CN113376797A

CN113376797A - Optical system, lens module and terminal equipment

Info

Publication number: CN113376797A
Application number: CN202010117217.6A
Authority: CN
Inventors: 蔡雄宇; 兰宾利; 周芮
Original assignee: Tianjin OFilm Opto Electronics Co Ltd
Current assignee: Tianjin OFilm Opto Electronics Co Ltd
Priority date: 2020-02-25
Filing date: 2020-02-25
Publication date: 2021-09-10

Abstract

The embodiment of the application discloses an optical system, a lens module and terminal equipment. The optical system includes a plurality of lenses arranged in order from an object side to an image side, the plurality of lenses including: the first lens element with negative refractive power; the second lens element with negative refractive power has a concave object-side surface and a convex image-side surface; the third lens element with positive refractive power has a convex object-side surface; the fourth lens element with positive refractive power; the fifth lens element with negative refractive power; the sixth lens element with positive refractive power; the seventh lens element with negative refractive power has a concave object-side surface; the eighth lens element with positive refractive power. This application is through the plane type of the refractive power of restriction first lens to eighth lens and second lens, third lens and seventh lens among optical system for optical system has high pixel, the formation of image information of seizure that can be more clear, and the picture quality is better, simultaneously, has widened formation of image field range.

Description

Optical system, lens module and terminal equipment

Technical Field

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

Background

With the development of the vehicle-mounted industry, the technical requirements of vehicle-mounted cameras such as automobile data recorders and reversing images are higher and higher. Not only miniaturization and weight reduction are required, but also the pixel image quality is required to be higher and higher.

At present, as terminal equipment tends to be light and thin, a camera with high performance is arranged in the terminal equipment, and the optical system of the traditional camera cannot meet the requirements in the aspects of pixels, a visual field range and the like, so that the imaging quality is poor, and the information quantity of a space range which can be acquired by the optical system is limited.

Therefore, how to raise the pixels of the lens to meet the requirement of high image quality of the lens and widen the imaging view field range to obtain sufficient object space information is the research and development direction in the industry.

Disclosure of Invention

The embodiment of the application provides an optical system, a lens module and terminal equipment, and the optical system solves the problems of poor pixel and visual field range of the traditional camera. The optical system has high pixels, can more clearly capture imaging information, has better image quality, has more details in pictures, and simultaneously widens the imaging visual field range, particularly, not only increases the field angle range, but also deepens the imaging depth range.

In a first aspect, an optical system includes, in order from an object side to an image side, 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, wherein the first lens element has negative refractive power; the second lens element with negative refractive power has a concave object-side surface and a convex image-side surface; the third lens element with positive refractive power has a convex object-side surface; the fourth lens element with positive refractive power; the fifth lens element with negative refractive power; the sixth lens element with positive refractive power; the seventh lens element with negative refractive power has a concave object-side surface; the eighth lens element with positive refractive power.

This application is through the plane type of the refractive power of restriction first lens to eighth lens element and second lens, third lens and seventh lens in optical system for optical system has high pixel, the formation of image information of seizure that can be more clear, and the image quality is better, and the picture has more details, and simultaneously, has widened formation of image field range, specifically speaking, not only has increased the field angle scope, has still deepened the formation of image depth scope, with the clear presentation in the imaging element position of the formation of image information that camera system can catch. The road surface information acquisition system is used in the vehicle-mounted industry, can accurately capture road surface information in real time and transmit the road surface information to the system for image analysis, and provides guarantee for safe driving.

In one embodiment, in all lenses of the optical system, at least two of the lenses have aspheric object-side surfaces and/or image-side surfaces, which is beneficial to correcting system aberration and improving system imaging quality.

In one embodiment, an image-side surface of the fourth lens element is cemented to an object-side surface of the fifth lens element. The fourth lens and the fifth lens are arranged to be glued to form the cemented lens, so that the eccentric sensitivity of the optical imaging system is reduced, the assembly yield is improved, and the production cost is reduced.

In one embodiment, the optical system satisfies the conditional expression: -3< f1/f < -1.5; f1 is the focal length of the first lens, and f is the effective focal length of the optical system. The first lens element with negative refractive power is arranged close to the object side, and the ratio of the focal length of the first lens element to the effective focal length of the optical system is limited, so that large-angle light can be emitted into the optical system, the field angle range of the optical system is enlarged, and the optical system has the characteristics of low sensitivity and miniaturization. If f1/f ≧ 1.5, which results in too short focal length and too large refractive power of the first lens element, the sensitivity of the imaging plane will increase due to the change of the first lens element during imaging, resulting in larger aberration; if f1/f is less than or equal to-3, the refractive power of the first lens element is small, which is not favorable for large-angle light to enter the optical system, and is not favorable for wide-angle of the optical system.

In one embodiment, the optical system satisfies the conditional expression: -16 < f2/f < -5; f2 is the focal length of the second lens, and f is the effective focal length of the optical system. The second lens is set to be a lens with negative refractive power, the ratio of the focal length of the second lens to the effective focal length of the optical system is limited, the width of light beams is favorably enlarged, the light beams which are incident after large-angle light rays are refracted by the first lens are widened and are full of pupils, and the light beams are fully transmitted to a high-pixel imaging surface, so that a wider field range is obtained, and the characteristic of high pixels of the optical system is favorably realized. If f2/f is ≧ 5 or f2/f is ≦ -16, it is unfavorable for correcting the aberration of the optical system, thereby degrading the imaging quality.

