CN111624738A

CN111624738A - Optical system, lens module and terminal equipment

Info

Publication number: CN111624738A
Application number: CN202010548807.4A
Authority: CN
Inventors: 杨健; 李明
Original assignee: OFilm Tech Co Ltd
Current assignee: Nanchang OFilm Precision Optical Products Co Ltd; OFilm Group Co Ltd
Priority date: 2020-06-16
Filing date: 2020-06-16
Publication date: 2020-09-04

Abstract

The embodiment of the application discloses an optical system, a lens module and terminal equipment. The optical system comprises a first lens element with positive refractive power, a third lens element with negative refractive power, a second lens element with refractive power, a fourth lens element with refractive power, a fifth lens element with refractive power, a sixth lens element with refractive power, a seventh lens element with refractive power and an eighth lens element with refractive power, wherein an object-side surface of the first lens element is convex at an optical axis, an image-side surface of the third lens element is concave at the optical axis, and an image-side surface of the fourth lens element is convex at the optical axis; the optical system satisfies the following conditional expression: TTL/f is less than 1.1, TTL is the distance between the object side surface of the first lens element and the imaging surface of the optical system on the optical axis, and f is the focal length of the optical system. The optical system has the characteristics of long focal length and good imaging quality while meeting the requirement of micro design by reasonably configuring the refractive power and the surface type of the first lens to the eighth lens in the optical system and limiting the TTL/f to be less than 1.1.

Description

Optical system, lens module and terminal equipment

Technical Field

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

Background

With the wide application of mobile phones, tablet computers, unmanned planes, computers and other electronic products in life, various technological improvements are emerging. Among them, the improvement and innovation of the shooting effect of the camera lens in the novel electronic product become the key points of people's attention.

The current camera lens generally needs to have a miniaturized feature, and along with the increase of the requirement of long-range shooting, the camera lens needs to have a long focal length, but the problems of insufficient definition, poor image quality and the like easily occur, so that the long-range shooting effect is not ideal.

Therefore, how to increase the focal length and improve the image quality while satisfying the micro design so as to clearly image the scene with a longer object distance on the imaging plane should be the research and development direction in the industry.

Disclosure of Invention

The embodiment of the application provides an optical system, a lens module and a terminal device, and the optical system meets the requirement of micro design, increases the focal length of the system, improves the image quality, and can shoot a picture with clear image quality even under a dark light condition.

In a first aspect, an embodiment of the present application provides an optical system including a plurality of lenses, each of the plurality of lenses including a first lens element, a second lens element, a third lens element, a fourth lens element, a fifth lens element, a sixth lens element, a seventh lens element and an eighth lens element arranged in order from an object side (where the object side refers to a side on which light is incident) to an image side (where the image side refers to a side on which light is emitted), wherein the first lens element has positive refractive power, the third lens element has negative refractive power, and the rest of the lens elements have refractive power; the object side surface of the first lens is a convex surface on the optical axis, the image side surface of the third lens is a concave surface on the optical axis, and the image side surface of the fourth lens is a convex surface on the optical axis. The refractive power of the second lens element, the fourth lens element, the fifth lens element, the sixth lens element, the seventh lens element and the eighth lens element is a refractive power, which means that the second lens element, the fourth lens element, the fifth lens element, the sixth lens element, the seventh lens element and the eighth lens element have positive refractive power or negative refractive power, and positive refractive power means that the lens elements converge the light beam, and negative refractive power means that the lens elements diverge the light beam. For example, in a preferred embodiment, the refractive powers of the eight lens elements may be that the first lens element has positive refractive power, the second lens element has negative refractive power, the third lens element has negative refractive power, the fourth lens element has positive refractive power, the fifth lens element has negative refractive power, the sixth lens element has negative refractive power, the seventh lens element has negative refractive power, the eighth lens element L8 has positive refractive power, and the refractive powers of the eight lens elements may have other preferred combinations. 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 optical system satisfies the following conditional expression: TTL/f is less than 1.1, TTL is the distance between the object side surface of the first lens and the imaging surface of the optical system on the optical axis, and f is the focal length of the optical system.

By reasonably configuring the refractive powers of the first lens element to the eighth lens element and the surface types of the first lens element, the third lens element and the fourth lens element in the optical system and limiting the TTL/f to be less than 1.1, the optical system has the characteristic of long focal length and good imaging quality while meeting the requirement of micro-design, and a shot picture has high painting texture, high resolution and high definition.

In one embodiment, the object-side surface and the image-side surface of all the lenses are aspheric, which is beneficial to correcting spherical aberration of the optical system and improving the imaging quality of the optical system.

