CN110716282B

CN110716282B - Imaging optical system, image capturing device and electronic device

Info

Publication number: CN110716282B
Application number: CN201810770893.6A
Authority: CN
Inventors: 邹海荣; 俞炳泽; 兰宾利
Original assignee: Jiangxi Jingchao Optical Co Ltd
Current assignee: Jiangxi Jingchao Optical Co Ltd
Priority date: 2018-07-13
Filing date: 2018-07-13
Publication date: 2022-05-13
Anticipated expiration: 2038-07-13
Also published as: CN110716282A

Abstract

The invention discloses an imaging optical system, an image capturing device and an electronic device. The imaging optical system sequentially comprises a first lens element with positive refractive power, a second lens element with negative refractive power, a third lens element with positive refractive power and a fourth lens element with refractive power from an object side to an image side. The object side surface of the first lens is a convex surface, and the image side surface of the first lens is a concave surface. The object side surface of the second lens is a concave surface, and the image side surface of the second lens is a concave surface or a plane. The object side surface of the third lens is a concave surface, and the image side surface of the third lens is a convex surface. 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 includes at least one inflection point. The imaging optical system satisfies the following conditions: TTL/Imgh is less than or equal to 0.75. The imaging optical system of the embodiment of the invention meets the requirements of ultrashort and ultrathin property and high pixel requirement by reasonably matching the four lenses, and has the characteristics of large aperture and large field angle.

Description

Imaging optical system, image capturing device and electronic device

Technical Field

The present invention relates to the field of optical imaging technologies, and in particular, to an imaging optical system, an image capturing device and an electronic device.

Background

With the development of chip technology, the pixel size of the chip applied to the imaging optical system is smaller and smaller, and the imaging optical system gradually develops toward high pixel and miniaturization trend. In an imaging optical system conventionally mounted on an electronic device, a three-piece lens structure is often used. However, the conventional three-lens assembly cannot meet the requirements of high pixel and high imaging quality.

Disclosure of Invention

The embodiment of the invention provides an imaging optical system, an image capturing device and an electronic device.

The imaging optical system of the present disclosure includes, in order from an object side to an image side, a first lens element with positive refractive power, a second lens element with negative refractive power, a third lens element with positive refractive power, and a fourth lens element with refractive power. The object side surface of the first lens is a convex surface, and the image side surface of the first lens is a concave surface. The object side surface of the second lens is a concave surface, and the image side surface of the second lens is a concave surface or a plane. The object side surface of the third lens is a concave surface, and the image side surface of the third lens is a convex surface. 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 includes at least one inflection point. The imaging optical system satisfies the following conditions: TTL/Imgh is less than or equal to 0.75; wherein TTL is a distance on an optical axis from an object-side surface of the first lens element to an imaging surface, and Imgh is a maximum imaging height of the imaging optical system.

The imaging optical system of the embodiment of the invention meets the requirements of ultrashort and ultrathin property and high pixel requirement by reasonably matching the four lenses, and has the characteristics of large aperture and large field angle.

In certain embodiments, the imaging optical system satisfies the following condition: TTL/Imgh is less than or equal to 0.68.

Thus, the imaging optical system can meet the requirements of high pixel and miniaturization.

In certain embodiments, the imaging optical system satisfies the following condition: CT 2/Sigma CT is more than or equal to 0.15; wherein CT2 is the center thickness of the second lens, and Σ CT is the sum of the center thicknesses of the first lens, the second lens, the third lens, and the fourth lens.

Therefore, the second lens can be formed, the uniformity of the second lens is increased, the sensitivity is reduced, the yield is improved, and the total length of the imaging optical system is shortened.

In certain embodiments, the imaging optical system satisfies the following condition: T12/TD is more than or equal to 0.05; wherein T12 is an air gap between the first lens element and the second lens element, and TD is a distance on an optical axis between an object-side surface of the first lens element and an image-side surface of the fourth lens element.

Therefore, the sensitivity of the imaging optical system can be reduced, the yield is improved, and the total length of the imaging optical system is favorably shortened.