In one embodiment, the optical system satisfies the conditional expression: the ratio of (1/| R2R | +1/| R3f |)/D23 is less than or equal to 0.1 and less than 0.5; R2R is a radius of curvature of the image-side surface of the second lens element at the optical axis, R3f is a radius of curvature of the object-side surface of the third lens element at the optical axis, and D23 is a distance between the image-side surface of the second lens element and the object-side surface of the third lens element at the optical axis. By limiting (1/| R2R | +1/| R3f |)/D23 to be more than or equal to 0.1, the angle of incidence of the chief ray of the peripheral visual angle to an imaging surface is favorably reduced, and the probability of generating ghost images is reduced; (1/| R2R | +1/| R3f |)/D23 < 0.5, which is advantageous for suppressing the occurrence of astigmatism.

In one embodiment, the optical system satisfies the conditional expression: f3/f is more than 1 and less than 3; f3 is the focal length of the third lens, and f is the effective focal length of the optical system. Because the light rays are emitted by the first lens and the second lens with stronger refractive power, and the marginal light rays are emitted to the imaging surface to easily generate a larger field area, the ratio of the focal length of the third lens to the effective focal length of the optical system is limited by arranging the third lens with positive refractive power, so that the marginal aberration can be corrected, and the imaging resolution can be improved. If f3/f is not less than 3 or f3/f is not more than 1, it is not favorable to correct the aberration of the optical system, thereby reducing the imaging quality.

In one embodiment, the optical system satisfies the conditional expression: 1 < (D12+ CT2)/(CT3+ D34) < 2; d12 is a distance between an image-side surface of the first lens element and an object-side surface of the second lens element along an optical axis, CT2 is a thickness of the second lens element along the optical axis, CT3 is a thickness of the third lens element along the optical axis, and D34 is a distance between the image-side surface of the third lens element and an object-side surface of the fourth lens element along the optical axis. By limiting the range of (D12+ CT2)/(CT3+ D34), the method is beneficial to correcting system aberration, improves imaging resolution, ensures compact system structure and meets the characteristic of miniaturization. If (D12+ CT2)/(CT3+ D34) ≥ 2 or (D12+ CT2)/(CT3+ D34) ≤ 1, it is not favorable for correcting aberration of the optical system, thereby reducing imaging quality, and at the same time, too large air space and lens thickness increase the total length of the optical system, which is not favorable for miniaturization of the optical system.

In one embodiment, the optical system satisfies the conditional expression: -9< f45/f < 0; f45 is the combined focal length of the fourth lens and the fifth lens, and f is the effective focal length of the optical system. The cemented lens formed by the combination of the fourth lens and the fifth lens has negative refractive power, and the accumulated tolerance of the fourth lens and the fifth lens can be converted into the tolerance of the cemented lens by arranging the cemented lens and reasonably configuring the ratio range of f45/f, so that the aberration of an optical system can be corrected, the eccentricity sensitivity can be reduced, the system assembly sensitivity can be reduced, the problems of lens process manufacturing and lens assembly can be solved, the yield can be improved, and meanwhile, the imaging resolution can be improved by correcting the system aberration. If f45/f is not less than 0 or f45/f is not more than-9, it is not favorable to correct the aberration of the optical system, thereby reducing the imaging quality.

In one embodiment, the optical system satisfies the conditional expression: 2< f6/f < 5; f6 is the focal length of the sixth lens, and f is the effective focal length of the optical system. By limiting the ratio of the focal length of the sixth lens to the effective focal length of the optical system, the correction of chromatic aberration is facilitated, the eccentricity sensitivity is reduced, the system aberration is corrected, and the imaging resolution is improved. If f6/f is not less than 5 or f6/f is not more than 2, it is not favorable to correct the aberration of the optical system, thereby reducing the imaging quality.

In one embodiment, the optical system satisfies the conditional expression: -9< f7/f < -2; f7 is the focal length of the seventh lens, and f is the effective focal length of the optical system. By limiting the ratio of the focal length of the seventh lens to the effective focal length of the optical system, the chromatic aberration can be corrected, the eccentricity sensitivity can be reduced, the system aberration can be corrected, and the imaging resolution can be improved. If f6/f is ≧ 2 or f6/f is ≦ -9, it is unfavorable to correct the aberration of the optical system, thereby degrading the imaging quality.

In one embodiment, the optical system satisfies the conditional expression: 2< CT8/CT7 < 4; CT7 is the thickness of the seventh lens element on the optical axis, and CT8 is the thickness of the eighth lens element on the optical axis. The refractive power of each lens is related to the thickness of the lens, the thickness of the seventh lens and the thickness of the eighth lens on the optical axis are reasonably set, the refractive power relation between the seventh lens and the eighth lens can be effectively adjusted, the wide angle and the miniaturization of an optical system are facilitated, the optical performance of the system is improved, the emergent angle of light rays emitted out of the optical system is reduced, the light rays are incident on the photosensitive element in a mode close to vertical incidence, the optical system has a telecentric characteristic, the sensitivity of the photosensitive element can be improved, and the probability of generating a dark angle by the system is reduced. If CT8/CT7 is greater than or equal to 4 or CT8/CT7 is less than or equal to 2, the refractive power distribution between the seventh lens element and the eighth lens element will be unreasonable, which is not favorable for correcting the aberration of the optical system.

