in the lens module and reasonably configuring the surface shapes and the refractive powers of the lenses of the first lens to the fifth lens, the five-piece type optical system can meet the requirements of high pixels and high resolution.

The embodiment of the application provides electronic equipment, and the electronic equipment comprises a shell and a lens module provided by the embodiment of the application. The lens module and the electronic photosensitive element are arranged in the shell. The electronic device can be a smart phone, a Personal Digital Assistant (PDA), a tablet computer, a smart watch, an unmanned aerial vehicle, an electronic book reader, a vehicle event data recorder, a wearable device and the like. According to the application, the lens module is arranged in the electronic equipment, so that the electronic equipment can meet the requirements of high pixels and high resolution.

The present disclosure provides an optical system including, in order from an object side to an image side in an optical axis direction, a stop, a first lens element, a second lens element, a third lens element, a fourth lens element, and a fifth lens element. In the first to fifth lenses, any two adjacent lenses may have an air space therebetween.

Specifically, the specific shape and structure of the five lenses are as follows:

the first lens element with positive refractive power has a convex object-side surface and a concave image-side surface; the second lens element with negative refractive power has a convex object-side surface and a concave image-side surface; a third lens element with refractive power; a fourth lens element with refractive power; the fifth lens element with negative refractive power has a concave image-side surface at the paraxial region thereof, and at least one inflection point is formed on the object-side surface or the image-side surface of the fifth lens element; the optical system satisfies the conditional expression: ET2/CT2< 2; wherein ET2 is the edge thickness of the second lens and CT2 is the center thickness of the second lens. By reasonably configuring the surface shapes and the refractive powers of the first lens element to the fifth lens element, the five-piece optical system can meet the requirements of high pixel and good image quality. When the optical system meets the conditional expression, the ratio of the edge thickness of the second lens to the center thickness of the second lens can be reasonably controlled in a certain range, and the processing and production of the second lens are facilitated.

In a specific embodiment, the optical system satisfies the conditional expression: f tan (hfov) >4.1 mm; wherein f is a focal length of the optical system, and the HFOV is a half field angle of the optical system. When the optical system satisfies the above conditional expressions, the optical system can be made to have a characteristic of a large image plane, thereby making the optical system have high pixels and high definition.

In a specific 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 imaging surface of the optical system, and f is a focal length of the optical system. When the optical system meets the condition formula, the ratio of the total length to the focal length of the optical system can be reasonably controlled to be smaller than a certain range, so that the system has the characteristic of miniaturization, and meanwhile, the ratio of the total length to the focal length of the optical system is controlled to be larger than a certain range, so that the sensitivity of the optical system can be weakened, and the processing and production of products are facilitated.

In a specific embodiment, the optical system satisfies the conditional expression: l R5/R6 l < 15; wherein, R5 is the radius of curvature of the object-side surface of the third lens element at the optical axis, and R6 is the radius of curvature of the image-side surface of the third lens element at the optical axis. When the optical system meets the conditional expression, the object side curvature radius and the image side curvature radius of the third lens can be reasonably controlled within a certain range, 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 a specific embodiment, the optical system satisfies the conditional expression: l f1/f < 1.5; wherein f1 is the focal length of the first lens, and f is the focal length of the optical system. When the optical system meets the conditional expression, the ratio of the focal length of the first lens to the focal length of the optical system can be reasonably controlled, and the chromatic aberration of the position of the optical system can be effectively corrected.

In a specific embodiment, the optical system satisfies the conditional expression: f/EPD <2.0, where f is the focal length of the optical system and EPD is the entrance pupil diameter of the optical system. When the optical system meets the conditional expression, the optical system has the characteristic of large aperture, so that the optical system has larger light incoming quantity, and the shooting effect under dark conditions is improved.

Referring to fig. 7, in one embodiment, the optical system satisfies the following conditional expression: (L41p1-L41p2) - (L32p1-L32p2) <0.4mm, wherein L32p1 represents the maximum perpendicular distance from the optical axis of the intersection of the fringe field of view with the image-side surface of the third lens, L32p2 represents the minimum perpendicular distance from the optical axis of the intersection of the fringe field of view with the image-side surface of the third lens, L41p1 represents the maximum perpendicular distance from the optical axis of the intersection of the fringe field of view with the object-side surface of the fourth lens, and L41p2 represents the minimum perpendicular distance from the optical axis of the intersection of the fringe field of view with the object-side surface of the fourth lens, the fringe field of view being a light beam incident and converging to the farthest point from the optical axis of the imaging surface of the optical imaging system. When the optical system meets the condition formula, the difference value between the light aperture of the object side surface of the fourth lens and the light aperture of the image side surface of the third lens can be reasonably controlled in a certain range, the structural offset of the third lens and the fourth lens can be effectively reduced, the marginal field light is smoother, and the processing and production stability of products are easy.

