CN112180557A

CN112180557A - Optical system, camera module and terminal equipment

Info

Publication number: CN112180557A
Application number: CN202011146898.5A
Authority: CN
Inventors: 蔡雄宇; 赵迪; 兰宾利; 周芮
Original assignee: Tianjin OFilm Opto Electronics Co Ltd
Current assignee: Tianjin OFilm Opto Electronics Co Ltd
Priority date: 2020-10-23
Filing date: 2020-10-23
Publication date: 2021-01-05

Abstract

The embodiment of the application discloses an optical system, a camera module and terminal equipment. The optical system comprises a first lens with positive refractive power; the second lens element with negative refractive power has a concave object-side surface and a concave image-side surface at a paraxial region; the third lens element with positive refractive power has a convex object-side surface and a convex image-side surface at paraxial region; a fourth lens element with positive refractive power; a fifth lens element with negative refractive power; the optical system satisfies the conditional expression: 3.5< (R2-R3)/D12<7, wherein R2 is the curvature radius of the image side surface of the first lens at the optical axis, R3 is the curvature radius of the object side surface of the second lens at the optical axis, and D12 is the air space between the first lens and the second lens on the optical axis. The optical system meets the requirements of high pixel and miniaturization at the same time by reasonably configuring the refractive power, the surface shape and the limitation (R2-R3)/D12 of the first lens, the second lens and the third lens.

Description

Optical system, camera module and terminal equipment

Technical Field

The application belongs to the technical field of optical imaging, and particularly relates to an optical system, a camera module and terminal equipment.

Background

With the continuous development of automobile safety technologies, such as an auxiliary driving technology, automatic driving and unmanned driving, the application of the vehicle-mounted camera is more and more popular.

The vehicle-mounted cameras are different in mounting position and function, and the forward-looking camera can master the front road condition in real time in the driving process due to the fact that the forward-looking camera needs to observe images beyond a long distance, and provides guarantee for safe driving, so that the forward-looking camera can use a long focal length under the condition of guaranteeing high-pixel imaging. The existing front-view camera has the characteristic that the whole pixel is difficult to guarantee due to the characteristic that a long-distance object is captured and observed, and meanwhile, due to the limitation of installation space, the camera needs to meet the characteristic of miniaturization.

Therefore, how to make the camera have the feature of miniaturization and have high imaging quality of pixels is the research and development direction in the industry.

Disclosure of Invention

The embodiment of the application provides an optical system, a camera module and terminal equipment, and the optical system meets the requirements of high pixel, large aperture and miniaturization.

In a first aspect, an optical system includes a plurality of lenses, each of the plurality of lenses includes a first lens having positive refractive power and arranged in sequence from an object side (where an object side refers to a side on which light is incident) to an image side (where an image side refers to a side on which light is emitted); the second lens element with negative refractive power has a concave object-side surface and a concave image-side surface at a paraxial region; the third lens element with positive refractive power has a convex object-side surface and a convex image-side surface at a paraxial region; a fourth lens element with positive refractive power having convex object-side and image-side surfaces at paraxial region; a fifth lens element with negative refractive power; the optical system satisfies the following conditional expression: 3.5< (R2-R3)/D12<7, wherein R2 is the curvature radius of the image side surface of the first lens at the optical axis, R3 is the curvature radius of the object side surface of the second lens at the optical axis, and D12 is the air space between the first lens and the second lens on the optical axis.

The refractive power is the focal power, and represents the ability of the optical system to deflect light, positive refractive power represents the converging effect of the lens on the light beam, and negative refractive power represents the diverging effect of the lens on the light beam. When the lens has no refractive power, that is, when the focal power is zero, the lens is plane refraction, and at this time, the axially parallel light beams are still axially parallel light beams after being refracted, and the refraction phenomenon does not occur.

The refractive power of the first lens, the second lens, the third lens and the fourth lens in the optical system, the surface shape of the second lens, the third lens and the fourth lens are reasonably configured, and 3.5< (R2-R3)/D12<7 is limited, so that the optical system can meet the requirements of high pixel and miniaturization at the same time. Specifically, by defining (R2-R3)/D12, it is advantageous to control the radii of curvature of the image-side surface of the first lens and the object-side surface of the second lens, reducing the generation of ghost images, and at the same time, by controlling the air gap between the first lens and the second lens, while ensuring high pixel imaging quality, it is advantageous to make the optical system compact, and ensure the miniaturization feature.

