CN112882189A

CN112882189A - Optical system, camera module and electronic device

Info

Publication number: CN112882189A
Application number: CN201911207169.3A
Authority: CN
Inventors: 邹金华; 刘彬彬; 李明
Original assignee: Jiangxi Jingchao Optical Co Ltd
Current assignee: Jiangxi Jingchao Optical Co Ltd
Priority date: 2019-11-29
Filing date: 2019-11-29
Publication date: 2021-06-01

Abstract

The invention relates to an optical system, a camera module and an electronic device. The optical system includes in order from an object side to an image side: a first lens element with positive refractive power; a second lens; a third lens; the image side surface of the fourth lens is a concave surface at the optical axis, both the object side surface and the image side surface of the fourth lens are aspheric surfaces, and at least one surface of the object side surface and the image side surface of the fourth lens has an inflection point; the optical system comprises an aperture, wherein the aperture is arranged on the object side of the first lens or between the first lens and the fourth lens; the optical system satisfies: SL/TTL is more than 0.5 and less than 0.9; -1 < SAG31/CT3 < 0; SL is the distance from the aperture stop to the imaging surface of the optical system on the optical axis, TTL is the distance from the object-side surface of the first lens element to the imaging surface of the optical system on the optical axis, SAG31 is the rise of the object-side surface of the third lens element, and CT3 is the thickness of the third lens element on the optical axis. The optical system satisfying the above relationship has excellent image quality.

Description

Optical system, camera module and electronic device

Technical Field

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

Background

In recent years, with the development of photography technology, the demands of consumers for the function diversification and high imaging quality of camera modules are increasing. However, for a general camera module, when the camera module is used for macro photography, the relative brightness of the optical system in the marginal field of view is insufficient, resulting in poor imaging quality.

Disclosure of Invention

Therefore, it is necessary to provide an optical system, a camera module and an electronic device for improving the imaging quality of the camera module during macro shooting.

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

a first lens element with positive refractive power;

a second lens element with refractive power;

a third lens element with refractive power; and

the image side surface of the fourth lens element is concave at the optical axis, both the object side surface and the image side surface of the fourth lens element are aspheric, and at least one of the object side surface and the image side surface of the fourth lens element has an inflection point;

the optical system comprises an aperture, and the aperture is arranged on the object side of the first lens or between the first lens and the fourth lens;

and the optical system satisfies the relationship:

0.5＜SL/TTL＜0.9；

-1＜SAG31/CT3＜0；

wherein SL is an axial distance between the aperture stop and the image plane of the optical system, TTL is an axial distance between the object-side surface of the first lens element and the image plane of the optical system, SAG31 is a rise of the object-side surface of the third lens element, SAG31 is a vector between an intersection point of the object-side surface of the third lens element on the optical axis and the maximum effective half aperture position of the third lens element, the vector is positive in the image-side direction of the optical system and negative in the object-side direction, and CT3 is an axial thickness of the third lens element.

When the refractive power configuration and relationship of the lens are satisfied, the optical system has the characteristic of a small field of view, is beneficial to improving the imaging quality during macro shooting, and has the characteristics of small depth of field and virtual background. Specifically, when the optical system satisfies the relationship of SL/TTL being greater than 0.5 and less than 0.9, the optical system has a structure with a middle aperture, and the aperture is reasonably disposed in the optical system, so that the aperture of the object-side surface of the first lens is increased, thereby effectively controlling the cone angle of light rays in the marginal field when entering the optical system, adjusting the light entering amount of the optical system, increasing the relative brightness of the marginal field, and further improving the imaging quality. When the condition that SAG31/CT3 is more than-1 and less than 0 is met, the distortion and the field curvature of the optical system are favorably corrected, and the imaging quality is improved. When SAG31/CT3 is more than or equal to 0, the surface shape of the object side surface of the third lens at the circumference (the maximum effective half aperture) is too smooth, so that the refractive power of the light rays in the off-axis field is insufficient, and the distortion and the field curvature aberration are not corrected. When SAG31/CT3 is less than or equal to-1, the surface shape of the object side surface of the third lens at the circumference (the position of the maximum effective half aperture) is excessively bent, thus the lens molding is poor easily, and the manufacturing yield is influenced.

In one embodiment, the optical system satisfies the relationship:

0.4＜DT11/DT42＜0.9；

wherein DT11 is the maximum effective half aperture at the object side of the first lens, and DT42 is the maximum effective half aperture at the image side of the fourth lens. When the relation is met, the maximum effective half apertures of the object side surface of the first lens and the image side surface of the fourth lens are reasonably configured, so that the incident angle of the chief ray can be effectively controlled, the relative brightness of the marginal field of view is improved, and the imaging quality of the optical system is improved.

In one embodiment, the optical system satisfies the relationship:

20mm＜OBL＜40mm；

the OBL is the distance between the object plane of the optical system and the object side surface of the first lens on the optical axis, and a shot object located on the object plane can form clear imaging on the imaging plane of the optical system. When the optical system meets the relation that 20mm < OBL < 40mm, a shot object positioned on the object plane (or understood to be positioned in the distance range) can form clear imaging on the imaging plane of the optical system, so that the macro shooting performance of the optical system is fully embodied.

In one embodiment, the optical system satisfies the relationship:

0.1＜|SAG41|/CT4＜2.0；

SAG41 is the rise of the object side surface of the fourth lens, namely SAG41 is a vector from the intersection point of the object side surface of the fourth lens on the optical axis to the position of the maximum effective half aperture of the surface in the direction parallel to the optical axis, the vector is positive when facing the image side direction of the optical system and negative when facing the object side direction, and CT4 is the thickness of the fourth lens on the optical axis. When the relation is met, the incidence angle of the chief ray incident to the imaging surface of the optical system can be reduced, and meanwhile, the incidence angle of the ray at the maximum view field on the object side surface of the fourth lens can be effectively controlled, so that when the slope change of the object side surface of the fourth lens is large, the reflection energy caused by uneven coating can be reduced, and the generation of stray light is avoided.

In one embodiment, the optical system satisfies the relationship:

-1≤f1/f2≤1；

wherein f1 is the effective focal length of the first lens, and f2 is the effective focal length of the second lens. The first lens provides positive refractive power for the optical system, so that light rays are favorably converged and enter the optical system better, and the optical system has a long-focus characteristic. When the optical system satisfies the condition that f1/f2 is more than or equal to-1 and less than or equal to 0, the second lens provides negative refractive power for the optical system, so that light rays are favorably diverged, and aberration is effectively corrected. When the optical system satisfies the condition that f1/f2 is more than 0 and less than or equal to 1, the main surface of the optical system moves forwards, so that the focal length of the optical system can be increased, the optical system has the characteristic of small visual field and the characteristic of long focal length, and the excellent macro shooting effect is realized.