In one embodiment, the optical system satisfies the conditional expression: -1.8< f1/f28< -0.5, f1 being the focal length of the first lens, f28 being the combined focal length of the second to eighth lenses. By limiting the reasonable range of f1/f28, the reasonable distribution of the focal power of the first lens to the eighth lens of the optical system is facilitated, the chromatic aberration of the system can be better corrected, and the imaging performance of the system is improved.

In one embodiment, the optical system satisfies the conditional expression: TTL/ct56>4, where TTL is an axial distance from an object-side surface of the first lens element to an image plane of the optical system, and ct56 is an axial distance from an object-side surface of the fifth lens element to an image-side surface of the sixth lens element. By reasonably limiting the range of TTL/ct56, a plurality of lenses of the optical system can be compactly arranged, and only a thick space ring needs to be arranged between the fifth lens and the sixth lens, so that the number of accessories can be reduced, and the system tolerance is reduced.

In one embodiment, the optical system satisfies the conditional expression: (L81-L82)/2 × L83 > 0.7, a beam of light is incident to a farthest point from an optical axis of an imaging surface of the optical system, the light and an image-side surface of the eighth lens element have a first intersection point, L81 is a maximum distance from the first intersection point to a vertical projection point of the first intersection point on the optical axis, L82 is a minimum distance from the first intersection point to a vertical projection point of the first intersection point on the optical axis, a beam of light is incident to a center point of the imaging surface of the optical system, the light and the image-side surface of the eighth lens element have a second intersection point, and L83 is a maximum distance from the second intersection point to a vertical projection point of the second intersection point on the optical axis. By limiting the proper range of (L81-L82)/2 × L83, the relative brightness of the optical system is improved, and the clear imaging effect can be achieved when the camera is shot in a dark environment.

In one embodiment, the optical system satisfies the conditional expression: TTL/Imgh is less than 2.5, wherein TTL is the distance between the object side surface of the first lens and the imaging surface of the optical system on the optical axis, and Imgh is the image height corresponding to half of the maximum field angle of the optical system. When the image forming surface is fixed, the TTL/Imgh is limited to be less than 2.5, the total length of the optical system can be reduced, and the requirement for miniaturization of the optical system can be met.

In one embodiment, the optical system satisfies the conditional expression: FNO <2.4, the f-number of the optical system. Through the f-number of injecing optical system, can also acquire big luminous flux under optical system has the condition of long focal length, even shoot under darker environment, also can reach clear formation of image effect.

In one embodiment, the optical system satisfies the conditional expression: imgh/tan (hfov) >5mm, Imgh being the image height corresponding to half of the maximum field angle of the optical system, tan (hfov) being the tangent value of half of the maximum field angle of the optical system. By limiting the range of Imgh/tan (hfov), the system can have a long focal length, and the magnification of imaging can be increased, which is advantageous for long-range shooting.

In a second aspect, the present application provides a lens module, which includes a photosensitive element and the optical system of any one of the foregoing embodiments, wherein 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 lens module.

By reasonably configuring the refractive powers of the first lens element to the eighth lens element in the optical system, the surface types of the first lens element, the third lens element and the fourth lens element and limiting the TTL/f to be less than 1.1, the optical system has the characteristic of long focal length and good imaging quality while meeting the requirement of micro-design, and can shoot a picture with clear image quality even under the condition of dark light, so that the shot picture has high picture quality, high resolution and high definition.

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

fig. 14 is a longitudinal spherical aberration curve, an astigmatism curve, and a distortion curve of the optical system of the seventh embodiment;

fig. 15 is a schematic structural diagram of an optical system according to an eighth embodiment of the present application;

fig. 16 is a longitudinal spherical aberration curve, an astigmatism curve, and a distortion curve of the optical system of the eighth embodiment;

fig. 17 is a schematic structural diagram of an optical system provided in a ninth embodiment of the present application;

fig. 18 is a longitudinal spherical aberration curve, an astigmatism curve, and a distortion curve of the optical system of the ninth embodiment;

fig. 19 is a schematic diagram of an optical system provided in the present application applied in a terminal device.

Detailed Description

Embodiments of the present application are described below with reference to the drawings in the present application.

An optical system provided by the present application includes eight 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, a fifth lens, a sixth lens, a seventh lens and an eighth lens.

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

the first lens element with positive refractive power, the third lens element with negative refractive power, and the rest of the lens elements with refractive power; the object side surface of the first lens is a convex surface on the optical axis, the image side surface of the third lens is a concave surface on the optical axis, and the image side surface of the fourth lens is a convex surface on the optical axis.

