CN112433349A

CN112433349A - Optical system, camera module and terminal equipment

Info

Publication number: CN112433349A
Application number: CN202011495662.2A
Authority: CN
Inventors: 乐宇明; 蔡雄宇; 周芮; 赵迪
Original assignee: Tianjin OFilm Opto Electronics Co Ltd
Current assignee: Tianjin OFilm Opto Electronics Co Ltd
Priority date: 2020-12-17
Filing date: 2020-12-17
Publication date: 2021-03-02

Abstract

The embodiment of the application discloses an optical system, a camera module and terminal equipment. The optical system includes a first lens, a second lens, a third lens, a fourth lens, and a fifth lens. The first lens element, the third lens element, and the fourth lens element with positive refractive power, the second lens element and the fifth lens element with negative refractive power have concave image-side surfaces at paraxial regions thereof, the second lens element has concave object-side surfaces at paraxial regions thereof, the third lens element has convex object-side surfaces at paraxial regions thereof, and the fifth lens element has convex image-side surfaces at paraxial regions thereof; the optical system satisfies: 2< TTL/DOS <3, wherein TTL is the distance between the object side surface of the first lens element and the imaging surface on the optical axis, and DOS is the distance between the object side surface of the first lens element and the diaphragm surface of the optical system on the optical axis. By reasonably configuring the refractive power and the surface type of the first lens element to the fifth lens element in the optical system and limiting the ratio range of TTL/DOS, the optical system has the characteristics of miniaturization and large field angle.

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 development of the vehicle-mounted industry, the vehicle-mounted driving technology is gradually mature. In the driver monitoring system, the state of the driver is required to be monitored, and the state outside the driver cab is also required to be monitored and identified so as to comprehensively judge the driving environment change of the driver, so that safety early warning is provided, the change of the driving state of the driver is reminded, and prevention is made in advance.

In the driver monitoring system, the image captured is analyzed by software, and it is detected whether the driver is dozing off or inattentive particularly from the movement of the eyelids and eyeball of the driver, but the viewing angle of the conventional optical system is narrow, and the eyelids or pupils may be out of the photographing field of view when the seating position of the driver is deviated. The optical system has a limited installation space on the dashboard of the speedometer or in the speedometer, and therefore, the optical system is required to have a feature of miniaturization.

Therefore, how to realize the features of miniaturization and large field angle of the optical system should be the research and development direction in the industry.

Disclosure of Invention

The embodiment of the application provides an optical system, a camera module and a terminal device, wherein the optical system has the characteristics of miniaturization and large field angle.

In a first aspect, an embodiment of the present application provides an optical system, which includes a plurality of lenses, each of the lenses including a first lens element with positive refractive power arranged in order 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 incident), and an image-side surface of the first lens element being concave at a paraxial region; a second lens element with negative refractive power having a concave object-side surface at paraxial region; a third lens element with positive refractive power having a convex object-side surface at paraxial region; a fourth lens element with positive refractive power; a fifth lens element with negative refractive power having a convex image-side surface at paraxial region; the optical system satisfies the following conditional expression: 2< TTL/DOS <3, wherein TTL is the distance between the object side surface of the first lens and the imaging surface in the optical system on the optical axis, and DOS is the distance between the object side surface of the first lens and the diaphragm surface of the optical system 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 element to the fifth lens element in the optical system, and the surface type of the first lens element, the second lens element, the third lens element and the fifth lens element are reasonably configured, and the ratio range of TTL/DOS is further limited, so that the optical system has the characteristics of miniaturization and large field angle.

Specifically, the total length of the optical system is influenced by the distance from the object side surface of the first lens to the diaphragm surface on the optical axis, and the total length of the optical system is favorably controlled by limiting the ratio range of TTL/DOS, so that the optical system is miniaturized, a large-angle light beam is favorably emitted into the optical system, the object space imaging range of the optical system is improved, and the wide angle of the optical system is realized.

In one embodiment, at least one of the lenses has an abbe number of 25.5 or less, and the reference wavelength of the abbe number is 587.56 nm. The abbe number is limited to be less than or equal to 25.5, so that chromatic aberration can be better corrected, and the imaging quality of the optical system is improved.

