CN113484983A

CN113484983A - Optical system, lens module and electronic equipment

Info

Publication number: CN113484983A
Application number: CN202110682807.8A
Authority: CN
Inventors: 党绪文; 刘彬彬; 李明
Original assignee: Jiangxi Jingchao Optical Co Ltd
Current assignee: Jiangxi Jingchao Optical Co Ltd
Priority date: 2021-06-18
Filing date: 2021-06-18
Publication date: 2021-10-08
Anticipated expiration: 2041-06-18
Also published as: CN113484983B

Abstract

The invention provides an optical system, a lens module and an electronic device, wherein the optical system comprises the following components in sequence from an object side to an image side along an optical axis direction: the first lens element to the eighth lens element with refractive power, the third lens element and the sixth lens element with positive refractive power, and the fourth lens element with negative refractive power. The object-side surfaces of the second, fifth, seventh and eighth lenses and the image-side surfaces of the first, second and sixth lenses are convex at a paraxial region, and the object-side surface of the fourth lens is concave at a paraxial region. The optical system satisfies the conditional expression: 51deg < FOV/FNO < 56.5 deg; wherein, FOV is the maximum field angle of the optical system, and FNO is the f-number of the optical system. By reasonably configuring the refractive powers of the eight optical lenses and the surface shapes at the positions close to the optical axes and enabling the optical system to satisfy the relational expression, the optical system has the characteristics of miniaturization, lightness and thinness while ensuring high imaging quality and wide visual angle.

Description

Optical system, lens module and electronic equipment

Technical Field

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

Background

In recent years, various mobile electronic devices equipped with an imaging device, including various portable information terminals such as digital cameras, smart phones, notebook computers, and tablet computers, have been rapidly spreading. Among them, the portability of mobile devices is increasing, and higher requirements are put forward on the thickness of the imaging device, and with the development of high functionality of electronic devices, the demands for wide viewing angle and high image quality have become a necessary trend.

However, to satisfy the wide viewing angle requirement inevitably leads to an increase in the size of the imaging apparatus, and the demand for miniaturization cannot be satisfied. The use of the low-sheet-number imaging system structure is beneficial to thickness reduction, but can cause the imaging quality to be reduced at the same time, and can not meet the requirements of the imaging quality.

Disclosure of Invention

The invention aims to provide an optical system, a lens module and an electronic device, which can keep high imaging quality and wide visual angle and have the characteristics of miniaturization and lightness.

In order to realize the purpose of the invention, the invention provides the following technical scheme:

in a first aspect, the present invention provides an optical system, in order from an object side to an image side along an optical axis direction, comprising: the first lens element with positive refractive power has a convex object-side surface at a paraxial region and a concave image-side surface at a paraxial region; a second lens element with refractive power having a convex object-side surface at a paraxial region and at a paraxial region; a third lens element with positive refractive power having a convex object-side surface at paraxial region and a concave image-side surface at a paraxial region; a fourth lens element with negative refractive power having a convex image-side surface at a paraxial region and at a paraxial region; a fifth lens element with refractive power having a concave image-side surface at a paraxial region; a sixth lens element with positive refractive power having a concave object-side surface at a paraxial region and a convex image-side surface at a paraxial region; a seventh lens element with refractive power having a convex object-side surface at a paraxial region and a concave object-side surface at a paraxial region; the image side surface of the seventh lens element is concave at a paraxial region and convex at a peripheral region; an eighth lens element with refractive power having a convex object-side surface at paraxial region; the image-side surface of the eighth lens element is concave at a paraxial region and convex at a peripheral region. The optical system satisfies the conditional expression: FOV/FNO is more than 51 and less than 56.5; the FOV is the maximum field angle of the optical system, the FNO is the f-number of the optical system, and the deg is an angle unit.

The image side surface of the first lens element is convex near the optical axis, which is beneficial to enhancing the refractive power of the first lens element and providing a reasonable light incident angle for introducing a small wide angle. The third lens has positive refractive power, is beneficial to shortening the total length of the optical system, compresses the light trend of each field of view, reduces spherical aberration and meets the requirement of high image quality miniaturization of the optical system. The fourth lens element with negative refractive power has a concave object-side surface at a paraxial region, so that the fourth lens element can form a flat surface, reduce tolerance sensitivity, and improve compactness. The object side surface of the eighth lens is a convex surface near the optical axis, which is beneficial to correcting distortion, astigmatism and field curvature generated by a small wide angle, and further meets the requirement of the wide angle and the small distortion. The image side surface of the eighth lens is a convex surface at a position close to the circumference, so that the incident angle of light on the image surface can be kept in a reasonable range, and the requirement of a chip matching angle is met. By enabling the optical system to satisfy the relational expression, the optical system can have a reasonable ratio of the field angle to the f-number, the requirements of design difficulty and the field angle are considered, and a combined effect of a wide field angle and a large aperture is provided. Below the lower limit of the relational expression, the relationship between the wide viewing angle and the large aperture is contradictory, the small viewing angle is matched with the large aperture, the design difficulty is increased, the aperture of the lens is further enlarged, and the reduction of tolerance sensitivity and the improvement of assembly yield are not facilitated; if a large viewing angle is matched with a small aperture, the relative illumination of the peripheral viewing field will be insufficient, and the resolution will be insufficient. Exceeding the upper limit of the relational expression, the simultaneous combination of the wide viewing angle and the ultra-large aperture has very high design requirements, the tolerance sensitivity of the lens is difficult to ensure, and the control of the assembly yield is not facilitated in an eight-piece optical imaging system.

In one embodiment, the optical system satisfies the conditional expression: 6.6 < SD82/CT8 < 7.8; wherein SD82 is the maximum effective aperture of the image side surface of the eighth lens element, and CT8 is the thickness of the eighth lens element on the optical axis. The ratio of the lens caliber to the thickness can reflect the basic shape characteristics of the lens. The eighth lens has a larger aperture value, the thickness (namely the medium thickness value) of the eighth lens on the optical axis is properly constrained, the overall thickness transition of the eighth lens from the center to the edge is flat, the thickness ratio is uniform, the manufacturability is good, and the die forming risk is low. Exceeding the upper limit of the relational expression, the lens is easy to be in a shape with large caliber, medium thickness and small thickness, the medium thickness and small thickness are very unfavorable for the production of the lens with large caliber, and the process risk is high.