The optical system satisfies the following conditional expression: TTL/f is less than 1.1, TTL is the distance between the object side surface of the first lens and the imaging surface of the optical system on the optical axis, and f is the focal length of the optical system.

The refractive power of the first lens element to the eighth lens element in the optical system, the surface shape of the first lens element, the third lens element and the fourth lens element, and the limited TTL/f <1.1 are reasonably configured, so that the optical system has the characteristic of long focal length and good imaging quality while satisfying the micro-design, and the shot picture has high picture quality, high resolution and high definition.

The present application is described in detail below with reference to nine 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 sixth lens L6 away from the fifth lens L5 is an image side 13. In the optical system provided in this embodiment, the stop STO, the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, the sixth lens L6, the seventh lens L7, the eighth lens L8, and the infrared filter element IRCF 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 along the optical axis, a concave object-side surface S1 along the circumference, and a convex image-side surface S2 along the optical axis and the circumference.

The second lens element L2 with negative refractive power is made of plastic material, and has an object-side surface S3 being convex along the optical axis and at the circumference, and an image-side surface S4 being concave along the optical axis and at the circumference.

The third lens element L3 with negative refractive power is made of plastic material, and has an object-side surface S5 being convex along the optical axis and at the circumference, and an image-side surface S6 being concave along the optical axis and at the circumference.

The fourth lens element L4 with positive refractive power has a concave object-side surface S7 along the optical axis and at the circumference, and a convex image-side surface S8 along the optical axis and at the circumference.

The fifth lens element L5 with negative refractive power is made of plastic material, and has a convex object-side surface S9 along the optical axis, a concave object-side surface S9 along the circumference, and a concave image-side surface S10 along the optical axis and the circumference.

The sixth lens element L6 with negative refractive power is made of plastic material, and has a concave object-side surface S11 along the optical axis, a convex object-side surface S11 along the circumference, and a concave image-side surface S12 along the optical axis and the circumference.

The seventh lens element L7 with negative refractive power is made of plastic material, and has a convex object-side surface S13 along the optical axis, a concave object-side surface S13 along the circumference, and a concave image-side surface S14 along the optical axis and the circumference.

The eighth lens element L8 with positive refractive power is made of plastic material, and has a convex object-side surface S15 along the optical axis, a concave object-side surface S15 along the circumference, a concave image-side surface S16 along the optical axis, and a convex image-side surface S16 along the circumference.

The stop STO may be located between the object plane of the optical system and the eighth lens, and the stop STO in this embodiment is disposed on the object side surface of the first lens L1 and may be used to control the amount of incoming light.

The infrared filter element IRCF is disposed behind the eighth lens L8 and includes an object side surface S17 and an image side surface S18, and is configured to filter infrared light, so that the light incident on the image plane is visible light, the wavelength of the visible light is 380nm to 780nm, and the infrared filter element IRCF is made of glass.

The image forming surface S19 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 optical axis.

TABLE 1a

Wherein f is a focal length of the optical system, FNO is an f-number of the optical system, FOV is a maximum field angle of the optical system, 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 through the eighth lens L8 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 high-order coefficient values A4, A6, A8, a10, a12, a14, a16, a18, and a20 that can be used for each aspherical mirror surface S1, S2, S3, S4, S5, S6, S7, S8, S9, S10, S11, S12, S13, S14, S15, S16 in the first embodiment.

TABLE 1b

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 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, wherein S represents the sagittal direction, and T represents the meridional direction; the distortion curve represents the distortion magnitude values corresponding to different angles of view. 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 sixth lens L6 away from the fifth lens L5 is an image side 13. In the optical system provided in this embodiment, the stop STO, the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, the sixth lens L6, the seventh lens L7, the eighth lens L8, and the infrared filter element IRCF are arranged in order from the object side 12 to the image side 13.

The second lens element L2 with positive refractive power has a convex object-side surface S3 along the optical axis and at the circumference, and a concave image-side surface S4 along the optical axis and at the circumference.

The third lens element L3 with negative refractive power is made of plastic material, and has a convex object-side surface S5 along the optical axis, a concave object-side surface S5 along the circumference, and a concave image-side surface S6 along the optical axis and the circumference.

The sixth lens element L6 with negative refractive power is made of plastic material, and has a concave object-side surface S11 along the optical axis, a convex object-side surface S11 along the circumference, a concave image-side surface S12 along the optical axis, and a convex image-side surface S12 along the circumference.