In one embodiment, the optical system satisfies the conditional expression: 3 is less than or equal to (Nd5-Nd4) 100 is less than 50; nd4 is a refractive index of the fourth lens, and Nd5 is a refractive index of the fifth lens. Specifically, in the present embodiment, the refractive indices of the fourth lens and the fifth lens are refractive indices for light having a wavelength of 587.56nm, and the limitation of (Nd5-Nd4) × 100 is advantageous for optimizing aberrations and improving imaging analysis capability. If (Nd5-Nd4) 100 is greater than or equal to 50 or (Nd5-Nd4) 100 <3, it is 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: 2< Imgh/Tan (1/2FOV) < 3; the FOV is the angle of view in the diagonal direction of the optical system, and Imgh is half of the diagonal length of the effective pixel area of the optical system. Since the field angle range of the optical system determines the amount of information in the spatial range that can be acquired by the optical system, limiting the range of Imgh/Tan (1/2FOV) allows the optical system to have a sufficient field angle to meet the high field angle requirements of electronic products such as mobile phones, cameras, vehicles, monitors, and medical care, and also reduces the angle at which light enters the photosensitive element to improve the photosensitive performance. If Imgh/Tan (1/2FOV) is more than or equal to 3, the visual angle is insufficient, and enough object space information can not be obtained, and if Imgh/Tan (1/2FOV) is less than or equal to 2, the brightness is insufficient, and the requirement of high-definition shooting can not be met.

In one embodiment, the optical system further comprises a diaphragm, and the optical system satisfies the conditional expression: EPL/TTL is more than 0.4 and less than 0.7; the EPL is a distance between a diaphragm of the optical system and an imaging surface on an optical axis, and the TTL is a distance between an object-side surface of the first lens of the optical system and the imaging surface of the optical system on the optical axis. By limiting the EPL/TTL to be more than 0.4, the pupil is far away from the imaging plane, light rays are incident on the photosensitive element in a mode of approaching to vertical incidence, the optical system has telecentric characteristics, the telecentric characteristics improve the light sensitivity of the electronic photosensitive element, the light sensitivity of the electronic photosensitive element can be improved, and the possibility of generating dark angles by the system is reduced. By limiting the EPL/TTL to be less than 0.7, the total length of the optical system is favorably limited, and the system has the characteristic of miniaturization.

In one embodiment, the optical system satisfies the conditional expression: f/EPD is less than or equal to 1.7; f is the effective focal length of the optical system, EPD is the entrance pupil diameter of the optical system. The f/EPD is limited, so that the control on the light incoming quantity and the diaphragm number of the system is facilitated, the visual field of an imaging plane is brighter, the system has the effect of a large diaphragm and a farther depth of field range, namely a wider imaging depth, and a user or a user system is facilitated to accurately identify and judge imaging pictures from far to near. If f/EPD is more than 7, the f-number of the optical system is too large, the larger the f-number is, the darker the image plane is, the smaller the depth of field range of the optical system is, and thus the imaging quality is reduced.

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.

This application is through the refracting power and the second lens of rational configuration first lens to eighth lens, the face type of third lens and seventh lens, make optical system have high pixel, can be more clear seizure imaging information, the image quality is better, the picture has more details, and simultaneously, the formation of image field of vision scope has been widened, particularly, not only increased the field angle scope, imaging depth scope has still been deepened, the clear presentation of imaging information that can the camera system catch is in the imaging element position, be used in on-vehicle trade, can be real-time accurate the information of snatching the road surface and transmit the system and carry out image analysis, guarantee is provided for safe driving.

Drawings

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

FIG. 1 is a schematic diagram of an optical system provided herein in a terminal device;

FIG. 2 is a schematic diagram of an optical system according to a first embodiment of the present application;

FIG. 3 is a spherical aberration curve of the optical system of the first embodiment;

fig. 4 is an astigmatism curve of the optical system of the first embodiment;

fig. 5 is a distortion curve of the optical system of the first embodiment;

FIG. 6 is a schematic diagram of an optical system according to a second embodiment of the present application;

FIG. 7 is a spherical aberration curve of the optical system of the second embodiment;

fig. 8 is an astigmatism curve of the optical system of the second embodiment;

FIG. 9 is a distortion curve of the optical system of the second embodiment;

FIG. 10 is a schematic diagram of an optical system provided in a third embodiment of the present application;

FIG. 11 is a spherical aberration curve of the optical system of the third embodiment;

fig. 12 is an astigmatism curve of the optical system of the third embodiment;

fig. 13 is a distortion curve of the optical system of the third embodiment;

FIG. 14 is a schematic diagram of an optical system according to a fourth embodiment of the present application;

FIG. 15 is a spherical aberration curve of the optical system of the fourth embodiment;

fig. 16 is an astigmatism curve of the optical system of the fourth embodiment;

fig. 17 is a distortion curve of the optical system of the fourth embodiment;

fig. 18 is a schematic structural diagram of an optical system provided in a fifth embodiment of the present application;

fig. 19 is a spherical aberration curve of the optical system of the fifth embodiment;

fig. 20 is an astigmatism curve of the optical system of the fifth embodiment;

fig. 21 is a distortion curve of the optical system of the fifth embodiment.