In one embodiment, the optical system satisfies the relationship:

FNO≤3.55；

wherein FNO is an f-number of the optical system. When the relation is met, the light transmission quantity of the optical system can be increased, the optical system can acquire clear detailed information of a shot object under a dark environment or under the condition of insufficient light, and therefore the imaging quality is improved.

In one embodiment, the optical system satisfies the relationship:

0.5＜CT3/CT2＜3.0；

wherein CT2 is the thickness of the second lens element on the optical axis, and CT3 is the thickness of the third lens element on the optical axis. When the relation is satisfied, the relative brightness of the edge view field of the optical system can be effectively improved, and meanwhile, the yield of the lens during assembly can be improved.

In one embodiment, the optical system satisfies the relationship:

0.1＜R1/R9＜0.7；

wherein R1 is a curvature radius of an object side surface of the first lens at an optical axis, and R9 is a curvature radius of an image side surface of the fourth lens at the optical axis. When the above relationship is satisfied, the incident angle of light entering the optical system can be reduced, and the angle of field of the optical system can be made small.

In one embodiment, the optical system satisfies the relationship:

-3＜(f2+f4)/f＜1；

wherein f2 is an effective focal length of the second lens, f4 is an effective focal length of the fourth lens, and f is an effective focal length of the optical system. When the relationship is met, the effective focal lengths of the second lens and the fourth lens and the effective focal length of the optical system can form reasonable configuration, the magnification of the optical system in a macro shooting distance is ensured, the identification precision is ensured, meanwhile, the aberration of the optical system can be reduced, and the imaging quality of the optical system is improved.

An image capturing module includes a light sensing element and the optical system of any of the above embodiments, wherein the light sensing element is disposed on an image side of the fourth lens element.

By adopting the optical system, the camera module has the characteristics of small visual angle, small depth of field and virtual background. Simultaneously, when the module of making a video recording is being applied to the microspur when shooing, the relative luminance of marginal visual field will be promoted to can effectively improve the imaging quality.

In one embodiment, the camera module satisfies the following relationship:

TTL/ImgH＜2.65；

wherein ImgH is half of the diagonal length of the effective pixel area on the photosensitive element. When the above relation is satisfied, the camera module can meet the high pixel requirement, and the miniaturization of the module size is maintained.

An electronic device comprises a shell and the camera module, wherein the camera module is arranged on the shell.

Through adopting the camera module, the electronic device has excellent imaging quality when shooting at a micro distance.

Drawings

FIG. 1 is a schematic view of an optical system according to a first embodiment of the present disclosure;

fig. 2 is a spherical aberration diagram (mm), an astigmatism diagram (mm), and a distortion diagram (%);

FIG. 3 is a schematic view of an optical system provided in a second embodiment of the present application;

fig. 4 is a spherical aberration diagram (mm), an astigmatism diagram (mm), and a distortion diagram (%);

FIG. 5 is a schematic view of an optical system provided in a third embodiment of the present application;

fig. 6 is a spherical aberration diagram (mm), an astigmatism diagram (mm), and a distortion diagram (%);

FIG. 7 is a schematic view of an optical system provided in a fourth embodiment of the present application;

fig. 8 is a spherical aberration diagram (mm), an astigmatism diagram (mm), and a distortion diagram (%);

fig. 9 is a schematic view of an optical system provided in a fifth embodiment of the present application;

fig. 10 is a spherical aberration diagram (mm), an astigmatism diagram (mm), and a distortion diagram (%);

FIG. 11 is a schematic view of an optical system provided in a sixth embodiment of the present application;

fig. 12 is a spherical aberration diagram (mm), an astigmatism diagram (mm), and a distortion diagram (%)' of the optical system in the sixth embodiment;

fig. 13 is a schematic view of a camera module according to an embodiment of the present application;

fig. 14 is a schematic view of an electronic device according to an embodiment of the disclosure.

Detailed Description

To facilitate an understanding of the invention, the invention will now be described more fully with reference to the accompanying drawings. Preferred embodiments of the present invention are shown in the drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

It will be understood that when an element is referred to as being "secured to" 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. In contrast, when an element is referred to as being "directly on" another element, there are no intervening elements present. The terms "vertical," "horizontal," "left," "right," and the like as used herein are for illustrative purposes only.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

In fig. 1, in an embodiment of the present application, an optical system 10 includes, in order from an object side to an image side, a first lens element L1 with positive refractive power, a second lens element L2 with refractive power, a third lens element L3 with refractive power and a fourth lens element L4 with refractive power. The optical system 10 further includes a stop STO disposed between the first lens L1 and the second lens L2. The lenses and the stop STO of the optical system 10 are coaxially arranged, that is, the centers of the lenses and the stop STO are located on the same straight line, which may also be referred to as the optical axis of the optical system 10.

In some embodiments, the stop STO may also be disposed on the object side of the first lens L1. In other embodiments, the stop STO is disposed between the first lens L1 and the fourth lens L4, for example, between the second lens L2 and the third lens L3 or between the third lens L3 and the fourth lens L4. On the other hand, in some embodiments, the stop STO can be disposed on the object-side surface or the image-side surface of any lens in the optical system 10, and in this case, the projection of the stop STO on the optical axis and the projection of the lens on the optical axis overlap. In the above, it can be understood that the stop STO can be disposed between the object side of the first lens L1 and the fourth lens L4.

In this embodiment, the first lens L1, the second lens L2, the third lens L3, and the fourth lens L4 each include only one lens. It should be noted that, in some embodiments, any one of the first lens L1, the second lens L2, the third lens L3 and the fourth lens L4 may be a lens group composed of two or more lenses, for example, the first lens L1, the second lens L2 and the third lens L3 respectively include only one lens, and the fourth lens L4 is composed of two or more lenses; or the first lens L1 and the second lens L2 each include only one piece of lens, and the third lens L3 and the fourth lens L4 each include two pieces of lens.