In one embodiment, the optical system satisfies the conditional expression: 6.3 < SD72/CT7 < 7.8; wherein SD72 is the maximum effective aperture of the image side surface of the seventh lens, and CT7 is the thickness of the seventh lens on the optical axis. The seventh lens has a larger aperture value, the thickness (namely the medium thickness value) of the seventh lens on the optical axis is properly constrained, the overall thickness of the seventh lens from the center to the edge is flat in transition, the thickness ratio is uniform, and the seventh lens is easy to mold and process.

In one embodiment, the optical system satisfies the conditional expression: 4 < | R61/R62| < 92; wherein R61 is a radius of curvature of an object-side surface of the sixth lens element at an optical axis, and R62 is a radius of curvature of an image-side surface of the sixth lens element at the optical axis. The size of the curvature radius shows the surface type change trend near the center of the lens, the relation is satisfied, the sixth lens has reasonable curvature radius difference between the object side and the image side, namely the curvature radius of the object side is larger than that of the image side, the sixth lens is in a D-like shape, the D-like shape has small introduction of aberration, the D-like shape can deviate light rays in a full field of view at a small angle, and tolerance sensitivity is good. If | exceeds the upper limit of the relational expression, the object side surface of the sixth lens is close to a plane, the improvement effect on aberration is not obvious, the curvature radius of the image side surface is easy to further reduce, a shape with a convex center being obvious is formed, an anti-ghost image in the lens which is not easy to improve is possibly brought, and the imaging purity is influenced.

In one embodiment, the optical system satisfies the conditional expression: i R21/R22I < 1.2; wherein R21 is a curvature radius of an object side surface of the second lens at an optical axis, and R22 is a curvature radius of an image side surface of the second lens at the optical axis. The second lens has reasonable curvature radius difference between the object side and the image side, small surface shape change between the object side and the image side, good refraction effect, and reduced process difficulty and tolerance sensitivity.

In one embodiment, the optical system further includes a diaphragm located between the first lens and the second lens, and the optical system satisfies the conditional expression: 2 < | f1/f | < 37; wherein f1 is the focal length of the first lens, and f is the effective focal length of the optical system. Through making the diaphragm be located between first lens and the second lens, can provide the visual angle of broad, and compare in the leading structure of diaphragm, avoided the not good phenomenon of first lens face type that wide visual angle and leading diaphragm brought. In addition, the first lens can have multiple surface types, and meanwhile, the angle contraction of the wide-angle light rays at the entrance pupil position is considered, so that the introduction of large distortion and spherical aberration is avoided. The first lens element has proper refractive power distribution in the lens assembly, flexible surface shape change, large field angle support, less aberration introduction amount, and easy aberration correction and image quality balance of the whole lens assembly.

In one embodiment, the optical system satisfies the conditional expression: 0.8 < (ET2+ ET3+ ET4)/(CT2+ CT3+ CT4) < 1.0; ET2 is that the effective bore of object side face of second lens is located extremely the effective bore of image side face of second lens is in the ascending distance of optical axis direction, ET3 is the effective bore of object side face of third lens is located extremely the effective bore of image side face of third lens is in the ascending distance of optical axis direction, ET4 is the effective bore of object side face of fourth lens is located extremely the effective bore of image side face of fourth lens is in the ascending distance of optical axis direction, CT2 is the thickness of second lens on the optical axis, CT3 is the thickness of third lens on the optical axis, CT4 is the thickness of fourth lens on the optical axis. The sum of the edge thicknesses (namely the thicknesses of the lenses on the circumference) of the second lens element, the third lens element and the fourth lens element is smaller than the sum of the middle thicknesses, which means that the combination of the second lens element, the third lens element and the fourth lens element can be similar to a positive lens element with the middle thickness larger than the edge thickness, and has a certain positive refractive power to smoothly smooth down the incident light with large angle, and then the incident light is extended outwards by the fifth lens element. In addition, the front lens group is simple in surface type, small in variation and controllable in aberration introduction amount, pressure of aberration correction is not brought to the seventh lens and the eighth lens, and the surface type is simple and is good in assistance in the aspects of manufacturability and tolerance sensitivity.

In one embodiment, the optical system satisfies the conditional expression: SD52/R51 is more than 0.02 and less than 0.25; wherein SD52 is the maximum effective aperture of the image side surface of the fifth lens, and R51 is the curvature radius of the object side surface of the fifth lens at the optical axis. The effective caliber of the image side surface of the fifth lens is obviously smaller than the curvature radius, and the curvature radius keeps a larger level, which indicates that the surface of the fifth lens is in a flatter state, the thickness ratio from the center to the effective caliber changes little, and the lens is uniform, so that the manufacturability is good, and the tolerance sensitivity is low. When the curvature radius of the image side surface of the fifth lens exceeds the upper limit of the relational expression, the curvature radius of the image side surface of the fifth lens is obviously reduced, the surface shape is changed violently and is not easy to form, and excessive aberration is introduced into the complex surface shape, so that the aberration balance and the image quality of the whole lens group are not favorably improved.

In one embodiment, the optical system satisfies the conditional expression: 0.9 < (CT23+ CT34+ CT45+ CT56+ CT67+ CT78)/FFL < 1.35; wherein, CT23 is the second lens with the third lens is at the distance of separation on the optical axis, CT34 is the third lens with the fourth lens is at the distance of separation on the optical axis, CT45 is the fourth lens with the fifth lens is at the distance of separation on the optical axis, CT56 is the fifth lens with the sixth lens is at the distance of separation on the optical axis, CT67 is the sixth lens with the seventh lens is at the distance of separation on the optical axis, CT78 is the seventh lens with the eighth lens is at the distance of separation on the optical axis, FFL is the minimum distance of the image side surface of the eighth lens to the image plane on the optical axis. The size of the lens gap and the back focus of the optical system can be effectively controlled, the good compactness of the optical system is kept, and the miniaturization design of the eight-piece type optical system is facilitated. And the back focal length is wide enough, the fit clearance between the lens group and the chip is good, and the actual assembly difficulty can be reduced. Exceeding the upper limit of the relation reduces the compactness of the lens, shortens the back focus, and is not favorable for the thinning of the optical system.

In one embodiment, the optical system satisfies the conditional expression: 0.15 < | f56/f78| < 0.95; wherein f56 is a combined focal length of the fifth lens and the sixth lens, and f78 is a combined focal length of the seventh lens and the eighth lens. The fifth lens and the sixth lens are matched with the seventh lens and the eighth lens, so that reasonable deflection of light rays with different view fields can be realized, point-to-point imaging is realized, and matching of the lens group and the electronic photosensitive chip is facilitated. Meanwhile, the four lenses provide higher primary aberration introduction amount and corresponding aberration compensation amount, so that the aberration of the whole field of view is well balanced. The refractive power of the fifth lens element and the refractive power of the sixth lens element are reasonably distributed, the surface shape changes smoothly, the introduced aberration amount is low, the seventh lens element and the eighth lens element are wavy, the optical lenses have good deflection effect and aberration correction capability on the light rays of the inner field and the outer field, and good resolution power can be obtained in the full field by matching with an integral eight-piece scheme.