In a possible implementation manner, the object-side surface and/or the image-side surface of at least one of the lenses is/are aspheric, which is beneficial to correcting the aberration of the optical system and improving the imaging quality of the optical system.

In a possible embodiment, at least one of said lenses has an abbe number of less than 25 or greater than 70, said abbe number having a reference wavelength of 587.6 nm. The abbe number of the lens is limited, so that the chromatic aberration of the optical system can be corrected, and the imaging quality of the optical system can be improved.

In a possible embodiment, the optical system satisfies the conditional expression: 7< f1/CT1<9, f1 is the focal length of the first lens, and CT1 is the thickness of the first lens on the optical axis. The optical system has good imaging quality by reasonably configuring f1/CT1, wherein f1/CT1 is more than 9, and the refractive power is insufficient when the focal length of the first lens is too large, so that the high-order aberration is not favorably inhibited, and the high-order spherical aberration, the coma aberration and other phenomena influence the resolution and the imaging quality of the optical system; f1/CT1<7, too strong refractive power of the first lens element causes the width of the light beam to shrink rapidly, thereby increasing the incident angle of the light beam incident on other lens elements and increasing the difficulty of reducing the emergent angle of the light beam by other lens elements.

In a possible embodiment, the optical system satisfies the conditional expression: -14< f23/(CT3-CT2) < -9, f23 is a combined focal length of the second lens and the third lens, CT3 is a thickness of the third lens on an optical axis, and CT2 is a thickness of the second lens on the optical axis. By reasonably configuring the thickness relationship between the second lens element and the third lens element, the refractive powers of the second lens element with negative refractive power and the third lens element with positive refractive power are reasonably matched, which is beneficial to the mutual correction of aberration, so that the second lens element and the third lens element have the minimum influence on the aberration of the optical system. The requirement of-14 < f23/(CT3-CT2) < -9 is met, the phenomenon that the gluing process is affected due to overlarge thickness difference of the second lens and the third lens is avoided, the phenomena of glue cracking or glue failure and the like are easily caused due to large cold and hot deformation caused by the thickness difference under the condition of large environmental temperature change are avoided, and meanwhile, the limitation of f23/(CT3-CT2) is beneficial to avoiding overlarge combined focal length of the second lens and the third lens, the serious astigmatism phenomenon is avoided, and therefore the improvement of the imaging quality is not facilitated.

In a possible embodiment, the optical system satisfies the conditional expression: 5*10^-6mm/℃<(CT3-CT2)*|α3-α2|<8*10^-6mm/° c, CT3 is a thickness of the third lens on an optical axis, CT2 is a thickness of the second lens on an optical axis, α 3 is a coefficient of thermal expansion of the third lens at-30 ℃ to 70 ℃, and α 2 is a coefficient of thermal expansion of the second lens at-30 ℃ to 70 ℃. The second lens and the third lens are glued, the influence of temperature on the optical system is reduced through reasonable matching of materials, the optical system keeps good imaging quality under the condition of high temperature or low temperature, the thickness difference and the material characteristic difference of the second lens and the third lens are reduced, and the risk of cracking of the glued lens is reduced.

In a possible embodiment, the optical system satisfies the conditional expression: 2.6< f4/CT4<4.3, f4 is the focal length of the fourth lens, and CT4 is the thickness of the fourth lens on the optical axis. f4/CT4 is more than 4.3, the focal length of the fourth lens element is too large, the refractive power is insufficient, the high-order aberration is not favorably inhibited, the resolution and the imaging quality of the optical system are influenced, f4/CT4 is less than 2.6, the thickness of the fourth lens element is too large, and the density of the fourth lens element is large when the fourth lens element is made of glass, so that the weight of the fourth lens element is large, and the light weight of the optical system is not favorably realized.

In a possible embodiment, the optical system satisfies the conditional expression: -40< f5/CT5< -9, f5 being the focal length of the fifth lens, CT5 being the thickness of the fifth lens on the optical axis. The thickness of the fifth lens and the focal length relation of the fifth lens are reasonably configured, so that the tolerance sensitivity of the thickness of the fifth lens can be reduced, the processing difficulty of the fifth lens is reduced, the assembly yield of an optical system is favorably improved, and the production cost is reduced. Through limiting-40 < f5/CT5< -9, the phenomenon that the fifth lens has too large focal length and generates difficult-to-correct astigmatism is avoided, so that the imaging quality of the optical system is reduced, meanwhile, the reasonable limitation of the thickness of the fifth lens is facilitated, the larger the thickness of the fifth lens is, the larger the weight of the fifth lens is, the light weight of the optical system is not facilitated, and the smaller the thickness of the fifth lens is, the larger the processing difficulty is caused.