Detailed Description

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

Referring to fig. 1, the optical system 10 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 monitor, a vehicle-mounted device, or the like. The light-sensing element 210 of the lens module 20 is located at the image side of the optical system 10, 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 embodiment provided, photosensitive element is located optical system's image side for incidenting the light on the electron photosensitive element and passing first lens to eighth lens converts the signal of telecommunication of image into. The electron sensor may be a Complementary Metal Oxide Semiconductor (CMOS) or a Charge-coupled Device (CCD). Through installing this optical system in the camera lens module, make the camera lens module have high pixel, the formation of image information of seizure that can be more clear, the image quality is better, and the picture has more details, simultaneously, has widened formation of image field of vision scope, with the clear presentation in imaging element position of the formation of image information that camera system can catch.

The application further provides a terminal device, and the terminal device comprises the lens module provided by the embodiment of the application. The terminal equipment can be a mobile phone, a monitor, a vehicle and the like. Through this lens module of installation in terminal equipment, make terminal equipment have high pixel, the seizure formation of image information that can be more clear, the image quality is better, and the picture has more details, simultaneously, has widened formation of image field of vision scope, with the clear presentation in imaging element position of the formation of image information that camera system can catch.

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. The fourth lens and the fifth lens form a cemented lens, the cemented lens has negative refractive power, and the cemented lens formed by the fourth lens and the fifth lens is favorable for reducing the eccentricity sensitivity of the optical imaging system, improving the assembly yield and reducing the production cost.

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

a first lens element with negative refractive power; the second lens element with negative refractive power has a concave object-side surface and a convex image-side surface; a third lens element with positive refractive power having a convex object-side surface; a fourth lens element with positive refractive power; a fifth lens element with negative refractive power; a sixth lens element with positive refractive power; the seventh lens element with negative refractive power has a concave object-side surface; the eighth lens element with positive refractive power.

The refractive power of the first lens element, the second lens element, the third lens element and the seventh lens element and the surface shape of the second lens element, the third lens element and the seventh lens element are reasonably configured, so that the optical system has high pixels, can capture imaging information more clearly, has better image quality, has more details on a picture, widens the imaging visual field range, particularly increases the field angle range, deepens the imaging depth range, and clearly presents the imaging information which can be captured by the camera system at the position of the imaging element. The road surface information acquisition system is used in the vehicle-mounted industry, can accurately capture road surface information in real time and transmit the road surface information to the system for image analysis, and provides guarantee for safe driving.

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

In one embodiment, the image-side surface of the fourth lens element is cemented to the object-side surface of the fifth lens element. The fourth lens and the fifth lens are arranged to be glued to form the cemented lens, so that the eccentric sensitivity of the optical imaging system is reduced, the assembly yield is improved, and the production cost is reduced.

In one embodiment, the optical system satisfies the conditional expression: the ratio of (1/| R2R | +1/| R3f |)/D23 is less than or equal to 0.1 and less than 0.5; R2R is a radius of curvature of the image-side surface of the second lens element at the optical axis, R3f is a radius of curvature of the object-side surface of the third lens element at the optical axis, and D23 is a distance between the image-side surface of the second lens element and the object-side surface of the third lens element at the optical axis. By limiting (1/| R2R | +1/| R3f |)/D23 to be more than or equal to 0.1, the angle of incidence of the chief ray of the peripheral visual angle to the imaging surface is favorably reduced, and the probability of generating ghost image is reduced. (1/| R2R | +1/| R3f |)/D23 < 0.5, which is advantageous for suppressing the occurrence of astigmatism.

In one embodiment, the optical system satisfies the conditional expression: 1 < (D12+ CT2)/(CT3+ D34) < 2; d12 is a distance between an image-side surface of the first lens element and an object-side surface of the second lens element along the optical axis, CT2 is a thickness of the second lens element along the optical axis, CT3 is a thickness of the third lens element along the optical axis, and D34 is a distance between the image-side surface of the third lens element and the object-side surface of the fourth lens element along the optical axis. By limiting the range of (D12+ CT2)/(CT3+ D34), the method is beneficial to correcting system aberration, improves imaging resolution, ensures compact system structure and meets the characteristic of miniaturization. If (D12+ CT2)/(CT3+ D34) ≥ 2 or (D12+ CT2)/(CT3+ D34) ≤ 1, it is not favorable for correcting aberration of the optical system, thereby reducing imaging quality, and at the same time, too large air space and lens thickness increase the total length of the optical system, which is not favorable for miniaturization of the optical system.

In one embodiment, the optical system satisfies the conditional expression: 3 is less than or equal to (Nd5-Nd4) 100 is less than 50; nd4 is a refractive index of the fourth lens, and Nd5 is a refractive index of the fifth lens. Specifically, the refractive indices of the fourth lens and the fifth lens in the present embodiment are refractive indices for light having a wavelength of 587.56nm, and the limitation of (Nd5-Nd4) × 100 is advantageous for optimizing aberration and improving imaging analysis capability. If (Nd5-Nd4) 100 is greater than or equal to 50 or (Nd5-Nd4) 100 <3, it is 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: 2< Imgh/Tan (1/2FOV) < 3; the FOV is the angle of view in the diagonal direction of the optical system, and Imgh is half the length of the diagonal of the effective pixel region of the optical system. Since the field angle range of the optical system determines the amount of information in the spatial range that can be acquired by the optical system, limiting the range of Imgh/Tan (1/2FOV) allows the optical system to have a sufficient field angle to meet the high field angle requirements of electronic products such as mobile phones, cameras, vehicles, monitors, and medical care, and also reduces the angle at which light enters the photosensitive element to improve the photosensitive performance. If Imgh/Tan (1/2FOV) is more than or equal to 3, the visual angle is insufficient, and enough object space information can not be obtained, and if Imgh/Tan (1/2FOV) is less than or equal to 2, the brightness is insufficient, and the requirement of high-definition shooting can not be met.