In certain embodiments, the imaging optical system satisfies the following condition: i R2/R3I < 1; wherein R2 is a radius of curvature of an image-side surface of the first lens, and R3 is a radius of curvature of an object-side surface of the second lens.

Therefore, the second lens element is favorable for correcting the aberration from the first lens element and adjusting the proper refractive power to improve the resolution of the imaging optical system.

In certain embodiments, the imaging optical system satisfies the following condition: r4/f > 5; wherein R4 is a radius of curvature of an image-side surface of the second lens, and f is a focal length of the imaging optical system.

Therefore, the main point of the imaging optical system is far away from the image side surface of the imaging optical system, so that the total length of the imaging optical system is shortened.

In certain embodiments, the imaging optical system satisfies the following condition: the | < SAG31| < 0.15, | < SAG32| < 0.35; SAG31 is the horizontal distance between the position of the maximum effective diameter of the object side surface of the third lens and the optical axis of the object side surface of the third lens, and SAG32 is the horizontal distance between the position of the maximum effective diameter of the image side surface of the third lens and the optical axis of the image side surface of the third lens.

Therefore, the processing difficulty of the third lens can be reduced, and the yield is improved.

In certain embodiments, the imaging optical system satisfies the following condition: the | < SAG31| < 0.1, | < SAG32| < 0.2; SAG31 is the horizontal distance between the position of the maximum effective diameter of the object side surface of the third lens and the optical axis of the object side surface of the third lens, and SAG32 is the horizontal distance between the position of the maximum effective diameter of the image side surface of the third lens and the optical axis of the image side surface of the third lens.

In certain embodiments, the imaging optical system satisfies the following condition: SD/CT4< 5.5; wherein SD is a distance on an optical axis from an object-side surface of the first lens element to an image-side surface of the third lens element, and CT4 is a center thickness of the fourth lens element.

Therefore, the space occupied by each lens close to the object side end of the imaging optical system can be effectively reduced, and the arrangement of each lens in the imaging optical system is more compact.

The image capturing device of the embodiment of the invention comprises the imaging optical system and the photosensitive element of any one of the embodiments. The photosensitive element is arranged on the image side of the imaging optical system.

In the image capturing device of the embodiment of the invention, the imaging optical system not only meets the requirement of ultrashort and ultrathin property, but also meets the requirement of high pixel by reasonably matching the four lenses, and simultaneously has the characteristics of large aperture and large field angle.

The electronic device according to the embodiment of the present invention includes a housing and the image capturing device according to the above embodiment. The image capturing device is installed in the shell.

In the electronic device of the embodiment of the invention, the imaging optical system meets the requirements of ultrashort and ultrathin property and high pixel by reasonably matching the four lenses, and has the characteristics of large aperture and large field angle.

Additional aspects and advantages of embodiments of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.

Drawings

The above and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:

fig. 1 is a schematic structural view of an imaging optical system according to a first embodiment of the present invention;

fig. 2 is a spherical aberration diagram (mm) of an imaging optical system according to a first embodiment of the present invention;

fig. 3 is an astigmatism diagram (mm) of an imaging optical system according to a first embodiment of the present invention;

fig. 4 is a distortion diagram (%) of the imaging optical system according to the first embodiment of the present invention;

fig. 5 is a schematic structural view of an imaging optical system of a second embodiment of the present invention;

FIG. 6 is a spherical aberration chart (mm) of an imaging optical system according to a second embodiment of the present invention;

fig. 7 is an astigmatism diagram (mm) of an imaging optical system of a second embodiment of the present invention;

fig. 8 is a distortion diagram (%) of the imaging optical system of the second embodiment of the present invention;

fig. 9 is a schematic structural view of an imaging optical system of a third embodiment of the present invention;

fig. 10 is a spherical aberration diagram (mm) of an imaging optical system of a third embodiment of the present invention;

fig. 11 is an astigmatism diagram (mm) of an imaging optical system of a third embodiment of the present invention;

fig. 12 is a distortion diagram (%) of an imaging optical system of a third embodiment of the present invention;

fig. 13 is a schematic configuration diagram of an imaging optical system of a fourth embodiment of the present invention;

FIG. 14 is a spherical aberration chart (mm) of an imaging optical system of a fourth embodiment of the present invention;

fig. 15 is an astigmatism diagram (mm) of an imaging optical system of a fourth embodiment of the present invention;

fig. 16 is a distortion diagram (%) of an imaging optical system according to a fourth embodiment of the present invention;

fig. 17 is a schematic structural diagram of an image capturing device according to an embodiment of the present invention;

FIG. 18 is a schematic structural diagram of an electronic device according to an embodiment of the invention;

fig. 19 is another schematic structural diagram of the electronic device according to the embodiment of the invention.