In one embodiment, the optical system satisfies the conditional expression: TTL is more than 5.1mm and less than 6.2 mm; wherein, TTL is the total length of the optical system. By controlling the total length of the optical system within the range of 5.1 mm-6.2 mm, the whole lens is thin, the compactness of the lens is high, and the miniaturization can be realized while the high imaging quality is ensured. If the total length of the optical system is too short below the lower limit of the relational expression, the focal length is too short, and a complete and clear image cannot be obtained on an imaging surface; exceeding the upper limit of the relational expression, the optical system assembly is too long, which is not favorable for miniaturization design.

In a second aspect, the present invention further provides a lens module, which includes a lens barrel, a photosensitive element and the optical system according to any one of the embodiments of the first aspect, wherein the first lens to the eighth lens of the optical system are mounted in the lens barrel, and the photosensitive element is mounted on an image side of the optical system. By adding the optical system provided by the invention into the lens module, the lens module has better imaging quality and wider field angle, and is easy to realize miniaturization and lightness.

In a third aspect, the present invention further provides an electronic device, which includes a housing and the lens module set in the second aspect, wherein the lens module set is disposed in the housing. By adding the lens module provided by the invention into the electronic equipment, the electronic equipment has higher imaging quality, wider field angle and smaller volume, thereby having higher competitiveness.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.

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

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

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

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

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

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

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

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

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

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

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

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

FIG. 7a is a schematic structural diagram of an optical system of a seventh embodiment;

fig. 7b is a longitudinal spherical aberration curve, an astigmatism curve and a distortion curve of the seventh embodiment.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.

The optical system according to the embodiment of the present invention includes, in order from an object side to an image side in an optical axis direction, a first lens element, a second lens element, a third lens element, a fourth lens element and a fifth lens element. Any adjacent two lenses of the first to fifth lenses may have an air space therebetween.

Specifically, the specific shape and structure of the eight lenses are as follows: the first lens element with positive refractive power has a convex object-side surface at a paraxial region and a concave image-side surface at a paraxial region; a second lens element with refractive power having a convex object-side surface at a paraxial region and at a paraxial region; a third lens element with positive refractive power having a convex object-side surface at paraxial region and a concave image-side surface at a paraxial region; a fourth lens element with negative refractive power having a convex image-side surface at a paraxial region and at a paraxial region; a fifth lens element with refractive power having a concave image-side surface at a paraxial region; a sixth lens element with positive refractive power having a concave object-side surface at a paraxial region and a convex image-side surface at a paraxial region; a seventh lens element with refractive power having a convex object-side surface at a paraxial region and a concave object-side surface at a paraxial region; the image side surface of the seventh lens element is concave at a paraxial region and convex at a peripheral region; an eighth lens element with refractive power having a convex object-side surface at paraxial region; the image-side surface of the eighth lens element is concave at a paraxial region and convex at a peripheral region. The optical system satisfies the conditional expression: 51deg < FOV/FNO < 56.5 deg; the FOV is the maximum field angle of the optical system, the FNO is the f-number of the optical system, and the deg is an angle unit. In the examples of this application, 90deg < FOV < 105 deg.

An infrared cut-off filter can be arranged between the eighth lens and the imaging surface and is used for transmitting visible light wave bands and cutting off infrared light wave bands, so that the phenomenon of false color or ripple caused by interference of light waves in non-working wave bands is avoided, and meanwhile, the effective resolution and the color reducibility can be improved.

In one embodiment, the optical system further includes a diaphragm located between the first lens and the second lens, and the optical system satisfies the conditional expression: 2 < | f1/f | < 37; wherein f1 is the focal length of the first lens, and f is the effective focal length of the optical system. The stop STO is disposed between the first lens L1 and the second lens L2. Through making the diaphragm be located between first lens and the second lens, can be used for controlling the light inlet quantity, can also provide the wider visual angle, and compare in the leading structure of diaphragm, avoided the not good phenomenon of first lens face type that wide visual angle and leading diaphragm brought. In addition, the first lens can have multiple surface types, and meanwhile, the angle contraction of the wide-angle light rays at the entrance pupil position is considered, so that the introduction of large distortion and spherical aberration is avoided. The first lens element has proper refractive power distribution in the lens assembly, flexible surface shape change, large field angle support, less aberration introduction amount, and easy aberration correction and image quality balance of the whole lens assembly.

In one embodiment, the optical system satisfies the conditional expression: 0.9 < (CT23+ CT34+ CT45+ CT56+ CT67+ CT78)/FFL < 1.35; wherein, CT23 is a distance between the second lens element and the third lens element on the optical axis, CT34 is a distance between the third lens element and the fourth lens element on the optical axis, CT45 is a distance between the fourth lens element and the fifth lens element on the optical axis, CT56 is a distance between the fifth lens element and the sixth lens element on the optical axis, CT67 is a distance between the sixth lens element and the seventh lens element on the optical axis, CT78 is a distance between the seventh lens element and the eighth lens element on the optical axis, and FFL is a minimum distance between the image-side surface of the eighth lens element and the image-side surface on the optical axis, in this embodiment, FFL > 0.89 mm. The size of the lens gap and the back focus of the optical system can be effectively controlled, the good compactness of the optical system is kept, and the miniaturization design of the eight-piece type optical system is facilitated. And the back focal length is wide enough, the fit clearance between the lens group and the chip is good, and the actual assembly difficulty can be reduced. Exceeding the upper limit of the relation reduces the compactness of the lens, shortens the back focus, and is not favorable for the thinning of the optical system.

In one embodiment, the optical system satisfies the conditional expression: 1.43 < TTL/IMGH < 1.47, wherein the IMGH is the image height corresponding to half of the maximum field angle of the optical system. The relation is satisfied, the miniaturization design requirement of the optical system is favorably satisfied, and the height of the lens is reduced. Above the upper limit of the conditional expression, the optical system is too large to fit into the equipment; below the conditional lower limit, the optical system is too small to easily balance aberrations, resulting in a reduction in imaging quality.

