CN113514937B

CN113514937B - Optical system, camera module and electronic equipment

Info

Publication number: CN113514937B
Application number: CN202110582862.XA
Authority: CN
Inventors: 华露; 杨健; 李明
Original assignee: Jiangxi Jingchao Optical Co Ltd
Current assignee: Jiangxi Jingchao Optical Co Ltd
Priority date: 2021-05-27
Filing date: 2021-05-27
Publication date: 2023-11-07
Anticipated expiration: 2041-05-27
Also published as: CN113514937A

Abstract

The invention relates to an optical system, an imaging module and electronic equipment. The optical system sequentially comprises from an object side to an image side along an optical axis: the first lens element with negative 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 positive refractive power having a convex object-side surface at a paraxial region; the third lens element with positive refractive power has a convex object-side surface at a paraxial region and a convex image-side surface at a paraxial region; a fourth lens element with negative refractive power having a concave image-side surface at a paraxial region; a fifth lens element with positive refractive power having a concave image-side surface at a paraxial region, wherein the object-side surface and the image-side surface of the fifth lens element are aspheric, and at least one of the object-side surface and the image-side surface of the fifth lens element has a rotationally asymmetric surface; and the optical system satisfies the conditional expression: 3.0mm ^‑1 <tan(semiFOV)/sag11<4.5mm ^‑1 . The above design is advantageous for the optical system to effectively increase the angle of view.

Description

Optical system, camera module and electronic equipment

Technical Field

The present invention relates to the field of photography imaging technology, and in particular, to an optical system, a camera module, and an electronic device.

Background

The wide-angle lens is widely applied in the smart phone industry nowadays, and is an important module for realizing an essential shooting mode of the mobile phone. The wider the angle of view of the wide-angle lens, the larger the range of the scene which can be taken, and the characteristics of deep sense of the picture space, long scene depth and the like. However, most of the aspherical lenses used in the wide-angle imaging lens at present inevitably cause larger distortion while realizing wide-angle imaging, especially the outer edge field of view, and the influence of the distortion is greatest. The excessive distortion of the marginal field of view can cause the increase of off-axis aberration, obvious image distortion, reduced user experience feel and limit the further expansion and development of the field of view.

Therefore, how to further improve the imaging quality of an optical system applied to a portable electronic product while taking into consideration the shooting range is a problem to be solved.

Disclosure of Invention

Based on this, it is necessary to provide an optical system, an imaging module, and an electronic apparatus for solving the problem of how to better realize a large viewing angle.

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

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

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

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

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

a fifth lens element with positive refractive power having a concave image-side surface at a paraxial region, wherein the object-side surface and the image-side surface of the fifth lens element are aspheric, and at least one of the object-side surface and the image-side surface of the fifth lens element has an asymmetric surface;

And the optical system satisfies the conditional expression:

3.0mm ^-1 <tan(semiFOV)/sag11<4.5mm ^-1 wherein semiFOV is half of the maximum field angle of the optical system, tan (semiFOV) is the tangent of half of the maximum field angle of the optical system, sag11 is the object side surface of the first lens at maximum effectiveSagittal height at caliber.

Through the lens design, the large visual angle design of the optical system is facilitated, and the last lens of the optical system has a non-rotationally symmetrical plane shape, namely, the design freedom degree of the refractive surface of the fifth lens is improved, so that the final correction of meridian field curvature and sagittal field curvature of the optical system is facilitated, and the aberration such as field curvature, astigmatism and distortion of the optical system can be effectively restrained, and the imaging quality is improved.

When tan (semiFOV)/sag 11 is less than or equal to 3.0, the sagittal height of the object side surface of the first lens at the maximum effective caliber is too large, so that the surface of the object side surface S1 is excessively bent and is not easy to mold, and the assembly stability of the first lens L1 is reduced; when tan (semiFOV)/sag 11 is greater than or equal to 4.5, the object side surface of the first lens is too gentle to be beneficial to increasing the angle of view of the optical system, and further to the development of the wide-angle characteristic of the optical system. Therefore, when the above 3.0mm is satisfied ^-1 <tan(semiFOV)/sag11<4.5mm ^-1 When the condition is met, the object side surface of the first lens can be reasonably restrained from rising at the position of the maximum effective caliber, and on one hand, the optical system is facilitated to obtain a larger field angle; on the other hand, the phenomenon that the object side surface of the first lens is bent too much to cause difficult processing of the first lens is avoided, and the processing feasibility of the first lens is improved.

In one embodiment, the optical system satisfies the conditional expression:

1.5<f5/f<2.0；

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

When f5/f is more than or equal to 2.0, the positive refractive power provided by the fifth lens is insufficient, which is not beneficial to the aberration balance of the whole optical system; when f 5/f.ltoreq.1.5, the positive refractive power contributed by the fifth lens element is excessively large, which is disadvantageous in correcting aberrations generated by the front lens group (i.e., the combination of the lens elements preceding the fifth lens element) to achieve aberration balance of the optical system as a whole, resulting in failure to obtain high imaging quality. Therefore, when the above condition of 1.5< f5/f <2.0 is satisfied, since the fifth lens is configured with a non-rotationally symmetrical plane shape and has a higher degree of freedom, by reasonably configuring the positive refractive power provided by the fifth lens, it is advantageous to correct the aberration generated by the front lens group (i.e., the first to fourth lenses), to balance the aberration of the optical system as a whole, and to reduce the deflection angle of the light rays of the external field, and to achieve a smooth transition of the light rays to the imaging plane, so as to improve the imaging quality.

In one embodiment, the optical system satisfies the conditional expression:

-1.6<f4/r42<-0.4；

where f4 is the effective focal length of the fourth lens element, and r42 is the radius of curvature of the image-side surface of the fourth lens element at the optical axis.

When f4/r42 is less than or equal to-1.6, the shape of the image side surface of the fourth lens is too complex, which is not beneficial to the processing and forming of the fourth lens; when f4/r42 is more than or equal to-0.4, the negative refractive power provided by the fourth lens is too small, so that the distortion of the whole optical system is not reduced, and the imaging quality is reduced. Therefore, when the above-mentioned condition-1.6 < f4/r42< -0.4 is satisfied, by controlling the ratio between the negative refractive power of the fourth lens element and the radius of curvature of the image side surface of the fourth lens element at the optical axis within a reasonable range, the distortion generated by the fourth lens element in combination with the fifth lens element before correction (i.e., the first to fourth lens elements) is beneficial to improving the imaging quality, and the control of the image side surface profile of the fourth lens element is beneficial to reducing the sensitivity and the processing difficulty of the fourth lens element.

In one embodiment, when the above-mentioned conditional expression of-1.6 < f4/r42< -0.4 is satisfied, the optical system further satisfies the conditional expression:

-2.70 < f4 < -2.07; when the relationship is satisfied, the negative refractive power of the fourth lens is controlled within a reasonable range, so that the fourth lens and the fifth lens are matched together to correct the distortion generated by the front lens group, the integral distortion of the optical system is effectively reduced, and the imaging quality is further improved.

r42 is more than 1.39 and less than 5.66; when the relation is satisfied, the curvature radius of the image side surface of the fourth lens is controlled within a reasonable range, so that the surface shape of the image side surface of the fourth lens is controlled, the sensitivity of the fourth lens is effectively reduced, and the lens processing is facilitated.