Detailed Description

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the accompanying drawings are illustrative only for the purpose of explaining the present invention, and are not to be construed as limiting the present invention.

In the description of the present invention, the terms "first" and "second" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implying any number of technical features indicated. Thus, features defined as "first", "second", may explicitly or implicitly include one or more of the described features. In the description of the present invention, "a plurality" means two or more unless specifically defined otherwise.

In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; may be mechanically connected, may be electrically connected or may be in communication with each other; either directly or indirectly through intervening media, either internally or in any other relationship. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.

In the present invention, unless otherwise expressly stated or limited, "above" or "below" a first feature means that the first and second features are in direct contact, or that the first and second features are not in direct contact but are in contact with each other via another feature therebetween. Also, the first feature being "on," "above" and "over" the second feature includes the first feature being directly on and obliquely above the second feature, or merely indicating that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature includes the first feature being directly above and obliquely above the second feature, or simply meaning that the first feature is at a lesser level than the second feature.

The following disclosure provides many different embodiments or examples for implementing different features of the invention. To simplify the disclosure of the present invention, the components and arrangements of specific examples are described below. Of course, they are merely examples and are not intended to limit the present invention. Furthermore, the present invention may repeat reference numerals and/or letters in the various examples, such repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. In addition, the present invention provides examples of various specific processes and materials, but one of ordinary skill in the art may recognize applications of other processes and/or uses of other materials.

Referring to fig. 1, 5, 9 and 13, the imaging optical system 10 according to the embodiment of the invention 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 negative refractive power, a third lens element L3 with positive refractive power and a fourth lens element L4 with refractive power.

The object-side surface S1 of the first lens element L1 is convex, and the image-side surface S2 is concave. The object-side surface S3 of the second lens element L2 is concave, and the image-side surface S4 is concave or planar. The object-side surface S5 of the third lens element L3 is concave, and the image-side surface S6 is convex. The object-side surface S7 and the image-side surface S8 of the fourth lens element L4 are aspheric, and at least one of the object-side surface S7 and the image-side surface S8 includes at least one inflection point.

The imaging optical system satisfies the following conditions: TTL/Imgh is less than or equal to 0.75. Wherein TTL is an axial distance from the object-side surface S1 of the first lens element L1 to the image plane S11, and Imgh is a maximum image height of the imaging optical system 10. Specifically, in some examples, TTL/Imgh can be 0.68, 0.65, 0.73, 0.75, or other values less than 0.75.

The imaging optical system 10 according to the embodiment of the present invention, by reasonably matching the four lenses, not only meets the requirement of ultra-short and ultra-thin, but also meets the requirement of high pixel, and has the characteristics of large aperture and large field angle.

It is understood that the imaging optical system 10 has a large aperture, and the light-entering amount can be increased, so that the imaging optical system 10 can image more clearly. Therefore, the imaging optical system 10 can be used in a strong-light environment or a weak-light environment, and the space used by the electronic device mounted thereon is widened; the imaging optical system 10 can be used in the daytime or at night, and the time for using the electronic device mounted thereon is widened.

Further, the provision of the inflection point on the fourth lens L4 effectively suppresses the angle at which the light rays of the off-axis field are incident on the photosensitive element 20 as shown in fig. 17, thereby correcting the aberration of the off-axis field and improving the imaging quality.

In some embodiments, the imaging optical system 10 satisfies the following condition: TTL/Imgh is less than or equal to 0.68; wherein TTL is an axial distance from the object-side surface S1 of the first lens element L1 to the image plane S11, and Imgh is a maximum image height of the imaging optical system 10.