The first lens L1 includes an object-side surface S1 and an image-side surface S2, the second lens L2 includes an object-side surface S3 and an image-side surface S4, the third lens L3 includes an object-side surface S5 and an image-side surface S6, the fourth lens L4 includes an object-side surface S7 and an image-side surface S8, the optical system 10 further includes an image-forming surface S11, the image-forming surface S11 is located on the image-side surface of the fourth lens L4, incident light can be imaged on the image-forming surface S11 after being adjusted by each lens of the optical system 10, and the image-forming surface S11 can be regarded as a photosensitive surface of a photosensitive element for convenience of understanding. The optical system 10 also has an object plane, and a subject on the object plane can form a clear image on the image forming plane S11.

In this embodiment, the object-side surface S7 and the image-side surface S8 of the fourth lens L4 are both aspheric, and the object-side surface S7 and the image-side surface S8 of the fourth lens L4 both have an inflection point. In some embodiments, the object-side and image-side surfaces of the first through fourth lenses L1-L4 are aspheric, and at least one of the object-side and image-side surfaces S7 and S8 of the fourth lens L4 has an inflection point. By configuring the fourth lens L4 as an aspheric lens and configuring the inflection point on the light-transmitting surface of the fourth lens L4, the aberration of the optical system 10 can be effectively corrected, the problem of distortion of the field of view can be solved, and at the same time, the fourth lens L4 can provide excellent optical effect for the optical system 10 in a smaller and thinner condition, and the volume of the optical system 10 can be reduced, so as to realize a miniaturized design.

The surface shape of the aspheric surface can be calculated by referring to an aspheric surface formula:

wherein Z is a distance from a corresponding point on the aspherical surface to a plane tangent to the surface vertex, r is a distance from a corresponding point on the aspherical surface to the optical axis, c is a curvature of the aspherical surface vertex, k is a conic constant, and Ai is a coefficient corresponding to the i-th high-order term in the aspherical surface type formula.

It should be noted that when a side of the lens is described as being convex at the optical axis (the central region of the side), it can be understood that the region of the side of the lens near the optical axis is convex, and thus the side can also be considered as being convex at the paraxial region; when one side of the lens is described as being concave at the circumference, it is understood that the side is concave in the region near the maximum effective half aperture. For example, when the side surface is convex at the optical axis and also convex at the circumference, the shape of the side surface from the center (optical axis) to the edge direction may be a pure convex surface; or first transition from a central convex shape to a concave shape and then become convex near the maximum effective half aperture. Here, examples are made only to explain the relationship between the optical axis and the circumference, and various shape structures (concave-convex relationship) of the side face are not fully embodied, but other cases can be derived from the above examples.

Specifically, the image-side surface S8 of the fourth lens element L4 in some embodiments has an inflection point, and the image-side surface S8 is concave at the optical axis and convex at the circumference. When the fourth lens element L4 satisfies the above-mentioned surface shape, the total length of the optical system 10 is advantageously shortened, and the incident angle of the marginal field of view onto the imaging plane S11 is effectively reduced, so as to improve the efficiency of the light receiving element on the imaging plane S11.

In some embodiments, the first lens L1, the second lens L2, the third lens L3 and the fourth lens L4 are all made of plastic. In other embodiments, the first lens L1 is made of glass, and the second lens L2, the third lens L3, and the fourth lens L4 are made of plastic, at this time, since the lens located at the object side in the optical system 10 is made of glass, the glass lenses located at the object side have a good tolerance effect on extreme environments, and are not easily affected by the object side environment to cause aging and the like, so that when the optical system 10 is in extreme environments such as exposure to high temperature, the structure can effectively avoid the situations that the imaging quality of the optical system 10 is reduced and the service life of the optical system is shortened. Plastic lenses can reduce the weight and cost of the optical system 10, while glass lenses can withstand higher temperatures and have superior optical performance. Of course, the material arrangement of each lens in the optical system 10 is not limited to the above embodiment, and any lens may be made of plastic or glass.

In some embodiments, the image side of the fourth lens L4 is provided with an infrared cut filter L5, or it is understood that an infrared cut filter L5 is disposed between the fourth lens L4 and the image plane S11. The infrared cut filter L5 includes an object side S9 and an image side S10. The infrared cut filter L5 is used to filter the infrared light and prevent the infrared light from reaching the imaging surface S11, thereby preventing the infrared light from interfering with normal imaging. The infrared cut filter L5 may be incorporated together with each lens as part of the optical system 10, or may be incorporated together between the optical system 10 and the light receiving element when the optical system 10 and the light receiving element are incorporated into an image pickup module. In some embodiments, an infrared cut filter L5 may also be disposed on the object side of the first lens L1. In addition, in some embodiments, the infrared cut filter L5 may not be provided, and a filter plating layer may be provided on any one of the first lens L1 to the fourth lens L4 to filter infrared light.

In some embodiments, the optical system 10 may further include an aperture STO, an infrared cut filter L5, a protective glass, a photosensitive element, a mirror for changing an incident light path, and the like, in addition to the lens having refractive power.

In some embodiments, the optical system 10 satisfies the following relationship:

0.5＜SL/TTL＜0.9；

-1＜SAG31/CT3＜0；

wherein SL is an axial distance from the stop STO to the image plane S11 of the optical system 10, TTL is an axial distance from the object-side surface S1 of the first lens L1 to the image plane S11 of the optical system 10, SAG31 is a rise of the object-side surface S5 of the third lens L3, namely SAG31 is a vector from an intersection point of the object-side surface S5 of the third lens L3 on the optical axis to a maximum effective half aperture position of the surface in a direction parallel to the optical axis, the vector is positive when facing the image side direction of the optical system 10 and negative when facing the object side direction, CT3 is an axial thickness of the third lens L3, or CT3 is understood as a central thickness of the third lens L3. In some embodiments, the SL/TTL may be 0.600, 0.610, 0.620, 0.650, 0.700, 0.750, 0.800, 0.830, 0.840, 0.850, or 0.860. In some embodiments, SAG31/CT3 can be-0.840, -0.830, -0.800, -0.750, -0.600, -0.580, -0.500, -0.400, -0.300, -0.200, -0.150, -0.130, or-0.120. When the above relationship and the lens configuration are satisfied, the imaging quality of the optical system 10 during macro photography is improved, and the optical system 10 will have the characteristics of small depth of field and virtual background. Specifically, when the optical system 10 satisfies the relationship of 0.5 < SL/TTL < 0.9, the optical system 10 has a structure with a central aperture, so that the aperture STO is reasonably disposed in the optical system 10, and thus the aperture of the object-side surface S1 of the first lens L1 is increased, thereby effectively controlling the light cone angle of the marginal field light when entering the optical system 10, adjusting the light entering amount of the optical system 10, increasing the relative brightness of the marginal field, and further improving the imaging quality. When the optical system 10 satisfies-1 < SAG31/CT3 < 0, the distortion and the field curvature of the optical system 10 are favorably corrected, and the imaging quality is improved. When SAG31/CT3 is more than or equal to 0, the surface shape of the object side S5 of the third lens L3 at the circumference (the maximum effective half aperture) is too smooth, so that the refractive power of the light rays in the off-axis field is insufficient, and the distortion and the field curvature aberration are not corrected. When SAG31/CT3 is less than or equal to-1, the surface shape of the object side surface S5 of the third lens L3 at the circumference (the position of the maximum effective half aperture) is excessively bent, which easily causes poor lens forming and influences the manufacturing yield.