In one embodiment, the optical system satisfies the conditional expression:

1.0<(r12-r11)/f1<4.5；

where r12 is a radius of curvature of the image side surface of the first lens element at the optical axis, r11 is a radius of curvature of the object side surface of the first lens element at the optical axis, and f1 is an effective focal length of the first lens element.

When the above conditional expression is satisfied, the positive refractive power of the first lens element and the surface profile are matched, and the refractive power of the first lens element and the surface profile bending difference between the object side surface and the image side surface of the first lens element are reasonably configured, so that on one hand, light rays entering at a large angle are favorable to obtain large field of view characteristics, meanwhile, excessive deflection of marginal light rays when passing through the two side surfaces of the first lens element is also favorable to avoiding, the bending degree of the light rays at the image side surface of the first lens element is favorable to reducing the astigmatic quantity of the optical system, the optical system has larger field angle and small distortion, and further the imaging quality is improved. In one embodiment, the optical system satisfies the conditional expression:

0.7<(ct1+ct5)/(ct2+ct3+ct4)<0.8；

Wherein, ct1 is the thickness of the first lens element on the optical axis, ct5 is the thickness of the fifth lens element on the optical axis, ct2 is the thickness of the second lens element on the optical axis, ct3 is the thickness of the third lens element on the optical axis, and ct4 is the thickness of the fourth lens element on the optical axis.

When the above conditional expression is satisfied, the ratio of the thicknesses of the lenses (the first lens element to the fifth lens element) on the optical axis in the optical system is controlled, so that the refractive power distribution of the lenses in the optical system is balanced, and the spherical aberration of the system is balanced, so that the optical system has better imaging quality and assembly stability.

In one embodiment, the optical system satisfies the conditional expression:

0.45<(et3+et4)/(sd31+sd42)<0.55；

wherein, et3 is the distance between the maximum effective half-caliber of the object side surface of the third lens and the maximum effective half-caliber of the image side surface of the third lens in the optical axis direction, that is, et3 is the thickness of the edge of the third lens in the optical axis direction (abbreviated as edge thickness), et4 is the distance between the maximum effective half-caliber of the object side surface of the fourth lens and the maximum effective half-caliber of the image side surface of the fourth lens in the optical axis direction, that is, et4 is the thickness of the edge of the fourth lens in the optical axis (abbreviated as edge thickness), sd31 is the maximum effective half-caliber of the object side surface of the third lens, and sd42 is the maximum effective half-caliber of the image side surface of the fourth lens.

When the above conditional expression is satisfied, the numerical value of (et 3+et 4)/(sd 31+sd 42) is controlled in a reasonable range, so that the excessive difference between the edge thickness and the maximum effective half caliber of the third lens and the fourth lens can be avoided, the volume of the optical system can be reduced, the miniaturization characteristic can be satisfied, the over-bending of the whole surface of the third lens and the fourth lens can be avoided, the assembly difficulty can be effectively reduced, and the resolution of the optical system can be improved.

In one embodiment, the optical system satisfies the conditional expression:

0.35<sd52/TTL<0.40；

where sd52 is the maximum effective half-caliber of the image side of the fifth lens, and TTL is the total optical length of the optical system.

The above conditional expression is satisfied, which is favorable for shortening the total length of the optical system and leaving enough back focal space for lens barrel design on the premise that marginal rays at the image side surface of the fifth lens smoothly transition to the imaging surface at a smaller deflection angle, and is also favorable for reducing the molding and assembling difficulty of each lens and improving the imaging quality.

In one embodiment, the optical system further includes an aperture stop disposed between the first lens and the second lens, and the optical system satisfies the following condition:

f/EPD<2.3；

where f is the effective focal length of the optical system and EPD is the entrance pupil diameter of the optical system. On the premise that the aperture diaphragm is arranged between the first lens and the second lens, when the condition is met, the optical system can have larger aperture and higher light flux, so that the imaging effect of the optical system when working in a dark environment is improved, and the aberration of the marginal view field is reduced.

In one embodiment, the optical system satisfies the conditional expression:

0.8<tan(semiFOV)/TVDmax<1.3；

wherein tan (semiFOV) is the tangent of the half field angle of the optical system; TVDmax is the maximum percentage value of the absolute value of the TV distortion value of the optical system at the reference wavelength of 555 nm. The method has the advantages that the condition is met, the degree of freedom of the curved surface of the fifth lens is increased by introducing a non-rotation symmetrical surface shape into at least one of the object side surface and the image side surface of the fifth lens, and then the maximum absolute value of the grid distortion value of the optical system is controlled to be within 2.5% when the reference wavelength is 555nm, so that TV distortion is further reduced on the basis of realizing a large field angle, the degree of image distortion can be obviously reduced, the imaging quality is improved, and more real shooting experience with large depth of field and large field angle is brought to users.

An image pickup module comprises an image sensor and any one of the optical systems, wherein the image sensor is arranged on the image side of the optical system. By adopting the optical system, the optical distortion of the camera module can be effectively inhibited, so that the imaging quality can be improved.

An electronic device comprises a fixing piece and the camera shooting module, wherein the camera shooting module is arranged on the fixing piece. When the electronic equipment is used for shooting scenes, the distortion degree of the image frames can be effectively controlled, and the shooting quality can be better improved.

Drawings

Fig. 1 is a schematic structural diagram of an optical system according to a first embodiment of the present application;

FIG. 2 is a plot of RMS spot diameter versus reference for the optical system in the first embodiment;

fig. 3 is a TV distortion chart of the optical system in the first embodiment;

FIG. 4 is a schematic diagram of an optical system according to a second embodiment of the present application;

FIG. 5 is a plot of RMS spot diameter versus reference for an optical system in a second embodiment;

fig. 6 is a TV distortion chart of the optical system in the second embodiment;

FIG. 7 is a schematic diagram of an optical system according to a third embodiment of the present application;

FIG. 8 is a plot of RMS spot diameter versus reference for an optical system in a third embodiment;

fig. 9 is a TV distortion chart of an optical system in the third embodiment;

fig. 10 is a schematic structural diagram of an optical system according to a fourth embodiment of the present application;

FIG. 11 is a plot of RMS spot diameter versus reference for an optical system in a fourth embodiment;

fig. 12 is a TV distortion chart of an optical system in the fourth embodiment;

fig. 13 is a schematic structural view of an optical system according to a fifth embodiment of the present application;

FIG. 14 is a plot of RMS spot diameter versus reference for an optical system in a fifth embodiment;

fig. 15 is a TV distortion chart of an optical system in the fifth embodiment;

FIG. 16 is a schematic structural diagram of an image capturing module according to an embodiment of the present application;

fig. 17 is a schematic structural diagram of an electronic device according to an embodiment of the present application.

Detailed Description

In order that the above-recited objects, features and advantages of the present application will become more readily apparent, a more particular description of the application will be rendered by reference to the appended drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application. The present application may be embodied in many other forms than described herein and similarly modified by those skilled in the art without departing from the spirit of the application, whereby the application is not limited to the specific embodiments disclosed below.

