CN111239987A

CN111239987A - Optical imaging system, image capturing device and electronic equipment

Info

Publication number: CN111239987A
Application number: CN202010240193.3A
Authority: CN
Inventors: 谢晗; 刘彬彬; 李明
Original assignee: OFilm Tech Co Ltd
Current assignee: Nanchang OFilm Precision Optical Products Co Ltd; OFilm Group Co Ltd
Priority date: 2020-03-30
Filing date: 2020-03-30
Publication date: 2020-06-05

Abstract

The invention provides an optical imaging system, an image capturing device and an electronic device. The optical imaging system provided by the invention comprises the following components in sequence from an object side to an image side: a first lens having a positive optical power; a second lens having an optical power; a third lens having optical power; and a fourth lens having a focal power; wherein the optical imaging system satisfies the following conditional expression: TTL is less than or equal to 2.644 mm; wherein, TTL is a distance on the optical axis from the object-side surface of the first lens element to the image plane. The total length of the optical imaging system is less than or equal to 2.644mm, and the requirement of camera ultra-thinning can be well met.

Description

Optical imaging system, image capturing device and electronic equipment

Technical Field

The present disclosure relates to optical imaging technologies, and particularly to an optical imaging system, an image capturing device and an electronic apparatus.

Background

With the development of technologies such as mobile phone face unlocking, automobile automatic driving, human-computer interface and game, industrial machine vision and measurement, security monitoring and the like, people require that the equipment has Three-Dimensional (3D) face recognition, object restoration, mobile payment and other functions, and the realization of the functions puts higher requirements on the technology of the camera. The Time of flight (TOF) imaging technology is applied to a camera, so that a 3D face recognition function of the camera can be well realized, and good object reducibility is achieved.

Disclosure of Invention

In view of this, embodiments of the present invention provide an optical imaging system, which has a short total length and can well meet the requirement of ultra-thinning of a camera.

It is also necessary to provide an image capturing apparatus using the above optical imaging system.

In addition, it is necessary to provide an electronic device using the image capturing apparatus.

An embodiment of the present invention provides an optical imaging system, which sequentially includes, from an object side to an image side:

a first lens having a positive optical power;

a second lens having an optical power;

a third lens having optical power; and

a fourth lens having an optical power;

wherein the optical imaging system satisfies the following conditional expression:

TTL≤2.644mm；

wherein, TTL is a distance on the optical axis from the object-side surface of the first lens element to the image plane.

The total length of the optical imaging system is fully compressed, and the requirement of ultra-thinning can be well met.

The first lens is characterized in that the object side surface of the first lens is a convex surface at the position close to the optical axis; the image side surface is concave at the paraxial axis. The object side surface is convex at the position close to the optical axis, so that the convergence of light rays is more facilitated, the first lens has enough positive focal power, the total length of the optical imaging system is further shortened, and the light rays are converged at the side surface of the image side surface complex.

The object side surface of the third lens is a concave surface at the position close to the optical axis; the image side surface is convex at the position close to the optical axis. The image side surface is convex at the position close to the optical axis, so that the capability of the third lens for correcting aberration can be ensured.

The object side surface of the fourth lens is a convex surface at the position close to the optical axis; the image side surface is concave at the paraxial axis. The image side surface of the fourth lens is concave at the paraxial position, so that curvature of field of the optical imaging system is corrected, excessive increase of a chief ray incident angle of an off-axis field is restrained, and meanwhile, aberration of the off-axis field is corrected.

At least one of the object side surface and the image side surface of the fourth lens is provided with at least one inflection point. The inflection point can be used for correcting the aberration of the off-axis field of view, inhibiting the incident angle of light to an imaging surface and matching the photosensitive element more accurately.

0.8<tan(FOV/2)<1.0；

wherein the FOV is a maximum field angle of the optical imaging system.

When tan (FOV/2) is less than 0.8, the field angle of the optical imaging system is too small to obtain a wide image, and the effective focal length of the optical imaging system may become long, which is not favorable for lens length compression. When 0.8< tan (FOV/2) <1.0, the image range of the optical imaging system can be expanded.

FNO≤1.6；

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

When FNO is less than or equal to 1.6, the optical imaging system has larger luminous flux and higher relative brightness.

FNO≤1.3；

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

When FNO is less than or equal to 1.3, the optical imaging system has larger luminous flux and higher relative brightness.