In one embodiment, the optical system further comprises a diaphragm, and the optical system satisfies the conditional expression: EPL/TTL is more than 0.4 and less than 0.7; the EPL is a distance between a stop of the optical system and an image plane of the optical system on the optical axis, and the TTL is a distance between an object-side surface of the first lens element of the optical system and the image plane of the optical system on the optical axis. By limiting the EPL/TTL to be more than 0.4, the pupil is far away from the imaging plane, light rays are incident on the photosensitive element in a mode of approaching to vertical incidence, the optical system has telecentric characteristics, the telecentric characteristics improve the light sensitivity of the electronic photosensitive element, the light sensitivity of the electronic photosensitive element can be improved, and the possibility of generating dark angles by the system is reduced. By limiting the EPL/TTL to be less than 0.7, the total length of the optical system is favorably limited, and the system has the characteristic of miniaturization.

In one embodiment, the optical system satisfies the conditional expression: f/EPD is less than or equal to 1.7; f is the effective focal length of the optical system and EPD is the entrance pupil diameter of the optical system. The f/EPD is limited, so that the control on the light incoming quantity and the diaphragm number of the system is facilitated, the visual field of an imaging plane is brighter, the system has the effect of a large diaphragm and a farther depth of field range, namely a wider imaging depth, and a user or a user system is facilitated to accurately identify and judge imaging pictures from far to near. If f/EPD is more than 7, the f-number of the optical system is too large, the larger the f-number is, the darker the image plane is, the smaller the depth of field range of the optical system is, and thus the imaging quality is reduced.

Through the definition of the above parameters, the optical system has good imaging quality, for example, it is preferable that: the value of f1/f can be-1.79 or-1.65 or-1.68, etc.; the value of f2/f can be-10.64 or-11.19 or-6.62, etc.; the value of (1/| R2R | +1/| R3f |)/D23 may be 0.15 or 0.27 or equal 0.23; the value of f3/f can be 1.92 or 1.95 or 1.97, etc.; the value of (D12+ CT2)/(CT3+ D34) may be 1.63 or 1.82 or 1.85, etc.

In all the lenses of the optical system, the object side surfaces and/or the image side surfaces of at least two lenses are aspheric surfaces, so that system aberration can be corrected, and the imaging quality of the system can be improved. The aspheric curve equation includes, but is not limited to, the following equation:

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.

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

Example one

As shown in fig. 2, the middle straight line represents the optical axis, and the left side of the optical system is the object side and the right side is the image side. 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, the sixth lens L6, the seventh lens L7, the eighth lens L8, the infrared filter IRCF, and the cover glass CG are disposed in order from the object side to the image side. The fourth lens L4 and the fifth lens L5 are cemented lenses, which is beneficial to reducing the eccentricity sensitivity of the optical imaging system, improving the assembly yield and reducing the production cost.

The first lens element L1 with negative refractive power has a convex object-side surface S1 and a concave image-side surface S2.

The second lens element L2 with negative refractive power has a concave object-side surface S3 and a convex image-side surface S4.

The third lens element L3 with positive refractive power has a convex object-side surface S5 and a convex image-side surface S6.

The fourth lens element L4 with positive refractive power has a convex object-side surface S7 and an aspheric image-side surface S8.

The fifth lens element L5 with negative refractive power has a concave object-side surface S9 and a concave image-side surface S10.

The sixth lens element L6 with positive refractive power has a convex object-side surface S11 and a convex image-side surface S12.

The seventh lens element L7 with negative refractive power has a concave object-side surface S13 and a convex image-side surface S14.

The eighth lens element L8 with positive refractive power has a convex object-side surface S13 and a convex image-side surface S14.

The stop STO may be located between the object side and the fifth lens of the optical system, and the stop STO in this embodiment is located behind the third lens L3, which tends to be at a middle position of the optical system, and is beneficial to balance the aberration of the optical system.

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 protective glass CG is located behind the infrared filter element IRCF and comprises an object side surface S19 and an image side surface S20, and the protective glass CG 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 influenced by dust and the like, and the imaging quality is ensured. The image formation surface S21 is an effective pixel region of the electrophotographic photosensitive member.

Table 1a shows a characteristic table of the optical system of the present embodiment.

TABLE 1a

Wherein f is the effective focal length of the optical system, FNO is the f-number of the optical system, and FOV is the angle of view of the optical system in the diagonal direction.

S8/S9 indicates that the image-side surface of the fourth lens and the object-side surface of the fifth lens, and the image-side surface S8 of the fourth lens and the object-side surface S9 of the fifth lens are cemented together, and thus are represented as one surface on data.

Table 1b shows the coefficients of the high-order terms a4, A6, A8, a10, a12, a14, a16, a18, and a20 that can be used for the respective aspherical mirrors S3, S4, S7, S11, and S12 in the first embodiment.