In some embodiments, optical system 10 satisfies the relationship: DT11/DT42 of 0.4 < 0.9; DT11 is the maximum effective half aperture of the object-side surface S1 of the first lens L1, and DT42 is the maximum effective half aperture of the image-side surface S8 of the fourth lens L4. In some embodiments, DT11/DT42 may be 0.580, 0.590, 0.600, 0.650, 0.700, 0.750, 0.800, 0.840, 0.850, 0.860, or 0.870. When the above relationship is satisfied, the maximum effective half apertures of the object-side surface S1 of the first lens L1 and the image-side surface S8 of the fourth lens L4 are reasonably configured, so that the incident angle of the chief ray can be effectively controlled, the relative brightness of the marginal field of view is improved, and the imaging quality of the optical system 10 is improved.

In some embodiments, optical system 10 satisfies the relationship: the OBL is more than 20mm and less than 40 mm; the OBL is a distance from an object plane of the optical system 10 to the object-side surface S1 of the first lens L1 on the optical axis, and a subject located on the object plane can form a clear image on the image plane S11 of the optical system 10. In some embodiments, the OBL may be 26mm, 27mm, 28mm, 29mm, or 30 mm. When the optical system 10 satisfies the relationship of 20mm < OBL < 40mm, the object located on the object plane (or understood to be located within the distance range) can form a clear image on the image plane S11 of the optical system 10, so that the macro shooting performance of the optical system 10 is fully embodied.

In some embodiments, optical system 10 satisfies the relationship: 0.1 < | SAG41|/CT4 < 2.0; here, SAG41 is the rise of the object-side surface S7 of the fourth lens L4, that is, SAG41 is a vector from the intersection point of the object-side surface of the fourth lens L4 on the optical axis to the maximum effective half aperture position of the surface in the direction parallel to the optical axis, the vector is positive when facing the image-side direction of the optical system 10 and negative when facing the object-side direction, CT4 is the thickness of the fourth lens L4 on the optical axis, or CT4 is understood as the center thickness of the fourth lens L4. In some embodiments, | SAG41|/CT4 may be 0.220, 0.240, 0.250, 0.300, 0.350, 0.500, 0.600, 0.650, 0.700, 1.000, 1.300, 1.400, 1.430, or 1.450. When the above relationship is satisfied, the incident angle of the chief ray incident on the imaging surface S11 of the optical system 10 can be reduced, and the incident angle of the light beam at the maximum field of view on the object-side surface S7 of the fourth lens L4 can be effectively controlled, so that when the slope of the object-side surface S7 of the fourth lens L4 changes greatly, the reflection energy caused by uneven coating can be reduced, and the generation of stray light can be avoided.

In some embodiments, optical system 10 satisfies the relationship: -1. ltoreq. f1/f 2. ltoreq.1; where f1 is the effective focal length of the first lens L1, and f2 is the effective focal length of the second lens L2. The first lens element L1 provides positive refractive power to the optical system 10, thereby facilitating better convergence and entrance of light into the optical system 10, and providing the optical system 10 with a long-focus characteristic. In some embodiments, f1/f2 can be-0.700, -0.690, -0.650, -0.400, -0.200, 0.400, 0.600, 0.700, 0.750, 0.800, 0.820, or 0.840. Specifically, when the optical system 10 satisfies-1 ≦ f1/f2 < 0, the second lens element L2 provides negative refractive power to the optical system 10, which is favorable for light divergence, thereby effectively correcting aberration. When the optical system 10 satisfies the condition that f1/f2 is more than 0 and less than or equal to 1, the main surface of the optical system 10 moves forwards, so that the focal length of the optical system 10 can be increased, the optical system 10 has the characteristic of a small visual field and the characteristic of a long focal length, and an excellent macro shooting effect is realized.

In some embodiments, optical system 10 satisfies the relationship: FNO is less than or equal to 3.55; wherein FNO is the f-number of the optical system 10. In some embodiments, the FNO may be 2.50, 2.55, 2.60, 2.70, 2.80, 2.90, 3.00, 3.20, 3.40, 3.45, 3.50, or 3.55. When the above relationship is satisfied, the light transmission amount of the optical system 10 can be increased, and the optical system 10 can acquire clear detailed information of the object even in a dark environment or under the condition of insufficient light, so that the imaging quality is improved.

In some embodiments, optical system 10 satisfies the relationship: 0.5 < CT3/CT2 < 3.0; wherein CT3 is the thickness of the third lens L3 on the optical axis, CT2 is the thickness of the second lens L2 on the optical axis, or CT3 can be understood as the center thickness of the third lens L3, or CT2 can be understood as the center thickness of the second lens L2. In some embodiments, CT3/CT2 may be 0.950, 0.960, 1.000, 1.300, 1.500, 1.800, 2.000, 2.200, 2.500, 2.600, 2.650, 2.700, 2.730, or 2.750. When the above relationship is satisfied, the relative brightness of the edge field of view of the optical system 10 can be effectively improved, and the yield of the lens assembly can be improved.

In some embodiments, optical system 10 satisfies the relationship: R1/R9 is more than 0.1 and less than 0.7; wherein R1 is a radius of curvature of the object-side surface S1 of the first lens element L1 at the optical axis, and R9 is a radius of curvature of the image-side surface S8 of the fourth lens element L4 at the optical axis. In some embodiments, R1/R9 may be 0.220, 0.230, 0.250, 0.300, 0.350, 0.400, 0.450, 0.470, 0.500, 0.520, or 0.530. When the above relationship is satisfied, the incident angle at which light enters the optical system 10 can be reduced, and the angle of field of the optical system 10 can be made small.