In the description of the present application, it should be understood that the terms "center," "longitudinal," "transverse," "length," "thickness," "upper," "front," "rear," "axial," "radial," and the like indicate orientations or positional relationships based on the orientation or positional relationships shown in the drawings, merely to facilitate description of the present application and simplify the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be configured and operated in a particular orientation, and thus should not be construed as limiting the present application.

Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature. In the description of the present invention, the meaning of "plurality" means at least two, for example, two, three, etc., unless specifically defined otherwise.

In the present invention, unless explicitly specified and limited otherwise, the terms "mounted," "connected," "secured," and the like are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; either directly or indirectly, through intermediaries, or both, may be in communication with each other or in interaction with each other, unless expressly defined otherwise. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art according to the specific circumstances.

It will be understood that when an element is referred to as being "fixed" or "disposed" on another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present.

Referring to fig. 1, in an embodiment of the present application, the optical system 10 includes, in order from an object side to an image side along an optical axis 101, a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, and a fifth lens L5. The first lens element L1 with negative refractive power, the second lens element L2 with positive refractive power, the third lens element L3 with positive refractive power, the fourth lens element L4 with negative refractive power, and the fifth lens element L5 with positive refractive power. The lenses in the optical system 10 are coaxially arranged, i.e. the optical axes of the lenses are all on the same line, which may be the optical axis 101 of the optical system 10. Each lens in the optical system 10 is mounted in a lens barrel to be assembled into an imaging lens.

The first lens element L1 has an object-side surface S1 and an image-side surface S2, the second lens element L2 has an object-side surface S3 and an image-side surface S4, the third lens element L3 has an object-side surface S5 and an image-side surface S6, the fourth lens element L4 has an object-side surface S7 and an image-side surface S8, and the fifth lens element L5 has an object-side surface S9 and an image-side surface S10. The optical system 10 further has an imaging surface S11, the imaging surface S11 is located at the image side of the fifth lens L5, the central field of view of the optical system 10 corresponds to an object located at the object plane, and the light from the object located at the object plane of the optical system 10 can be converged at the imaging surface S11 after being adjusted by each lens of the optical system 10. In general, the imaging surface S11 of the optical system 10 coincides with the photosensitive surface of the image sensor.

In the embodiment of the application, the object-side surface S1 of the first lens element L1 is convex at a paraxial region, and the image-side surface S2 thereof is concave at a paraxial region;

the object side surface S3 of the second lens element L2 is convex at a paraxial region; the object side surface S5 of the third lens element L3 is convex at a paraxial region, and the image side surface S6 thereof is convex at a paraxial region; the image-side surface S8 of the fourth lens element L4 is concave at a paraxial region; the image-side surface S10 of the fifth lens element L5 is concave at a paraxial region. When describing that the lens surface has a certain profile at the paraxial region, i.e. the lens surface has such a profile near the optical axis 101, the lens surface may have the same profile or an opposite profile in the region near the maximum effective clear aperture.

Further, the object-side surface S9 and the image-side surface S10 of the fifth lens element L5 are aspheric, and at least one of the object-side surface S9 and the image-side surface S10 of the fifth lens element L5 has a non-rotationally symmetrical surface shape.

Through the lens design, the optical system 10 is beneficial to realizing a large viewing angle and a large image plane design, and the last lens of the optical system 10 has a non-rotationally symmetrical plane shape, namely, the design freedom degree of the refractive surface of the fifth lens L5 is improved, so that the final correction of the noon curvature and the sagittal curvature of the optical system 10 is beneficial to realizing, and the aberration such as curvature of field, astigmatism and distortion of the optical system 10 can be effectively restrained, thereby improving the imaging quality.

In an embodiment of the present application, the optical system 10 also satisfies the conditional expression:

3.0mm ^-1 <tan(semiFOV)/sag11<4.5mm ^-1 the semiFOV is half of the maximum angle of view of the optical system 10, tan (semiFOV) is a tangent of half of the maximum angle of view of the optical system 10, sag11 is a sagittal height of the object side surface S1 of the first lens L1 at the maximum effective aperture, that is, a horizontal displacement amount (the horizontal displacement amount is defined as positive toward the image side and as negative toward the object side surface) from an intersection point of the object side surface S1 of the first lens L1 on the optical axis 101 to the maximum effective radius of the object side surface S1 of the first lens L1 in the optical axis 101 direction. If tan (semiFOV)/sag 11 is less than or equal to 3.0, the sagittal height of the object side surface S1 of the first lens L1 at the maximum effective caliber is too large, so that the object side surface S1 is excessively curved, and is not easy to form, thereby reducing the assembly stability of the first lens L1; if tan (semiFOV)/sag 11 is greater than or equal to 4.5, the object-side surface S1 of the first lens L1 is too gentle to facilitate increasing the angle of view of the optical system 10, and further facilitates the wide-angle performance of the optical system 10. Thus, when 3.0mm is satisfied ^-1 <tan(semiFOV)/sag11<4.5mm ^-1 In this case, the object side surface S1 of the first lens element L1 can be reasonably constrained to have a sagittal height at the maximum effective aperture, which is beneficial for the optical system 10 to obtain a larger angle of view; on the other hand, the object side surface S1 of the first lens L1 is advantageously prevented from being excessively bent, which may cause difficulty in processing the first lens L1, and the processing feasibility of the first lens is improved. In some embodiments, the conditional expression satisfied by the optical system 10 may be specifically 3.10mm ^-1 、3.48mm ^-1 、3.49mm ^-1 、4.01mm ^-1 、4.22mm ^-1 、4.30mm ^-1 Or 4.45mm ^-1 。

1.5< f5/f <2.0; where f5 is the effective focal length of the fifth lens L5, and f is the effective focal length of the optical system 10. It should be noted that, if f5/f is greater than or equal to 2.0, the positive refractive power provided by the fifth lens element L5 is insufficient, which is not beneficial to the aberration balance of the entire optical system 10; when f5/f is less than or equal to 1.5, the positive refractive power contributed by the fifth lens element L5 is too large to correct the aberration generated by the front lens group (i.e., the combination of the lens elements before the fifth lens element L5) to achieve the aberration balance of the entire optical system 10, resulting in failure to obtain high imaging quality. Therefore, when the above condition of 1.5< f5/f <2.0 is satisfied, since the fifth lens L5 is configured with a non-rotationally symmetrical plane shape, which has a higher degree of freedom, by reasonably configuring the positive refractive power provided by the fifth lens L5, it is advantageous to correct the aberration generated by the front lens group, ensure the aberration balance of the optical system 10 as a whole, and in addition, it is advantageous to reduce the deflection angle of the external field light, and it is possible to achieve a smooth transition of the light beam to the imaging plane S11, so as to improve the imaging quality. In some embodiments, the conditional expression satisfied by the optical system 10 may be specifically 1.58, 1.65, 1.78, 1.82, 1.85, 1.90, or 1.98.