The embodiment of the invention provides a lens module, which comprises a lens barrel and an optical system provided by the embodiment of the invention, wherein a first lens to an eighth lens of the optical system are arranged in the lens barrel, a light sensing surface of an electronic light sensing element is positioned on an imaging surface of the optical system, light rays of an object which penetrates through the first lens to the eighth lens and is incident on the light sensing surface of the electronic light sensing element can be converted into an electric signal of an image, and the electronic light sensing element can be a CMOS (complementary metal oxide semiconductor) or a Charge-coupled Device (CCD). The lens module can be an independent lens of a digital camera, and can also be an imaging module integrated on electronic equipment such as a smart phone, a tablet personal computer and the like. By adding the optical system provided by the invention into the lens module, the lens module has the characteristics of high imaging quality, wide visual angle and miniaturization.

The embodiment of the invention provides electronic equipment, which comprises a shell and a lens module provided by the embodiment of the invention, wherein the lens module is arranged in the shell. The electronic equipment can be a smart phone, a Personal Digital Assistant (PDA), a tablet personal computer, an intelligent watch, an unmanned aerial vehicle, an electronic book reader, a vehicle traveling recorder, a wearable device and the like, and is particularly suitable for projection type display equipment. By adding the lens module provided by the invention into the electronic equipment, the electronic equipment has higher imaging quality, wider field angle and smaller volume, thereby having higher competitiveness.

First embodiment

Referring to fig. 1a and fig. 1b, the optical system of the present embodiment, in order from an object side to an image side along an optical axis, includes:

the first lens element L1 with positive refractive power has an object-side surface S1 of the first lens element L1 being concave at a paraxial region thereof and convex at a paraxial region thereof, and an image-side surface S2 of the first lens element L1 being convex at a paraxial region thereof and concave at a peripheral region thereof;

the second lens element L2 with negative refractive power has a convex object-side surface S3 at a paraxial region and a concave image-side surface S4 at a paraxial region and a concave image-side surface S2 at a paraxial region and a near periphery of the second lens element L2;

the third lens element L3 with positive refractive power has a convex object-side surface S5 at a paraxial region and a convex near-circumferential region of the third lens element L3, and has a convex image-side surface S6 at a paraxial region and a convex near-circumferential region of the third lens element L3;

the fourth lens element L4 with negative refractive power has a convex object-side surface S7 at paraxial region and peripheral region of the fourth lens element L4; the image-side surface S8 of the fourth lens element L4 is concave at both the paraxial region and the paraxial region;

the fifth lens element L5 with negative refractive power has a convex object-side surface S9 at a paraxial region and a concave image-side surface S10 at a paraxial region and a concave image-side surface S5 at a paraxial region and a near periphery of the fifth lens element L5;

the sixth lens element L6 with positive refractive power has a concave object-side surface S11 at a paraxial region and a convex image-side surface S12 at a paraxial region and a convex image-side surface L6 of the sixth lens element L6;

the seventh lens element L7 with negative refractive power has a convex object-side surface S13 at a paraxial region and a concave image-side surface at a paraxial region of the seventh lens element L7, and an image-side surface S14 of the seventh lens element L7 is concave at a paraxial region and convex at a peripheral region;

the eighth lens element L8 with negative refractive power has a convex object-side surface S15 at a paraxial region and a convex near-circumferential region of the eighth lens element L8, and has a concave image-side surface S16 at a paraxial region and a convex near-circumferential region of the eighth lens element L8.

The first lens element L1 to the eighth lens element L8 are all made of Plastic (Plastic).

In addition, the optical system further includes an infrared cut filter IR and an imaging plane IMG. The infrared cut filter IR is disposed between the image side surface S16 and the image side surface IMG of the eighth lens L8, and includes an object side surface S17 and an image side surface S18, and is configured to filter out infrared light, so that the light incident on the image side surface IMG is visible light, and the wavelength of the visible light is 380nm to 780 nm. The material of the infrared cut-off filter is Glass (Glass), and the Glass can be coated with a film. The effective pixels of the electron-sensitive elements are located on the imaging plane IMG.

Table 1a shows a table of characteristics of the optical system of the present embodiment in which each data is obtained using visible light having a wavelength of 587nm, and the units of the Y radius, the thickness, and the effective focal length are all millimeters (mm).

TABLE 1a

Wherein f is an effective 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 the object-side surface S1 of the first lens L1 to the image plane IMG.

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 surfaces, and the surface shape x of each aspheric lens can be defined by, but is not limited to, the following aspheric surface formula:

wherein x is the rise of the distance from the aspheric surface vertex to the aspheric surface vertex when the aspheric surface is at the position with the height of h along the optical axis direction; c is the paraxial curvature of the aspheric surface, c being 1/R (i.e., paraxial curvature c is the inverse of radius R of Y in table 1a above); k is a conic coefficient; ai is the correction coefficient of the i-th order of the aspherical surface. Table 1b shows the high-order coefficient A4, A6, A8, A10, A12, A14, A16, A18 and A20 that can be used for each of the aspherical mirrors S1-S12 in the first embodiment.