In one embodiment, the optical system satisfies the conditional expression: 9< f1/CT1<12, f1 is the focal length of the first lens, and CT1 is the thickness of the first lens on the optical axis. By limiting the ratio range of f1/CT1, the optical system is beneficial to have good imaging quality. If f1/CT1 is more than 12, the focal length of the first lens is too large, which results in insufficient refractive power and is not beneficial to inhibiting high-order aberration, so that high-order spherical aberration, coma aberration and the like are easy to occur to influence the imaging resolution and the imaging quality of the optical system; if f1/CT1 is less than 9, the refractive power of the first lens element is too strong, which causes the light beam width to shrink rapidly, thereby increasing the incident angle of the light beam incident on the rear lens element, and further increasing the correction load of the rear lens element, i.e. reducing the light angle of the light beam exiting from the optical system, the design requirements of the rear lens element are more strict.

In one embodiment, the optical system satisfies the conditional expression: -6< f2/CT2< -3, f2 being the focal length of the second lens, CT2 being the thickness of the second lens on the optical axis. The second lens is set to be a lens with negative refractive power, so that the negative refractive power is provided for the system, the light beam width can be favorably expanded, large-angle light rays are prevented from excessively diverging after being refracted by the first lens, the light beam width shot by the rear lens group is expanded, the pupil is filled, and the light rays are fully transmitted to a high-pixel imaging surface, so that a wider field range is obtained, and the characteristic of high pixel of the system can be favorably embodied. f2/CT2 > -3 or f2/CT2< -6 are not favorable for correcting the aberration of the optical system, thereby reducing the imaging quality.

In one embodiment, the optical system satisfies the conditional expression: 16< R2/Sagf2<20, R2 being a radius of curvature of an image side surface of the first lens at an optical axis, and Sagf2 being a distance from a maximum clear aperture of the image side surface of the first lens to a center point of the first lens in a direction parallel to the optical axis. The curvature radius of the image-side surface of the first lens element affects the refractive power of the first lens element, and the curved image-side surface of the first lens element is more favorable for the light beam to shrink, and then the light beam is refracted to an image plane for focusing through the second lens element, the third lens element, the fourth lens element and the fifth lens element. By limiting the ratio range of R2/Sagf2, the astigmatism generated by the refraction of the light beam on the surface of the first lens element can be effectively corrected while the refractive power strength of the first lens element is ensured, and the increase of the processing difficulty of the lens element caused by the excessive bending of the image side surface of the first lens element is avoided. If R2/Sagf2 is greater than 20, the refractive power of the first lens element is insufficient, and the aberration cannot be effectively corrected; if R2/Sagf2< 16, the image side of the first lens is too curved, increasing the difficulty of processing the lens.

In one embodiment, the optical system satisfies the conditional expression: 1< f3/CT3<4.5, f3 is the focal length of the third lens, and CT3 is the thickness of the third lens on the optical axis. By reasonably limiting the ratio range of f3/CT3, the thickness tolerance sensitivity of the third lens can be reduced, the processing difficulty of the single lens is reduced, the assembly yield of the optical system is favorably improved, and the production cost is further reduced. If f3/CT3 is more than 4.5, the optical system is too sensitive to the thickness of the third lens, and the processing of the single lens is difficult to meet the required tolerance requirement, so that the assembly yield of the optical system is reduced, and the reduction of the production cost is not facilitated; if f3/CT3< 1, the thickness of the third lens is too large, which results in a larger weight of the lens and is not favorable for the light weight of the optical system.

In one embodiment, the optical system satisfies the conditional expression: -3.5< f5/f < -1, f5 being the focal length of the fifth lens, f being the effective focal length of the optical system. The fifth lens provides negative refractive power for the system, which is beneficial to expanding the light beam width, so that large-angle light rays are not excessively dispersed after being refracted by the first lens to the fourth lens, the light beam width of the light beam shot by the optical system is expanded, the pupil is filled, and the light beam is fully transmitted to a high-pixel imaging surface, so that a wider field range is obtained, and the characteristic of high pixels of the system is favorably embodied; if f5/f > -1 or f5/f < -3.5, the aberration of the optical system is disadvantageously corrected, thereby degrading the imaging quality.

