CN112578529A

CN112578529A - Optical system, lens module and electronic equipment

Info

Publication number: CN112578529A
Application number: CN201910922714.0A
Authority: CN
Inventors: 邹金华; 李明; 刘彬彬
Original assignee: Jiangxi Jingchao Optical Co Ltd
Current assignee: Jiangxi Jingchao Optical Co Ltd
Priority date: 2019-09-27
Filing date: 2019-09-27
Publication date: 2021-03-30

Abstract

The invention provides an optical system, a lens module and an electronic device, wherein the optical system comprises the following components in order from an object side to an image side along an optical axis direction: a first lens having a positive optical power; a second lens having an optical power; a third lens having a negative optical power; the fourth lens is provided with positive focal power, and the object side surface and the image side surface of the fourth lens are convex surfaces; a fifth lens having a negative optical power; wherein the optical system satisfies the following relation: 0.2< TD/f < 0.5; TD is the distance on the optical axis from the object side surface of the first lens to the image side surface of the fifth lens, f is the effective focal length of the optical system, and the long-focus telescopic function is realized and the requirements of miniaturization and high imaging quality are met by reasonably configuring the surface type and the focal power of each of the first lens to the fifth lens.

Description

Optical system, lens module and electronic equipment

Technical Field

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

Background

In recent years, with the development of related technologies of smart phones, the demands for miniaturization of mobile phone lenses and high quality imaging quality are increasing, and with the advance of semiconductor processing technology, the reduction of pixel size of photosensitive elements, and light, thin, short, and high performance electronic products are inevitably a development trend. The module of making a video recording is used more and more extensively, and the module device of making a video recording also can become a big trend of future science and technology development in various intelligent electronic product, car-mounted device, identification system, amusement motion equipment.

Nowadays, a mobile phone carries one, two or even more than three lenses with different image capturing functions, which has become the mainstream of the mobile phone market. The volume of the existing lens is not easy to reduce, the lens is difficult to miniaturize, and the quality of shot remote detail imaging is not good, so that the lens cannot conform to the large trend of scientific and technological development and is difficult to apply to the mainstream mobile phone market.

Disclosure of Invention

The invention aims to provide an optical system which can simultaneously meet the requirements of a telephoto function, miniaturization and high imaging quality.

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: a first lens having a positive refractive power; a second lens having optical power; a third lens having a negative focal power; the fourth lens has positive focal power, and both the object-side surface and the image-side surface of the fourth lens are convex surfaces; a fifth lens having a negative focal power; wherein the optical system satisfies the following relation: 0.2< TD/f < 0.5; TD is a distance on an optical axis from an object-side surface of the first lens element to an image-side surface of the fifth lens element, and f is an effective focal length of the optical system. By reasonably configuring the surface type and focal power of each of the first lens to the fifth lens, the long-focus telescopic function is realized, and the requirements of miniaturization and high imaging quality are met. When TD/f is more than or equal to 0.5, the optical lens structure is not compact enough, so that the length of the lens is too long, and the assembly of the lens is not facilitated. When TD/f is less than or equal to 0.2, the length of the optical lens is too small, the aberration of the lens is difficult to correct, and the telephoto imaging quality is poor. The TD/f value is reasonably set, the focal power of the lens is further reasonably distributed, the shape of the lens is further configured, the miniaturization of the lens is met, and the telephoto capability of the lens is also favorably improved.

In one embodiment, the optical system satisfies the conditional expression: -1< f12/f345< -0.2; wherein f12 is a combined focal length of the first lens and the second lens, and f345 is a combined focal length of the third lens, the fourth lens, and the fifth lens. By controlling the combined focal length of the first lens and the second lens and the size and the direction of the combined focal length of the third lens, the fourth lens and the fifth lens, the camera lens can realize the balance of the spherical aberration of the system, obtain the good imaging quality of an on-axis view field, and meanwhile, the main surface of the system can be far away from an imaging surface, so that the telephoto function of the lens is enhanced.