19<Vd1<25；

19<Vd2<25；

19<Vd3<25；

19<Vd4<25；

wherein Vd1 is the abbe number of the first lens, Vd2 is the abbe number of the second lens, Vd3 is the abbe number of the third lens, and Vd4 is the abbe number of the fourth lens.

When Vd1, Vd2, Vd3 and Vd4 are all larger than 19 and smaller than 25, the optical imaging system is facilitated to obtain a higher modulation transfer function, and the imaging quality of the optical imaging system is improved.

0.5<CT2/CT3<1.5；

wherein CT2 is the center thickness of the second lens and CT3 is the center thickness of the third lens.

When 0.5< CT2/CT3<1.5, the assembly of the optical imaging system can be made more stable.

0<R5/R6<2.2；

wherein R5 is a radius of curvature of the object-side surface of the second lens element along the optical axis, and R6 is a radius of curvature of the image-side surface of the second lens element along the optical axis.

When the ratio of 0< R5/R6<2.2, the shape of the object side surface and the shape of the image side surface of the second lens are similar, the molding is more uniform, and the object side surface and the image side surface are bent at the same side, which is beneficial to improving the resolution of the optical imaging system.

0.18<R7/R8<1.1；

wherein R7 is a radius of curvature of the object-side surface of the third lens element along the optical axis, and R8 is a radius of curvature of the image-side surface of the third lens element along the optical axis.

When the optical imaging system is 0.18< R7/R8<1.1, the shape of the object side surface and the shape of the image side surface of the third lens are similar, the third lens is molded more uniformly, and the object side surface and the image side surface are bent at the same side, which is beneficial to improving the resolution of the optical imaging system.

0.4<R10/f<0.8；

wherein R10 is a curvature radius of the image-side surface of the fourth lens element on the optical axis, and f is an effective focal length of the optical imaging system.

When 0.4< R10/f <0.8, the image side surface of the fourth lens is concave at the paraxial region and convex at the periphery, which helps to correct curvature of field of the optical imaging system, suppress excessive increase of the incident angle of chief rays in the off-axis field, and correct aberration in the off-axis field.

-1<f1/f23<0.5；

wherein f1 is the effective focal length of the first lens, and f23 is the combined focal length of the second lens and the third lens.

The first lens provides most positive focal power, the focal power of the second lens and the focal power of the third lens are reasonably configured, the positive spherical aberration generated by the first lens can be corrected, and a small part of positive focal power is compensated for the optical imaging system, so that the optical imaging system has higher imaging quality.

An embodiment of the present invention further provides an image capturing apparatus, which includes:

the optical imaging system described above; and

a photosensitive element located on an image side of the optical imaging system.

The orientation device disclosed by the invention is small in thickness and can be used for preparing an ultrathin camera.

The image capturing device has wider focusing range and imaging quality while ensuring miniaturization.

An embodiment of the present invention further provides an electronic device, which includes:

an apparatus main body; and

the image capturing device is mounted on the main body of the apparatus.

The camera of the electronic equipment is small in thickness, and the size of the electronic equipment is favorably reduced.

Therefore, the total length of the optical imaging system is smaller than or equal to 2.644mm, and the requirement of camera ultra-thinning can be well met.

Drawings

To more clearly illustrate the structural features and effects of the present invention, a detailed description is given below with reference to the accompanying drawings and specific embodiments.

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

Fig. 1-2 are graphs of spherical aberration, astigmatism and distortion of the optical imaging system of the first embodiment of the present invention from left to right in sequence.

Fig. 2-1 is a schematic structural view of an optical imaging system of a second embodiment of the present invention.

Fig. 2-2 is a graph showing the spherical aberration, astigmatism and distortion of the optical imaging system according to the second embodiment of the present invention from left to right.

Fig. 3-1 is a schematic structural view of an optical imaging system according to a third embodiment of the present invention.

Fig. 3-2 is a graph showing the spherical aberration, astigmatism and distortion of the optical imaging system according to the third embodiment of the present invention from left to right.

Fig. 4-1 is a schematic structural view of an optical imaging system according to a fourth embodiment of the present invention.

Fig. 4-2 is a graph showing the spherical aberration, astigmatism and distortion of the optical imaging system according to the fourth embodiment of the present invention from left to right.