In a possible embodiment, the optical system satisfies the conditional expression: 2.4< f13/f45<4.4, f13 being a combined focal length of the first lens, the second lens, and the third lens, f45 being a combined focal length of the fourth lens and the fifth lens. By limiting f13/f45, the incident width of light rays is favorably controlled, high-order aberration of the optical system is reduced, and simultaneously the emergent angle of the main light rays passing through the fourth lens and the fifth lens can be reduced, so that the relative brightness of the optical system is improved.

In a possible embodiment, the optical system satisfies the conditional expression: 1.8< TTL/f <2.5, wherein TTL is the distance between the object side surface of the first lens and an imaging surface in the optical system on the optical axis, and f is the focal length of the optical system. By limiting TTL/f, the total length of the optical system is controlled while satisfying the field angle range of the optical system, and the characteristic of downsizing the optical system is satisfied. TTL/f is more than 2.5, the total length of the optical system is too long, miniaturization is not facilitated, TTL/f is less than 1.8, the focal length of the optical system is too long, the field angle range of the optical system is not satisfied, and enough object space information cannot be obtained.

In a second aspect, the present application provides a camera module, including a photosensitive element and the optical system of any one of the foregoing embodiments, where the photosensitive element is located on an image side of the optical system.

In a third aspect, the present application provides a terminal device, including the camera module.

By reasonably configuring the refractive power of the first lens, the second lens, the third lens and the fourth lens in the optical system and defining the surface shape of the second lens, the third lens and the fourth lens to be 3.5< (R2-R3)/D12<7, the optical system simultaneously meets the requirements of high pixel and miniaturization.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments or the background art of the present application, the drawings required to be used in the embodiments or the background art of the present application will be described below.

Fig. 1 is a schematic structural diagram of an optical system provided in a first embodiment of the present application;

fig. 2 is a longitudinal spherical aberration curve, an astigmatism curve, and a distortion curve of the optical system of the first embodiment;

FIG. 3 is a schematic diagram of an optical system according to a second embodiment of the present application;

FIG. 4 is a longitudinal spherical aberration curve, an astigmatism curve, and a distortion curve of the optical system of the second embodiment;

FIG. 5 is a schematic diagram of an optical system provided in a third embodiment of the present application;

fig. 6 is a longitudinal spherical aberration curve, an astigmatism curve, and a distortion curve of the optical system of the third embodiment;

FIG. 7 is a schematic diagram of an optical system according to a fourth embodiment of the present application;

fig. 8 is a longitudinal spherical aberration curve, an astigmatism curve, and a distortion curve of the optical system of the fourth embodiment;

fig. 9 is a schematic structural diagram of an optical system provided in a fifth embodiment of the present application;

fig. 10 is a longitudinal spherical aberration curve, an astigmatism curve, and a distortion curve of the optical system of the fifth embodiment;

fig. 11 is a schematic diagram of an optical system applied in a terminal device.

Detailed Description

The embodiments of the present application will be described below with reference to the drawings.

An optical system provided by the present application includes five lenses, which are, in order from an object side to an image side, a first lens, a second lens, a third lens, a fourth lens and a fifth lens.

Specifically, the surface shapes and refractive powers of the five lenses are as follows:

a first lens element with positive refractive power; the second lens element with negative refractive power has a concave object-side surface and a concave image-side surface at a paraxial region; the third lens element with positive refractive power has a convex object-side surface and a convex image-side surface at a paraxial region; a fourth lens element with positive refractive power having convex object-side and image-side surfaces at paraxial region; the fifth lens element with negative refractive power.

The optical system satisfies the following conditional expression: 3.5< (R2-R3)/D12<7, wherein R2 is the curvature radius of the image side surface of the first lens at the optical axis, R3 is the curvature radius of the object side surface of the second lens at the optical axis, and D12 is the air space between the first lens and the second lens on the optical axis.