TABLE 1b

Number of noodles	K	A4	A6	A8	A10
						S1	-9.900E+01	1.809E-02	-3.616E-02	6.351E-02	-7.302E-02
S2	-9.856E+01	-2.335E-02	1.197E-01	-2.867E-01	4.909E-01
						S3	-4.026E+01	2.139E-01	-8.335E-01	2.463E+00	-5.499E+00
S4	-2.431E+01	8.878E-02	-5.824E-01	1.636E+00	-3.482E+00
						S5	-1.923E+01	1.644E-02	-7.862E-02	9.293E-02	-1.103E-01
S6	1.546E+01	-4.859E-02	1.167E-01	-2.594E-01	2.910E-01
						S7	-1.961E+01	-5.102E-02	1.076E-01	-1.541E-01	4.668E-02
S8	-1.126E+01	4.455E-02	-2.798E-02	8.164E-02	-1.860E-01
						S9	2.793E+01	-8.758E-02	5.948E-02	-1.277E-01	2.486E-01
S10	1.882E+01	-1.904E-01	3.862E-01	-6.797E-01	7.070E-01
						S11	9.747E+01	-2.340E-01	7.082E-01	-1.033E+00	8.308E-01
S12	-3.757E+00	-5.881E-02	1.627E-01	-2.710E-01	2.634E-01
						S13	5.012E+00	2.708E-01	-3.732E-01	2.784E-01	-1.675E-01
S14	-6.434E+01	2.694E-01	-3.266E-01	1.981E-01	-8.113E-02
						S15	-7.086E+00	-1.194E-01	-6.558E-02	7.485E-02	-2.919E-02
S16	-3.348E+00	-1.525E-01	6.432E-02	-2.134E-02	6.206E-03
						Number of noodles	A12	A14	A16	A18	A20
S1	5.524E-02	-2.768E-02	8.852E-03	-1.601E-03	1.212E-04
						S2	-6.038E-01	5.029E-01	-2.640E-01	7.857E-02	-1.005E-02
S3	8.430E+00	-8.582E+00	5.531E+00	-2.029E+00	3.215E-01
						S4	5.306E+00	-5.533E+00	3.767E+00	-1.497E+00	2.623E-01
S5	1.026E-01	-5.499E-02	1.475E-02	-1.780E-03	2.669E-04
						S6	-1.898E-01	7.179E-02	-1.568E-02	2.002E-03	2.587E-05
S7	1.162E-01	-1.482E-01	7.837E-02	-1.972E-02	1.879E-03
						S8	2.275E-01	-1.527E-01	5.771E-02	-1.153E-02	1.008E-03
S9	-2.789E-01	1.991E-01	-8.683E-02	2.131E-02	-2.427E-03
						S10	-4.480E-01	1.632E-01	-2.257E-02	-3.389E-03	9.921E-04
S11	-3.745E-01	6.463E-02	2.094E-02	-1.230E-02	1.725E-03
						S12	-1.643E-01	6.550E-02	-1.534E-02	1.805E-03	-7.392E-05
S13	7.866E-02	-2.657E-02	5.849E-03	-7.304E-04	3.863E-05
						S14	2.279E-02	-4.254E-03	5.025E-04	-3.407E-05	1.013E-06
S15	6.440E-03	-8.804E-04	7.404E-05	-3.517E-06	7.229E-08
						S16	-1.355E-03	1.923E-04	-1.637E-05	7.568E-07	-1.456E-08

Fig. 1b shows a longitudinal spherical aberration curve, an astigmatism curve and a distortion curve of the optical system of the first embodiment. The longitudinal spherical aberration curve is obtained by drawing by taking a focal value as an abscissa and a longitudinal spherical aberration value as an ordinate, and the longitudinal spherical aberration curve represents the deviation of convergence focuses of light rays with different wavelengths after passing through each lens of the optical system; the astigmatism curve is obtained by drawing with a focal value as an abscissa and an image height as an ordinate, and represents the meridional imaging plane curvature T and the sagittal imaging plane curvature S; the distortion curve is obtained by drawing with the percentage of distortion as an abscissa and the image height as an ordinate, and the distortion curve represents distortion magnitude values corresponding to different field angles. As can be seen from fig. 1b, the optical system according to the first embodiment can achieve good imaging quality.

Second embodiment

Referring to fig. 2a and fig. 2b, the optical system of the present embodiment, in order from an object side to an image side along an optical axis direction, includes:

the first lens element L1 with positive refractive power has an object-side surface S1 of the first lens element L1 being convex at a paraxial region and a paraxial region, and an image-side surface S2 of the first lens element L1 being convex at a paraxial region and being concave at a peripheral region;

the fifth lens element L5 with negative refractive power has a convex object-side surface S9 at a paraxial region and a convex near-circumference region of the fifth lens element L5, and has a concave image-side surface S10 at a paraxial region and a convex near-circumference region of the fifth lens element L5;

the eighth lens element L8 with negative refractive power has a convex object-side surface S15 at a paraxial region and a concave object-side surface at a peripheral region of the eighth lens element L8, and has a concave image-side surface S16 at a paraxial region and a convex image-side surface at a peripheral region of the eighth lens element L8.

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

Table 2a shows a table of characteristics of the optical system of the present embodiment in which each data is obtained using visible light having a wavelength of 587nm, and the units of the Y radius, the thickness, and the effective focal length are all millimeters (mm).

TABLE 2a

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

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

TABLE 2b

Fig. 2b shows a longitudinal spherical aberration curve, an astigmatism curve and a distortion curve of the optical system of the second embodiment, wherein the longitudinal spherical aberration curve is plotted with a focal value as an abscissa and a longitudinal spherical aberration value as an ordinate, and the longitudinal spherical aberration curve represents the convergent focus deviation of light rays with different wavelengths after passing through each lens of the optical system; the astigmatism curve is obtained by drawing with a focal value as an abscissa and an image height as an ordinate, and represents the meridional imaging plane curvature T and the sagittal imaging plane curvature S; the distortion curve is obtained by drawing with the percentage of distortion as an abscissa and the image height as an ordinate, and the distortion curve represents distortion magnitude values corresponding to different field angles. As can be seen from fig. 2b, the optical system according to the second embodiment can achieve good imaging quality.

Third embodiment

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

the first lens element L1 with negative refractive power has an object-side surface S1 of the first lens element L1 being concave at a paraxial region thereof and convex at a paraxial region thereof, and an image-side surface S2 of the first lens element L1 being convex at a paraxial region thereof and concave at a peripheral region thereof;

the second lens element L2 with positive refractive power has a convex object-side surface S3 at a paraxial region and a concave image-side surface S4 at a paraxial region and a concave image-side surface S2 at a paraxial region and a near circumference of the second lens element L2;

the fifth lens element L5 with positive refractive power has a convex object-side surface S9 at a paraxial region and a concave image-side surface S10 at a paraxial region and a concave image-side surface S5 at a paraxial region and a near circumference of the fifth lens element L5;

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

Table 3a shows a table of characteristics of the optical system of the present embodiment in which each data is obtained using visible light having a wavelength of 587nm, and the units of the Y radius, the thickness, and the effective focal length are all millimeters (mm).