Thus, the imaging optical system 10 can satisfy both the demand for high pixels and the demand for miniaturization. Specifically, in some examples, TTL/Imgh can be 0.68, 0.65, 0.61, 0.58, or other values less than 0.68.

In some embodiments, the imaging optical system 10 satisfies the following condition: CT 2/Sigma CT is more than or equal to 0.15; CT2 is the center thickness of the second lens L2, and Σ CT is the sum of the center thicknesses of the first lens L1, the second lens L2, the third lens L3, and the fourth lens L4.

Thus, the formability of the second lens L2 is ensured, which is helpful for increasing the uniformity of the second lens L2, reducing the sensitivity, increasing the yield, and reducing the total length of the imaging optical system 10. In some examples, CT2/Σ CT may take on a value of 0.1875, 0.174, 0.15, 0.168, or other value greater than 0.15.

In some embodiments, the imaging optical system 10 satisfies the following condition: T12/TD is more than or equal to 0.05; t12 is an air gap between the first lens element L1 and the second lens element L2, and TD is the distance on the optical axis from the object-side surface S1 of the first lens element L1 to the image-side surface S8 of the fourth lens element L4.

Thus, the sensitivity of the imaging optical system 10 can be reduced, the yield can be improved, and the total length of the imaging optical system 10 can be shortened. In some examples, T12/TD may take on a value of 0.05, 0.08, 0.1, 0.13, or other values greater than 0.05.

In some embodiments, the imaging optical system 10 satisfies the following condition: i R2/R3I < 1; where R2 is the radius of curvature of the image-side surface S2 of the first lens L1, and R3 is the radius of curvature of the object-side surface S3 of the second lens L2.

Thus, it is advantageous for the second lens element L2 to correct the aberration from the first lens element L1 and adjust the appropriate refractive power to improve the resolution of the imaging optical system 10. Specifically, in some examples, | R2/R3| can take on a value of 0.09, 0.27, 0.11, 0.10, or other numerical value less than 1.

In some embodiments, the imaging optical system 10 satisfies the following condition: r4/f > 5; where R4 is the radius of curvature of the image-side surface S4 of the second lens L2, and f is the focal length of the imaging optical system 10.

In this way, it is advantageous for the principal point of the imaging optical system 10 to be away from the image-side surface of the imaging optical system 10, so as to shorten the overall length of the imaging optical system 10. In some examples, R4/f may take on a value of 5.1, 15.75, 6.85, 8.63, or other values greater than 5.

In some embodiments, the imaging optical system 10 satisfies the following condition: the | < SAG31| < 0.15, | < SAG32| < 0.35; here, SAG31 is the horizontal distance between the maximum effective diameter of the object-side surface S5 of the third lens L3 and the optical axis of the object-side surface S5 of the third lens L3, and SAG32 is the horizontal distance between the maximum effective diameter of the image-side surface S6 of the third lens L3 and the optical axis of the image-side surface S6 of the third lens L3.

Thus, the processing difficulty of the third lens L3 can be reduced, and the yield can be improved. Specifically, in some examples, | SAG31| can take on values of 0.085, 0.088, 0.083, 0.123, 0.15, or other values less than 0.15, | SAG32| can take on values of 0.208, 0.21, 0.195, 0.301, 0.35, or other values less than 0.35.

In some embodiments, the imaging optical system 10 satisfies the following condition: the | < SAG31| < 0.1, | < SAG32| < 0.2; here, SAG31 is the horizontal distance between the maximum effective diameter of the object-side surface S5 of the third lens L3 and the optical axis of the object-side surface S5 of the third lens L3, and SAG32 is the horizontal distance between the maximum effective diameter of the image-side surface S6 of the third lens L3 and the optical axis of the image-side surface S6 of the third lens L3.

Thus, the processing difficulty of the third lens L3 can be reduced, and the yield can be improved. Specifically, in some examples, | SAG31| can take on values of 0.085, 0.088, 0.083, 0.1, or other values less than 0.1, | SAG32| can take on values of 0.195, 0.188, 0.197, 0.2, or other values less than 0.2.