Fig. 5-1 is a schematic structural view of an optical imaging system according to a fifth embodiment of the present invention.

Fig. 5-2 is a graph showing the spherical aberration, astigmatism and distortion of the optical imaging system according to the fifth embodiment of the present invention from left to right.

Fig. 6-1 is a schematic structural view of an optical imaging system according to a sixth embodiment of the present invention.

Fig. 6-2 is a graph showing the spherical aberration, astigmatism and distortion of the optical imaging system according to the sixth embodiment of the present invention from left to right.

Fig. 7 is a schematic structural diagram of an image capturing apparatus according to an embodiment of the invention.

Fig. 8 is a schematic structural diagram of an electronic device according to an embodiment of the present invention.

DETAILED DESCRIPTION OF EMBODIMENT (S) OF INVENTION

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

Referring to fig. 1-1, fig. 2-1, fig. 3-1, fig. 4-1, fig. 5-1 and fig. 6-1, the optical imaging system 100 according to the embodiment of the present invention is suitable for infrared band imaging, and can be applied to lenses of imaging devices such as computers, mobile phones, tablet computers, vehicles, monitors, security, medical devices, game machines, robots, etc., and includes, in order from an object side to an image side, a first lens L1 with positive optical power, a second lens L2 with optical power, a third lens L3 with optical power, a fourth lens L4 with optical power, and an imaging plane 50. The optical imaging system 100 satisfies the following conditional expression:

TTL≤2.644mm；

wherein, TTL is the distance from the object-side surface of the first lens element L1 to the image plane 50 on the optical axis, i.e. the total length of the optical imaging system 100.

More specifically, TTL can be 2.3mm, 2.35mm, 2.4mm, 2.45mm, 2.5mm, 2.55mm, 2.6mm, 2.64 mm.

When TTL is less than or equal to 2.644mm, the total length of the optical imaging system 100 is fully compressed, and the requirement of camera ultra-thinning can be well met.

The term "focal power" as used herein characterizes the ability of an optical system to deflect light rays.

The total length of the optical imaging system 100 is less than or equal to 2.644mm, and the requirement of camera ultra-thinning can be well met.

Optionally, the first lens element L1 is made of glass or plastic and has an object-side surface S1 and an image-side surface S2. Object-side surface S1 is convex near the optical axis; the circumference can be convex or concave. The image side surface S2 may be concave near the optical axis, convex at the circumference, or concave. The object side surface S101 is convex at a position near the optical axis, which is more favorable for light convergence, so that the first lens L1 has sufficient positive focal power, thereby shortening the total length of the optical imaging system 100, and the image side surface S2 complex converges light at the side surface.

Optionally, the second lens element L2 is made of glass or plastic and has an object-side surface S3 and an image-side surface S4. The second lens L2 may have a positive power or a negative power. The object side surface S3 near the optical axis can be convex or concave; the circumference can be convex or concave. The image-side surface S4 may be convex or concave near the optical axis; the circumference can be convex or concave.

Optionally, the third lens element L3 is made of glass or plastic and has an object-side surface S5 and an image-side surface S6. The third lens L3 may have a positive power or a negative power. Object-side surface S5 is concave near the optical axis; the circumference can be convex or concave. The image side surface S6 may be convex near the optical axis, convex at the circumference, or concave. The image-side surface S6 of the third lens element L3 is convex near the optical axis, so that the third lens element can correct aberrations.

Optionally, the fourth lens element L4 is made of glass or plastic and has an object-side surface S7 and an image-side surface S8. The fourth lens L4 may have a positive power or a negative power. Object-side surface S7 is convex near the optical axis; the circumference can be convex or concave. The image side surface S8 may be concave near the optical axis, convex at the circumference, or concave. When the image side surface S8 of the fourth lens L4 is concave at the paraxial region and convex at the peripheral region, it helps correct curvature of field of the optical imaging system 100, suppress excessive increase of the incident angle of the chief ray of the off-axis field, and correct aberration of the off-axis field.

In some embodiments, at least one of the object-side surface S7 and the image-side surface S8 of the fourth lens L4 is provided with at least one inflection point. "inflection point" refers to an inflection point where the radius of curvature changes from positive to negative or negative to positive. The inflection point can be used to correct the aberrations of the off-axis field, suppress the incidence angle of the light to the image plane 50, and more precisely match the photosensitive elements (see fig. 7 and the following embodiments).