By reasonably configuring the refractive power of the first lens, the second lens, the third lens and the fourth lens in the optical system and defining the surface shape of the second lens, the third lens and the fourth lens to be 3.5< (R2-R3)/D12<7, the optical system simultaneously meets the requirements of high pixel and miniaturization. Specifically, by defining (R2-R3)/D12, it is advantageous to control the radii of curvature of the image-side surface of the first lens and the object-side surface of the second lens, reducing the generation of ghost images, and at the same time, by controlling the air gap between the first lens and the second lens, while ensuring high pixel imaging quality, it is advantageous to make the optical system compact, and ensure the miniaturization feature.

In a possible embodiment, the optical system satisfies the conditional expression: 5*10^-6mm/℃<(CT3-CT2)*|α3-α2|<8*10^-6mm/DEG C, CT3 is the thickness of the third lens on the optical axis, CT2 isThe thickness of the second lens on the optical axis, alpha 3 is the thermal expansion coefficient of the third lens at-30 ℃ to 70 ℃, and alpha 2 is the thermal expansion coefficient of the second lens at-30 ℃ to 70 ℃. The second lens and the third lens are glued, the influence of temperature on the optical system is reduced through reasonable matching of materials, the optical system keeps good imaging quality under the condition of high temperature or low temperature, the thickness difference and the material characteristic difference of the second lens and the third lens are reduced, and the risk of cracking of the glued lens is reduced.

The present application is described in detail below by way of five specific examples, wherein the reference wavelength of the optical system of the present application is 546.074nm, and wherein the reference wavelength of the refractive index and abbe number is 587.6 nm.

Example one

As shown in fig. 1, a straight line 11 indicates an optical axis, a side of the first lens L1 away from the second lens L2 is an object side 12, and a side of the fifth lens L5 away from the fourth lens L4 is an image side 13. In the optical system provided in this embodiment, the first lens L1, the stop STO, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, and the protective glass CG are arranged in order from the object side 12 to the image side 13.

The first lens element L1 with positive refractive power has a convex object-side surface S1 at a paraxial region and a concave image-side surface S2 at a paraxial region, and is made of glass.

The second lens element L2 with negative refractive power is made of glass, and has a concave object-side surface S3 and a spherical image-side surface S4 at a paraxial region.

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

The fourth lens element L4 with positive refractive power is made of glass, and has a convex object-side surface S7 and a convex image-side surface S8 at a paraxial region.

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

The stop STO may be located on the object side of the first lens L1 or between any two adjacent lenses, and the stop STO in the present embodiment is disposed between the first lens L1 and the second lens L2.

The protective glass CG is located behind the fifth lens L5 and includes an object side surface S11 and an image side surface S12, and is used for protecting the photosensitive element, so that the photosensitive element is prevented from being exposed outside, the photosensitive element is prevented from being affected by dust and the like, and the imaging quality is ensured.

The image forming surface S13 is a surface on which an image is formed by the light of the subject passing through the optical system.

Table 1a shows a characteristic table of the optical system of the present embodiment, in which the radius of curvature in the present embodiment is the radius of curvature of each lens at the paraxial region.

TABLE 1a

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

S4/S5 indicates that the image-side surface of the second lens and the object-side surface of the third lens, and the image-side surface S4 of the second lens and the object-side surface S5 of the third lens are cemented together, and thus are represented as one surface on data.

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

wherein Z is a distance from a corresponding point on the aspherical surface to a plane tangent to the surface vertex, r is a distance from a corresponding point on the aspherical surface to the optical axis, c is a curvature of the aspherical surface vertex, k is a conic constant, and Ai is a coefficient corresponding to the i-th high-order term in the aspherical surface type formula.

Table 1b shows the high-order term coefficients a4, A6, A8, a10, a12, a14, a16, a18, and a20 that can be used for the respective aspherical mirrors S1, S2, S7, S8 in the first embodiment.