In one embodiment, the optical system satisfies the conditional expression: 0.3< f1/f < 0.5; wherein f1 is the effective focal length of the first lens. When f1/f is more than or equal to 0.5, the focal power of the first lens is too large, the aberration of the negative lens of the system is difficult to correct, and the imaging quality is poor; when f1/f is less than or equal to 0.3, the power distribution of the first lens is uneven, resulting in insufficient telephoto capability of the optical lens. The focal power of the first lens is reasonably distributed, so that the telephoto capability of the system is improved, the spherical aberration of the system is reduced, and the definition of an image plane is improved.

In one embodiment, the optical system satisfies the conditional expression: -1.5< f5/f < -0.5; wherein f5 is the effective focal length of the fifth lens. By configuring the fifth lens with negative focal power and reasonably setting the value of f5/f, the lens can realize the telephoto function with longer focal length through the fifth lens with smaller size, and can achieve the effects of providing narrower visual field and forming larger target images.

In one embodiment, the optical system satisfies the following conditional expression: 0< R4/R5< 3.0; wherein R4 is the object side curvature radius of the second lens, and R5 is the image side curvature radius of the second lens. When R4/R5 is less than or equal to 0, the second lens surface will be excessively bent, resulting in poor molding and affecting the production yield. R4/R5 is more than or equal to 3, the surface shape of the second lens is too smooth, so that aberration correction is difficult, the astigmatism of an external view field is too large, and the imaging quality of the telephoto lens is influenced. By adjusting the curvature radius of the second lens, the processing feasibility of the second lens is ensured, the spherical aberration and astigmatism of the system are effectively corrected, and the imaging quality of the camera is improved.

In one embodiment, the optical system satisfies the following conditional expression: 1.4< SD11/SD52< 2.0. Wherein SD11 is the maximum effective half aperture of the object side surface of the first lens, and SD52 is the maximum effective half aperture of the image side surface of the fifth lens. The reasonable setting of the SD11/SD52 value is beneficial to controlling the outer diameter of the lens system group of the camera lens. To facilitate reduction of the thickness in the radial direction, thereby miniaturizing the lens.

In one embodiment, the optical system satisfies the following conditional expression: 0.5< (CT2+ CT3+ CT4+ CT5)/CT1< 1.5; wherein CT1 is a thickness of the first lens on an optical axis, CT2 is a thickness of the second lens on an optical axis, CT3 is a thickness of the third lens on an optical axis, CT4 is a thickness of the fourth lens on an optical axis, and CT5 is a thickness of the fifth lens on an optical axis. The reasonable setting of the value of (CT2+ CT3+ CT4+ CT5)/CT1 can enhance the resistance of the first lens to the environment, and thus the proper configuration of the thickness of each lens is beneficial to the structure miniaturization design, and the influence of the lens strength due to the too thin lens on the manufacturing yield is avoided.

In one embodiment, the optical system satisfies the following conditional expression: 1.0< TTL/ImgH-FFL/ImgH < 3.0; wherein, TTL is a distance on an optical axis from an object side surface of the first lens element to an imaging surface of the optical system, FFL is a distance on the optical axis from an image side surface of the fifth lens element to the imaging surface of the optical system, and ImgH is a half of a diagonal length of an effective pixel area of the imaging surface. The TTL/ImgH-FFL/ImgH value is reasonably set, the size of the lens group can be effectively controlled while the telephoto function is satisfied, and the optical system has enough imaging size to increase the image brightness, so that the imaging quality is improved.

In one embodiment, the optical system satisfies the following conditional expression: 1.0< T23/T34< 3.0; wherein T23 is an air separation distance on the optical axis between the second lens and the third lens, and T34 is an air separation distance on the optical axis between the third lens and the fourth lens. The value of T23/T34 is reasonably set, so that enough space can be ensured between the third lens and the fourth lens, the interference of the lenses is avoided, meanwhile, the space can be fully utilized, the assembly of the lenses is facilitated, and the requirement for miniaturization of the optical lens is met.