In some embodiments, the imaging optical system 10 satisfies the following condition: SD/CT4< 5.5; wherein SD is the distance on the optical axis from the object-side surface S1 of the first lens L1 to the image-side surface S6 of the third lens L3, and CT4 is the center thickness of the fourth lens L4.

Thus, the space occupied by each lens near the object side of the imaging optical system 10 can be effectively reduced, and the arrangement of each lens in the imaging optical system 10 is more compact. Specifically, in some examples, SD/CT4 may take on values of 4.55, 4.51, 5.31, 3.13, or other values less than 5.5.

In some embodiments, the imaging optical system 10 further includes an optical filter L5. The filter L5 is disposed on the image side of the fourth lens L4. In the embodiment of the present invention, the filter L5 is an infrared filter. When the imaging optical system 10 is used for imaging, light rays emitted or reflected by a subject enter the imaging optical system 10 from the object side direction, pass through the first lens L1, the second lens L2, the third lens L3, the fourth lens L4 and the filter L5 in sequence, and finally converge on the imaging surface S11.

In certain embodiments, the imaging optical system 10 further includes a stop STO. The stop STO may be an aperture stop or a field stop. The stop STO may be provided on the surface of any one of the lenses, or before the first lens L1, or between any two of the lenses, or between the fourth lens L4 and the filter L5. For example, in the first to third embodiments, as shown in fig. 1, 5, and 9, the stop STO is disposed before the first lens L1; in the fourth embodiment, a stop STO (not shown in fig. 13) is provided on the object side S1 of the first lens L1.

The surface shape of the aspheric surface is determined by the following formula:

wherein h is the height from any point on the aspheric surface to the optical axis, c is the vertex curvature, k is the conic constant, and Ai is the correction coefficient of the i-th order of the aspheric surface.

The present invention will be described in detail by the following specific embodiments with reference to the attached drawings.

The first embodiment is as follows:

referring to fig. 1 to 4, the imaging optical system 10 of the present embodiment includes, from an object side to an image side, a first lens element L1, a second lens element L2, a third lens element L3, a fourth lens element L4 and an infrared filter L5.

The first lens element L1 with positive refractive power is made of plastic, and has a convex object-side surface S1 and a concave image-side surface S2. The second lens element L2 with negative refractive power is made of plastic and has a concave object-side surface S3 and a concave image-side surface S4. The third lens element L3 with positive refractive power is made of plastic, and has a concave object-side surface S5 and a convex image-side surface S6. The fourth lens element L4 with refractive power is made of plastic, and has an object-side surface S7 being convex along an optical axis and concave along a circumference, and an image-side surface S8 being concave along the optical axis and convex along the circumference.

The stop STO is disposed between the subject and the first lens L1. The f-number FNO of the imaging optical system 10 is 2.3.

The infrared filter L5 is made of glass, and is disposed between the fourth lens element L4 and the image plane S11 without affecting the focal length of the imaging optical system 10.

In the first embodiment, the effective focal length f of the imaging optical system 10 is 2.15mm, the f-number of the imaging optical system 10 is FNO 2.3, and the field angle FOV of the imaging optical system 10 is 80 degrees. The imaging optical system 10 satisfies the following conditions: TTL/Imgh is 0.68, CT2/Σ CT is 0.1875, T12/TD is 0.08, | R2/R3| 0.09, R4/f is 5.1, | SAG31| 0.085mm, | SAG32| 0.208mm, SD/CT4 is 4.55. The imaging optical system 10 also satisfies the conditions of the following table:

TABLE 1

TABLE 2

Example two:

referring to fig. 5 to 8, the imaging optical system 10 of the present embodiment includes, from an object side to an image side, a first lens element L1, a second lens element L2, a third lens element L3, a fourth lens element L4 and an infrared filter L5.

The first lens element L1 with positive refractive power is made of plastic, and has a convex object-side surface S1 and a concave image-side surface S2. The second lens element L2 with negative refractive power is made of plastic, and has a concave object-side surface S3 and a concave image-side surface S4 along the optical axis, and is substantially planar along the circumference. The third lens element L3 with positive refractive power is made of plastic, and has a concave object-side surface S5 and a convex image-side surface S6. The fourth lens element L4 with refractive power is made of plastic, and has an object-side surface S7 being convex along an optical axis and concave along a circumference, and an image-side surface S8 being concave along the optical axis and convex along the circumference.