In one embodiment, the optical system satisfies the conditional expression: -4< (R9+ R10)/(R9-R10) < -1, R9 being the radius of curvature of the object-side face of the fifth lens at the optical axis, R10 being the radius of curvature of the image-side face of the fifth lens at the optical axis. By defining the ratio range of (R9+ R10)/(R9-R10), it is advantageous to reduce the angle at which the principal rays of the fringe field of view are incident on the imaging plane, thereby suppressing the generation of astigmatism.

In one embodiment, the optical system satisfies the conditional expression: 4< SDs10/Sagf10<8.5, SDs10 being the maximum clear aperture of the object side of the fifth lens, Sagf10 being the distance in a direction parallel to the optical axis from the maximum clear aperture at the object side of the fifth lens to the center point of the fifth lens. By limiting the ratio range of SDs10/Sagf10 to be more than 4, the surface type of the object side surface of the fifth lens can be prevented from over-bending, the processing difficulty of the fifth lens is reduced, the problem of uneven coating caused by over-bending of the fifth lens is reduced, and meanwhile, the over-bending of the fifth lens is not beneficial to the incidence of large-angle light rays to an optical system, so that the imaging quality of the optical system is influenced. By defining SDs10/Sagf10<8.5, it is possible to avoid that the object side of the fifth lens is too flat, reducing the risk of creating ghost images.

In one embodiment, the optical system satisfies the conditional expression: 1< f123/f45<6.5, f123 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. The ratio range of f123/f45 is reasonably limited, so that the incident angle of light rays can be controlled, the width of the light beams is not too large or too small, and the high-level aberration of an optical system can be reduced; meanwhile, the emergent angle of the chief ray passing through the fourth lens and the fifth lens can be reduced, and the relative brightness of an imaging surface of the optical system is improved.

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 element to the fifth lens element and the surface shape of the first lens element, the second lens element, the third lens element and the fifth lens element in the optical system, and further limiting the ratio range of TTL/DOS, the optical system has the characteristics of miniaturization and large field angle.

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 structural diagram of an optical system provided in a sixth embodiment of the present application;

fig. 12 is a longitudinal spherical aberration curve, an astigmatism curve, and a distortion curve of the optical system of the sixth embodiment;

fig. 13 is a schematic diagram of an optical system provided in the present application 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:

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

The optical system satisfies the following conditional expression: 2< TTL/DOS <3, wherein TTL is the distance between the object side surface of the first lens and the imaging surface in the optical system on the optical axis, and DOS is the distance between the object side surface of the first lens and the diaphragm surface of the optical system on the optical axis.

In one embodiment, the optical system satisfies the conditional expression: 9< f1/CT1<12, f1 is the focal length of the first lens, and CT1 is the thickness of the first lens on the optical axis. By limiting the ratio range of f1/CT1, the optical system is beneficial to have good imaging quality. If f1/CT1 is more than 12, the focal length of the first lens is too large, which results in insufficient refractive power and is not beneficial to inhibiting high-order aberration, so that high-order spherical aberration, coma aberration and the like are easy to occur to influence the imaging resolution and the imaging quality of the optical system; if f1/CT1 is less than 9, the refractive power of the first lens element is too strong, which causes the width of the light beam to shrink rapidly, thereby increasing the incident angle of the light beam incident on the rear lens element, and further increasing the correction load of the rear lens element, i.e. reducing the angle of the light beam exiting from the optical system, which imposes a strict requirement on the design of the rear lens element.

The present application is described in detail below with reference to six specific examples.

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 second lens L2, the third lens L3, the stop STO, 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 has a concave object-side surface S3 at a paraxial region and a concave image-side surface S4 at a paraxial region, and is made of glass.

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

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

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 surface of the first lens L1 or between any two adjacent lenses, or on the image-side surface of the fifth lens L5, and the stop STO in the present embodiment is disposed between the third lens L3 and the fourth lens L4.

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.

It should be noted that the materials of the first lens element to the fifth lens element in the present embodiment may also be plastics, and the present application is not limited thereto.