In a specific embodiment, the optical system satisfies the conditional expression: r5 > 27, where R5 is the radius of curvature of the third lens object-side surface at the optical axis. When the optical system meets the conditional expression, the curvature radius of the object side surface of the third lens can be reasonably controlled within a certain range, and the imaging quality is favorably improved.

In a first embodiment of the present invention, the first,

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 an object-side surface S1 of the first lens element L1 being convex at paraxial region and an image-side surface S2 being concave at paraxial region; the object-side surface S1 of the first lens element L1 is convex at the circumference, and the image-side surface S2 is convex at the circumference.

A second lens element L2 with negative refractive power having an object-side surface S3 of the second lens element L2 being convex at paraxial region and an image-side surface S4 being concave at paraxial region; the object-side surface S3 of the second lens element L2 is convex at the circumference, and the image-side surface S4 is concave at the circumference.

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

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

The fifth lens element L5 with negative refractive power has an object-side surface S9 of the fifth lens element L5 being convex at paraxial region and an image-side surface S10 being concave at paraxial region; the object-side surface S9 of the fifth lens element L5 is convex at the circumference, and the image-side surface S10 is convex at the circumference.

The first lens element L1 to the fifth lens element L5 are all made of plastic.

Further, the optical system includes a stop STO, an infrared filter L6, and an image plane S13. The stop STO is provided on the side of the first lens L1 away from the second lens L2, and controls the amount of light entering. In other embodiments, the stop STO can be disposed between two adjacent lenses, or on other lenses. The infrared filter L6 is disposed on the image side of the fifth lens L5, and includes an object side surface S11 and an image side surface S12, and the infrared filter L6 is configured to filter infrared light, so that the light incident on the image surface S13 is visible light, and the wavelength of the visible light is 380nm-780 nm. The infrared filter L6 is made of glass, and may be coated with a film. The image plane S13 is a plane on which an image formed by the light of the subject passing through the optical system is located.

Table 1a shows a table of characteristics of the optical system of the present embodiment, and the units of the Y radius, thickness, and focal length are all millimeters (mm).

TABLE 1a

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

In the present embodiment, the object-side surface and the image-side surface of any one of the first lens L1 to the fifth lens L5 are aspheric surfaces, and the surface shape x of each aspheric lens can be defined by, but is not limited to, the following aspheric surface formula:

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

TABLE 1b

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

In a second embodiment of the present invention, the first 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 an object-side surface S5 of the third lens element L3 being concave at a paraxial region and an image-side surface S6 being convex at a paraxial region; the object-side surface S5 of the third lens element L3 is concave at the circumference, and the image-side surface S6 is convex at 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, and the units of the Y radius, thickness, and focal length are all millimeters (mm).

TABLE 2a

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

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

TABLE 2b

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

Third embodiment

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

The third lens element L3 with positive refractive power has an object-side surface S1 of the third lens element L3 being concave at a paraxial region and an image-side surface S2 being convex at a paraxial region; the object-side surface S5 of the third lens element L3 is concave at the circumference, and the image-side surface S6 is convex at the circumference.

A fourth lens element L4 with negative refractive power having a concave object-side surface S7 and a convex image-side surface S8 at paraxial region, respectively, of the fourth lens element L4; the object-side surface S7 of the fourth lens element L4 is concave at the circumference, and the image-side surface S8 is convex at the circumference.

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

Table 3a shows a table of characteristics of the optical system of the present embodiment, and the units of the Y radius, thickness, and focal length are all millimeters (mm).

TABLE 3a

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

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

TABLE 3b

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

In a fourth embodiment of the present invention,

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 an object-side surface S1 of the third lens element L3 being convex at paraxial region and an image-side surface S2 being convex at paraxial region; the object-side surface S5 of the third lens element L3 is concave at the circumference, and the image-side surface S6 is convex at 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, and the units of the Y radius, thickness, and focal length are all millimeters (mm).

TABLE 4a

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

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

TABLE 4b

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

In the fifth embodiment, the first 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 fourth lens element L4 with positive refractive power has an object-side surface S7 of the fourth lens element L4 being convex at paraxial region and an image-side surface S8 being convex at paraxial region; the object-side surface S7 of the fourth lens element L4 is concave at the circumference, and the image-side surface S8 is convex 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, and the units of the Y radius, thickness, and focal length are all millimeters (mm).