TABLE 1b

Number of noodles	S1	S2	S7	S8
					K	0.00E+00	0.00E+00	0.00E+00	0.00E+00
A4	9.46E-05	1.32E-04	3.71E-05	1.43E-04
					A6	1.62E-06	1.96E-06	1.91E-07	-5.47E-07
A8	1.22E-08	-3.12E-09	3.88E-09	1.64E-08
					A10	1.26E-10	-1.15E-09	-1.51E-11	-1.70E-10
A12	-1.13E-12	-5.39E-12	-1.28E-12	-1.60E-12
					A14	0.00E+00	0.00E+00	0.00E+00	0.00E+00
A16	0.00E+00	0.00E+00	0.00E+00	0.00E+00
					A18	0.00E+00	0.00E+00	0.00E+00	0.00E+00
A20	0.00E+00	0.00E+00	0.00E+00	0.00E+00

Fig. 2 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 convergence focuses of light rays with different wavelengths after passing through each lens of the optical system, and the reference wavelengths of the longitudinal spherical aberration curve are 656.2730nm, 587.5620nm, 546.0740nm, 486.1330nm and 450.0000 nm; the astigmatism curves represent meridional image surface curvature and sagittal image surface curvature, wherein S represents sagittal direction, T represents meridional direction, and the reference wavelength of the astigmatism curves is 546.0740 nm; the distortion curve represents the distortion magnitude values corresponding to different angles of view, and the reference wavelength of the distortion curve is 546.0740 nm. As can be seen from fig. 2, the optical system according to the first embodiment can achieve good imaging quality.

Example two

As shown in fig. 3, a straight line 11 indicates an optical axis, a side of the first lens L1 away from the second lens L2 is an object side 12, and a side of the fifth lens L5 away from the fourth lens L4 is an image side 13. In the optical system provided in this embodiment, the first lens L1, the stop STO, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, and the protective glass CG are arranged in order from the object side 12 to the image side 13.

Table 2a shows a characteristic table of the optical system of the present embodiment, in which the radius of curvature in the present embodiment is the radius of curvature of each lens at the paraxial region.

TABLE 2a

Table 2b shows the high-order term coefficients a4, A6, A8, a10, a12, a14, a16, a18, and a20 that can be used for the respective aspherical mirror surfaces S1, S2, S7, S8 in the second embodiment, wherein the respective aspherical mirror surface types can be defined by the formulas given in the first embodiment.

TABLE 2b

Fig. 4 shows a longitudinal spherical aberration curve, an astigmatism curve, and a distortion curve of the optical system of the second embodiment. The longitudinal spherical aberration curve represents the deviation of convergence focuses of light rays with different wavelengths after passing through each lens of the optical system, and the reference wavelengths of the longitudinal spherical aberration curve are 656.2730nm, 587.5620nm, 546.0740nm, 486.1330nm and 450.0000 nm; the astigmatism curves represent meridional image surface curvature and sagittal image surface curvature, wherein S represents sagittal direction, T represents meridional direction, and the reference wavelength of the astigmatism curves is 546.0740 nm; the distortion curve represents the distortion magnitude values corresponding to different angles of view, and the reference wavelength of the distortion curve is 546.0740 nm. As can be seen from fig. 4, the optical system according to the second embodiment can achieve good imaging quality.

EXAMPLE III

As shown in fig. 5, a straight line 11 indicates an optical axis, a side of the first lens L1 away from the second lens L2 is an object side 12, and a side of the fifth lens L5 away from the fourth lens L4 is an image side 13. In the optical system provided in this embodiment, the first lens L1, the stop STO, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, and the protective glass CG are arranged in order from the object side 12 to the image side 13.

Table 3a shows a characteristic table of the optical system of the present embodiment, in which the radius of curvature in the present embodiment is the radius of curvature of each lens at the paraxial region.

TABLE 3a

Table 3b shows the high-order term coefficients a4, A6, A8, a10, a12, a14, a16, a18, and a20 that can be used for the respective aspherical mirror surfaces S1, S2, S7, S8 in the third embodiment, wherein the respective aspherical mirror surface types can be defined by the formulas given in the first embodiment.

TABLE 3b

Fig. 6 shows a longitudinal spherical aberration curve, an astigmatism curve, and a distortion curve of the optical system of the third embodiment. The longitudinal spherical aberration curve represents the deviation of convergence focuses of light rays with different wavelengths after passing through each lens of the optical system, and the reference wavelengths of the longitudinal spherical aberration curve are 656.2730nm, 587.5620nm, 546.0740nm, 486.1330nm and 450.0000 nm; the astigmatism curves represent meridional image surface curvature and sagittal image surface curvature, wherein S represents sagittal direction, T represents meridional direction, and the reference wavelength of the astigmatism curves is 546.0740 nm; the distortion curve represents the distortion magnitude values corresponding to different angles of view, and the reference wavelength of the distortion curve is 546.0740 nm. As can be seen from fig. 6, the optical system according to the third embodiment can achieve good image quality.