In some embodiments, optical system 10 satisfies the relationship: -3 < (f2+ f4)/f < 1; where f2 is the effective focal length of the second lens L2, f4 is the effective focal length of the fourth lens L4, and f is the effective focal length of the optical system 10. In some embodiments, (f2+ f4)/f may be-2.500, -2.400, -2.000, -1.000, 0.100, 0.200, 0.300, 0.400, or 0.500. When the above relationship is satisfied, the effective focal lengths of the second lens L2 and the fourth lens L4 and the effective focal length of the optical system 10 can form a reasonable configuration, which ensures the magnification of the optical system 10 within the macro shooting distance, ensures the recognition accuracy, and simultaneously, can also reduce the aberration of the optical system 10, and improve the imaging quality of the optical system 10.

In some embodiments, a photosensitive element is disposed on the image side of the optical system 10, and the photosensitive element is used for receiving the light modulated by the optical system 10, and the optical system 10 and the photosensitive element form an image capturing module. In some embodiments, the camera module satisfies the relationship: TTL/ImgH is less than 2.65; where ImgH is half the diagonal length of the effective pixel area on the photosensitive element, or ImgH is understood to be half the diagonal length of the effective pixel area on the imaging plane S11. In some embodiments, the TTL/ImgH may be 2.35, 2.40, 2.45, 2.50, 2.55, 2.60, or 2.63. When the above relation is satisfied, the camera module can meet the high pixel requirement, and the miniaturization of the module size is maintained.

The optical system 10 of the present application will now be described with reference to more specific embodiments.

First embodiment

Referring to fig. 1 and 2, 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 positive refractive power, an aperture stop STO, a second lens element L2 with negative refractive power, a third lens element L3 with positive refractive power, and a fourth lens element L4 with negative refractive power. Fig. 2 includes a spherical aberration diagram (mm), an astigmatism diagram (mm), and a distortion diagram (%) of the optical system 10 in the first embodiment, wherein the astigmatism diagram and the distortion diagram are data diagrams at a wavelength of 555 nm.

Here, the ordinate of the astigmatism diagram and the distortion diagram can be understood as half of the diagonal length of the effective pixel area on the imaging plane S11 of the optical system 10.

The object-side surface S1 of the first lens element L1 is convex at the optical axis and convex at the circumference; the image side surface S2 is convex at the optical axis; convex at the circumference.

The object-side surface S3 of the second lens element L2 is concave at the optical axis and convex at the circumference; the image side surface S4 is concave at the optical axis and concave at the circumference.

The object-side surface S5 of the third lens element L3 is concave at the optical axis and concave at the circumference; the image side surface S6 is convex at the optical axis and convex at the circumference.

The object-side surface S7 of the fourth lens element L4 is convex at the optical axis and concave at the circumference; the image side surface S8 is concave at the optical axis and convex at the circumference. The image-side surface S8 of the fourth lens L4 has an inflection point.

Since the image-side surface S8 of the fourth lens element L4 has an inflection point, and the image-side surface S8 is concave at the optical axis and convex at the circumference, the total length of the optical system 10 is advantageously shortened, and meanwhile, the incident angle of the marginal field of view onto the imaging surface S11 is effectively reduced, and the efficiency of the light receiving element on the imaging surface S11 is improved.

The object-side surface S7 and the image-side surface S8 of the first lens L1, the second lens L2, the third lens L3, and the fourth lens L4 are all aspheric. By matching the aspheric surface type of each lens in the optical system 10, the problem of distortion of the field of view of the optical system 10 can be effectively solved, and the lens can achieve excellent optical effect under the condition of small and thin lens, so that the optical system 10 has smaller volume, and the optical system 10 is beneficial to realizing miniaturization design.

The first lens L1, the second lens L2, the third lens L3 and the fourth lens L4 are all made of plastic. The use of the plastic lens can reduce the manufacturing cost of the optical system 10 while reducing the weight of the optical system 10.

As shown in fig. 1, an infrared cut filter L5 for filtering infrared light is further disposed on the image side of the fourth lens element L4. In some embodiments, the ir-cut filter L5 is part of the optical system 10, for example, the ir-cut filter L5 is assembled with each lens to a lens barrel. In other embodiments, the infrared cut filter L5 is installed between the optical system 10 and the light-sensing element when the optical system 10 and the light-sensing element are assembled into a camera module.

In the first embodiment, the optical system 10 satisfies the following relationships:

SL/TTL＝0.869；

SAG31/CT3＝-0.184；

wherein SL is an axial distance from the stop STO to the image plane S11 of the optical system 10, TTL is an axial distance from the object-side surface S1 of the first lens L1 to the image plane S11 of the optical system 10, SAG31 is a rise of the object-side surface S5 of the third lens L3, namely SAG31 is a vector from an intersection point of the object-side surface S5 of the third lens L3 on the optical axis to a maximum effective half aperture position of the surface in a direction parallel to the optical axis, the vector is positive when facing the image side direction of the optical system 10 and negative when facing the object side direction, CT3 is an axial thickness of the third lens L3, or CT3 is understood as a central thickness of the third lens L3. When the above relationship is satisfied, the macro shooting performance of the optical system 10 can be fully embodied, thereby being beneficial to improving the imaging quality of the optical system 10 during macro shooting, and meanwhile, the optical system 10 also has the characteristics of small depth of field and virtual background. Specifically, the optical system 10 has a structure with a central aperture, so that the aperture STO is reasonably disposed in the optical system 10, and thus the aperture of the object-side surface S1 of the first lens L1 is increased, so that the light cone angle of the marginal field light when entering the optical system 10 can be effectively controlled, the light entering amount of the optical system 10 is adjusted, the relative brightness of the marginal field is improved, and the imaging quality is improved. In addition, satisfying the above relationship is advantageous for correcting distortion and curvature of field of the optical system 10, and improving the imaging quality.

DT11/DT42 ═ 0.605; DT11 is the maximum effective half aperture of the object-side surface S1 of the first lens L1, and DT42 is the maximum effective half aperture of the image-side surface S8 of the fourth lens L4. When the above relationship is satisfied, the maximum effective half apertures of the object-side surface S1 of the first lens L1 and the image-side surface S8 of the fourth lens L4 are reasonably configured, so that the incident angle of the chief ray can be effectively controlled, the relative brightness of the marginal field of view is improved, and the imaging quality of the optical system 10 is improved.