The seventh lens element L7 with negative refractive power is made of plastic material, and has a concave object-side surface S13 along the optical axis and at the periphery, a convex image-side surface S14 along the optical axis, and a concave image-side surface S14 along the periphery.

The eighth lens element L8 with negative refractive power is made of plastic material, and has a concave object-side surface S15 along the optical axis and at the circumference, and a convex image-side surface S16 along the optical axis and at the circumference.

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 optical axis.

TABLE 2a

Table 2b shows high-order coefficient A4, A6, A8, a10, a12, a14, a16, a18, and a20, which can be used for each aspherical mirror surface S1, S2, S3, S4, S5, S6, S7, S8, S9, S10, S11, S12, S13, S14, S15, S16 in the second embodiment, wherein each aspherical mirror surface type can be defined by the formula 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 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, wherein S represents the sagittal direction, and T represents the meridional direction; the distortion curve represents the distortion magnitude values corresponding to different angles of view. 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 sixth lens L6 away from the fifth lens L5 is an image side 13. In the optical system provided in this embodiment, the stop STO, the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, the sixth lens L6, the seventh lens L7, the eighth lens L8, and the infrared filter element IRCF are arranged in order from the object side 12 to the image side 13.

The fifth lens element L5 with negative refractive power is made of plastic material, and has an object-side surface S9 being convex along the optical axis and at the circumference, and an image-side surface S10 being concave along the optical axis and at the circumference.

The seventh lens element L7 with negative refractive power is made of plastic material, and has a concave object-side surface S13 along the optical axis and at the circumference, and a convex image-side surface S14 along the optical axis and at the circumference.

The eighth lens element L8 with positive refractive power is made of plastic material, and has a convex object-side surface S15 along the optical axis, a concave object-side surface S15 along the circumference, and a concave image-side surface S16 along the optical axis and the circumference.

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 optical axis.

TABLE 3a

Table 3b shows high-order coefficient A4, A6, A8, a10, a12, a14, a16, a18, and a20, which can be used for each aspherical mirror surface S1, S2, S3, S4, S5, S6, S7, S8, S9, S10, S11, S12, S13, S14, S15, S16 in the third embodiment, wherein each aspherical mirror surface type can be defined by the formula given in the first embodiment.

TABLE 3b

Number of noodles	K	A4	A6	A8	A10
						S1	-1.5927	0.0383	0.0058	-0.0150	0.0374
S2	-0.5411	0.0728	-0.0943	0.0780	0.0068
						S3	-54.0522	-0.0228	0.0443	-0.2186	0.4926
S4	-52.8856	-0.1064	0.5556	-1.4723	1.9014
						S5	-50.3669	-0.0536	0.4573	-0.8476	-1.0347
S6	-5.3633	-0.0628	0.6052	-1.9371	3.4718
						S7	97.1066	0.1124	-0.0865	0.7395	-3.5234
S8	-26.4300	0.2440	-0.5512	2.2389	-6.4464
						S9	89.0000	0.0871	-0.6040	1.9220	-3.8201
S10	-78.4730	-0.0499	-0.0998	0.3176	-0.3732
						S11	-5.6393	0.0002	-0.2762	0.4536	-0.4762
S12	-0.4504	0.1226	-0.4444	0.6009	-0.5452
						S13	-13.2306	0.1168	-0.2188	0.0977	0.0475
S14	-42.9930	-0.0504	0.1287	-0.2262	0.2036
						S15	-1.3708	-0.1396	0.1671	-0.1518	0.1022
S16	-17.6617	-0.1058	0.0483	-0.0270	0.0214
						Number of noodles	A12	A14	A16	A18	A20
S1	-0.0497	0.0401	-0.0194	0.0052	-0.0006
						S2	-0.0913	0.1070	-0.0636	0.0196	-0.0024
S3	-0.5896	0.4458	-0.2197	0.0644	-0.0083
						S4	-1.0027	-0.2168	0.5265	-0.2325	0.0337
S5	5.6308	-8.6056	6.6739	-2.6768	0.4410
						S6	-5.3002	7.6411	-8.1037	4.9782	-1.2817
S7	8.7537	-13.5185	12.4727	-6.1117	1.2047
						S8	13.9810	-20.5251	18.2451	-8.7741	1.7471
S9	6.1392	-7.1828	5.2685	-2.1178	0.3542
						S10	0.3081	-0.1594	0.0260	0.0174	-0.0071
S11	0.2617	-0.0256	-0.0437	0.0204	-0.0028
						S12	0.3297	-0.1293	0.0317	-0.0045	0.0003
S13	-0.0734	0.0361	-0.0091	0.0012	-0.0001
						S14	-0.1062	0.0336	-0.0064	0.0007	0.0000
S15	-0.0503	0.0166	-0.0034	0.0004	0.0000
						S16	-0.0130	0.0045	-0.0009	0.0001	0.0000