In some embodiments, the first lens L1, the second lens L2, the third lens L3, and the fourth lens L4 include glass lenses and plastic lenses. For example, the first lens L1 is a glass lens, and the second lens L2, the third lens L3, and the fourth lens L4 are all plastic lenses. The first lens L1 closest to the object side is made of glass, so that the first lens can better withstand the influence of the ambient temperature on the object side, and the second lens L2, the third lens L3 and the fourth lens L4 are plastic lenses, so that the weight of the optical imaging system 100 can be well reduced, and the production cost can be reduced. In addition, the optical imaging system 100 in which the glass lens and the plastic lens are mixed has higher light transmittance and more stable chemical properties than an optical imaging system including only the plastic lens, and can improve imaging quality at different light and dark contrasts.

In some embodiments, the first lens L1, the second lens L2, the third lens L3, and the fourth lens L4 are all aspheric lenses. The aspheric lens is beneficial to correcting aberration of the optical imaging system 100 and improving imaging quality of the optical imaging system 100. Can be easily manufactured into shapes other than spherical surfaces, obtain more control variables, obtain good imaging by using fewer lenses, further reduce the number of lenses and meet the requirement of miniaturization. "aspherical lens" refers to a lens at least one side of which is aspherical.

In some embodiments, when the object-side surface and/or the image-side surface of the first lens L1, the second lens L2, the third lens L3, and the fourth lens L4 are aspheric, the aspheric surfaces satisfy the following relationship:

wherein Z is the distance from the corresponding point on the aspheric surface to the plane tangent to the vertex of the object side surface or the image side surface, r is the distance from the corresponding point on the aspheric surface to the optical axis, c is the curvature of the vertex (at the optical axis) of the aspheric surface, k is a conic coefficient, and Ai is the ith order aspheric coefficient of the object side surface or the image side surface.

Optionally, the optical imaging system 100 further comprises a diaphragm 10. Specifically, the stop 10 may be located between the object side of the first lens L1 and the object side S8 of the fourth lens L4. More specifically, the stop 10 is located between the first lens L1 and the second lens L2, which is advantageous for enlarging the field angle of the optical imaging system 100. The stop 10 may be located at any position between the object side of the first lens L1 and the object side S8 of the fourth lens L4, and the present invention is not particularly limited as to the position of the stop 10.

Optionally, the optical imaging system 100 further comprises an infrared band pass filter 30. The infrared band pass filter 30 is located between the fourth lens L4 and the image plane 50. Infrared bandpass filter 30 has a first face 31 and a second face 32. The infrared band pass filter 30 is made of glass, which can increase the transmittance of light in the infrared band, so that the optical imaging system 100 can be better applied to infrared imaging.

The term "ghost image" is also called ghost image in the present invention, and refers to an additional image generated near the focal plane of the optical imaging system due to the reflection of the lens surface, which is generally dark in brightness and is offset from the original image.

In some embodiments, the optical imaging system 100 satisfies the following conditional expression:

0.8<tan(FOV/2)<1.0；

wherein the FOV is the maximum field angle of the optical imaging system 100.

That is, tan (FOV/2) can be any value between 0.8 and 1.0, for example: 0.81, 0.85, 0.90, 0.95, 0.99, etc.

When tan (FOV/2) is less than 0.8, the field angle of the optical imaging system 100 is too small to acquire a wide image, and the effective focal length of the optical imaging system 100 may become long, which is not favorable for lens length compression. When 0.8< tan (FOV/2) <1.0, the image range of the optical imaging system 100 can be expanded.

FNO≤1.6；

wherein FNO is the f-number of the optical imaging system 100.

That is, FNO may be any number less than or equal to 1.6, such as 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, and the like.

When FNO is less than or equal to 1.6, the optical imaging system 100 has a larger luminous flux and higher relative brightness.

FNO≤1.3；

wherein FNO is the f-number of the optical imaging system 100.

That is, FNO may be any value of 1.3 or less, e.g., 0.91, 0.95, 1.0, 1.1, 1.2, 1.3, etc.

When FNO is less than or equal to 1.3, the optical imaging system 100 has a larger luminous flux and a higher relative brightness.