TABLE 1b

Number of noodles	S3	S4	S7	S11	S12
						K	0.00E+00	0.00E+00	0.00E+00	0.00E+00	0.00E+00
A4	4.54E-04	1.65E-04	-6.08E-04	6.87E-05	2.15E-04
						A6	8.74E-06	-8.67E-07	-2.42E-05	2.09E-05	-9.55E-06
A8	2.15E-07	2.37E-07	-4.49E-07	-7.08E-07	7.57E-07
						A10	4.89E-09	-5.30E-09	-2.85E-08	-1.65E-08	-5.55E-08
A12	1.53E-21	-3.56E-22	-2.79E-22	-1.57E-22	4.73E-22
						A14	-4.54E-25	-3.15E-25	-4.14E-25	-3.74E-25	-4.12E-25
A16	0.00E+00	0.00E+00	0.00E+00	0.00E+00	0.00E+00
						A18	0.00E+00	0.00E+00	0.00E+00	0.00E+00	0.00E+00
A20	0.00E+00	0.00E+00	0.00E+00	0.00E+00	0.00E+00

FIG. 3 shows a spherical aberration curve of the optical system of the first embodiment, which represents the deviation of the converging focal points of light rays of different wavelengths after passing through the lenses of the optical system;

fig. 4 shows astigmatism curves of the optical system of the first embodiment, which represent meridional field curvature and sagittal field curvature;

fig. 5 shows distortion curves of the optical system of the first embodiment, which represent distortion magnitude values corresponding to different angles of view;

as can be seen from fig. 3, 4, and 5, the optical system according to the first embodiment can achieve good image quality.

Example two

As shown in fig. 6, the middle straight line represents the optical axis, and the left side of the optical system is the object side and the right side is the image side. 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, the sixth lens L6, the seventh lens L7, the eighth lens L8, and the protective glass CG are disposed in order from the object side to the image side. The fourth lens L4 and the fifth lens L5 are cemented lenses, which is beneficial to reducing the eccentricity sensitivity of the optical imaging system, improving the assembly yield and reducing the production cost.

The fourth lens element L4 with positive refractive power has a convex object-side surface S7 and a convex image-side surface S8.

The sixth lens element L6 with positive refractive power has a concave object-side surface S11 and a convex image-side surface S12.

The eighth lens element L8 with positive refractive power has a convex object-side surface S13 and a concave image-side surface S14.

The protective glass CG is located behind the eighth lens L8 and includes an object-side surface S17 and an image-side surface S18, and is used for protecting the photosensitive element, so that the photosensitive element is prevented from being exposed to the outside, the photosensitive element is prevented from being affected by dust and the like, and the imaging quality is ensured. The image formation surface S19 is an effective pixel region of the electrophotographic photosensitive member.

Table 2a shows a characteristic table of the optical system of the present embodiment.

TABLE 2a

Table 2b shows the high-order term coefficients a4, A6, A8, a10, a12, a14, a16, a18, and a20 which can be used for the respective aspherical mirror surfaces S3, S4, S11, S12, S15, S16 in the second embodiment.

TABLE 2b

Number of noodles

S3

S4

S11

S12

S15

S16

K

0.00E+00

A4

6.40E-05

4.80E-05

-7.61E-04

1.85E-05

-2.33E-04

-4.32E-04

A6

4.18E-06

6.36E-08

-1.62E-05

-2.37E-06

4.29E-06

1.76E-06

A8

-5.60E-08

8.56E-08

-7.13E-07

-1.41E-07

-2.93E-08

0.00E+00

A10

6.10E-09

-1.22E-09

2.39E-08

1.88E-08

0.00E+00

A12

0.00E+00

A14

0.00E+00

A16

0.00E+00

A18

0.00E+00

A20

0.00E+00

FIG. 7 shows a spherical aberration curve of the optical system of the second embodiment, which represents the deviation of the converging focal points of light rays of different wavelengths after passing through the lenses of the optical system;

FIG. 8 shows astigmatism curves of the optical system of the second embodiment, which represent meridional field curvature and sagittal field curvature;

fig. 9 shows distortion curves of the optical system of the second embodiment, which represent distortion magnitude values corresponding to different angles of view;

as can be seen from fig. 7, 8, and 9, the optical system according to the second embodiment can achieve good image quality.

EXAMPLE III

As shown in fig. 10, the middle straight line represents the optical axis, and the left side of the optical system is the object side and the right side is the image side. 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, the sixth lens L6, the seventh lens L7, the eighth lens L8, and the protective glass CG are disposed in order from the object side to the image side. The fourth lens L4 and the fifth lens L5 are cemented lenses, which is beneficial to reducing the eccentricity sensitivity of the optical imaging system, improving the assembly yield and reducing the production cost.

Table 3a shows a characteristic table of the optical system of the present embodiment.

TABLE 3a

Table 3b shows the high-order term coefficients a4, A6, A8, a10, a12, a14, a16, a18, and a20 that can be used for the respective aspherical mirror surfaces S3, S4, S11, S12, S15, and S16 in the third embodiment.