OBL 30 mm; the OBL is a distance from an object plane of the optical system 10 to the object-side surface S1 of the first lens L1 on the optical axis, and a subject located on the object plane can form a clear image on the image plane S11 of the optical system 10. When the above relationship is satisfied, the subject located on the object plane (or understood to be located within the distance range) can form a sharp image on the image plane S11 of the optical system 10, so that the macro photography performance of the optical system 10 is fully embodied.

0.712 of SAG 41/CT 4; SAG41 is the rise of the object-side surface S7 of the fourth lens L4, that is, SAG41 is a vector from the intersection point of the object-side surface S7 of the fourth lens L4 on the optical axis to the maximum effective half aperture position of the surface in the direction parallel to the optical axis, the vector is positive when facing the image-side direction of the optical system 10 and negative when facing the object-side direction, and CT4 is the thickness of the fourth lens L4 on the optical axis. When the above relationship is satisfied, the incident angle of the chief ray incident on the imaging surface S11 of the optical system 10 can be reduced, and the incident angle of the light beam at the maximum field of view on the object-side surface S7 of the fourth lens L4 can be effectively controlled, so that when the slope of the object-side surface S7 of the fourth lens L4 changes greatly, the reflection energy caused by uneven coating can be reduced, and the generation of stray light can be avoided.

f1/f2 is-0.646; where f1 is the effective focal length of the first lens L1, and f2 is the effective focal length of the second lens L2. The first lens element L1 provides positive refractive power to the optical system 10, thereby facilitating better convergence and entrance of light into the optical system 10, and providing the optical system 10 with a long-focus characteristic. When the above relationship is satisfied, the second lens element L2 provides negative refractive power to the optical system 10, which is favorable for light divergence, thereby effectively correcting aberration.

FNO 3.00; wherein FNO is the f-number of the optical system 10. When the above relationship is satisfied, the light transmission amount of the optical system 10 can be increased, and the optical system 10 can acquire clear detailed information of the object even in a dark environment or under the condition of insufficient light, so that the imaging quality is improved.

CT3/CT2 is 1.339; wherein CT3 is the thickness of the third lens element L3 on the optical axis, and CT2 is the thickness of the second lens element L2 on the optical axis. When the above relationship is satisfied, the relative brightness of the edge field of view of the optical system 10 can be effectively improved, and the yield of the lens assembly can be improved.

R1/R9 ═ 0.459; wherein R1 is a radius of curvature of the object-side surface S1 of the first lens element L1 at the optical axis, and R9 is a radius of curvature of the image-side surface S8 of the fourth lens element L4 at the optical axis. When the above relationship is satisfied, the incident angle at which light enters the optical system 10 can be reduced, and the angle of field of the optical system 10 can be made small.

(f2+ f 4)/f-2.588; where f2 is the effective focal length of the second lens L2, f4 is the effective focal length of the fourth lens L4, and f is the effective focal length of the optical system 10. When the above relationship is satisfied, the effective focal lengths of the second lens L2 and the fourth lens L4 and the effective focal length of the optical system 10 can form a reasonable configuration, which ensures the magnification of the optical system 10 within the macro shooting distance, ensures the recognition accuracy, and simultaneously, can also reduce the aberration of the optical system 10, and improve the imaging quality of the optical system 10.

In some embodiments, a photosensitive element is disposed on the image side of the optical system 10, and the photosensitive element is used for receiving the light modulated by the optical system 10, and the optical system 10 and the photosensitive element form a camera module. In some embodiments, the camera module satisfies the relationship: TTL/ImgH is 2.63; when the above relation is satisfied, the camera module can meet the high pixel requirement, and the miniaturization of the module size is maintained.

When the refractive power configuration and relationship of the above lenses are satisfied, the optical system 10 has a small field of view characteristic, and the macro shooting performance of the optical system 10 can be fully embodied, thereby being beneficial to improving the imaging quality of the optical system 10 during macro shooting. At the same time, the optical system 10 will also have a small depth of field and a blurred background.

In addition, each lens parameter of the optical system 10 is given by table 1 and table 2, where K in table 2 is a conic constant, and Ai is a coefficient corresponding to the i-th high-order term in the aspherical surface type formula. The elements from the object plane to the image plane S11 were arranged in the order of the elements from top to bottom in table 1.

Surface numbers

1 and 2 respectively indicate an object-side surface S1 and an image-side surface S2 of the first lens L1, that is, a surface having a smaller surface number is an object-side surface and a surface having a larger surface number is an image-side surface in the same lens. The Y radius in table 1 is the radius of curvature of the object-side or image-side surface at the paraxial (or understood to be on the optical axis) of the corresponding surface number. The first value of the lens in the "thickness" parameter set is the thickness of the lens on the optical axis, and the second value is the distance from the image-side surface of the lens to the object-side surface of the next lens on the optical axis. The "thickness" parameter in the face number 2 is the distance from the image-side face S4 of the second lens L2 to the stop STO. The numerical value of the stop STO in the "thickness" parameter column is the distance on the optical axis from the stop STO to the vertex of the object-side surface (the vertex refers to the intersection point of the lens and the optical axis) of the subsequent lens (the second lens L2 in this embodiment), the direction from the object-side surface to the image-side surface of the last lens is the positive direction of the optical axis by default, when the value is negative, it indicates that the stop STO is disposed on the right side of the vertex of the object-side surface of the lens (or understood to be located on the image side of the vertex), and when the "thickness" parameter of the stop STO is positive, the stop STO is disposed on the left side of the vertex of the object-side surface of the lens (or understood to be located on the. The optical axes of the lenses in the embodiment of the present application are on the same straight line as the optical axis of the optical system 10. The "thickness" parameter value in the surface number 9 is the distance on the optical axis from the image-side surface S8 of the fourth lens L4 to the object-side surface S9 of the infrared cut filter L5. The "thickness" parameter value corresponding to the surface number 11 of the ir-cut filter L5 is the distance on the optical axis from the image side surface S10 of the ir-cut filter L5 to the image surface (image surface S11) of the optical system 10.

In the first embodiment, the effective focal length f of the optical system 10 is 4.140mm, the f-number FNO is 3.0, the maximum field angle (diagonal view angle) FOV is 40.1 °, the total optical length TTL is 5.208mm, and the total optical length TTL is the distance on the optical axis from the object-side surface S1 of the first lens L1 to the image plane S11 of the optical system 10.

In the following examples (first, second, third, fourth, fifth, and sixth examples), the refractive index, abbe number, and focal length of each lens were all numerical values at a wavelength of 555 nm. In addition, the relational expression calculation and the lens surface type in each example are based on lens parameters (for example, table 1, table 2, table 3, table 4, and the like).