Example four

As shown in fig. 7, a straight line 11 indicates an optical axis, a side of the first lens L1 away from the second lens L2 is an object side 12, and a side of the fifth lens L5 away from the fourth lens L4 is an image side 13. In the optical system provided in this embodiment, the first lens L1, the stop STO, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, and the protective glass CG are arranged in order from the object side 12 to the image side 13.

Table 4a shows a characteristic table of the optical system of the present embodiment, in which the radius of curvature in the present embodiment is the radius of curvature of each lens at the paraxial region.

TABLE 4a

Table 4b shows the high-order term coefficients a4, A6, A8, a10, a12, a14, a16, a18, and a20 that can be used for the respective aspherical mirror surfaces S1, S2, S7, S8 in the fourth embodiment, wherein the respective aspherical mirror surface types can be defined by the formulas given in the first embodiment.

TABLE 4b

Fig. 8 shows a longitudinal spherical aberration curve, an astigmatism curve, and a distortion curve of the optical system of the fourth embodiment. The longitudinal spherical aberration curve represents the deviation of convergence focuses of light rays with different wavelengths after passing through each lens of the optical system, and the reference wavelengths of the longitudinal spherical aberration curve are 656.2730nm, 587.5620nm, 546.0740nm, 486.1330nm and 450.0000 nm; the astigmatism curves represent meridional image surface curvature and sagittal image surface curvature, wherein S represents sagittal direction, T represents meridional direction, and the reference wavelength of the astigmatism curves is 546.0740 nm; the distortion curve represents the distortion magnitude values corresponding to different angles of view, and the reference wavelength of the distortion curve is 546.0740 nm. As can be seen from fig. 8, the optical system according to the fourth embodiment can achieve good image quality.

EXAMPLE five

As shown in fig. 9, a straight line 11 indicates an optical axis, a side of the first lens L1 away from the second lens L2 is an object side 12, and a side of the fifth lens L5 away from the fourth lens L4 is an image side 13. In the optical system provided in this embodiment, the first lens L1, the stop STO, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, and the protective glass CG are arranged in order from the object side 12 to the image side 13.

Table 5a shows a characteristic table of the optical system of the present embodiment, in which the radius of curvature in the present embodiment is the radius of curvature of each lens at the paraxial region.

TABLE 5a

Table 5b shows the high-order term coefficients a4, A6, A8, a10, a12, a14, a16, a18, and a20 that can be used for the respective aspherical mirror surfaces S1, S2, S7, S8 in the fifth embodiment, wherein the respective aspherical mirror surface types can be defined by the formulas given in the first embodiment.

TABLE 5b

Fig. 10 shows a longitudinal spherical aberration curve, an astigmatism curve, and a distortion curve of the optical system of the fifth embodiment. The longitudinal spherical aberration curve represents the deviation of convergence focuses of light rays with different wavelengths after passing through each lens of the optical system, and the reference wavelengths of the longitudinal spherical aberration curve are 656.2730nm, 587.5620nm, 546.0740nm, 486.1330nm and 450.0000 nm; the astigmatism curves represent meridional image surface curvature and sagittal image surface curvature, wherein S represents sagittal direction, T represents meridional direction, and the reference wavelength of the astigmatism curves is 546.0740 nm; the distortion curve represents the distortion magnitude values corresponding to different angles of view, and the reference wavelength of the distortion curve is 546.0740 nm. As can be seen from fig. 10, the optical system according to the fifth embodiment can achieve good image quality.

Table 6 shows values of (R2-R3)/D12, f1/CT1, f23/(CT3-CT2), (CT3-CT2) | α 3- α 2|, f4/CT4, f5/CT5, f13/f45, and TTL/f of the optical systems of the first to fifth embodiments.