19<Vd1<25；

19<Vd2<25；

19<Vd3<25；

19<Vd4<25；

vd1 is the abbe number of the first lens L1, Vd2 is the abbe number of the second lens L2, Vd3 is the abbe number of the third lens L3, and Vd4 is the abbe number of the fourth lens L4.

That is, Vd1, Vd2, Vd3, and Vd4 may be any number between 19 and 25, such as 19.1, 20, 21, 22, 23, 24, 24.9, etc., respectively.

When the Vd1, the Vd2, the Vd3 and the Vd4 are all larger than 19 and smaller than 25, the optical imaging system 100 is favorable for obtaining a higher modulation transfer function, and the imaging quality of the optical imaging system 100 is improved.

The term "Modulation Transfer Function" is also called a spatial contrast Transfer Function (spatial contrast Transfer Function) and a spatial frequency contrast sensitivity Function (spatial frequency contrast sensitivity Function) according to the present invention, which reflects the capability of the optical imaging system 100 to Transfer various frequency sine wave modulations. The higher the modulation transfer function of the optical imaging system 100, the better the imaging quality.

0.5<CT2/CT3<1.5；

wherein, CT2 is the central thickness of the second lens L2, i.e. the distance on the optical axis from the object-side surface S3 to the image-side surface S4 of the second lens L2; the CT3 is the central thickness of the third lens L3, i.e., the distance on the optical axis from the object-side surface S5 to the image-side surface S6 of the third lens L3.

That is, CT2/CT3 may be any number between 0.5 and 1.5, such as 0.51, 0.6, 0.7, 0.8, 0.85, 0.9, 0.95, 1.0, 1.04, 1.2, 1.3, 1.49, and so forth.

When 0.5< CT2/CT3<1.5, the assembly of the optical imaging system 100 can be made more stable.

0<R5/R6<2.2；

wherein R5 is a radius of curvature of the object-side surface S3 of the second lens element L2 along the optical axis, and R6 is a radius of curvature of the image-side surface S4 of the second lens element L2 along the optical axis.

That is, R5/R6 can be any number between 0 and 2.2, such as 0.1, 0.6, 0.8, 1.0, 1.5, 2.0, 2.1, 2.19, and the like.

When 0< R5/R6<2.2, the shape of the object-side surface S3 and the shape of the image-side surface S4 of the second lens L2 are similar, so that the molding is more uniform, and the object-side surface S3 and the image-side surface S4 are curved on the same side, which is beneficial to improving the resolution of the optical imaging system 100.

0.18<R7/R8<1.1；

wherein R7 is a radius of curvature of the object-side surface S5 of the third lens element L3 along the optical axis, and R8 is a radius of curvature of the image-side surface S6 of the third lens element L3 along the optical axis.

That is, R7/R8 can be any number between 0.18 and 1.1, such as 0.3, 0.5, 0.6, 0.8, 0.9, 1.0, 1.09, and the like.

When 0.18< R7/R8<1.1, the shape of the object-side surface S5 and the shape of the image-side surface S6 of the third lens L3 are similar, so that the third lens L is formed more uniformly, and the object-side surface S5 and the image-side surface S6 are bent at the same side, which is beneficial to improving the resolution of the optical imaging system 100.

0.4<R10/f<0.8；

wherein R10 is a curvature radius of the image-side surface S8 of the fourth lens element L4 along the optical axis, and f is an effective focal length of the optical imaging system 100. .

That is, 0.4< R10/f <0.8 can be any value between 0.4 and 0.8, such as 0.41, 0.5, 0.6, 0.7, 0.79, etc.

When 0.4< R10/f <0.8, the image side surface S8 of the fourth lens element L4 is concave at the paraxial region and convex at the peripheral region, which helps to correct curvature of field of the optical imaging system 100, suppress excessive increase of the incident angle of chief rays in the off-axis (off-axis) field, and correct aberrations in the off-axis field.

-1<f1/f23<0.5；

wherein f1 is the effective focal length of the first lens L1, and f23 is the combined focal length of the second lens L2 and the third lens L3. .

That is, f1/f23 can be any number between-1 and 0.5, such as-0.99, -0.8, -0.5, -0.1, 0.2, 0.3, 0.49, etc.

Most of the positive focal power is provided by the first lens L1, and the focal powers of the second lens L2 and the third lens L3 are reasonably configured, so that the positive spherical aberration generated by the first lens L1 can be corrected, a small part of the positive focal power can be compensated for the optical imaging system 100, and the optical imaging system 100 has higher imaging quality.