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 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, wherein S represents the sagittal direction, and T represents the meridional direction; the distortion curve represents the distortion magnitude values corresponding to different angles of view. 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 sixth lens L6 away from the fifth lens L5 is an image side 13. In the optical system provided in this embodiment, the stop STO, the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, the sixth lens L6, the seventh lens L7, the eighth lens L8, and the infrared filter element IRCF are arranged in order from the object side 12 to the image side 13.

The second lens element L2 with negative refractive power has a convex object-side surface S3 along the optical axis and at the periphery, a concave image-side surface S4 along the optical axis, and a convex image-side surface S4 along the periphery.

The seventh lens element L7 with negative refractive power is made of plastic material, and has a concave object-side surface S13 along the optical axis, a convex object-side surface S13 along the circumference, a convex image-side surface S14 along the optical axis, and a concave image-side surface S14 along the circumference.

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 optical axis.

TABLE 4a

Table 4b shows high-order coefficient A4, A6, A8, a10, a12, a14, a16, a18, and a20, which can be used for each aspherical mirror surface S1, S2, S3, S4, S5, S6, S7, S8, S9, S10, S11, S12, S13, S14, S15, S16 in the fourth embodiment, wherein each aspherical mirror surface type can be defined by the formula 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 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, wherein S represents the sagittal direction, and T represents the meridional direction; the distortion curve represents the distortion magnitude values corresponding to different angles of view. 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 sixth lens L6 away from the fifth lens L5 is an image side 13. In the optical system provided in this embodiment, the stop STO, the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, the sixth lens L6, the seventh lens L7, the eighth lens L8, and the infrared filter element IRCF are arranged in order from the object side 12 to the image side 13.

The first lens element L1 with positive refractive power is made of plastic material, and has a convex object-side surface S1 along an optical axis, a concave object-side surface S1 along a circumference, a concave image-side surface S2 along the optical axis, and a convex image-side surface S2 along the circumference.

The second lens element L2 with negative refractive power is made of plastic material, and has a concave object-side surface S3 along the optical axis, a convex object-side surface S3 along the circumference, and a concave image-side surface S4 along the optical axis and the circumference.

The fifth lens element L5 with negative refractive power is made of plastic material, and has a concave object-side surface S9 along the optical axis and at the circumference, and a concave image-side surface S10 along the optical axis and at the circumference.

The seventh lens element L7 with negative refractive power is made of plastic material, and has a concave object-side surface S13 along the optical axis, a convex object-side surface S13 along the circumference, a concave image-side surface S14 along the optical axis, and a convex image-side surface S14 along the circumference.

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 optical axis.

TABLE 5a

Table 5b shows high-order coefficient A4, A6, A8, a10, a12, a14, a16, a18, and a20, which can be used for each aspherical mirror surface S1, S2, S3, S4, S5, S6, S7, S8, S9, S10, S11, S12, S13, S14, S15, S16 in the fifth embodiment, wherein each aspherical mirror surface type can be defined by the formula 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 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, wherein S represents the sagittal direction, and T represents the meridional direction; the distortion curve represents the distortion magnitude values corresponding to different angles of view. 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 sixth lens L6 away from the fifth lens L5 is an image side 13. In the optical system provided in this embodiment, the stop STO, the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, the sixth lens L6, the seventh lens L7, the eighth lens L8, and the infrared filter element IRCF are arranged in order from the object side 12 to the image side 13.

The fourth lens element L4 with positive refractive power is made of plastic material, and has a convex object-side surface S7 along the optical axis, a concave object-side surface S7 along the circumference, and a convex image-side surface S8 along the optical axis and the circumference.

The sixth lens element L6 with positive refractive power has a convex object-side surface S11 along the optical axis and at the periphery, a concave image-side surface S12 along the optical axis, and a convex image-side surface S12 along the periphery.

The seventh lens element L7 with positive refractive power is made of plastic material, and has an object-side surface S13 being convex along the optical axis and at the circumference, an image-side surface S14 being concave along the optical axis, and an image-side surface S14 being convex along the circumference.

The eighth lens element L8 with negative refractive power is made of plastic material, and has an object-side surface S15 being concave along the optical axis and at the periphery, an image-side surface S16 being convex along the optical axis, and an image-side surface S16 being concave along the periphery and being aspheric.