TABLE 6

	(R2-R3)/D12	f1/CT1	f23/(CT3-CT2)	(CT3-CT2)*\|α3-α2\|
					First embodiment	3.949	8.427	-9.819	7.568
Second embodiment	6.625	7.365	-13.516	6.646
					Third embodiment	4.225	8.889	-13.091	5.400
Fourth embodiment	5.073	8.042	-13.531	5.400
					Fifth embodiment	5.037	8.126	-13.347	5.400
	f4/CT4	f5/CT5	f13/f45	TTL/f
					First embodiment	3.104	-32.666	4.054	2.169
Second embodiment	4.125	-39.367	2.583	2.225
					Third embodiment	3.194	-39.797	4.287	2.371
Fourth embodiment	2.901	-10.248	3.435	2.000
					Fifth embodiment	3.069	-9.388	3.553	2.005

As can be seen from table 6, each example satisfies: 3.5<(R2-R3)/D12<7，7<f1/CT1<9，-14<f23/(CT3-CT2)<-9，5*10^-6mm/℃<(CT3-CT2)*|α3-α2|<8*10^-6mm/℃，2.6<f4/CT4<4.3，-40<f5/CT5<-9，2.4<f13/f45<4.4，1.8<TTL/f<2.5。

Referring to fig. 11, the optical system according to the present application is applied to a camera module 20 in a terminal device 30. The terminal device 30 may be a mobile phone, a tablet computer, an unmanned aerial vehicle, a computer, a vehicle, a monitor, a security, a medical device, or the like. The photosensitive element of the camera module 20 is located on the image side of the optical system, and the camera module 20 is assembled inside the terminal device 30.

The application provides a camera module, including photosensitive element and the optical system that this application embodiment provided, photosensitive element is located optical system's image side for incidenting the light on the electron photosensitive element and convert the signal of telecommunication of image into with passing first lens to fifth lens. The electron sensor may be a Complementary Metal Oxide Semiconductor (CMOS) or a Charge-coupled Device (CCD). By installing the optical system in the camera module, the camera module can meet the requirements of high pixel and miniaturization.

The application also provides a terminal device, and the terminal device comprises the camera module provided by the embodiment of the application. The terminal equipment can be a mobile phone, a tablet personal computer, an unmanned aerial vehicle, a computer, a vehicle, monitoring, security protection, medical treatment and the like. By installing the camera module in the terminal equipment, the terminal equipment can meet the requirements of high pixel and miniaturization.

The foregoing is a preferred embodiment of the present application, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present application, and these modifications and decorations are also regarded as the protection scope of the present application.

Claims

1. An optical system comprising a plurality of lenses, the plurality of lenses comprising, arranged in order from an object side to an image side:

a first lens element with positive refractive power;

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

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

a fourth lens element with positive refractive power having convex object-side and image-side surfaces at paraxial region;

a fifth lens element with negative refractive power;

the optical system satisfies the following conditional expression:

3.5<(R2-R3)/D12<7，

r2 is a curvature radius of an image side surface of the first lens element at an optical axis, R3 is a curvature radius of an object side surface of the second lens element at the optical axis, and D12 is an air space between the first lens element and the second lens element at the optical axis.

2. The optical system of claim 1, wherein the object-side surface and/or the image-side surface of at least one of the lenses is aspheric.

3. The optical system of claim 1, wherein at least one of the lenses has an abbe number of less than 25 or greater than 70, and the reference wavelength of the abbe number is 587.6 nm.

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

7<f1/CT1<9，

f1 is the focal length of the first lens, and CT1 is the thickness of the first lens on the optical axis.

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

-14<f23/(CT3-CT2)<-9，

f23 is a combined focal length of the second lens and the third lens, CT3 is an optical thickness of the third lens, and CT2 is an optical thickness of the second lens.

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

5*10^-6mm/℃<(CT3-CT2)*|α3-α2|<8*10^-6mm/℃，

CT3 is the thickness of the third lens on the optical axis, CT2 is the thickness of the second lens on the optical axis, α 3 is the thermal expansion coefficient of the third lens at-30 ℃ to 70 ℃, α 2 is the thermal expansion coefficient of the second lens at-30 ℃ to 70 ℃.

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

2.6<f4/CT4<4.3，

f4 is the focal length of the fourth lens, and CT4 is the thickness of the fourth lens on the optical axis.

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

-40<f5/CT5<-9，

f5 is the focal length of the fifth lens, and CT5 is the thickness of the fifth lens on the optical axis.

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

2.4<f13/f45<4.4，

f13 is a combined focal length of the first, second, and third lenses, and f45 is a combined focal length of the fourth and fifth lenses.

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

1.8<TTL/f<2.5，

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

11. A camera module comprising a photosensitive element and the optical system according to any one of claims 1 to 10, wherein the photosensitive element is located on the image side of the optical system.

12. A terminal device characterized by comprising the camera module according to claim 11.