The infrared filter L5 is made of glass, and is disposed between the fourth lens element L4 and the image plane S11 without affecting the focal length of the imaging optical system 10. The imaging optical system 10 also satisfies the conditions of the following table:

TABLE 3

TABLE 4

The following data can be obtained from tables 3 and 4:

F(mm)	2.14	\|R2/R3\|	0.27
				FNO	2.3	R4/f	15.75
FOV (degree)	80	\|SAG31\|(mm)	0.088
				TTL/Imgh	0.68	\|SAG32\|(mm)	0.21
CT2/∑CT	0.1875	SD/CT4	4.51
				T12/TD	0.08

Example three:

referring to fig. 9 to 12, the imaging optical system 10 of the present embodiment includes, from an object side to an image side, a first lens element L1, a second lens element L2, a third lens element L3, a fourth lens element L4 and an infrared filter L5.

TABLE 5

TABLE 6

The following data can be obtained from tables 5 and 6:

F(mm)	2.14	\|R2/R3\|	0.09
				FNO	2.3	R4/f	6.85
FOV (degree)	81	\|SAG31\|(mm)	0.083
				TTL/Imgh	0.68	\|SAG32\|(mm)	0.195
CT2/∑CT	0.174	SD/CT4	5.31
				T12/TD	0.10

Example four:

referring to fig. 13 to 16, the imaging optical system 10 of the present embodiment includes, from an object side to an image side, a first lens element L1, a second lens element L2, a third lens element L3, a fourth lens element L4 and an infrared filter L5.

The first lens element L1 with positive refractive power is made of plastic, and has a convex object-side surface S1 and a concave image-side surface S2. The second lens element L2 with negative refractive power is made of plastic, and has a concave object-side surface S3 and a concave image-side surface S4. The third lens element L3 with positive refractive power is made of plastic, and has a concave object-side surface S5 and a convex image-side surface S6. The fourth lens element L4 with refractive power is made of plastic, and has an object-side surface S7 being convex along an optical axis and concave along a circumference, and an image-side surface S8 being concave along the optical axis and convex along the circumference.

The stop STO is disposed on the object side S1 of the first lens L1. The f-number FNO of the imaging optical system 10 is 2.2.

TABLE 7

TABLE 8

The following data can be obtained from tables 7 and 8:

f(mm)	2.14	\|R2/R3\|	0.10
				FNO	2.2	R4/f	8.63
FOV (degree)	80.8	\|SAG31\|(mm)	0.123
				TTL/Imgh	0.75	\|SAG32\|(mm)	0.301
CT2/∑CT	0.15	SD/CT4	3.13
				T12/TD	0.10

Referring to fig. 1 and 17, an image capturing apparatus 100 according to an embodiment of the present invention includes an imaging optical system 10 and a photosensitive element 20 according to any one of the above embodiments. The photosensitive element 20 is disposed on the image side of the imaging optical system 10.

In the image capturing apparatus 100 according to the embodiment of the invention, the imaging optical system 10 not only meets the requirement of ultra-short and ultra-thin but also meets the requirement of high pixel by reasonably matching the four lenses, and has the characteristics of large aperture and large field angle.

Specifically, the photosensitive element 20 may be a Complementary Metal Oxide Semiconductor (CMOS) image sensor or a Charge-coupled Device (CCD) image sensor.

Further, in the embodiment of fig. 17, the image capturing apparatus 100 further includes a lens barrel 30, a lens base 40 and a circuit board 50, the photosensitive element 20 is disposed on the circuit board 50 and electrically connected to the circuit board 50, the lens base 40 is disposed on the circuit board 50, the lens barrel 30 is connected to the lens base 40, and the imaging optical system 10 is disposed in the lens barrel 30.

Referring to fig. 18 and fig. 19, an electronic device 1000 according to an embodiment of the present invention includes a housing 200 and the image capturing device 100 according to the above embodiment. The image capturing device 100 is mounted in the housing 200.