The optical imaging system 100 of the present invention is described in further detail below with reference to specific embodiments.

First embodiment

Referring to fig. 1-1 and fig. 1-2, wherein fig. 1-1 is a schematic structural diagram of an optical imaging system 100 according to a first embodiment, and fig. 1-2 are graphs of spherical aberration, astigmatism and distortion of the first embodiment of the invention from left to right. As can be seen from fig. 1-1, the optical imaging system 100 of the present embodiment includes, in order from an object side to an image side, a first lens L1 with positive power, a stop 10, a second lens L2 with positive power, a third lens L3 with negative power, a fourth lens L4 with positive power, an infrared band-pass filter 30, and an image plane 50.

The first lens element L1 is made of plastic and has an object-side surface S1 and an image-side surface S2. The object side surface S1 is convex near the optical axis and concave at the circumference. The image side surface S2 is concave near the optical axis and convex at the circumference.

The second lens L2 is made of plastic material and has an object-side surface S3 and an image-side surface S4. The object side surface S3 is concave both near the optical axis and at the circumference. The image side surface S4 is convex both near the optical axis and at the circumference.

The third lens element L3 is made of plastic and has an object-side surface S5 and an image-side surface S6. The object side surface S5 is concave both near the optical axis and at the circumference. The image side surface S6 is convex both near the optical axis and at the circumference.

The fourth lens element L4 is made of plastic and has an object-side surface S7 and an image-side surface S8. The object side surface S7 is convex both near the optical axis and at the circumference. The image side surface S8 is concave near the optical axis and convex at the circumference.

In this example, TTL is 2.63 mm; FOV 86.68 °, tan (FOV/2) 0.944; FNO 1.2; CT 2-0.314, CT 3-0.215; CT2/CT 3-1.460; r5 ═ -1.808, R6 ═ -0.849, R5/R6 ═ 2.130; r7 ═ 0.677, R8 ═ 3.857, R7/R8 ═ 0.176; r10 ═ 0.813, f ═ 1.691, R10/f ═ 0.481; f 1-2.61, f 23-3.21, f1/f 23-0.813.

In the present embodiment, the optical imaging system 100 satisfies the conditions of table 1 and table 2 below.

Table 2 shows aspheric data of the first embodiment, where k is a conic coefficient of each surface, and A4-A20 are aspheric coefficients of 4 th to 20 th order of each surface.

As can be seen from fig. 1-1 and fig. 1-2, the optical imaging system 100 of the present invention has a higher imaging quality while satisfying the miniaturization.

Second embodiment

Referring to fig. 2-1 and 2-2, wherein fig. 2-1 is a schematic structural diagram of an optical imaging system 100 according to a second embodiment, and fig. 2-2 is a graph of spherical aberration, astigmatism and distortion in the second embodiment of the invention from left to right. As can be seen from fig. 2-1, the optical imaging system 100 of the present embodiment includes, in order from the object side to the image side, a first lens L1 with positive power, a stop 10, a second lens L2 with negative power, a third lens L3 with negative power, a fourth lens L4 with positive power, an infrared band-pass filter 30, and an imaging plane 50.

The first lens element L1 is made of plastic and has an object-side surface S1 and an image-side surface S2. The object side surface S1 is convex both near the optical axis and at the circumference. The image side surface S2 is concave near the optical axis and convex at the circumference.

The second lens L2 is made of plastic material and has an object-side surface S3 and an image-side surface S4. The object side surface S3 is convex near the optical axis and concave at the circumference. The image side surface S4 is concave near the optical axis and convex at the circumference.

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

In this example, TTL is 2.63 mm; FOV 82.7 °, tan (FOV/2) 0.880; FNO 1.40; CT 2-0.2, CT 3-0.315; CT2/CT3 ═ 0.635; r5 ═ 7.766, R6 ═ 6.85, R5/R6 ═ 1.134; r7 ═ 0.998, R8 ═ 1.78, R7/R8 ═ 0.561; r10 ═ 0.748, f ═ 1.81, R10/f ═ 0.413; f 1-2.46, f 23-4.22, f1/f 23-0.583.

In the present embodiment, the optical imaging system 100 satisfies the conditions of tables 3 and 4 below.