In one embodiment, the optical system satisfies the following conditional expression: 20< V3< 60; wherein V3 is the abbe number of the third lens. Through reasonably setting the dispersion coefficient of the third lens, the deflection degree of light passing through the third lens can be controlled, the aberration correction capability of the lens can be enhanced, and chromatic aberration can be balanced.

In one embodiment, the optical system satisfies the following conditional expression: 20< V5< 60; wherein V5 is the abbe number of the fifth lens. Through the reasonable arrangement of the dispersion coefficient of the fifth lens, the deflection degree of light passing through the fifth lens can be controlled, the aberration correction capability of the lens can be enhanced, and chromatic aberration can be balanced.

In one embodiment, the optical system satisfies the following conditional expression: 0.5< T12+ T23+ T34+ T45< 2.5; wherein T12 is an air separation distance on the optical axis between the first lens and the second lens, and T45 is an air separation distance on the optical axis between the fourth lens and the fifth lens. When T12+ T23+ T34+ T45 is less than or equal to 0.5, the margin of the space allocated between the lenses is too small, resulting in increased sensitivity of the optical system and unfavorable for assembling the lenses. When T12+ T23+ T34+ T45 is larger than or equal to 2.5, the miniaturization requirement of the telephoto lens is not facilitated. The value of T12+ T23+ T34+ T45 is reasonably set, the spacing distance of the lenses is fully compressed while the assembly manufacturability of the lens is ensured, and the telephoto lens has the characteristic of miniaturization.

In a second aspect, the present invention provides a lens module, a lens barrel and the optical system of the first aspect, wherein the first to fifth lenses of the optical system are mounted in the lens barrel. By installing the first lens element to the fifth lens element of the optical system of the first aspect in the lens module, the lens module satisfies the requirements of a telephoto function, miniaturization, and high imaging quality.

In a third aspect, the present invention further provides an electronic device, including: the lens module of casing, electron photosensitive element and second aspect, the lens module with electron photosensitive element sets up in the casing, electron photosensitive element sets up on optical system's the image plane, be used for will pass first lens extremely the fourth lens is incited to the light of the thing on the electron photosensitive element converts the signal of telecommunication of image. Through the lens module of adding the second aspect in electronic equipment for electronic equipment can realize the shooting function of long focus telephoto, satisfies the miniaturized requirement of equipment, reaches the effect that the imaging quality is high.

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 embodiment of the invention provides a lens module, a lens barrel and an optical system. 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. By installing the first lens to the fifth lens of the optical system in the lens module, the lens module can meet the requirements of long-focus telephoto function, miniaturization and high imaging quality.

An embodiment of the present invention further provides an electronic device, including: the lens module and the electronic photosensitive element are arranged in the shell, and the electronic photosensitive element is arranged on an imaging surface of the optical system and used for converting light rays of objects which penetrate through the first lens to the fourth lens and enter the electronic photosensitive element into electric signals of images. The electron sensor may be a Complementary Metal Oxide Semiconductor (CMOS) or a Charge-coupled Device (CCD). The electronic device can be a smart phone, a Personal Digital Assistant (PDA), a tablet computer, a smart watch, an unmanned aerial vehicle, an electronic book reader, a vehicle event data recorder, a wearable device and the like. Through the lens module of adding the second aspect in electronic equipment for electronic equipment can realize the shooting function of long focus telephoto, satisfies the miniaturized requirement of equipment, reaches the effect that the imaging quality is high.

An optical system according to an embodiment of the present invention, in order from an object side to an image side along an optical axis, includes: the lens includes a first lens, a second lens, a third lens, a fourth lens and a fifth lens. In the first lens to the fifth lens, an air space is provided between any two adjacent lenses.