Table 6a 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.

TABLE 6a

Table 6b shows high-order coefficient A4, A6, A8, a10, a12, a14, a16, a18, and a20, which can be used for each aspherical mirror surface S1, S2, S3, S4, S5, S6, S7, S8, S9, S10, S11, S12, S13, S14, S15, S16 in the sixth embodiment, wherein each aspherical mirror surface type can be defined by the formula given in the first embodiment.

TABLE 6b

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 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, wherein S represents the sagittal direction, and T represents the meridional direction; the distortion curve represents the distortion magnitude values corresponding to different angles of view. As can be seen from fig. 12, the optical system according to the sixth embodiment can achieve good image quality.

EXAMPLE seven

As shown in fig. 13, 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 sixth lens L6 away from the fifth lens L5 is an image side 13. In the optical system provided in this embodiment, the stop STO, the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, the sixth lens L6, the seventh lens L7, the eighth lens L8, and the infrared filter element IRCF are arranged in order from the object side 12 to the image side 13.

The fourth lens element L4 with negative refractive power is made of plastic material, and has a concave object-side surface S7 along the optical axis, a convex object-side surface S7 along the circumference, and a convex image-side surface S8 along the optical axis and the circumference.

The fifth lens element L5 with positive refractive power is made of plastic material, and has a convex object-side surface S9 along the optical axis, a concave object-side surface S9 along the circumference, and a concave image-side surface S10 along the optical axis and the circumference.

The seventh lens element L7 with positive refractive power is made of plastic material, and has a convex object-side surface S13 along the optical axis, a concave object-side surface S13 along the circumference, and a concave image-side surface S14 along the optical axis and the circumference.

The eighth lens element L8 with negative refractive power is made of plastic material, and has a convex object-side surface S15 along the optical axis, a concave object-side surface S15 along the circumference, a concave image-side surface S16 along the optical axis, and a convex image-side surface S16 along the circumference.

Table 7a 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.

TABLE 7a

Table 7b shows high-order coefficient coefficients A4, A6, A8, a10, a12, a14, a16, a18, and a20, which can be used for each aspherical mirror surface S1, S2, S3, S4, S5, S6, S7, S8, S9, S10, S11, S12, S13, S14, S15, S16 in the seventh embodiment, wherein each aspherical mirror surface type can be defined by the formula given in the first embodiment.

TABLE 7b

Fig. 14 shows a longitudinal spherical aberration curve, an astigmatism curve, and a distortion curve of the optical system of the seventh 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, wherein S represents the sagittal direction, and T represents the meridional direction; the distortion curve represents the distortion magnitude values corresponding to different angles of view. As can be seen from fig. 14, the optical system according to the seventh embodiment can achieve good image quality.

Example eight

As shown in fig. 15, 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 sixth lens L6 away from the fifth lens L5 is an image side 13. In the optical system provided in this embodiment, the stop STO, the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, the sixth lens L6, the seventh lens L7, the eighth lens L8, and the infrared filter element IRCF are arranged in order from the object side 12 to the image side 13.

The second lens element L2 with positive refractive power has a convex object-side surface S3 along the optical axis and at the periphery, a convex image-side surface S4 along the optical axis, and a concave image-side surface S4 along the periphery.

The third lens element L3 with negative refractive power has a concave object-side surface S5 along the optical axis and at the circumference, and a concave image-side surface S6 along the optical axis and at the circumference.

The sixth lens element L6 with negative refractive power is made of plastic material, and has a concave object-side surface S11 along the optical axis, a convex object-side surface S11 along the circumference, and a convex image-side surface S12 along the optical axis and the circumference.

The seventh lens element L7 with negative refractive power is made of plastic material, and has an object-side surface S13 being convex along the optical axis and at the circumference, and an image-side surface S14 being concave along the optical axis and at the circumference.

The eighth lens element L8 with negative refractive power is made of plastic material, and has a concave object-side surface S15 along the optical axis, a convex object-side surface S15 along the circumference, a convex image-side surface S16 along the optical axis, and a concave image-side surface S16 along the circumference.

Table 8a 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.

TABLE 8a

Table 8b shows high-order coefficient A4, A6, A8, a10, a12, a14, a16, a18, and a20, which can be used for each aspherical mirror surface S1, S2, S3, S4, S5, S6, S7, S8, S9, S10, S11, S12, S13, S14, S15, S16 in the eighth embodiment, wherein each aspherical mirror surface type can be defined by the formula given in the first embodiment.