TABLE 3b

Number of noodles

S3

S4

S11

S12

S15

S16

K

0.00E+00

-3.24E+19

A4

1.15E-04

7.68E-05

-1.26E-03

5.66E-07

4.96E-05

-7.60E-04

A6

1.05E-05

2.44E-06

4.68E-06

7.94E-06

-3.29E-06

0.00E+00

A8

-1.79E-07

6.02E-08

-6.29E-06

-2.90E-06

3.90E-08

0.00E+00

A10

2.79E-08

1.71E-09

3.46E-07

1.69E-07

0.00E+00

A12

0.00E+00

A14

0.00E+00

A16

0.00E+00

A18

0.00E+00

A20

0.00E+00

FIG. 11 shows a spherical aberration curve of the optical system of the third embodiment, which represents the deviation of the converging focal points of light rays of different wavelengths after passing through the lenses of the optical system;

fig. 12 shows astigmatism curves of the optical system of the third embodiment, which represent meridional field curvature and sagittal field curvature;

fig. 13 shows distortion curves of the optical system of the third embodiment, which represent distortion magnitude values corresponding to different angles of view;

as can be seen from fig. 11, 12, and 13, the optical system according to the third embodiment can achieve good image quality.

Example four

As shown in fig. 14, the middle straight line represents the optical axis, and the left side of the optical system is the object side and the right side is the image side. 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, the sixth lens L6, the seventh lens L7, the eighth lens L8, and the protective glass CG are disposed in order from the object side to the image side. The fourth lens L4 and the fifth lens L5 are cemented lenses, which is beneficial to reducing the eccentricity sensitivity of the optical imaging system, improving the assembly yield and reducing the production cost.

The seventh lens element L7 with negative refractive power has a concave object-side surface S13 and a concave image-side surface S14.

Table 4a shows a characteristic table of the optical system of the present embodiment.

TABLE 4a

Table 4b shows the high-order term coefficients a4, A6, A8, a10, a12, a14, a16, a18, and a20 which can be used for the respective aspherical mirror surfaces S3, S4, S11, S12, S15, and S16 in the fourth embodiment.

TABLE 4b

Number of noodles

S3

S4

S11

S12

S15

S16

K

0.00E+00

-3.24E+19

A4

5.09E-04

2.00E-04

1.30E-03

2.12E-03

1.07E-04

-8.57E-04

A6

2.49E-05

2.86E-06

-3.18E-05

-3.35E-05

-3.06E-05

2.98E-06

A8

-4.95E-07

1.15E-07

-9.28E-08

2.29E-07

8.50E-07

-9.98E-08

A10

7.14E-08

2.00E-09

4.06E-08

3.65E-08

-9.33E-09

0.00E+00

A12

-7.75E-20

0.00E+00

-7.78E-20

-7.74E-20

0.00E+00

A14

0.00E+00

A16

0.00E+00

A18

0.00E+00

A20

0.00E+00

FIG. 15 shows a spherical aberration curve of the optical system of the fourth embodiment, which represents the deviation of the converging focal points of light rays of different wavelengths after passing through the lenses of the optical system;

fig. 16 shows astigmatism curves of the optical system of the fourth embodiment, which represent meridional field curvature and sagittal field curvature;

fig. 17 shows distortion curves of the optical system of the fourth embodiment, which represent distortion magnitude values corresponding to different angles of view;

as can be seen from fig. 15, 16, and 17, the optical system according to the fourth embodiment can achieve good image quality.

EXAMPLE five

As shown in fig. 18, the middle straight line represents the optical axis, and the left side of the optical system is the object side and the right side is the image side. 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, the sixth lens L6, the seventh lens L7, the eighth lens L8, and the protective glass CG are disposed in order from the object side to the image side. The fourth lens L4 and the fifth lens L5 are cemented lenses, which is beneficial to reducing the eccentricity sensitivity of the optical imaging system, improving the assembly yield and reducing the production cost.

Table 5a shows a characteristic table of the optical system of the present embodiment.

TABLE 5a

Table 5b shows the high-order term coefficients a4, A6, A8, a10, a12, a14, a16, a18, and a20 which can be used for the respective aspherical mirror surfaces S3, S4, S11, S12, S15, S16 in the fifth embodiment.

TABLE 5b

FIG. 19 shows a spherical aberration curve of the optical system of the fifth embodiment, which represents the deviation of the converging focal points of light rays of different wavelengths after passing through the lenses of the optical system;

fig. 20 shows astigmatism curves of the optical system of the fifth embodiment, which represent meridional field curvature and sagittal field curvature;

fig. 21 shows distortion curves of the optical system of the fifth embodiment, which represent distortion magnitude values corresponding to different angles of view;

as can be seen from fig. 19, 20, and 21, the optical system according to the fifth embodiment can achieve good image quality.

Table 6 shows values of f1/f, f2/f, (1/| R2R | +1/| R3f |)/D23, f3/f, (D12+ CT2)/(CT3+ D34), f45/f, f6/f, f7/f, CT8/CT7, (Nd5-Nd4) × 100, Imgh/Tan (1/2FOV), EPL/TTL, and f/EPD of the optical systems of the first to fifth embodiments.