The optical system further comprises a diaphragm, and the diaphragm can be arranged at any position between the first lens and the fifth lens, such as between the first lens and the second lens.

A first lens having a positive refractive power; a second lens having optical power; a third lens having a negative focal power; the fourth lens has positive focal power, and both the object side surface and the image side surface of the fourth lens are convex surfaces; a fifth lens having a negative focal power;

wherein the optical system satisfies the following relation:

0.2<TD/f<0.5；

and TD is the distance between the object side surface of the first lens and the image side surface of the fifth lens on the optical axis, and f is the effective focal length of the optical system.

By reasonably configuring the surface type and focal power of each of the first lens to the fifth lens, the long-focus telescopic function is realized, and the requirements of miniaturization and high imaging quality are met. When TD/f is more than or equal to 0.5, the optical lens structure is not compact enough, so that the length of the lens is too long, and the assembly of the lens is not facilitated. When TD/f is less than or equal to 0.2, the length of the optical lens is too small, the aberration of the lens is difficult to correct, and the telephoto imaging quality is poor. The TD/f value is reasonably set, the focal power of the lens is further reasonably distributed, the shape of the lens is further configured, the miniaturization of the lens is met, and the telephoto capability of the lens is also favorably improved.

In one embodiment, the optical system satisfies the conditional expression: -1< f12/f345< -0.2; where f12 is the combined focal length of the first lens and the second lens, and f345 is the combined focal length of the third lens, the fourth lens, and the fifth lens. By controlling the combined focal length of the first lens and the second lens and the size and the direction of the combined focal length of the third lens, the fourth lens and the fifth lens, the camera lens can realize the balance of the spherical aberration of the system, obtain the good imaging quality of an on-axis view field, and meanwhile, the main surface of the system can be far away from an imaging surface, so that the telephoto function of the lens is enhanced.

In one embodiment, the optical system satisfies the conditional expression: 0.3< f1/f < 0.5; where f1 is the effective focal length of the first lens. When f1/f is more than or equal to 0.5, the focal power of the first lens is too large, the aberration of the negative lens of the system is difficult to correct, and the imaging quality is poor; when f1/f is less than or equal to 0.3, the power distribution of the first lens is uneven, resulting in insufficient telephoto capability of the optical lens. The focal power of the first lens is reasonably distributed, so that the telephoto capability of the system is improved, the spherical aberration of the system is reduced, and the definition of an image plane is improved.

In one embodiment, the optical system satisfies the conditional expression: -1.5< f5/f < -0.5; where f5 is the effective focal length of the fifth lens. By configuring the fifth lens with negative focal power and reasonably setting the value of f5/f, the lens can realize the telephoto function with longer focal length through the fifth lens with smaller size, and can achieve the effects of providing narrower visual field and forming larger target images.

In one embodiment, the optical system satisfies the following conditional expression: 0< R4/R5< 3.0; wherein, R4 is the curvature radius of the object side surface of the second lens, and R5 is the curvature radius of the image side surface of the second lens. When R4/R5 is less than or equal to 0, the second lens surface will be excessively bent, resulting in poor molding and affecting the production yield. R4/R5 is more than or equal to 3, the surface shape of the second lens is too smooth, so that aberration correction is difficult, the astigmatism of an external view field is too large, and the imaging quality of the telephoto lens is influenced. By adjusting the curvature radius of the second lens, the processing feasibility of the second lens is ensured, the spherical aberration and astigmatism of the system are effectively corrected, and the imaging quality of the camera is improved.

In one embodiment, the optical system satisfies the following conditional expression: 1.4< SD11/SD52< 2.0. Wherein SD11 is the maximum effective half aperture of the object-side surface of the first lens, and SD52 is the maximum effective half aperture of the image-side surface of the fifth lens. The reasonable setting of the SD11/SD52 value is beneficial to controlling the outer diameter of the lens system group of the camera lens. To facilitate reduction of the thickness in the radial direction, thereby miniaturizing the lens.