TABLE 3a

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

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

TABLE 3b

Number of noodles	K	A4	A6	A8	A10
						S1	-6.313E+01	1.147E-02	-1.280E-02	2.948E-02	-3.583E-02
S2	-9.900E+01	1.059E-04	7.358E-05	4.627E-02	-9.285E-02
						S3	-3.707E+01	2.921E-01	-1.257E+00	3.633E+00	-7.652E+00
S4	-2.220E+01	7.332E-02	-5.143E-01	1.181E+00	-1.709E+00
						S5	-1.403E+01	1.001E-02	-1.099E-01	1.558E-01	-1.042E-02
S6	1.548E+01	1.063E-02	-1.105E-01	1.498E-01	-4.925E-02
						S7	-1.265E+01	1.120E-02	-1.002E-01	1.929E-01	-2.208E-01
S8	-1.009E+01	5.189E-02	-4.238E-02	7.013E-02	-1.121E-01
						S9	1.962E+01	-8.137E-02	7.564E-02	-1.449E-01	2.254E-01
S10	1.821E+01	-1.104E-01	1.368E-01	-2.312E-01	2.496E-01
						S11	8.641E+01	-9.242E-02	2.276E-01	-3.077E-01	2.605E-01
S12	-2.627E+00	-7.977E-02	1.558E-01	-2.070E-01	1.658E-01
						S13	-1.631E+01	9.878E-02	-9.291E-02	-4.238E-03	3.761E-02
S14	-2.095E+01	1.867E-01	-2.314E-01	1.418E-01	-5.852E-02
						S15	-6.319E+00	-1.265E-01	-3.325E-02	4.953E-02	-1.906E-02
S16	-2.903E+00	-1.753E-01	8.908E-02	-3.679E-02	1.168E-02
						Number of noodles	A12	A14	A16	A18	A20
S1	2.375E-02	-8.715E-03	1.557E-03	-3.971E-05	-1.705E-05
						S2	7.473E-02	-2.212E-02	-4.301E-03	4.234E-03	-7.199E-04
S3	1.109E+01	-1.070E+01	6.560E+00	-2.307E+00	3.536E-01
						S4	1.551E+00	-5.838E-01	-2.654E-01	3.384E-01	-9.316E-02
S5	-1.011E-01	6.770E-02	-1.528E-02	-3.927E-04	4.978E-05
						S6	-8.779E-02	9.074E-02	-2.878E-02	1.461E-03	1.822E-05
S7	1.548E-01	-8.357E-02	3.879E-02	-1.050E-02	9.327E-04
						S8	1.215E-01	-8.462E-02	3.566E-02	-7.724E-03	6.464E-04
S9	-2.272E-01	1.562E-01	-6.881E-02	1.708E-02	-1.815E-03
						S10	-1.765E-01	8.243E-02	-2.313E-02	3.444E-03	-2.279E-04
S11	-1.591E-01	6.951E-02	-1.953E-02	3.122E-03	-2.304E-04
						S12	-7.805E-02	1.648E-02	1.814E-03	-1.508E-03	1.958E-04
S13	-2.557E-02	8.681E-03	-1.593E-03	1.489E-04	-5.524E-06
						S14	1.642E-02	-3.023E-03	3.475E-04	-2.259E-05	6.333E-07
S15	3.970E-03	-5.024E-04	3.884E-05	-1.702E-06	3.266E-08
						S16	-2.550E-03	3.609E-04	-3.152E-05	1.545E-06	-3.251E-08

Fig. 3b shows a longitudinal spherical aberration curve, an astigmatism curve and a distortion curve of the optical system of the third embodiment, wherein the longitudinal spherical aberration curve is plotted with a focal value as an abscissa and a longitudinal spherical aberration value as an ordinate, and the longitudinal spherical aberration curve represents the convergent focus deviation of light rays with different wavelengths after passing through each lens of the optical system; the astigmatism curve is obtained by drawing with a focal value as an abscissa and an image height as an ordinate, and the astigmatism curve represents the bending of a meridional imaging plane and the bending of a sagittal imaging plane; the distortion curve is obtained by drawing with the percentage of distortion as an abscissa and the image height as an ordinate, and the distortion curve represents distortion magnitude values corresponding to different field angles. As can be seen from fig. 3b, the optical system according to the third embodiment can achieve good imaging quality.

Fourth embodiment

Referring to fig. 4a and 4b, the optical system of the present embodiment, in order from an object side to an image side along an optical axis direction, includes:

the third lens element L3 with positive refractive power has a convex object-side surface S5 at a paraxial region and a concave object-side surface at a paraxial region of the third lens element L3, and has a convex image-side surface S6 at a paraxial region and a convex image-side surface at a peripheral region of the third lens element L3;

the fourth lens element L4 with negative refractive power has a concave object-side surface S7 at a paraxial region and a concave object-side surface at a peripherical region of the fourth lens element L4; the image-side surface S8 of the fourth lens element L4 is concave at both the paraxial region and the paraxial region;

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

Table 4a shows a table of characteristics of the optical system of the present embodiment in which each data is obtained using visible light having a wavelength of 587nm, and the units of the Y radius, the thickness, and the effective focal length are all millimeters (mm).

TABLE 4a

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

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

TABLE 4b

Fig. 4b shows a longitudinal spherical aberration curve, an astigmatism curve and a distortion curve of the optical system of the fourth embodiment, wherein the longitudinal spherical aberration curve is plotted with a focal value as an abscissa and a longitudinal spherical aberration value as an ordinate, and the longitudinal spherical aberration curve represents the convergent focus deviation of light rays with different wavelengths after passing through each lens of the optical system; the astigmatism curve is obtained by drawing with a focal value as an abscissa and an image height as an ordinate, and represents the meridional imaging plane curvature T and the sagittal imaging plane curvature S; the distortion curve is obtained by drawing with the percentage of distortion as an abscissa and the image height as an ordinate, and the distortion curve represents distortion magnitude values corresponding to different field angles. As can be seen from fig. 4b, the optical system according to the fourth embodiment can achieve good imaging quality.

Fifth embodiment

Referring to fig. 5a and 5b, the optical system of the present embodiment, in order from an object side to an image side along an optical axis direction, includes:

the fifth lens element L5 with negative refractive power has a convex object-side surface S9 at a paraxial region and a concave object-side surface at a paraxial region of the fifth lens element L5, and has a concave image-side surface S10 at a paraxial region and a concave image-side surface at a peripheral region of the fifth lens element L5;

the seventh lens element L7 with positive refractive power has a convex object-side surface S13 at a paraxial region and a concave image-side surface at a paraxial region of the seventh lens element L7, and an image-side surface S14 of the seventh lens element L7 is concave at a paraxial region and convex at a peripheral region;

the eighth lens element L8 with positive refractive power has a convex object-side surface S15 at a paraxial region and a concave object-side surface at a peripheral region of the eighth lens element L8, and an image-side surface S16 of the eighth lens element L8 is concave at the paraxial region and convex at the peripheral region.

The other structure of the fifth embodiment is the same as that of the first embodiment, and reference may be made thereto.

Table 5a shows a table of characteristics of the optical system of the present embodiment in which each data is obtained using visible light having a wavelength of 587nm, and the units of the Y radius, the thickness, and the effective focal length are all millimeters (mm).