Table 1 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 optical axis, the reference wavelengths of the focal length, refractive index, and abbe number are all 587.56nm, and the units of the radius of curvature, thickness, and focal length of the lens are all millimeters (mm). In addition, the first value in the "thickness" parameter column of the lens is the thickness of the lens on the optical axis, and the second value is the distance between the image side surface of the lens and the rear surface of the lens in the image side direction on the optical axis; the numerical value of the stop ST0 in the "thickness" parameter column is the distance on the optical axis from the stop ST0 to the vertex of the next surface (the vertex refers to the intersection point of the surface and the optical axis), and we default that the direction from the object side surface to the image side surface of the last lens of the first lens L1 is the positive direction of the optical axis, when the value is negative, it indicates that the stop ST0 is disposed on the right side of the vertex of the surface, and if the thickness of the stop STO is positive, the stop is on the left side of the vertex of the surface.

TABLE 1

Wherein f is the effective 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.

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 970.0000nm, 940.0000nm and 900.0000 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 940.0000 nm; the distortion curve represents the distortion magnitude values corresponding to different angles of view, and the reference wavelength of the distortion curve is 940.0000 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 second lens L2, the third lens L3, the stop STO, 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, and definitions of parameters in the characteristic table can be obtained from the description of the foregoing embodiments, which are not repeated herein. It is understood that, where the radius of curvature in the present embodiment is the radius of curvature of each lens at the optical axis, the reference wavelengths of the focal length, refractive index and abbe number are all 587.56nm, and the units of the radius of curvature, thickness and focal length of the lens are all millimeters (mm).

TABLE 2a

In the present embodiment, the object-side surface and the image-side surface of 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 parallel to the optical axis, r is a perpendicular distance from the 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 term higher order term in the aspherical surface type formula.

Table 2b 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 S9, S10 in the second embodiment.

TABLE 2b

Number of noodles	S9	S10
			K	0.000E+00	0.000E+00
A4	5.999E-03	1.296E-02
			A6	-2.698E-03	-6.307E-03
A8	2.760E-03	5.902E-03
			A10	-1.911E-03	-3.281E-03
A12	6.770E-04	1.056E-03
			A14	-1.140E-04	-1.816E-04
A16	6.424E-06	1.281E-05
			A18	0.000E+00	0.000E+00
A20	0.000E+00	0.000E+00

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 970.0000nm, 940.0000nm and 900.0000 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 940.0000 nm; the distortion curve represents the distortion magnitude values corresponding to different angles of view, and the reference wavelength of the distortion curve is 940.0000 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 second lens L2, the third lens L3, the stop STO, 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 3 shows a characteristic table of the optical system of the present embodiment, and definitions of parameters in the characteristic table can be obtained from the description of the foregoing embodiments, which are not repeated herein. It is understood that, where the radius of curvature in the present embodiment is the radius of curvature of each lens at the optical axis, the reference wavelengths of the focal length, refractive index and abbe number are all 587.56nm, and the units of the radius of curvature, thickness and focal length of the lens are all millimeters (mm).

TABLE 3

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 970.0000nm, 940.0000nm and 900.0000 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 940.0000 nm; the distortion curve represents the distortion magnitude values corresponding to different angles of view, and the reference wavelength of the distortion curve is 940.0000 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 second lens L2, the third lens L3, the stop STO, 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 4 shows a characteristic table of the optical system of the present embodiment, and definitions of parameters in the characteristic table can be obtained from the description of the foregoing embodiments, which are not repeated herein. It is understood that, where the radius of curvature in the present embodiment is the radius of curvature of each lens at the optical axis, the reference wavelengths of the focal length, refractive index and abbe number are all 587.56nm, and the units of the radius of curvature, thickness and focal length of the lens are all millimeters (mm).

TABLE 4

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 970.0000nm, 940.0000nm and 900.0000 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 940.0000 nm; the distortion curve represents the distortion magnitude values corresponding to different angles of view, and the reference wavelength of the distortion curve is 940.0000 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 second lens L2, the third lens L3, the stop STO, 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 5 shows a characteristic table of the optical system of the present embodiment, and definitions of parameters in the characteristic table can be obtained from the description of the foregoing embodiments, which are not repeated herein. It is understood that, where the radius of curvature in the present embodiment is the radius of curvature of each lens at the optical axis, the reference wavelengths of the focal length, refractive index and abbe number are all 587.56nm, and the units of the radius of curvature, thickness and focal length of the lens are all millimeters (mm).

TABLE 5

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 970.0000nm, 940.0000nm and 900.0000 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 940.0000 nm; the distortion curve represents the distortion magnitude values corresponding to different angles of view, and the reference wavelength of the distortion curve is 940.0000 nm. As can be seen from fig. 10, the optical system according to the fifth embodiment can achieve good image quality.