-1.6< f4/r42< -0.4; where f4 is the effective focal length of the fourth lens element L4, and r42 is the radius of curvature of the image-side surface S8 of the fourth lens element L4 at the optical axis 101. If f4/r42 is less than or equal to-1.6, the image side surface S8 of the fourth lens L4 is too complex to facilitate the processing and forming of the fourth lens L4; if f4/r42 is not less than-0.4, the negative refractive power provided by the fourth lens element L4 is too small, which is not beneficial to reducing the distortion of the whole optical system 10 and reducing the imaging quality. When the above-mentioned condition-1.6 < f4/r42< -0.4 is satisfied, the ratio between the negative refractive power of the fourth lens element L4 and the radius of curvature r42 of the image-side surface S8 of the fourth lens element L4 at the optical axis is controlled within a reasonable range, which is advantageous for improving the imaging quality by correcting the distortion generated by the front lens group (i.e., the first lens element L1 to the fourth lens element L4) by combining the fourth lens element L4 with the fifth lens element L4, and for controlling the shape of the image-side surface S8 of the fourth lens element L4, reducing the sensitivity and reducing the processing difficulty of the fourth lens element L4. In some embodiments, the conditional expression satisfied by the optical system 10 may be specifically-1.52, -1.33, -1.13, -1.16, -0.87, -0.50, or-0.45.

When the above-mentioned conditional expression of-1.6 < f4/r42< -0.4 is satisfied, the optical system further satisfies the conditional expression:

-2.70 < f4 < -2.07; when this relationship is satisfied, the negative refractive power of the fourth lens element L4 is controlled within a reasonable range, which facilitates the co-operation of the fourth lens element L4 and the fifth lens element L5 to correct the distortion generated by the front lens group, thereby effectively reducing the distortion of the entire optical system 10 and further improving the imaging quality. In some embodiments, the conditional expression satisfied by the optical system 10 may be specifically-2.69, -2.56, -2.34, -2.19, -2.15, -2.079, or-2.071.

r42 is more than 1.39 and less than 5.66; when this relationship is satisfied, the curvature radius r42 of the image-side surface S8 of the fourth lens element L4 at the optical axis is controlled within a reasonable range, so that the surface shape of the image-side surface S8 of the fourth lens element L4 is controlled, thereby effectively reducing the sensitivity of the fourth lens element L4 and facilitating the lens processing. In some embodiments, the conditional expression satisfied by the optical system 10 may be specifically 1.40, 1.44, 1.89, 2.31, 4.52, 4.92, or 5.65.

1.0< (r 12-r 11)/f 1<4.5; wherein r12 is a radius of curvature of the image side surface S2 of the first lens element L1, and r11 is a radius of curvature of the object side surface S1 of the first lens element L1 at the optical axis 101; f1 is the effective focal length of the first lens L1. When the above condition is satisfied, the positive refractive power of the first lens element L1 and the surface profile are matched, and the refractive power of the first lens element L1 and the surface profile bending difference between the object-side surface S1 and the image-side surface S2 of the first lens element L1 are reasonably configured, so that on one hand, light incident at a large angle is advantageously obtained to obtain a large field of view characteristic, and meanwhile, excessive deflection of marginal light when passing through two side surfaces of the first lens element L1 is also advantageously avoided, the bending degree of the light at the image-side surface S2 of the first lens element L1 is advantageously reduced, the astigmatic quantity of the optical system 10 is reduced, the optical system 10 has a large field of view angle and also has small distortion, and further the imaging quality is improved. In some embodiments, the conditional expression satisfied by the optical system 10 may be specifically 1.03, 1.32, 1.85, 2.60, 3.39, 4.00, or 4.32.

0.7< (ct1+ct5)/(ct2+ct3+ct4) <0.8; wherein ct1 is the thickness of the first lens element L1 on the optical axis, ct5 is the thickness of the fifth lens element L5 on the optical axis, ct2 is the thickness of the second lens element L2 on the optical axis, ct3 is the thickness of the third lens element L3 on the optical axis, and ct4 is the thickness of the fourth lens element L4 on the optical axis. When the above conditional expressions are satisfied, the conditional expressions of controlling the thicknesses of the lenses (the first lens L1 to the fifth lens L5) in the optical system on the optical axis are beneficial to balancing the refractive power distribution of the lenses in the optical system 10 and balancing the spherical aberration of the system, so that the optical system 10 has better imaging quality and assembly stability. In some embodiments, the conditional expression satisfied by the optical system 10 may be specifically 0.72, 0.73, 0.74, 0.76, 0.77, 0.78, or 0.79.

0.45< (et3+et4)/(s31+s42) <0.55; wherein, et3 is the distance between the maximum effective half-caliber of the object side surface S5 of the third lens element L3 and the maximum effective half-caliber of the image side surface S6 of the third lens element L3, i.e., et3 is the thickness (abbreviated as side thickness) of the edge of the third lens element L3 in the optical axis direction, et4 is the distance between the maximum effective half-caliber of the object side surface S7 of the fourth lens element L4 and the maximum effective half-caliber of the image side surface S8 of the fourth lens element L4, i.e., et4 is the thickness (abbreviated as side thickness) of the edge of the fourth lens element L4 in the optical axis direction, sd31 is the maximum effective half-caliber of the object side surface S5 of the third lens element L3, and sd42 is the maximum effective half-caliber of the image side surface S8 of the fourth lens element L4. When the above conditional expression is satisfied, the numerical value of (et3+et4)/(sd 31+sd 42) is controlled within a reasonable range, so that the excessive difference between the edge thicknesses of the third lens L3 and the fourth lens L4 and the maximum effective half-caliber can be avoided, the volume of the optical system 10 can be reduced, the miniaturization characteristic can be satisfied, the overall surface shape of the third lens L3 and the fourth lens L4 can be avoided from being excessively bent, the assembly difficulty can be effectively reduced, and the resolution of the optical system 10 can be improved. In some embodiments, the conditional expression satisfied by the optical system 10 may be specifically 0.45, 0.47, 0.49, 0.50, 0.51, 0.52, or 0.54.

0.35< sd52/TTL <0.40; the sd52 is the maximum effective half-caliber of the image side surface S10 of the fifth lens element L5, and TTL is the total optical length of the optical system 10, i.e., the distance between the object side surface S1 of the first lens element L1 and the imaging surface S11 on the optical axis. Satisfying the above conditional expression is beneficial to shortening the total length of the optical system 10 on the premise of ensuring that the marginal light at the image side surface S10 of the fifth lens L5 smoothly transits to the imaging surface S11 at a smaller deflection angle, leaving enough back focal space for lens barrel design, and also beneficial to reducing the molding and assembling difficulty of each lens and improving the imaging quality. In some embodiments, the conditional expression satisfied by the optical system 10 may be specifically 0.351, 0.374, 0.378, 0.376, 0.380, 0.392, or 0.397.

f/EPD <2.3; where f is the effective focal length of the optical system 10 and EPD is the entrance pupil diameter of the optical system 10. On the premise that the aperture stop STO is disposed between the first lens L1 and the second lens L2, when the above conditional expression is satisfied, the optical system 10 can have a larger aperture and a higher light flux, so as to increase the imaging effect of the optical system 10 when working in a dark environment, and further, the aberration of the fringe field of view is reduced. In some embodiments, the conditional expression satisfied by the optical system 10 may be specifically 2.00, 2.07, 2.10, 2.13, 2.18, 2.20, or 2.30.