TABLE 5a

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

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

TABLE 5b

Number of noodles	K	A4	A6	A8	A10
						S1	-9.688E+01	1.269E-02	-8.113E-03	1.661E-02	-2.632E-02
S2	-9.900E+01	9.726E-03	4.537E-02	-1.109E-01	1.354E-01
						S3	-3.776E+01	2.889E-01	-1.305E+00	4.523E+00	-1.278E+01
S4	-2.371E+01	1.709E-01	-1.404E+00	6.985E+00	-2.826E+01
						S5	-1.825E+01	5.588E-02	-1.658E-01	-1.797E-02	4.119E-01
S6	1.513E+01	3.389E-03	-1.811E-01	7.151E-01	-1.524E+00
						S7	-2.376E+01	-2.762E-02	-1.372E-01	5.250E-01	-9.841E-01
S8	-1.262E+01	6.278E-02	-1.389E-01	3.048E-01	-4.276E-01
						S9	9.900E+01	-8.960E-02	6.955E-02	-5.501E-01	1.701E+00
S10	2.111E+01	-1.547E-01	3.842E-01	-1.137E+00	1.904E+00
						S11	9.525E+01	-1.427E-01	7.528E-01	-1.623E+00	2.118E+00
S12	-3.956E-01	-3.225E-01	8.405E-01	-1.364E+00	1.478E+00
						S13	-1.153E+01	1.488E-01	-1.034E-01	-9.033E-02	1.604E-01
S14	-3.040E+01	3.081E-01	-3.980E-01	2.611E-01	-1.195E-01
						S15	-4.627E+00	-5.561E-02	-1.750E-01	1.552E-01	-6.146E-02
S16	-2.735E+00	-1.503E-01	3.364E-02	5.871E-03	-5.022E-03
						Number of noodles	A12	A14	A16	A18	A20
S1	2.257E-02	-1.128E-02	3.293E-03	-5.122E-04	3.235E-05
						S2	-9.797E-02	3.691E-02	-1.531E-03	-3.708E-03	9.490E-04
S3	2.642E+01	-3.785E+01	3.529E+01	-1.910E+01	4.527E+00
						S4	7.908E+01	-1.439E+02	1.622E+02	-1.025E+02	2.770E+01
S5	-7.696E-01	7.821E-01	-3.429E-01	-5.108E-03	8.612E-04
						S6	1.749E+00	-1.032E+00	2.397E-01	2.072E-03	2.687E-05
S7	1.105E+00	-7.557E-01	3.094E-01	-7.035E-02	7.722E-03
						S8	3.975E-01	-2.307E-01	7.747E-02	-1.280E-02	1.133E-03
S9	-2.847E+00	2.935E+00	-1.815E+00	6.147E-01	-8.815E-02
						S10	-2.061E+00	1.454E+00	-6.199E-01	1.418E-01	-1.322E-02
S11	-1.903E+00	1.166E+00	-4.532E-01	9.940E-02	-9.309E-03
						S12	-1.070E+00	5.041E-01	-1.466E-01	2.374E-02	-1.635E-03
S13	-1.148E-01	4.666E-02	-1.096E-02	1.385E-03	-7.296E-05
						S14	3.835E-02	-8.198E-03	1.097E-03	-8.252E-05	2.659E-06
S15	1.413E-02	-2.002E-03	1.729E-04	-8.387E-06	1.754E-07
						S16	1.268E-03	-1.743E-04	1.390E-05	-6.021E-07	1.087E-08

Fig. 5b shows a longitudinal spherical aberration curve, an astigmatism curve and a distortion curve of the optical system of the fifth embodiment, wherein the longitudinal spherical aberration curve is plotted with a focal value as an abscissa and a longitudinal spherical aberration value as an ordinate, and the longitudinal spherical aberration curve represents the convergent focus deviation of light rays of different wavelengths after passing through each lens of the optical system; the astigmatism curve is obtained by drawing with a focal value as an abscissa and an image height as an ordinate, and represents the meridional imaging plane curvature T and the sagittal imaging plane curvature S; the distortion curve is obtained by drawing with the percentage of distortion as an abscissa and the image height as an ordinate, and the distortion curve represents distortion magnitude values corresponding to different field angles. As can be seen from fig. 5b, the optical system according to the fifth embodiment can achieve good image quality.

Sixth embodiment

Referring to fig. 6a and 6b, the optical system of the present embodiment, in order from an object side to an image side along an optical axis direction, includes:

a second lens element L2 with positive refractive power, an object-side surface S3 of the second lens element L2 being convex at a paraxial region and at a peripherical region, and an image-side surface S4 of the second lens element L2 being concave at the paraxial region and convex at the peripherical region;

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

the fourth lens element L4 with negative refractive power has a convex object-side surface S7 at a paraxial region and a concave object-side surface at a peripheral region of the fourth lens element L4; the image-side surface S8 of the fourth lens element L4 is concave at both the paraxial region and the paraxial region;

the eighth lens element L8 with positive refractive power has a convex object-side surface S15 at a paraxial region and a convex near-circumferential region of the eighth lens element L8, and has a concave image-side surface S16 at a paraxial region and a convex near-circumferential region of the eighth lens element L8.

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

Table 6a shows a table of characteristics of the optical system of the present embodiment in which each data is obtained using visible light having a wavelength of 587.6nm, and the units of the Y radius, the thickness, and the effective focal length are all millimeters (mm).

TABLE 6a

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

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

TABLE 6b

Fig. 6b shows a longitudinal spherical aberration curve, an astigmatism curve and a distortion curve of the optical system of the sixth embodiment, wherein the longitudinal spherical aberration curve is plotted with a focal value as an abscissa and a longitudinal spherical aberration value as an ordinate, and the longitudinal spherical aberration curve represents the convergent focus deviation of light rays of different wavelengths after passing through each lens of the optical system; the astigmatism curve is obtained by drawing with a focal value as an abscissa and an image height as an ordinate, and represents the meridional imaging plane curvature T and the sagittal imaging plane curvature S; the distortion curve is obtained by drawing with the percentage of distortion as an abscissa and the image height as an ordinate, and the distortion curve represents distortion magnitude values corresponding to different field angles. As can be seen from fig. 6b, the optical system according to the sixth embodiment can achieve good image quality.

Seventh embodiment

Referring to fig. 7a and 7b, the optical system of the present embodiment, in order from an object side to an image side along an optical axis direction, includes:

the second lens element L2 with positive refractive power has a convex object-side surface S3 at a paraxial region and a concave peripheral region of the second lens element L2, and has a convex image-side surface S4 at a paraxial region and a concave peripheral region of the second lens element L2;

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

the eighth lens element L8 with positive refractive power has a convex object-side surface S15 at a paraxial region and a concave object-side surface at a peripheral region of the eighth lens element L8, and has a concave image-side surface S16 at a paraxial region and a convex image-side surface at a peripheral region of the eighth lens element L8.