TABLE 6

	First embodiment	Second embodiment	Third embodiment	Fourth embodiment	Fifth embodiment
						f1/f	-1.79	-1.75	-1.89	-1.68	-1.65
f2/f	-10.64	-11.19	-6.62	-5.64	-6.88
						(1/\|R2r\|+1/\|R3f\|)/D23	0.15	0.27	0.23	0.16	0.10
f3/f	1.92	1.95	1.97	1.99	2.04
						(D12+CT2)/(CT3+D34)	1.63	1.82	1.85	1.26	1.36
f45/f	-8.93	-3.59	-3.91	-7.07	-7.10
						f6/f	2.29	3.52	3.13	4.02	3.96
f7/f	-2.81	-6.53	-7.89	-8.29	-7.40
						CT8/CT7	3.71	2.53	2.50	2.90	2.86
(Nd5-Nd4)*100	3.00	25.32	25.32	25.32	25.32
						Imgh/Tan(1/2FOV)	2.81	2.85	2.56	2.87	2.81
EPL/TTL	0.52	0.57	0.58	0.64	0.63
						f/EPD	1.60	1.65	1.65	1.60	1.60

As can be seen from table 6, each example satisfies: -3< f1/f < -1.5, -16 < f2/f < -5 >, 0.1 < 1/| R2R | +1/| R3f |)/D23 < 0.5, 1 < f3/f <3, 1 < (D12+ CT2)/(CT3+ D34) <2, -9< f45/f <0, 2< f6/f <5, -9< f7/f < -2, 2< CT8/CT7 < 4, 3< Nd5-Nd4) < 50, 2< Imgh/Tan (1/2FOV) 3, 0.4 < EPL/TTL 0.7, f/EPD < 1.7.

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 arranged in order from an object side to an image side, the plurality of lenses comprising:

a first lens element with negative refractive power;

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

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

a fourth lens element with positive refractive power;

a fifth lens element with negative refractive power;

a sixth lens element with positive refractive power;

the seventh lens element with negative refractive power has a concave object-side surface;

the eighth lens element with positive refractive power.

2. The optical system according to claim 1, wherein at least two of the lenses of the optical system have aspheric object-side surfaces and/or image-side surfaces.

3. The optical system of claim 1, wherein an image side surface of the fourth lens is cemented to an object side surface of the fifth lens.

4. An optical system according to any one of claims 1 to 3, characterized in that the optical system satisfies the conditional expression:

-3<f1/f<-1.5；

f1 is the focal length of the first lens, and f is the effective focal length of the optical system.

5. An optical system according to any one of claims 1 to 3, characterized in that the optical system satisfies the conditional expression:

-16＜f2/f＜-5；

f2 is the focal length of the second lens, and f is the effective focal length of the optical system.

6. An optical system according to any one of claims 1 to 3, characterized in that the optical system satisfies the conditional expression:

0.1≤(1/|R2r|+1/|R3f|)/D23＜0.5；

R2R is a radius of curvature of the image-side surface of the second lens element at the optical axis, R3f is a radius of curvature of the object-side surface of the third lens element at the optical axis, and D23 is a distance between the image-side surface of the second lens element and the object-side surface of the third lens element at the optical axis.

7. An optical system according to any one of claims 1 to 3, characterized in that the optical system satisfies the conditional expression:

1＜f3/f＜3；

f3 is the focal length of the third lens, and f is the effective focal length of the optical system.

8. An optical system according to any one of claims 1 to 3, characterized in that the optical system satisfies the conditional expression:

1＜(D12+CT2)/(CT3+D34)<2；

d12 is a distance between an image-side surface of the first lens element and an object-side surface of the second lens element along an optical axis, CT2 is a thickness of the second lens element along the optical axis, CT3 is a thickness of the third lens element along the optical axis, and D34 is a distance between the image-side surface of the third lens element and an object-side surface of the fourth lens element along the optical axis.

9. An optical system according to any one of claims 1 to 3, characterized in that the optical system satisfies the conditional expression:

-9＜f45/f<0；

f45 is the combined focal length of the fourth lens and the fifth lens, and f is the effective focal length of the optical system.

10. An optical system according to any one of claims 1 to 3, characterized in that the optical system satisfies the conditional expression:

2＜f6/f<5；

f6 is the focal length of the sixth lens, and f is the effective focal length of the optical system.

11. An optical system according to any one of claims 1 to 3, characterized in that the optical system satisfies the conditional expression:

-9<f7/f<-2；

f7 is the focal length of the seventh lens, and f is the effective focal length of the optical system.

12. An optical system according to any one of claims 1 to 3, characterized in that the optical system satisfies the conditional expression:

2＜CT8/CT7＜4；

CT7 is the thickness of the seventh lens element on the optical axis, and CT8 is the thickness of the eighth lens element on the optical axis.

13. An optical system according to any one of claims 1 to 3, characterized in that the optical system satisfies the conditional expression:

3≤(Nd5-Nd4)*100＜50；

nd4 is a refractive index of the fourth lens, and Nd5 is a refractive index of the fifth lens.

14. An optical system according to any one of claims 1 to 3, characterized in that the optical system satisfies the conditional expression:

2<Imgh/Tan(1/2FOV)<3；

the FOV is the angle of view in the diagonal direction of the optical system, and Imgh is half of the diagonal length of the effective pixel area of the optical system.

15. The optical system according to any one of claims 1 to 3, characterized in that the optical system further comprises a diaphragm, and the optical system satisfies the conditional expression:

0.4＜EPL/TTL＜0.7；

the EPL is a distance between a diaphragm of the optical system and an imaging surface on an optical axis, and the TTL is a distance between an object-side surface of the first lens of the optical system and the imaging surface of the optical system on the optical axis.

16. An optical system according to any one of claims 1 to 3, characterized in that the optical system satisfies the conditional expression:

f/EPD≤1.7；

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

17. A lens module comprising the optical system according to any one of claims 1 to 16 and a photosensitive element, wherein the photosensitive element is located on the image side of the optical system.

18. A terminal device, characterized by comprising the lens module according to claim 17.