TABLE 1

TABLE 2

Second embodiment

In the second embodiment, referring to fig. 3 and 4, the optical system 10 includes, in order from the object side to the image side, the first lens element L1 with positive refractive power, the stop STO, the second lens element L2 with positive refractive power, the third lens element L3 with positive refractive power, and the fourth lens element L4 with negative refractive power. Fig. 4 includes a spherical aberration diagram (mm), an astigmatism diagram (mm), and a distortion diagram (%) of the optical system 10 in the second embodiment, in which the astigmatism diagram and the distortion diagram are data diagrams at a wavelength of 555 nm.

The object-side surface S1 of the first lens element L1 is convex at the optical axis and convex at the circumference; the image side surface S2 is concave at the optical axis; the circumference is concave.

The object-side surface S3 of the second lens element L2 is convex at the optical axis and convex at the circumference; the image side surface S4 is concave at the optical axis and concave at the circumference.

The object-side surface S7 of the fourth lens element L4 is concave at the optical axis and concave at the circumference; the image side surface S8 is concave at the optical axis and convex at the circumference. The image-side surface S8 of the fourth lens L4 has an inflection point.

As shown in fig. 3, the image side of the fourth lens element L4 is further provided with an infrared cut filter L5 for filtering out infrared light. In some embodiments, the ir-cut filter L5 is part of the optical system 10, for example, the ir-cut filter L5 is assembled with each lens to a lens barrel. In other embodiments, the infrared cut filter L5 is installed between the optical system 10 and the light-sensing element when the optical system 10 and the light-sensing element are assembled into a camera module.

In the second embodiment, the effective focal length f of the optical system 10 is 3.968mm, the f-number FNO is 2.45, the maximum field angle (diagonal angle of view) FOV is 50.1 °, and the total optical length TTL is 4.62 mm.

In addition, the lens parameters of the optical system 10 are given in tables 3 and 4, wherein the definition of the parameters can be obtained from the first embodiment, which is not described herein.

TABLE 3

TABLE 4

From the above data, one can see:

third embodiment

In the third embodiment, referring to fig. 5 and 6, the optical system 10 includes, in order from the object side to the image side, the first lens element L1 with positive refractive power, the stop STO, the second lens element L2 with positive refractive power, the third lens element L3 with negative refractive power, and the fourth lens element L4 with negative refractive power. Fig. 6 includes a spherical aberration diagram (mm), an astigmatism diagram (mm), and a distortion diagram (%) of the optical system 10 in the third embodiment, in which the astigmatism diagram and the distortion diagram are data diagrams at a wavelength of 555 nm.

The object-side surface S3 of the second lens element L2 is convex at the optical axis and convex at the circumference; the image side surface S4 is concave at the optical axis and convex at the circumference.

As shown in fig. 5, the image side of the fourth lens element L4 is further provided with an infrared cut filter L5 for filtering out infrared light. In some embodiments, the ir-cut filter L5 is part of the optical system 10, for example, the ir-cut filter L5 is assembled with each lens to a lens barrel. In other embodiments, the infrared cut filter L5 is installed between the optical system 10 and the light-sensing element when the optical system 10 and the light-sensing element are assembled into a camera module.

In the third embodiment, the effective focal length f of the optical system 10 is 4.08mm, the f-number FNO is 3.1, the maximum field angle (diagonal angle of view) FOV is 38.7 °, and the total optical length TTL is 5.21 mm.

In addition, the lens parameters of the optical system 10 are given in tables 5 and 6, wherein the definition of the parameters can be obtained from the first embodiment, which is not described herein.

TABLE 5

TABLE 6

From the above data, one can see:

fourth embodiment

In the fourth embodiment, referring to fig. 7 and 8, the optical system 10 includes, in order from the object side to the image side, the first lens element L1 with positive refractive power, the second lens element L2 with negative refractive power, the stop STO, the third lens element L3 with negative refractive power, and the fourth lens element L4 with positive refractive power. Fig. 8 includes a spherical aberration diagram (mm), an astigmatism diagram (mm), and a distortion diagram (%) of the optical system 10 in the fourth embodiment, in which the astigmatism diagram and the distortion diagram are data diagrams at a wavelength of 555 nm.

The object-side surface S5 of the third lens element L3 is convex at the optical axis and concave at the circumference; the image side surface S6 is concave at the optical axis and convex at the circumference.

As shown in fig. 7, the image side of the fourth lens element L4 is further provided with an infrared cut filter L5 for filtering out infrared light. In some embodiments, the ir-cut filter L5 is part of the optical system 10, for example, the ir-cut filter L5 is assembled with each lens to a lens barrel. In other embodiments, the infrared cut filter L5 is installed between the optical system 10 and the light-sensing element when the optical system 10 and the light-sensing element are assembled into a camera module.

In the fourth embodiment, the effective focal length f of the optical system 10 is 4.23mm, the f-number FNO is 3.55, the maximum field angle (diagonal view angle) FOV is 38.2 °, and the total optical length TTL is 5.029 mm.

In addition, the lens parameters of the optical system 10 are given in tables 7 and 8, wherein the definition of the parameters can be obtained from the first embodiment, which is not described herein.

TABLE 7

TABLE 8

From the above data, one can see:

fifth embodiment

In the fifth embodiment, referring to fig. 9 and 10, the optical system 10 includes, in order from the object side to the image side, the first lens element L1 with positive refractive power, the second lens element L2 with negative refractive power, the stop STO, the third lens element L3 with negative refractive power, and the fourth lens element L4 with positive refractive power. Fig. 10 includes a spherical aberration diagram (mm), an astigmatism diagram (mm), and a distortion diagram (%) of the optical system 10 in the fifth embodiment, in which the astigmatism diagram and the distortion diagram are data diagrams at a wavelength of 555 nm.

The object-side surface S7 of the fourth lens element L4 is convex at the optical axis and convex at the circumference; the image side surface S8 is concave at the optical axis and convex at the circumference. The image-side surface S8 of the fourth lens L4 has an inflection point.

As can be seen from fig. 9, the image side of the fourth lens element L4 is further provided with an infrared cut filter L5 for filtering out infrared light. In some embodiments, the ir-cut filter L5 is part of the optical system 10, for example, the ir-cut filter L5 is assembled with each lens to a lens barrel. In other embodiments, the infrared cut filter L5 is installed between the optical system 10 and the light-sensing element when the optical system 10 and the light-sensing element are assembled into a camera module.