In one embodiment, the optical system satisfies the following conditional expression: 0.5< (CT2+ CT3+ CT4+ CT5)/CT1< 1.5; wherein CT1 is the thickness of the first lens on the optical axis, CT2 is the thickness of the second lens on the optical axis, CT3 is the thickness of the third lens on the optical axis, CT4 is the thickness of the fourth lens on the optical axis, and CT5 is the thickness of the fifth lens on the optical axis. The reasonable setting of the value of (CT2+ CT3+ CT4+ CT5)/CT1 can enhance the resistance of the first lens to the environment, and thus the proper configuration of the thickness of each lens is beneficial to the structure miniaturization design, and the influence of the lens strength due to the too thin lens on the manufacturing yield is avoided.

In one embodiment, the optical system satisfies the following conditional expression: 1.0< T23/T34< 3.0; where T23 is the air separation distance between the second lens and the third lens on the optical axis, and T34 is the air separation distance between the third lens and the fourth lens on the optical axis. The value of T23/T34 is reasonably set, so that enough space can be ensured between the third lens and the fourth lens, the interference of the lenses is avoided, meanwhile, the space can be fully utilized, the assembly of the lenses is facilitated, and the requirement for miniaturization of the optical lens is met.

In one embodiment, the optical system satisfies the following conditional expression: 0.5< T12+ T23+ T34+ T45< 2.5; wherein T12 is the air separation distance between the first lens and the second lens on the optical axis, and T45 is the air separation distance between the fourth lens and the fifth lens on the optical axis. When T12+ T23+ T34+ T45 is less than or equal to 0.5, the margin of the space allocated between the lenses is too small, resulting in increased sensitivity of the optical system and unfavorable for assembling the lenses. When T12+ T23+ T34+ T45 is larger than or equal to 2.5, the miniaturization requirement of the telephoto lens is not facilitated. The value of T12+ T23+ T34+ T45 is reasonably set, the spacing distance of the lenses is fully compressed while the assembly manufacturability of the lens is ensured, and the telephoto lens has the characteristic of miniaturization.

First embodiment

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

the first lens element L1 has positive refractive power, and the object-side surface S1 of the first lens element L1 is convex, and the image-side surface S2 of the first lens element L1 is convex.

The second lens L2 has positive refractive power, and the object-side surface S3 of the second lens L2 is convex, and the image-side surface S4 of the second lens L2 is concave.

The third lens L3 has negative refractive power, and the object-side surface S5 of the third lens L3 is concave, and the image-side surface S6 of the third lens L3 is concave.

The fourth lens L4 has positive refractive power, and the object-side surface S7 of the fourth lens L4 is convex, and the image-side surface S8 of the fourth lens L4 is convex.

The fifth lens L5 has negative refractive power, and the object-side surface S9 of the fourth lens L4 is concave, and the image-side surface S10 of the fourth lens L4 is concave.

The first lens element L1 to the fifth lens element L5 are all made of Plastic (Plastic).

Further, the optical system includes a stop STO, an infrared cut filter L6, and an image forming surface S13. A stop STO is provided at the object side surface S1 next to the first lens L1 for controlling the amount of light entering. In other embodiments, the stop STO can be disposed between two other adjacent lenses. The infrared cut filter L6 is disposed on the image side of the fifth lens L5, and includes an object side surface S11 and an image side surface S12, and the infrared cut filter L6 is configured to filter out infrared light, so that the light entering the image plane S13 is visible light, and the wavelength of the visible light is 380nm-780 nm. The material of the infrared cut filter L6 is Glass (Glass), and a film may be coated on the Glass. The electron photosensitive element is disposed on the image side of the optical system to receive light of an image formed by the optical system, and the surface on which the image formed by the optical system is located is an image forming surface S11.

Table 1a shows a table of characteristics of the optical system of the present embodiment, and the units of the Y radius, thickness, and focal length are all millimeters (mm).