The other structure of the seventh embodiment is the same as that of the first embodiment, and reference may be made thereto.

Table 7a shows a table of characteristics of the optical system of the present embodiment in which each data is obtained using visible light having a wavelength of 587nm, and the units of the Y radius, the thickness, and the effective focal length are all millimeters (mm).

TABLE 7a

Wherein the meanings of the parameters in Table 7a are the same as those of the first embodiment.

Table 7b shows the high-order term coefficients that can be used for each aspherical mirror surface in the seventh embodiment, wherein each aspherical mirror surface type can be defined by the formula given in the first embodiment.

TABLE 7b

Fig. 7b shows a longitudinal spherical aberration curve, an astigmatism curve and a distortion curve of the optical system of the seventh embodiment, wherein the longitudinal spherical aberration curve is plotted with a focal value as an abscissa and a longitudinal spherical aberration value as an ordinate, and the longitudinal spherical aberration curve represents the convergent focus deviation of light rays of different wavelengths after passing through each lens of the optical system; the astigmatism curve is obtained by drawing with a focal value as an abscissa and an image height as an ordinate, and represents the meridional imaging plane curvature T and the sagittal imaging plane curvature S; the distortion curve is obtained by drawing with the percentage of distortion as an abscissa and the image height as an ordinate, and the distortion curve represents distortion magnitude values corresponding to different field angles. As can be seen from fig. 7b, the optical system according to the seventh embodiment can achieve good image quality.

Table 8 shows values of FOV/FNO, SD82/CT8, SD72/CT7, | R61/R62|, R21/R22|, | f1/f |, (ET2+ ET3+ ET4)/(CT2+ CT3+ CT4), SD52/R51, (CT23+ CT34+ CT2+ CT45 6+ CT56+ CT67+ CT78)/FFL, | f56/f78| in the optical systems of the first to seventh embodiments.

TABLE 8

As can be seen from table 8, the optical systems of the first to seventh embodiments all satisfy the following conditional expressions: 51deg < FOV/FNO < 56.5deg, 6.6 < SD82/CT8 < 7.8, 6.3 < SD72/CT7 < 7.8, 4 < | R61/R62| < 92, | R21/R22| < 1.2, 2 < | f1/f | < 37, 0.8 < (ET2+ ET3+ ET4)/(CT2+ CT3+ CT4) < 1.0, 0.02 < SD52/R51 < 0.25, 0.9 < (CT23+ CT34+ CT45+ CT56+ CT67+ CT78)/FFL < 1.35, 0.15 < | f56/f78| < 0.95.

While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

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

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

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

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

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

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

a sixth lens element with positive refractive power having a concave object-side surface at a paraxial region and a convex image-side surface at a paraxial region;

a seventh lens element with refractive power having a convex object-side surface at a paraxial region and a concave object-side surface at a paraxial region; the image side surface of the seventh lens element is concave at a paraxial region and convex at a peripheral region;

an eighth lens element with refractive power having a convex object-side surface at paraxial region; the image side surface of the eighth lens element is concave at a paraxial region and convex at a peripheral region;

the optical system satisfies the conditional expression: 51deg < FOV/FNO < 56.5 deg;

the FOV is the maximum field angle of the optical system, the FNO is the f-number of the optical system, and the deg is an angle unit.

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

6.6＜SD82/CT8＜7.8；

wherein SD82 is the maximum effective aperture of the image side surface of the eighth lens element, and CT8 is the thickness of the eighth lens element on the optical axis.

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

6.3＜SD72/CT7＜7.8；

wherein SD72 is the maximum effective aperture of the image side surface of the seventh lens, and CT7 is the thickness of the seventh lens on the optical axis.

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

4＜|R61/R62|＜92；

wherein R61 is a radius of curvature of an object-side surface of the sixth lens element at an optical axis, and R62 is a radius of curvature of an image-side surface of the sixth lens element at the optical axis.

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

|R21/R22|＜1.2；

wherein R21 is a curvature radius of an object side surface of the second lens at an optical axis, and R22 is a curvature radius of an image side surface of the second lens at the optical axis.

6. The optical system according to claim 1, further comprising an optical stop between the first lens and the second lens, the optical system satisfying a conditional expression:

2＜|f1/f|＜37；

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

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

0.8＜(ET2+ET3+ET4)/(CT2+CT3+CT4)＜1.0；

ET2 is that the effective bore of object side face of second lens is located extremely the effective bore of image side face of second lens is in the ascending distance of optical axis direction, ET3 is the effective bore of object side face of third lens is located extremely the effective bore of image side face of third lens is in the ascending distance of optical axis direction, ET4 is the effective bore of object side face of fourth lens is located extremely the effective bore of image side face of fourth lens is in the ascending distance of optical axis direction, CT2 is the thickness of second lens on the optical axis, CT3 is the thickness of third lens on the optical axis, CT4 is the thickness of fourth lens on the optical axis.

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

0.02＜SD52/R51＜0.25；

wherein SD52 is the maximum effective aperture of the image side surface of the fifth lens, and R51 is the curvature radius of the object side surface of the fifth lens at the optical axis.

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

0.9＜(CT23+CT34+CT45+CT56+CT67+CT78)/FFL＜1.35；

wherein, CT23 is the second lens with the third lens is at the distance of separation on the optical axis, CT34 is the third lens with the fourth lens is at the distance of separation on the optical axis, CT45 is the fourth lens with the fifth lens is at the distance of separation on the optical axis, CT56 is the fifth lens with the sixth lens is at the distance of separation on the optical axis, CT67 is the sixth lens with the seventh lens is at the distance of separation on the optical axis, CT78 is the seventh lens with the eighth lens is at the distance of separation on the optical axis, FFL is the minimum distance of the image side surface of the eighth lens to the image plane on the optical axis.

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

0.15＜|f56/f78|＜0.95；

wherein f56 is a combined focal length of the fifth lens and the sixth lens, and f78 is a combined focal length of the seventh lens and the eighth lens.

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

5.1mm＜TTL＜6.2mm；

wherein, TTL is the total length of the optical system.

12. A lens module comprising a lens barrel, a photosensitive element, and the optical system according to any one of claims 1 to 11, wherein the first lens to the eighth lens of the optical system are mounted in the lens barrel, and the photosensitive element is disposed on an image side of the optical system.

13. An electronic apparatus, comprising a housing and the lens module as recited in claim 12, wherein the lens module is disposed in the housing.