0.8< tan (semiFOV)/TVDmax <1.3; here, tan (semiFOV) is the tangent of the half field angle of the optical system 10; TVDmax is the maximum percentage value of the absolute value of the TV distortion value at the reference wavelength of 555nm of the optical system 10. The above conditional expression is satisfied, by introducing a non-rotationally symmetrical plane shape into at least one of the object side surface S9 and the image side surface S10 of the fifth lens L5, the degree of freedom of the curved surface of the fifth lens L5 is increased, and then the maximum value of the absolute value of the grid distortion value of the optical system 10 is controlled within 2.5% when the reference wavelength is 555nm, which is beneficial to further reducing the TV distortion on the basis of realizing a large field angle, and can remarkably reduce the degree of image distortion, improve the imaging quality, and bring more realistic shooting experience with a large depth of field and a large field angle to users. In some embodiments, the conditional expression satisfied by the optical system 10 may be specifically 0.85, 0.88, 0.91, 0.93, 0.94, 1.18, or 1.26.

It should be noted that the refractive index, abbe number, and effective focal length in the above conditional expressions are all 587.6nm, and the effective focal length is at least the value of the corresponding lens or lens group at the paraxial region. And the above conditional expressions and the technical effects thereof are directed to the five-piece optical system 10 having the lens design described above. If the lens design (lens number, refractive power configuration, surface configuration, etc.) of the optical system 10 cannot be ensured, it is difficult to ensure that the optical system 10 still has the corresponding technical effects when these conditional expressions are satisfied, and even the imaging performance may be significantly degraded.

In some embodiments, at least one lens in the optical system 10 has an aspherical surface profile, i.e., when at least one side surface (object side or image side) of the lens is aspherical, the lens may be said to have an aspherical surface profile. Specifically, the object side surface and the image side surface of each lens can be designed to be aspherical. The aspheric surface type arrangement can further help the optical system 10 to eliminate aberration more effectively, improve imaging quality, and facilitate miniaturization design of the optical system 10, so that the optical system 10 can have excellent optical effects while maintaining miniaturization design. Of course, in other embodiments, at least one lens of the optical system 10 may have a spherical surface shape, and the design of the spherical surface shape may reduce the difficulty of manufacturing the lens and reduce the manufacturing cost. It should be noted that there may be some deviation in the ratio of the dimensions of the thickness, surface curvature, etc. of each lens in the drawings. It should also be noted that when the object side or image side of a lens is aspheric, the surface may have a curvature, and the shape of the surface from center to edge will change.

In some embodiments, the material of at least one lens in the optical system 10 is Plastic (PC), which may be a polycarbonate, a gum, or the like. In some embodiments, the material of at least one lens in the optical system 10 is Glass (GL). The lens with plastic material can reduce the production cost of the optical system 10, while the lens with glass material can withstand higher or lower temperature and has excellent optical effect and better stability. In some embodiments, at least two lenses of different materials may be disposed in the optical system 10, for example, a combination of glass lenses and plastic lenses may be used, but the specific configuration relationship may be determined according to practical needs, which is not meant to be exhaustive.

The optical system 10 of the present application is illustrated by the following more specific examples:

first embodiment

Referring to fig. 1, in the first embodiment, the optical system 10 includes, in order from an object side to an image side, a first lens element L1 with negative refractive power, a second lens element L2 with positive refractive power, an aperture stop STO, a third lens element L3 with positive refractive power, a fourth lens element L4 with negative refractive power, and a fifth lens element L5 with positive refractive power. The surface profile of each lens surface in the optical system 10 is as follows:

the object side surface S1 of the first lens element L1 is convex at a paraxial region, and the image side surface S2 is concave at a paraxial region; the object side surface S1 is convex at the circumference, and the image side surface S2 is convex at the circumference.

The object side surface S3 of the second lens element L2 is convex at a paraxial region, and the image side surface S4 is concave at a paraxial region; the object side surface S3 is concave at the circumference, and the image side surface S4 is concave at the circumference.

The third lens element L3 has a convex object-side surface S5 at a paraxial region and a convex image-side surface S6 at a paraxial region; the object side surface S5 is convex at the circumference and the image side surface S6 is concave at the circumference.

The fourth lens element L4 has a concave object-side surface S7 at a paraxial region and a concave image-side surface S8 at a paraxial region; the object side surface S7 is convex at the circumference and the image side surface S8 is concave at the circumference.

The fifth lens element L5 has a convex object-side surface S9 at a paraxial region and a concave image-side surface S10 at a paraxial region; the object side surface S9 is concave at the circumference and the image side surface S10 is convex at the circumference.

In the embodiments of the present application, when describing that the lens surface has a certain profile at the paraxial region, it means that the lens surface has the certain profile near the optical axis 101; when describing that the lens surface has a certain profile at the circumference, it is meant that the lens surface has this profile at a position where the effective light transmission area is close to the maximum effective aperture.

In the first embodiment, the object-side surface and the image-side surface of each of the first lens element L1 to the fifth lens element L5 are aspheric, and the material of each lens element is plastic, and particularly, the object-side surface S9 and the image-side surface S10 of the fifth lens element L5 have rotationally asymmetric surface shapes.

The various lens parameters of the optical system 10 in this embodiment are presented in table 1 below. The elements from the object side to the image side of the optical system 10 are sequentially arranged in the order from top to bottom of table 1, with the aperture stop characterizing the aperture stop STO. The filter 110 may be part of the optical system 10 or may be removable from the optical system 10, but the overall optical length of the optical system 110 remains the same after the filter 110 is removed. The filter 110 may be an infrared cut filter. In table 1, the radius Y is the radius of curvature of the corresponding surface of the lens element at the optical axis 101 along the Y direction, wherein the radius Y of the image side surface S10 of the fifth lens element L5 is the radius of curvature of the surface at the optical axis 101 along the Y direction, and the aperture Y is half of the maximum effective aperture of the corresponding lens element surface along the Y direction. The absolute value of the first value of the lens in the "thickness" parameter row is the thickness of the lens on the optical axis 101, and the absolute value of the second value is the distance from the image side of the lens to the subsequent optical element (lens or diaphragm) on the optical axis 101, wherein the thickness parameter of the diaphragm represents the distance from the diaphragm surface to the object side of the adjacent lens on the optical axis 101. SPH in the table means a sphere, ASP means an aspherical surface, and AAS means a non-rotational symmetry plane. The refractive index, abbe number, and focal length (effective focal length) of each lens in the table are 587.56nm, and the Y radius, thickness, and focal length (effective focal length) are all in millimeters (mm). In addition, the parameter data and the lens surface type structure used for the relational computation in the following embodiments are based on the data in the lens parameter table in the corresponding embodiments.

TABLE 1

As can be seen from table 1, the optical system 10 of the first embodiment has an effective focal length f of 1.256mm in the Y direction, an f-number FNO of 2.30, a maximum field angle FOV of 119.995 °, and an optical total length TTL of 4.950mm, and has a wide-angle characteristic. When the image sensor is assembled, the FOV can also be understood as the maximum field angle of the optical system 10 in the diagonal direction of the rectangular effective pixel area of the corresponding image sensor.

Table 2 below presents the aspherical coefficients of the corresponding lens surfaces in table 1, where K is a conic coefficient and Ai is a coefficient corresponding to the i-th order higher order term in the aspherical surface type formula.