Table 4 shows aspheric data of the second embodiment, where k is a conic coefficient of each surface and A4-A20 are aspheric coefficients of 4 th to 20 th order of each surface.

As can be seen from fig. 2-1 and 2-2, the optical imaging system 100 of the present invention has a higher imaging quality while satisfying the miniaturization.

Third embodiment

Referring to fig. 3-1 and 3-2, wherein fig. 3-1 is a schematic structural diagram of an optical imaging system 100 according to a third embodiment, and fig. 3-2 is a graph of spherical aberration, astigmatism and distortion in the third embodiment of the invention from left to right. As can be seen from fig. 3-1, the optical imaging system 100 of the present embodiment includes, in order from the object side to the image side, a first lens L1 with positive optical power, a stop 10, a second lens L2 with positive optical power, a third lens L3 with positive optical power, a fourth lens L4 with positive optical power, an infrared band-pass filter 30, and an image plane 50.

In this embodiment, TTL is 2.644 mm; FOV 85 °, tan (FOV/2) 0.916; FNO 1.60; CT 2-0.2, CT 3-0.339; CT2/CT3 is 0.590; r5 ═ 9.032, R6 ═ 7.493, R5/R6 ═ 1.205; r7 ═ 0.954, R8 ═ 1.067, R7/R8 ═ 0.894; r10 ═ 0.747, f ═ 1.797, R10/f ═ 0.416; f1 ═ 2.49, f23 ═ 42.755, and f1/f23 ═ 0.058.

In the present embodiment, the optical imaging system 100 satisfies the conditions of tables 5 and 6 below.

Table 6 shows aspheric data of the third embodiment, where k is a conic coefficient of each surface and A4-A20 are aspheric coefficients of 4 th to 20 th order of each surface.

As can be seen from fig. 3-1 and 3-2, the optical imaging system 100 of the present invention has a higher imaging quality while satisfying the miniaturization.

Fourth embodiment

Referring to fig. 4-1 and 4-2, wherein fig. 4-1 is a schematic structural diagram of an optical imaging system 100 according to a fourth embodiment, and fig. 4-2 is a graph of spherical aberration, astigmatism and distortion in the fourth embodiment of the invention from left to right. As can be seen from fig. 4-1, the optical imaging system 100 of the present embodiment includes, in order from the object side to the image side, a first lens L1 with positive power, a stop 10, a second lens L2 with positive power, a third lens L3 with negative power, a fourth lens L4 with positive power, an infrared band-pass filter 30, and an imaging plane 50.

The third lens element L3 is made of plastic and has an object-side surface S5 and an image-side surface S6. The object side surface S5 is concave both near the optical axis and at the circumference. The image side surface S6 is convex near the optical axis and concave at the circumference.

In this example, TTL is 2.63 mm; FOV is 87.1 °, tan (FOV/2) is 0.951; FNO 1.08; CT 2-0.228, CT 3-0.245; CT2/CT3 is 0.931; r5 ═ -1.826, R6 ═ -0.942, R5/R6 ═ 1.938; r7 ═ 0.878, R8 ═ 4.688, R7/R8 ═ 0.187; r10 ═ 1.241, f ═ 1.689, R10/f ═ 0.735; f 1-2.64, f 23-4.41, f1/f 23-0.599.

In the present embodiment, the optical imaging system 100 satisfies the conditions of the following tables 7 and 8.

Table 8 shows aspheric data of the fourth embodiment, where k is a conic coefficient of each surface and A4-A20 are aspheric coefficients of 4 th to 20 th order of each surface.

As can be seen from fig. 4-1 and 4-2, the optical imaging system 100 of the present invention has a higher imaging quality while satisfying the miniaturization.

Fifth embodiment

Referring to fig. 5-1 and 5-2, wherein fig. 5-1 is a schematic structural diagram of an optical imaging system 100 according to a fifth embodiment, and fig. 5-2 is a graph of spherical aberration, astigmatism and distortion in the fifth embodiment of the invention from left to right. As can be seen from fig. 5-1, the optical imaging system 100 of the present embodiment includes, in order from the object side to the image side, a first lens L1 with positive power, a stop 10, a second lens L2 with negative power, a third lens L3 with positive power, a fourth lens L4 with positive power, an infrared band-pass filter 30, and an image plane 50.