TABLE 1a

The EFL is an effective focal length of the optical system, the FNO is an f-number of the optical system, the FOV is a field angle of the optical system, and the TTL is a distance from an object side surface of the first lens to an imaging surface of the optical system on an optical axis.

In this embodiment, the object-side surface and the image-side surface of any one of the first lens L1 through the fourth lens L4 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 results that can be used

The high-order term coefficients A4, A6, A8, A10, A12, A14, A16, A18 and A20 of the respective aspherical mirrors S1-S8 in the first embodiment.

TABLE 1b

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 represents the deviation of the convergence focus of the light rays with different wavelengths after passing through each lens of the optical system; the astigmatism curves represent meridional image surface curvature and sagittal image surface curvature; the distortion curve represents the distortion magnitude values corresponding to different angles of view. 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 2b, the optical system of the present embodiment includes, once from the object side to the image side along the optical axis direction:

The second lens L2 has negative refractive power, and the object-side surface S3 of the second lens L2 is convex, and the image-side surface S4 of the second lens L2 is concave.

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, and the units of the Y radius, thickness, and 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. The longitudinal spherical aberration curve represents the deviation of the convergence focus of the light rays with different wavelengths after passing through each lens of the optical system; the astigmatism curves represent meridional image surface curvature and sagittal image surface curvature; the distortion curve represents the distortion magnitude values corresponding to different angles of view. 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 includes, once from the object side to the image side along the optical axis direction:

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, and the units of the Y radius, thickness, and 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

Fig. 3b shows a longitudinal spherical aberration curve, an astigmatism curve and a distortion curve of the optical system of the third embodiment. The longitudinal spherical aberration curve represents the deviation of the convergence focus of the light rays with different wavelengths after passing through each lens of the optical system; the astigmatism curves represent meridional image surface curvature and sagittal image surface curvature; the distortion curve represents the distortion magnitude values corresponding to different angles of view. 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 includes, once from the object side to the image side along the optical axis direction:

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, and the units of the Y radius, thickness, and 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. The longitudinal spherical aberration curve represents the deviation of the convergence focus of the light rays with different wavelengths after passing through each lens of the optical system; the astigmatism curves represent meridional image surface curvature and sagittal image surface curvature; the distortion curve represents the distortion magnitude values corresponding to different angles of view. 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 includes, once from the object side to the image side along the optical axis direction:

The third lens L3 has negative refractive power, and the object-side surface S5 of the third lens L3 is convex, and the image-side surface S6 of the third lens L3 is concave.

The fifth lens L5 has negative power, and the fourth lens L4 has a concave object-side surface S9, a concave image-side surface S10 at the optical axis of the fourth lens L4, and a convex image-side surface S10 at the circumference.

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, and the units of the Y radius, thickness, and 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

Fig. 5b shows a longitudinal spherical aberration curve, an astigmatism curve and a distortion curve of the optical system of the fifth embodiment. The longitudinal spherical aberration curve represents the deviation of the convergence focus of the light rays with different wavelengths after passing through each lens of the optical system; the astigmatism curves represent meridional image surface curvature and sagittal image surface curvature; the distortion curve represents the distortion magnitude values corresponding to different angles of view. 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 includes, once from the object side to the image side along the optical axis direction:

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, and the units of the Y radius, thickness, and 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. The longitudinal spherical aberration curve represents the deviation of the convergence focus of the light rays with different wavelengths after passing through each lens of the optical system; the astigmatism curves represent meridional image surface curvature and sagittal image surface curvature; the distortion curve represents the distortion magnitude values corresponding to different angles of view. 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 includes, once from the object side to the image side along the optical axis direction:

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, and the units of the Y radius, thickness, and 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. The longitudinal spherical aberration curve represents the deviation of the convergence focus of the light rays with different wavelengths after passing through each lens of the optical system; the astigmatism curves represent meridional image surface curvature and sagittal image surface curvature; the distortion curve represents the distortion magnitude values corresponding to different angles of view. 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 TD/f, f12/f345, f1/f, f5/f, R4/R5, SD11/SD52, (CT2+ CT3+ CT4+ CT5)/CT1, TTL/ImgH-FFL/ImgH, T23/T34, V3, V5, T12+ T23+ T34+ T45 of the optical systems of the first to seventh embodiments, and as can be seen from table 8, each embodiment satisfies the following conditional expressions: 0.2< TD/f <0.5, -1< f12/f345< -0.2, 0.3< f1/f <0.5, -1.5< f5/f < -0.5, 0< R4/R5<3.0, 1.4< SD11/SD52<2.0, 0.5< (CT2+ CT3+ CT4+ CT5)/CT1<1.5, 1.0< TTL/ImgH-FFL/ImgH <3.0, 1.0< T23/T34<3.0, 20< V3<60, 20< V5<60, 0.5< T12+ T23+ T34+ T45< 2.5.

TABLE 8

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 details 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, in order from an object side to an image side along an optical axis, comprising:

a first lens having a positive refractive power;

a second lens having optical power;

a third lens having a negative focal power;

the fourth lens has positive focal power, and both the object-side surface and the image-side surface of the fourth lens are convex surfaces;

a fifth lens having a negative focal power;

the optical system satisfies the following relation: 0.2< TD/f < 0.5;

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

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

-1<f12/f345<-0.2；

wherein f12 is a combined focal length of the first lens and the second lens, and f345 is a combined focal length of the third lens, the fourth lens, and the fifth lens.

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

0.3<f1/f<0.5；

wherein f1 is the effective focal length of the first lens.

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

-1.5<f5/f<-0.5；

wherein f5 is the effective focal length of the fifth lens.

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

0<R4/R5<3.0；

wherein R4 is the object side curvature radius of the second lens, and R5 is the image side curvature radius of the second lens.

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

1.4<SD11/SD52<2.0；

wherein SD11 is the maximum effective half aperture of the object side surface of the first lens, and SD52 is the maximum effective half aperture of the image side surface of the fifth lens.

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

0.5<(CT2+CT3+CT4+CT5)/CT1<1.5；

wherein CT1 is a thickness of the first lens on an optical axis, CT2 is a thickness of the second lens on an optical axis, CT3 is a thickness of the third lens on an optical axis, CT4 is a thickness of the fourth lens on an optical axis, and CT5 is a thickness of the fifth lens on an optical axis.

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

1.0<TTL/ImgH-FFL/ImgH<3.0；

wherein, TTL is a distance on an optical axis from an object side surface of the first lens element to an imaging surface of the optical system, FFL is a distance on the optical axis from an image side surface of the fifth lens element to the imaging surface of the optical system, and ImgH is a half of a diagonal length of an effective pixel area of the imaging surface.

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

1.0<T23/T34<3.0；

wherein T23 is an air separation distance on the optical axis between the second lens and the third lens, and T34 is an air separation distance on the optical axis between the third lens and the fourth lens.

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

20<V3<60；

wherein V3 is the abbe number of the third lens.

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

20<V5<60；

wherein V5 is the abbe number of the fifth lens.

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

0.5<T12+T23+T34+T45<2.5；

wherein T12 is an air separation distance on the optical axis between the first lens and the second lens, and T45 is an air separation distance on the optical axis between the fourth lens and the fifth lens.

13. A lens module, comprising: the optical system according to any one of claims 1 to 12, the first lens to the fifth lens of the optical system being mounted within the lens barrel.

14. An electronic device, comprising: a housing, an electronic photosensitive element and a lens module according to claim 13, wherein the lens module and the electronic photosensitive element are disposed in the housing, and the electronic photosensitive element is disposed on an image plane of the optical system and is used for converting light rays of an object incident on the electronic photosensitive element through the first lens to the fourth lens into an electrical signal of an image.