TABLE 2

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The surface type calculation of the aspherical surface can refer to an aspherical surface formula:

in the above equation (1), Z is the sagittal height of the corresponding position of the lens surface, r is the distance from the corresponding position of the lens surface to the optical axis, c is the curvature of the lens surface at the optical axis 101, k is the conic coefficient, and Ai is the coefficient corresponding to the i-th order higher order term. It should be noted that the actual planar shape of the lens is not limited to the shape shown in the drawings, which are not drawn to scale, and may differ from the actual planar structure of the lens to some extent.

Table 3 below shows the non-rotational surface coefficients of the surface of the fifth lens L5 in Table 1, where K is the conic coefficient, C _(j+1) Is a coefficient corresponding to the i-th order higher order term in the non-rotating surface type formula.

TABLE 3 Table 3

The Y radius is the radius of curvature of the respective lens surface at the optical axis 101 and in the Y direction, and the X radius is the radius of curvature of the respective lens surface at the optical axis 101 and in the X direction.

In the above equation (2), Z is the sagittal height of the corresponding position of the lens surface, r is the distance from the corresponding position of the lens surface to the optical axis, c is the curvature of the lens surface at the optical axis 101, k is the conic coefficient, and ZP _j Is the j th Zernike polynomial, C _(j+1) Is ZP _j Coefficients of (i.e., coefficients corresponding to the j-th Zernike polynomial); in Table 3 above, the Zernike polynomials are derived from ZP ₁ Item to ZP ₆₆ The term, having corresponding non-rotational surface coefficients from C2 to C67, gives no non-rotational surface coefficient of 0. It should be noted that the actual planar shape of the lens is not limited to the shape shown in the drawings, which are not drawn to scale, and may differ from the actual planar structure of the lens to some extent.

In the first embodiment, the optical system 10 satisfies the following conditional expressions:

tan (semiFOV)/sag11= 4.441; satisfying 3.0mm < tan (semiFOV)/sag 11<4.5mm, the sagittal height of the object side surface S1 of the first lens L1 can be reasonably constrained, which is beneficial for the optical system 10 to obtain a larger field of view; on the other hand, the object side surface S1 of the first lens L1 is advantageously prevented from being excessively bent, which may cause difficulty in processing the first lens L1, and the processing feasibility of the first lens is improved.

f5/f=1.577; when the above condition of 1.5< f5/f <2.0 is satisfied, since the fifth lens element L5 is configured with a non-rotationally symmetrical surface shape, and the non-rotationally symmetrical surface shape has a higher degree of freedom, the positive refractive power provided by the fifth lens element L5 is reasonably configured, which is favorable for correcting the aberration generated by the front lens group, ensuring the aberration balance of the optical system 10 as a whole, and reducing the deflection angle of the external field light, so that smooth transition of the light beam to the imaging surface S11 can be realized to improve the imaging quality.

f4/r42= -0.453; satisfying the above-mentioned condition-1.6 < f4/r42< -0.4, by controlling the ratio between the negative refractive power of the fourth lens element L4 and the radius of curvature r42 of the image-side surface S8 of the fourth lens element L4 at the optical axis within a reasonable range, on one hand, the distortion generated by the lens assembly (i.e., the first lens element L1-fourth lens element L4) before the fourth lens element L4 is corrected by matching with the fifth lens element L4 is facilitated to improve the imaging quality, on the other hand, the shape of the image-side surface S8 of the fourth lens element L4 is facilitated to be controlled, the sensitivity is reduced, and the processing difficulty of the fourth lens element L4 is reduced.

f4 -2.563; when-2.70 < f4 < -2.07 is satisfied, the negative refractive power of the fourth lens L4 is set to be-2.563, so that the fourth lens L4 and the fifth lens L5 are matched together to correct the distortion generated by the front lens group, the integral distortion of the optical system 10 is effectively reduced, and the imaging quality is further improved.

r42=5.658 mm; when 1.39 < r42< 5.66 is satisfied, the curvature radius r42 of the image side surface S8 of the fourth lens L4 at the optical axis is set to 5.658mm, so that the degree of surface curvature of the image side surface S8 of the fourth lens L4 is controlled, the sensitivity of the fourth lens L4 is effectively reduced, and the lens processing is facilitated.

(r12—r11)/f1=4.326; when the above condition of 1.0< (r 12-r 11)/f 1<4.5 is satisfied, by the cooperation of the positive refractive power of the first lens element L1 and the surface profile, and by reasonably configuring the refractive power of the first lens element L1 and the surface profile bending difference between the object side surface S1 and the image side surface S2 of the first lens element L1, on one hand, it is beneficial to obtain the light rays with large angles to obtain the large field of view characteristic, and on the other hand, it is beneficial to avoid the excessive deflection of the marginal light rays when passing through the two side surfaces of the first lens element L1, to reduce the bending degree of the light rays at the image side surface S2 of the first lens element L1, to reduce the astigmatic quantity of the optical system 10, to ensure that the optical system 10 has large field of view and small distortion, and to further improve the imaging quality.

(ct1+ct5)/(ct2+ct3+ct4) =0.760; satisfying the above condition of 0.7< (ct1+ct5)/(ct2+ct3+ct4) <0.8, the ratio of the thicknesses of the lenses (the first lens L1 to the fifth lens L5) in the optical system on the optical axis is controlled, which is beneficial to balancing the refractive power distribution of the lenses in the optical system 10 and balancing the spherical aberration of the system, so as to ensure the optical system 10 to have better imaging quality and assembly stability.

(et3+et4)/(sd31+sd42) =0.489; the numerical control of (et 3+ et 4)/(sd 31+ sd 42) is controlled in a reasonable range to satisfy the condition of 0.45< (et 3+ et 4)/(sd 31+ sd 42) <0.55, so that the excessive difference between the edge thickness and the maximum effective half caliber of the third lens L3 and the fourth lens L4 can be avoided, the volume of the optical system 10 can be reduced, the miniaturization characteristic can be satisfied, the over-bending of the whole surface type of the third lens L3 and the fourth lens L4 can be avoided, the assembly difficulty can be effectively reduced, and the resolution of the optical system 10 can be improved.

sd 52/ttl=0.489; satisfying the condition of 0.35< sd52/TTL <0.40 is beneficial to shortening the total length of the optical system 10 and leaving enough back focal space for lens barrel design under the premise of ensuring that the marginal light at the image side surface S10 of the fifth lens L5 smoothly transits to the imaging surface S11 at a smaller deflection angle, and is also beneficial to reducing the molding assembly difficulty of each lens and improving the imaging quality.

f/epd= 2.299; on the premise that the aperture stop STO is arranged between the first lens L1 and the second lens L2, when the f/EPD <2.3 condition is satisfied, the optical system 10 can have larger aperture and higher light flux, thereby increasing the imaging effect of the optical system 10 when working in dark environment, and reducing the aberration of the marginal field of view.

tan (semiFOV)/tvdmax=0.936; satisfying the above condition of 0.8< tan (semiFOV)/TVDmax <1.3, by introducing a non-rotationally symmetrical surface shape into at least one of the object side surface S9 and the image side surface S10 of the fifth lens L5, the degree of freedom of the curved surface of the fifth lens L5 is increased, and then the maximum value of the absolute value of the grid distortion value is controlled to be within 2.5% when the reference wavelength is 587.6nm, which is beneficial to further reducing the TV distortion on the basis of realizing a large field angle, can remarkably reduce the degree of image distortion, improve the imaging quality, and bring more realistic shooting experience with a large depth of field and a large field angle to users.