TABLE 8b

Number of noodles	K	A4	A6	A8	A10
						S1	-1.9598	0.0490	0.0008	-0.0056	0.0285
S2	0.0000	0.0458	-0.0173	0.0302	-0.1152
						S3	-49.6866	-0.0330	0.0136	0.1699	-0.6833
S4	-57.0050	-0.1849	0.9705	-2.6363	3.9094
						S5	-57.0050	-0.2023	1.3246	-4.3385	8.2137
S6	-4.8729	-0.0313	0.4411	-2.0219	4.8284
						S7	86.9060	0.1621	-0.0567	0.2286	-2.1164
S8	-49.7195	0.3297	-0.4951	1.1111	-1.1350
						S9	89.0000	0.0721	-0.5393	1.0971	0.6424
S10	-78.4730	-0.0582	-0.0529	0.0593	0.5863
						S11	-10.9160	-0.0588	0.0776	-0.1700	0.1468
S12	-35.5530	0.0017	0.1125	-0.2868	0.2929
						S13	0.0000	0.0729	-0.1379	0.0370	0.0709
S14	-42.9930	0.1424	-0.3037	0.2888	-0.1870
						S15	-26.3451	0.0424	-0.1011	0.0816	-0.0504
S16	0.0000	-0.0454	-0.0175	0.0210	-0.0139
						Number of noodles	A12	A14	A16	A18	A20
S1	-0.0504	0.0503	-0.0291	0.0092	-0.0013
						S2	0.2084	-0.1851	0.0839	-0.0184	0.0015
S3	1.2850	-1.3247	0.7743	-0.2430	0.0323
						S4	-2.8932	0.3720	0.9859	-0.6770	0.1420
S5	-9.5260	6.7535	-2.7366	0.5223	-0.0219
						S6	-6.9851	5.8839	-2.1462	-0.2782	0.3365
S7	6.9561	-13.2247	14.1647	-7.8153	1.7349
						S8	-0.3130	2.9986	-5.1346	4.0317	-1.2165
S9	-7.0954	16.8312	-20.2904	12.3777	-3.0301
						S10	-1.9332	3.1732	-3.0005	1.5845	-0.3642
S11	-0.0948	0.0593	-0.0290	0.0084	-0.0010
						S12	-0.1676	0.0568	-0.0111	0.0011	0.0000
S13	-0.0741	0.0328	-0.0078	0.0010	-0.0001
						S14	0.0862	-0.0270	0.0054	-0.0006	0.0000
S15	0.0255	-0.0092	0.0021	-0.0003	0.0000
						S16	0.0079	-0.0031	0.0007	-0.0001	0.0000

Fig. 16 shows a longitudinal spherical aberration curve, an astigmatism curve, and a distortion curve of the optical system of the eighth 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, wherein S represents the sagittal direction, and T represents the meridional direction; the distortion curve represents the distortion magnitude values corresponding to different angles of view. As can be seen from fig. 16, the optical system according to the eighth embodiment can achieve good image quality.

Example nine

As shown in fig. 17, 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 sixth lens L6 away from the fifth lens L5 is an image side 13. In the optical system provided in this embodiment, the stop STO, the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, the sixth lens L6, the seventh lens L7, the eighth lens L8, and the infrared filter element IRCF are arranged in order from the object side 12 to the image side 13.

The fourth lens element L4 with positive refractive power is made of plastic, and has a concave object-side surface S7 along the optical axis, a convex object-side surface S7 along the circumference, and a convex image-side surface S8 along the optical axis and the circumference.

The fifth lens element L5 with negative refractive power is made of plastic material, and has an object-side surface S9 being concave along the optical axis and at the periphery, an image-side surface S10 being convex along the optical axis, and an image-side surface S10 being concave along the periphery and being aspheric.

The seventh lens element L7 with negative refractive power is made of plastic material, and has a concave object-side surface S13 along the optical axis, a convex object-side surface S13 along the circumference, and a concave image-side surface S14 along the optical axis and the circumference.

The eighth lens element L8 with negative refractive power is made of plastic material, and has an object-side surface S15 being convex along the optical axis and at the circumference, and an image-side surface S16 being concave along the optical axis and at the circumference.

Table 9a 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.

TABLE 9a

Table 9b shows high-order coefficient A4, A6, A8, a10, a12, a14, a16, a18, and a20, which can be used for each aspherical mirror surface S1, S2, S3, S4, S5, S6, S7, S8, S9, S10, S11, S12, S13, S14, S15, S16 in the ninth embodiment, wherein each aspherical mirror surface type can be defined by the formula given in the first embodiment.