EXAMPLE six

As shown in fig. 11, 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 second lens L2, the third lens L3, the stop STO, 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 6 shows a characteristic table of the optical system of the present embodiment, and definitions of parameters in the characteristic table can be obtained from the description of the foregoing embodiments, which are not repeated herein. It is understood that, where the radius of curvature in the present embodiment is the radius of curvature of each lens at the optical axis, the reference wavelengths of the focal length, refractive index and abbe number are all 587.56nm, and the units of the radius of curvature, thickness and focal length of the lens are all millimeters (mm).

TABLE 6

Fig. 12 shows a longitudinal spherical aberration curve, an astigmatism curve, and a distortion curve of the optical system of the sixth 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 970.0000nm, 940.0000nm and 900.0000 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 940.0000 nm; the distortion curve represents the distortion magnitude values corresponding to different angles of view, and the reference wavelength of the distortion curve is 940.0000 nm. As can be seen from fig. 12, the optical system according to the sixth embodiment can achieve good image quality.

Table 7 shows values of TTL/DOS, f1/CT1, f2/CT2, R2/Sagf2, f3/CT3, f5/f, SDs10/Sagf10, f123/f45, (R9+ R10)/(R9-R10) of the optical systems of the first to sixth embodiments.

TABLE 7

As can be seen from Table 7, each example satisfies: 2< TTL/DOS <3, 9< f1/CT1<12, -6< f2/CT2< -3, 16< R2/Sagf2<20, 1< f3/CT3<4.5, -3.5< f5/f < -1, -4< (R9+ R10)/(R9-R10) < -1, 4< SDs10/Sagf10<8.5, 1< f123/f45< 6.5.

Referring to fig. 13, the optical system according to the present application is applied to the camera module 20 in the terminal device 30. The terminal device 30 may be a mobile phone, a tablet computer, an unmanned aerial vehicle, a computer, a vehicle, 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). The optical system is installed in the camera module, so that the camera module has the characteristics of miniaturization and large field angle.

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 and the like. The camera module is installed in the terminal equipment, so that the terminal equipment has the characteristics of miniaturization and large field angle.

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:

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

a second lens element with negative refractive power having a concave object-side surface at paraxial region;

a third lens element with positive refractive power having a convex object-side surface at paraxial region;

a fourth lens element with positive refractive power;

a fifth lens element with negative refractive power having a convex image-side surface at paraxial region;

the optical system satisfies the following conditional expression:

2<TTL/DOS<3，

TTL is the distance on the optical axis from the object side surface of the first lens to the imaging surface in the optical system, and DOS is the distance on the optical axis from the object side surface of the first lens to the diaphragm surface of the optical system.

2. The optical system of claim 1, wherein at least one of the lenses has an abbe number of 25.5 or less, and wherein the reference wavelength of the abbe number is 587.56 nm.

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

9<f1/CT1<12，

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

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

-6<f2/CT2<-3，

f2 is the focal length of the second lens, and CT2 is the thickness of the second lens on the optical axis.

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

16<R2/Sagf2<20，

r2 is a radius of curvature of an image-side surface of the first lens at an optical axis, and Sagf2 is a distance from a maximum clear aperture of the image-side surface of the first lens to a center point of the first lens in a direction parallel to the optical axis.

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

1<f3/CT3<4.5，

f3 is the focal length of the third lens, and CT3 is the thickness of the third lens on the optical axis.

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

-3.5<f5/f<-1，

f5 is the focal length of the fifth lens, and f is the effective focal length of the optical system.

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

-4<(R9+R10)/(R9-R10)<-1，

r9 is a radius of curvature of an object-side surface of the fifth lens at an optical axis, and R10 is a radius of curvature of an image-side surface of the fifth lens at the optical axis.

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

4<SDs10/Sagf10<8.5，

SDs10 is the maximum clear aperture of the object side of the fifth lens, and Sagf10 is the distance in the direction parallel to the optical axis from the maximum clear aperture of the object side of the fifth lens to the center point of the fifth lens.

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

1<f123/f45<6.5，

f123 is a combined focal length of the first lens, the second lens, and the third lens, and f45 is a combined focal length of the fourth lens and the fifth lens.

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.