Fig. 2 shows the relative magnitudes of RMS spots of the optical system 10 at different locations within a quadrant of the imaging plane (reference wavelength of the RMS spot plot is 555 nm) in the first embodiment, so as to reflect the relative dispersions of RMS spots in different areas of the imaging plane, corresponding to the central field of view of the optical system 10 at (0, 0). Fig. 2 shows the relationship between the RMS spot diameter and the true light image height, and the abscissa indicates the true light image height in the X direction and the ordinate indicates the true light image height in the Y direction. The scale of the abscissa (0.5 mm per cell) in the figure reflects the true scale of the effective imaging area of the imaging plane, while the size of each spot in the figure is an enlarged case. The actual size of each light spot should refer to the scale (0.027 mm per grid) at the upper right in the figure, and the actual size of the light spot at the corresponding position on the imaging surface can be obtained through the proportional relation between the size of the light spot in the figure and the scale. As can be seen from FIG. 2, the minimum RMS spot diameter is 0.0017529mm, the maximum RMS spot diameter is 0.0099466mm, the average of the RMS spot diameters is 0.0039795mm, and the standard deviation of the RMS spot diameter is 0.00020324mm. It can be seen that the light rays of most fields of view can achieve good convergence at the imaging surface S11, and the dispersion of the external field is well suppressed, so that the optical system 10 has excellent imaging definition.

Fig. 3 shows a TV distortion chart (reference wavelength of TV distortion chart is 555 nm) of the optical system 10 in the first embodiment, which shows the distortion difference between the actual imaging light and the paraxial imaging light in the vertical region and the horizontal region, TV distortion (V) in the chart refers to the distortion in the vertical region, and TV distortion (H) refers to the distortion in the horizontal region, and it is known from the TV distortion chart that the maximum distortion of the optical system 10 having the wide angle characteristic in the vertical region is 0.1074%, the maximum distortion of the optical system 10 in the horizontal region is 1.8500%, and the distortion degree is well controlled.

Second embodiment

Referring to fig. 4, in the second embodiment, the optical system 10 includes, in order from the object side to the image side, a first lens element L1 with negative refractive power, a second lens element L2 with positive refractive power, an aperture stop STO, a third lens element L3 with positive refractive power, a fourth lens element L4 with negative refractive power, and a fifth lens element L5 with positive refractive power. The surface profile of each lens surface in the optical system 10 is as follows:

the object side surface S1 of the first lens element L1 is convex at a paraxial region, and the image side surface S2 is concave at a paraxial region; the object side surface S1 is convex at the circumference, and the image side surface S2 is concave at the circumference.

In addition, the parameters of each lens of the optical system 10 in the second embodiment are given in tables 4, 5 and 6, wherein the definition of each structure and parameter can be obtained in the first embodiment, and the description thereof is omitted herein.

TABLE 4 Table 4

TABLE 5

TABLE 6

The optical system 10 in this embodiment satisfies the following relationship:

fig. 5 reflects the relative size of the RMS spot diameter of the optical system 10 in the corresponding area of the imaging surface S11 (reference wavelength of the RMS spot diagram is 555 nm), and specific parameters of the RMS spot can refer to the data given in the diagram, which shows that the dispersion degree of the RMS spot in each field area of the optical system 10 is effectively controlled. In summary, it can be determined that the optical system 10 of this embodiment can possess high-quality imaging. Fig. 6 shows a TV distortion chart (reference wavelength of TV distortion chart is 555 nm) of the optical system 10 in the second embodiment, the maximum distortion of the optical system 10 having the wide angle characteristic in the vertical region is-0.3850%, the maximum distortion of the optical system 10 in the horizontal region is 2.0721%, and the degree of distortion is well controlled.

Third embodiment

Referring to fig. 7, in the third embodiment, the optical system 10 includes, in order from the object side to the image side, a first lens element L1 with negative refractive power, a second lens element L2 with positive refractive power, an aperture stop STO, a third lens element L3 with positive refractive power, a fourth lens element L4 with negative refractive power, and a fifth lens element L5 with positive refractive power. The surface profile of each lens surface in the optical system 10 is as follows:

In addition, the parameters of each lens of the optical system 10 in the third embodiment are given in tables 7, 8 and 9, wherein the definition of each structure and parameter can be obtained in the first embodiment, and the description thereof is omitted herein.

TABLE 7

TABLE 8

TABLE 9

The optical system 10 in this embodiment satisfies the following relationship:

fig. 8 reflects the relative size of the RMS spot diameter of the optical system 10 in the corresponding area of the imaging surface S11 (reference wavelength of the RMS spot diagram is 555 nm), and specific parameters of the RMS spot can refer to the data given in the diagram, which shows that the dispersion degree of the RMS spot in each field area of the optical system 10 is effectively controlled. In summary, it can be determined that the optical system 10 of this embodiment can possess high-quality imaging. Fig. 9 shows a TV distortion chart (reference wavelength of TV distortion chart is 555 nm) of the optical system 10 in the third embodiment, the maximum distortion of the optical system 10 having the wide angle characteristic in the vertical region is-0.08106%, the maximum distortion of the optical system 10 in the horizontal region is 1.5937%, and the degree of distortion is well controlled.

Fourth embodiment

Referring to fig. 10, in the fourth embodiment, the optical system 10 includes, in order from the object side to the image side, a first lens element L1 with negative refractive power, a second lens element L2 with positive refractive power, an aperture stop STO, a third lens element L3 with positive refractive power, a fourth lens element L4 with negative refractive power, and a fifth lens element L5 with positive refractive power. The surface profile of each lens surface in the optical system 10 is as follows:

The fourth lens element L4 has a convex object-side surface S7 at a paraxial region and a concave image-side surface S8 at a paraxial region; the object side surface S7 is concave at the circumference, and the image side surface S8 is concave at the circumference.

The fifth lens element L5 has a convex object-side surface S9 at a paraxial region and a concave image-side surface S10 at a paraxial region; the object side surface S9 is convex at the circumference and the image side surface S10 is concave at the circumference.

In addition, the parameters of each lens of the optical system 10 in the fourth embodiment are given in tables 10, 11 and 12, wherein the definition of each structure and parameter can be derived from the first embodiment, and the details are not repeated here.

Table 10

TABLE 11

Table 12

The optical system 10 in this embodiment satisfies the following relationship:

fig. 11 reflects the relative size of the RMS spot diameter of the optical system 10 in the corresponding area of the imaging surface S11 (reference wavelength of the RMS spot diagram is 555 nm), and specific parameters of the RMS spot can refer to the data given in the diagram, which shows that the dispersion degree of the RMS spot in each field area of the optical system 10 is effectively controlled. In summary, it can be determined that the optical system 10 of this embodiment can possess high-quality imaging. Fig. 12 shows a TV distortion chart (reference wavelength of TV distortion chart is 555 nm) of the optical system 10 in the fourth embodiment, the maximum distortion of the optical system 10 having the wide angle characteristic in the vertical region is-0.8664%, the maximum distortion of the optical system 10 in the horizontal region is 2.1744%, and the degree of distortion is well controlled.