TABLE 9b

Fig. 18 shows a longitudinal spherical aberration curve, an astigmatism curve, and a distortion curve of the optical system of the ninth 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, wherein S represents the sagittal direction, and T represents the meridional direction; the distortion curve represents the distortion magnitude values corresponding to different angles of view. As can be seen from fig. 18, the optical system according to the ninth embodiment can achieve good image quality.

Table 10 shows values of TTL/Imgh, TTL/f, f1/f28, FNO, (L81-L82)/2 × L83, TTL/ct56, Imgh/tan (hfov) of the optical systems of the first to ninth embodiments.

Watch 10

As can be seen from table 10, each example satisfies: TTL/Imgh <2.5, TTL/f <1.1, -1.8< f1/f28< -0.5, FNO <2.4, (L81-L82)/2 x L83 > 0.7, TTL/ct56>4, Imgh/tan (HFOV) 5 mm.

Referring to fig. 19, the optical system according to the present application is applied to a lens 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, or the like. The light sensing element of the lens module 20 is located at the image side of the optical system, and the lens module 20 is assembled inside the terminal device 30.

The application provides a lens module, including photosensitive element and the optical system that this application provided, photosensitive element is located optical system's image side for will pass first lens to eighth lens and incide the light on the electron photosensitive element and convert the signal of telecommunication of image into. The electron sensitive element may be a Complementary Metal Oxide Semiconductor (CMOS) or a Charge-coupled Device (CCD). The optical system is arranged in the lens module, so that the lens module has the characteristic of long focal length and good imaging quality while meeting the requirement of micro design, and a shot picture has high painting texture, high resolution and high definition.

The application also provides a terminal device, and the terminal device comprises the lens module provided by the application. The terminal equipment can be a mobile phone, a tablet personal computer, an unmanned aerial vehicle, a computer and the like. By installing the lens module in the terminal equipment, the terminal equipment has the characteristic of long focal length while meeting the requirement of micro design, has good imaging quality and ensures that the shot picture has high painting texture, high resolution and high definition.

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 includes a plurality of lenses, where the plurality of lenses includes a first lens element, a second lens element, a third lens element, a fourth lens element, a fifth lens element, a sixth lens element, a seventh lens element and an eighth lens element arranged in order from an object side to an image side, where the first lens element has positive refractive power, the third lens element has negative refractive power, and the remaining lens elements have refractive power; the object side surface of the first lens is a convex surface at the optical axis, the image side surface of the third lens is a concave surface at the optical axis, and the image side surface of the fourth lens is a convex surface at the optical axis;

the optical system satisfies the following conditional expression:

TTL/f<1.1，

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.

2. The optical system of claim 1, wherein all of the lenses have aspheric object-side and image-side surfaces.

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

-1.8<f1/f28<-0.5，

f1 is the focal length of the first lens, and f28 is the combined focal length of the second lens to the eighth lens.

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

TTL/ct56>4，

TTL is an axial distance from an object-side surface of the first lens element to an image plane of the optical system, and ct56 is an axial distance from an object-side surface of the fifth lens element to an image-side surface of the sixth lens element.

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

(L81-L82)/2*L83＞0.7，

a beam of light is incident on the farthest point from the optical axis of the imaging surface of the optical system, the beam of light and the image-side surface of the eighth lens have a first intersection point, L81 is the maximum distance between the first intersection point and the vertical projection point of the first intersection point on the optical axis, L82 is the minimum distance between the first intersection point and the vertical projection point of the first intersection point on the optical axis, a beam of light is incident on the center point of the imaging surface of the optical system, the beam of light and the image-side surface of the eighth lens have a second intersection point, and L83 is the maximum distance between the second intersection point and the vertical projection point of the second intersection point on the optical axis.

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

TTL/Imgh<2.5，

TTL is a distance on an optical axis from an object-side surface of the first lens element to an image plane of the optical system, and Imgh is an image height corresponding to half of a maximum field angle of the optical system.

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

FNO<2.4，

the FNO is an f-number of the optical system.

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

Imgh/tan(HFOV)>5mm，

imgh is an image height corresponding to half of the maximum angle of view of the optical system, and tan (hfov) is a tangent value of half of the maximum angle of view of the optical system.

9. A lens module comprising the optical system of any one of claims 1 to 8 and a photosensitive element, wherein the photosensitive element is located on the image side of the optical system.

10. A terminal device characterized by comprising the lens module according to claim 9.