TABLE 5a

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

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

TABLE 5b

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

In a sixth embodiment of the present invention,

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 negative refractive power has an object-side surface S1 of the third lens element L3 being concave at paraxial region and an image-side surface S2 being concave at paraxial region; the object-side surface S5 of the third lens element L3 is concave at the circumference, and the image-side surface S6 is convex at 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, and the units of the Y radius, thickness, and focal length are all millimeters (mm).

TABLE 6a

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

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

TABLE 6b

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

Table 7 shows values of f/EPD, f tan (hfov), TTL/f, | R5/R6|, | f1/f |, ET2/CT2, (L41p1-L41p2) - (L32p1-L32p2), | R5| of the optical systems of the first to sixth embodiments.

TABLE 7

	f/EPD	f*tan(HFOV)	TTL/f	\|R5/R6\|
					First embodiment	1.99	4.14	1.18	1.60
Second embodiment	1.97	4.14	1.18	0.36
					Third embodiment	1.99	4.14	1.19	3.20
Fourth embodiment	1.99	4.23	1.18	10.10
					Fifth embodiment	1.99	4.14	1.18	1.36
Sixth embodiment	1.99	4.14	1.18	13.46
						\|f1/f\|	ET2/CT2	(L41p1-L41p2)-(L32p1-L32p2)	\|R5\|
First embodiment	0.81	1.45	0.35	\|-35.27\|
					Second embodiment	0.83	1.42	0.35	\|-34\|
Third embodiment	0.81	1.49	0.36	\|-27.97\|
					Fourth embodiment	0.80	1.33	0.36	\|1000\|
Fifth embodiment	0.84	1.46	0.34	\|-71.15/\|
					Sixth embodiment	0.85	1.50	0.36	\|-1346.29\|

As can be seen from table 7, each example satisfies the following conditional expressions f/EPD <2.0, f tan (hfov) >4.1, 1< TTL/f <1.5, | R5/R6| <15, | f1/f | <1.5, ET2/CT2<2, (L41p1-L41p2) - (L32p1-L32p2) <0.4mm, | R5| > 27.

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

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

Claims

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

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

the second lens element with negative refractive power has a convex object-side surface and a concave image-side surface;

a third lens element with refractive power;

a fourth lens element with refractive power;

the fifth lens element with negative refractive power has a concave image-side surface at the paraxial region thereof, and at least one inflection point is formed on the object-side surface or the image-side surface of the fifth lens element;

the optical system satisfies the conditional expression: ET2/CT2< 2; wherein ET2 is the edge thickness of the second lens and CT2 is the center thickness of the second lens.

2. The optical system according to claim 1, wherein the optical system satisfies the conditional expression: f tan (hfov) >4.1 mm; wherein f is a focal length of the optical system, and the HFOV is a half field angle of the optical system.

3. The optical system according to claim 1, wherein 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 imaging surface of the optical system, and f is a focal length of the optical system.

4. The optical system according to claim 1, wherein the optical system satisfies the conditional expression: l R5/R6 l < 15; 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.

5. The optical system according to claim 1, wherein the optical system satisfies the conditional expression: l f1/f < 1.5; wherein f1 is the focal length of the first lens, and f is the focal length of the optical system.

6. The optical system according to claim 1, wherein the optical system satisfies the conditional expression: f/EPD <2.0, where f is the focal length of the optical system and EPD is the entrance pupil diameter of the optical system.

7. The optical system according to claim 1, wherein the optical system satisfies the conditional expression: (L41p1-L41p2) - (L32p1-L32p2) <0.4mm, wherein L32p1 represents the maximum perpendicular distance from the optical axis of the intersection of the fringe field of view and the image-side surface of the third lens, L32p2 represents the minimum perpendicular distance from the optical axis of the intersection of the fringe field of view and the image-side surface of the third lens, L41p1 represents the maximum perpendicular distance from the optical axis of the intersection of the fringe field of view and the object-side surface of the fourth lens, and L41p2 represents the minimum perpendicular distance from the optical axis of the intersection of the fringe field of view and the object-side surface of the fourth lens.

8. The optical system according to claim 1, wherein the optical system satisfies the conditional expression: r5 > 27, where R5 is the radius of curvature of the third lens object-side surface at the optical axis.

9. A lens module comprising a lens barrel, an electro-optic element, and the optical system according to any one of claims 1 to 8, wherein the first to fifth lenses of the optical system are mounted in the lens barrel.

10. An electronic device comprising a housing and the lens module as claimed in claim 9, wherein the lens module is disposed in the housing.