Fifth embodiment

Referring to fig. 13, in the fifth embodiment, the optical system 10 includes, in order from the object side to the image side, a first lens element L1 with negative refractive power, a second lens element L2 with positive refractive power, an aperture stop STO, a third lens element L3 with positive refractive power, a fourth lens element L4 with negative refractive power, and a fifth lens element L5 with positive refractive power. The surface profile of each lens surface in the optical system 10 is as follows:

The third lens element L3 has a convex object-side surface S5 at a paraxial region and a convex image-side surface S6 at a paraxial region; the object side surface S5 is concave at the circumference and the image side surface S6 is convex at the circumference.

In addition, the parameters of each lens of the optical system 10 in the fifth embodiment are given in tables 13, 14 and 15, wherein the definition of each structure and parameter can be obtained in the first embodiment, and the details are not repeated here.

TABLE 13

TABLE 14

TABLE 15

The optical system 10 in this embodiment satisfies the following relationship:

fig. 14 reflects the relative size of the RMS spot diameter of the optical system 10 in the corresponding area of the imaging surface S11 (reference wavelength of the RMS spot diagram is 555 nm), and specific parameters of the RMS spot can refer to the data given in the diagram, which shows that the dispersion degree of the RMS spot in each field area of the optical system 10 is effectively controlled. In summary, it can be determined that the optical system 10 of this embodiment can possess high-quality imaging. Fig. 15 shows a TV distortion chart (reference wavelength of TV distortion chart is 555 nm) of the optical system 10 in the fourth embodiment, the maximum distortion of the optical system 10 having the wide angle characteristic in the vertical region is-0.9189%, the maximum distortion of the optical system 10 in the horizontal region is 2.4511%, and the degree of distortion is well controlled.

In the above first to fifth embodiments, the optical system 10 not only has the wide-angle characteristic but also can effectively suppress the longitudinal spherical aberration, curvature of field, astigmatism and distortion aberration of the optical system 10 by the corresponding refractive power, physical parameters and surface design (particularly, the last lens has the non-rotationally symmetrical surface shape), so that the high-quality imaging effect can be obtained.

In addition, referring to fig. 16, some embodiments of the present application further provide an image capturing module 20, where the image capturing module 20 may include the optical system 10 and the image sensor 210 according to any of the above embodiments, and the image sensor 210 is disposed on the image side of the optical system 10. The image sensor 210 may be a CCD (Charge Coupled Device ) or CMOS (Complementary Metal Oxide Semiconductor, complementary metal oxide semiconductor). Generally, the imaging surface S11 of the optical system 10 overlaps the photosensitive surface of the image sensor 210 at the time of assembly. By adopting the optical system 10, the optical distortion of the camera module 20 can be effectively inhibited, so that the imaging quality can be improved.

Referring to fig. 17, some embodiments of the present application also provide an electronic device 30. The electronic device 30 includes a fixing member 310, and the camera module 20 is mounted on the fixing member 310, where the fixing member 310 may be a display screen, a touch display screen, a circuit board, a middle frame, a rear cover, and the like. The electronic device 30 may be, but is not limited to, a smart phone, a smart watch, smart glasses, an electronic book reader, a vehicle-mounted camera device, a monitoring device, a drone, a medical device (e.g., an endoscope), a tablet computer, a biometric device (e.g., a fingerprint recognition device or a pupil recognition device, etc.), a PDA (Personal Digital Assistant, a personal digital assistant), a drone, etc. In some embodiments, when the electronic device 30 is a smart phone, the camera module 20 may be used as a rear camera module of the device. When the electronic device 30 is used to shoot a scene, the distortion degree of the image can be effectively controlled, and the shooting quality can be better improved.

The technical features of the above-described embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above-described embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be regarded as the scope of the description.

The above examples illustrate only a few embodiments of the invention, which are described in detail and are not to be construed as limiting the scope of the invention. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the invention, which are all within the scope of the invention. Accordingly, the scope of protection of the present invention is to be determined by the appended claims.

Claims

1. An optical system, characterized in that the number of lenses with refractive power in the optical system is five, and the optical system sequentially comprises, from an object side to an image side along an optical axis:

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

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

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

a fifth lens element with positive refractive power having a concave image-side surface at a paraxial region, wherein the object-side surface and the image-side surface of the fifth lens element are aspheric, and at least one of the object-side surface and the image-side surface of the fifth lens element has an asymmetric surface profile;

and the optical system satisfies the following conditional expression:

3.0mm ^-1 <tan(semiFOV)/sag11<4.5mm ^-1 ；

1.5<f5/f<2.0；

the semiFOV is half of the maximum field angle of the optical system, tan (semiFOV) is a tangent value of half of the maximum field angle of the optical system, sag11 is a sagittal height of the object side surface of the first lens at the maximum effective caliber, f5 is an effective focal length of the fifth lens, and f is an effective focal length of the optical system.

2. The optical system of claim 1, wherein the object side and the image side of the first lens, the second lens, the third lens, and the fourth lens are aspheric.

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

-1.6<f4/r42<-0.4；

wherein f4 is an effective focal length of the fourth lens element, and r42 is a radius of curvature of an image-side surface of the fourth lens element at an optical axis.

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

1.0<(r12-r11)/f1<4.5；

wherein r12 is a radius of curvature of the image side surface of the first lens element at the optical axis, r11 is a radius of curvature of the object side surface of the first lens element at the optical axis, and f1 is an effective focal length of the first lens element.

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

0.7<(ct1+ct5)/(ct2+ct3+ct4)<0.8；

wherein ct1 is the thickness of the first lens element on the optical axis, ct5 is the thickness of the fifth lens element on the optical axis, ct2 is the thickness of the second lens element on the optical axis, ct3 is the thickness of the third lens element on the optical axis, and ct4 is the thickness of the fourth lens element on the optical axis.

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

0.45<(et3+et4)/(sd31+sd42)<0.55；

wherein, et3 is the distance between the object-side surface maximum effective half caliber of the third lens and the image-side surface maximum effective half caliber of the third lens in the optical axis direction, et4 is the distance between the object-side surface maximum effective half caliber of the fourth lens and the image-side surface maximum effective half caliber of the fourth lens in the optical axis direction, sd31 is the object-side surface maximum effective half caliber of the third lens, sd42 is the image-side surface maximum effective half caliber of the fourth lens.

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

0.35<sd52/TTL<0.40；

wherein sd52 is the maximum effective half aperture of the image side surface of the fifth lens, and TTL is the total optical length of the optical system.

8. The optical system of claim 1, further comprising an aperture stop disposed between the first lens and the second lens, and wherein the optical system satisfies the conditional expression:

f/EPD<2.3；

wherein EPD is the entrance pupil diameter of the optical system.

9. An imaging module comprising an image sensor and the optical system of any one of claims 1 to 8, wherein the image sensor is disposed on an image side of the optical system.

10. An electronic device, comprising a fixing member and the camera module set according to claim 9, wherein the camera module set is disposed on the fixing member.