In the fifth embodiment, the effective focal length f of the optical system 10 is 4.10mm, the f-number FNO is 2.62, the maximum field angle (diagonal angle of view) FOV is 38.4 °, and the total optical length TTL is 5.00 mm.

In addition, the lens parameters of the optical system 10 are given in tables 9 and 10, wherein the definition of the parameters can be obtained from the first embodiment, which is not described herein.

TABLE 9

Watch 10

From the above data, one can see:

sixth embodiment

Referring to fig. 11 and 12, in the sixth embodiment, the optical system 10 includes, in order from the object side to the image side, the first lens element L1 with positive refractive power, the second lens element L2 with negative refractive power, the stop STO, the third lens element L3 with negative refractive power, and the fourth lens element L4 with positive refractive power. Fig. 12 includes a spherical aberration diagram (mm), an astigmatism diagram (mm), and a distortion diagram (%) of the optical system 10 in the sixth embodiment, in which the astigmatism diagram and the distortion diagram are data diagrams at a wavelength of 555 nm.

As shown in fig. 11, the image side of the fourth lens element L4 is further provided with an infrared cut filter L5 for filtering out infrared light. In some embodiments, the ir-cut filter L5 is part of the optical system 10, for example, the ir-cut filter L5 is assembled with each lens to a lens barrel. In other embodiments, the infrared cut filter L5 is installed between the optical system 10 and the light-sensing element when the optical system 10 and the light-sensing element are assembled into a camera module.

In the sixth embodiment, the effective focal length f of the optical system 10 is 4.11mm, the f-number FNO is 2.48, the maximum field angle (diagonal angle of view) FOV is 38.5 °, and the total optical length TTL is 5.21 mm.

In addition, the lens parameters of the optical system 10 are given in tables 11 and 12, wherein the definition of the parameters can be obtained from the first embodiment, which is not described herein.

TABLE 11

TABLE 12

From the above data, one can see:

referring to fig. 13, in an embodiment provided in the present application, the optical system 10 is assembled with the photosensitive element 210 to form the camera module 20, and at this time, an infrared cut filter L5 is disposed between the fourth lens L4 and the photosensitive element 210 in this embodiment. The photosensitive element 210 may be a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor). By adopting the optical system 10, the camera module 20 has the characteristics of small viewing angle, small depth of field and virtual background. Meanwhile, when the camera module 20 is applied to macro photography, the relative brightness of the edge view field is improved, so that the imaging quality during macro photography can be effectively improved.

In some embodiments, the distance between the photosensitive element 210 and each lens in the optical system 10 is relatively fixed, and the camera module 20 is a fixed focus module. In other embodiments, a driving mechanism such as a voice coil motor may be provided to enable the photosensitive element 210 to move relative to each lens in the optical system 10, so as to achieve a focusing effect. In some embodiments, an optical zoom effect may also be achieved by providing a drive mechanism to drive movement of a portion of the lenses in the optical system 10.

Referring to fig. 14, some embodiments of the present application further provide an electronic device 30, and the camera module 20 is applied to the electronic device 30. Specifically, the electronic device 30 includes a housing, and the camera module 20 is mounted to the housing. The electronic device 30 includes, but is not limited to, a smart phone, a smart watch, an e-book reader, a vehicle-mounted camera, a monitoring device, a medical device (such as an endoscope), a tablet computer, a biometric device (such as a fingerprint recognition device or a pupil recognition device), a PDA (Personal Digital Assistant), an unmanned aerial vehicle, and the like. By adopting the camera module 20, the electronic device 30 has the characteristics of small viewing angle, small depth of field and virtual background when shooting, and especially has excellent imaging quality when shooting at a micro distance.

Specifically, in some embodiments, the camera module 20 is applied to a smart phone, the smart phone includes a middle frame and a circuit board, the circuit board is disposed in the middle frame, the camera module 20 is installed in the middle frame of the smart phone, and the light sensing element is electrically connected to the circuit board. The camera module 20 can be used as a front camera module or a rear camera module of the smart phone.

The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims

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

a first lens element with positive refractive power;

a second lens element with refractive power;

a third lens element with refractive power; and

and the optical system satisfies the relationship:

0.5＜SL/TTL＜0.9；

-1＜SAG31/CT3＜0；

wherein SL is an axial distance between the aperture stop and the image plane of the optical system, TTL is an axial distance between the object-side surface of the first lens element and the image plane of the optical system, SAG31 is a rise of the object-side surface of the third lens element, and CT3 is an axial thickness of the third lens element.

2. The optical system of claim 1, wherein the optical system satisfies the relationship:

0.4＜DT11/DT42＜0.9；

wherein DT11 is the maximum effective half aperture at the object side of the first lens, and DT42 is the maximum effective half aperture at the image side of the fourth lens.

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

20mm＜OBL＜40mm；

and the OBL is the distance from the object plane of the optical system to the object side surface of the first lens on the optical axis.

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

0.1＜|SAG41|/CT4＜2.0；

wherein SAG41 is the rise of the object side of the fourth lens, and CT4 is the thickness of the fourth lens on the optical axis.

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

-1≤f1/f2≤1；

wherein f1 is the effective focal length of the first lens, and f2 is the effective focal length of the second lens.

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

FNO≤3.55；

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

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

0.5＜CT3/CT2＜3.0；

wherein CT2 is the thickness of the second lens on the optical axis.

8. The optical system of claim 1, wherein the optical system satisfies the relationship:

0.1＜R1/R9＜0.7；

wherein R1 is a curvature radius of an object side surface of the first lens at an optical axis, and R9 is a curvature radius of an image side surface of the fourth lens at the optical axis.

9. The optical system of claim 1, wherein the optical system satisfies the relationship:

-3＜(f2+f4)/f＜1；

wherein f2 is an effective focal length of the second lens, f4 is an effective focal length of the fourth lens, and f is an effective focal length of the optical system.

10. An image capturing module comprising a photosensitive element and the optical system of any one of claims 1 to 9, wherein the photosensitive element is disposed on the image side of the fourth lens element.

11. The camera module of claim 10, wherein the camera module satisfies the following relationship:

TTL/ImgH＜2.65；

wherein ImgH is half of the diagonal length of the effective pixel area on the photosensitive element.

12. An electronic device, comprising a housing and the camera module of claim 10 or 11, wherein the camera module is disposed on the housing.