In the electronic device 1000 according to the embodiment of the present invention, the imaging optical system 10 not only meets the requirement of ultra-short and ultra-thin but also meets the requirement of high pixel by reasonably matching the four lenses, and has the characteristics of large aperture and large field angle.

It is understood that the electronic device 1000 according to the embodiment of the present invention includes, but is not limited to, information terminal devices such as a smart phone, a Personal Digital Assistant (PDA), a tablet computer, a Personal Computer (PC), and a smart wearable device, or an electronic device with a photographing function. In the example of fig. 18, the electronic device 1000 is a smartphone. In the example of fig. 19, the electronic device 1000 is a notebook computer. The image capturing device 100 can be disposed on the back of the electronic device 1000 or disposed on the front of the electronic device 1000.

In the description of the specification, reference to the terms "certain embodiments," "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples" or the like means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

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

Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and those skilled in the art can make changes, modifications, substitutions and alterations to the above embodiments within the scope of the present invention, which is defined by the claims and their equivalents.

Claims

1. An imaging optical system, comprising 4 lens elements with refractive power, in order from an object side to an image side:

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

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

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

the fourth lens element with negative refractive power has aspheric object-side and image-side surfaces, and at least one of the object-side and image-side surfaces of the fourth lens element has at least one inflection point;

the imaging optical system satisfies the following conditions:

TTL/Imgh≤0.75；|SAG31|≤0.15，|SAG32|≤0.35；

wherein, TTL is a distance between an object-side surface of the first lens element and an image plane on an optical axis, Imgh is a maximum imaging height of the imaging optical system, SAG31 is a horizontal distance between a maximum effective diameter of an object-side surface of the third lens element and an optical axis of an object-side surface of the third lens element, and SAG32 is a horizontal distance between a maximum effective diameter of an image-side surface of the third lens element and an optical axis of an image-side surface of the third lens element.

2. The imaging optical system according to claim 1, wherein the imaging optical system satisfies the following condition:

TTL/Imgh≤0.68。

3. the imaging optical system according to claim 1, wherein the imaging optical system satisfies the following condition:

CT2/∑CT≥0.15；

wherein CT2 is the center thickness of the second lens, and Σ CT is the sum of the center thicknesses of the first lens, the second lens, the third lens, and the fourth lens.

4. The imaging optical system according to claim 1, wherein the imaging optical system satisfies the following condition:

T12/TD≥0.05；

wherein T12 is an air gap between the first lens element and the second lens element, and TD is a distance on an optical axis between an object-side surface of the first lens element and an image-side surface of the fourth lens element.

5. The imaging optical system according to claim 1, wherein the imaging optical system satisfies the following condition:

|R2/R3|<1；

wherein R2 is a radius of curvature of an image-side surface of the first lens, and R3 is a radius of curvature of an object-side surface of the second lens.

6. The imaging optical system according to claim 1, wherein the imaging optical system satisfies the following condition:

R4/f>5；

wherein R4 is a radius of curvature of an image-side surface of the second lens, and f is a focal length of the imaging optical system.

7. The imaging optical system according to claim 1, wherein the imaging optical system satisfies the following condition:

|SAG31|≤0.1，|SAG32|≤0.2；

SAG31 is the horizontal distance between the position of the maximum effective diameter of the object side surface of the third lens and the optical axis of the object side surface of the third lens, and SAG32 is the horizontal distance between the position of the maximum effective diameter of the image side surface of the third lens and the optical axis of the image side surface of the third lens.

8. The imaging optical system according to claim 1, wherein the imaging optical system satisfies the following condition:

SD/CT4<5.5；

wherein SD is a distance on an optical axis from an object-side surface of the first lens element to an image-side surface of the third lens element, and CT4 is a center thickness of the fourth lens element.

9. An image capturing apparatus, comprising:

the imaging optical system of any one of claims 1 to 8; and

and the photosensitive element is arranged on the image side of the imaging optical system.

10. An electronic device comprising a housing and the image capturing device of claim 9, wherein the image capturing device is mounted in the housing.