In this example, TTL is 2.63 mm; FOV 86.36 °, tan (FOV/2) 0.938; FNO 1.16; CT 2-0.209, CT 3-0.294; CT2/CT3 is 0.711; r5 ═ 3.523, R6 ═ 3.707, R5/R6 ═ 0.950; r7 ═ 1.162, R8 ═ 1.226, R7/R8 ═ 0.948; r10 ═ 0.796, f ═ 1.7, R10/f ═ 0.468; f 1-2.62, f 23-55.9, f1/f 23-0.047.

In the present embodiment, the optical imaging system 100 satisfies the conditions of tables 9 and 10 below.

Table 10 shows aspheric data of the fifth embodiment, where k is a conic coefficient of each surface and A4-A20 are aspheric coefficients of 4 th to 20 th order of each surface.

As can be seen from fig. 5-2, the optical imaging system 100 of the present invention has a higher resolution while satisfying miniaturization.

Sixth embodiment

Referring to fig. 6-1 and 6-2, wherein fig. 6-1 is a schematic structural diagram of an optical imaging system 100 according to a sixth embodiment, and fig. 6-2 is a graph of spherical aberration, astigmatism and distortion in the fifth embodiment of the invention from left to right. As can be seen from fig. 6-1, the optical imaging system 100 of the present embodiment includes, in order from the object side to the image side, a first lens L1 with positive power, a stop 10, a second lens L2 with positive power, a third lens L3 with positive power, a fourth lens L4 with negative power, an infrared band-pass filter 30, and an imaging plane 50.

In this example, TTL is 2.60 mm; FOV is 78 °, tan (FOV/2) is 0.81; FNO 1.40; CT 2-0.21, CT 3-0.307; CT2/CT3 is 0.684; r5 ═ 11.062, R6 ═ 116.012, R5/R6 ═ 0.095; r7 ═ -0.95, R8 ═ -0.887, R7/R8 ═ 1.071; r10 ═ 0.785, f ═ 1.831, R10/f ═ 0.429; f1 is 2.5, f23 is 5.727, and f1/f23 is 0.437.

In the present embodiment, the optical imaging system 100 satisfies the conditions of tables 11 and 12 below.

Table 12 shows aspheric data of the sixth embodiment, where k is a conic coefficient of each surface, and a4-a20 are aspheric coefficients of 4 th to 20 th orders of each surface.

As can be seen from fig. 6-1 and 6-2, the optical imaging system 100 of the present invention has a higher imaging quality while satisfying the miniaturization.

Referring to fig. 7, the image capturing apparatus 200 of the present invention further includes an optical imaging system 100 and a photosensitive element 210. The photosensitive element 210 is located on the image side of the optical imaging system 100.

The photosensitive element 210 of the present invention may be a Charge Coupled Device (CCD) or a Complementary Metal-Oxide Semiconductor (cmos) Device.

The image capturing device 200 of the present invention has a wider focusing range and imaging quality while ensuring miniaturization.

For other descriptions of the image capturing device 200, please refer to the above description, which is not repeated herein.

Referring to fig. 8, the present invention further provides an electronic apparatus 300, which includes an apparatus main body 310 and the image capturing device 200 of the present invention. The orientation device 200 is mounted on the apparatus body 310.

The electronic device 300 of the present invention includes, but is not limited to, a vehicle-mounted camera, a computer, a notebook computer, a tablet computer, a mobile phone, a camera, a smart bracelet, a smart watch, smart glasses, an electronic book reader, a portable multimedia player, a mobile medical device, and the like.

The camera of the electronic device 300 of the present invention has a small thickness, which is beneficial to reducing the volume of the electronic device 300.

While the invention has been described with reference to specific embodiments, the invention is not limited thereto, and various equivalent modifications and substitutions can be easily made by those skilled in the art within the technical scope of the invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

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

a first lens having a positive optical power;

a second lens having an optical power;

a third lens having optical power; and

a fourth lens having an optical power;

TTL≤2.644mm；

2. The optical imaging system of claim 1, wherein the first lens object side surface is convex near the optical axis; the image side surface is concave at the paraxial axis.

3. The optical imaging system of claim 1, wherein the third lens object side surface is concave at the paraxial region; the image side surface is convex at the position close to the optical axis.

4. The optical imaging system of claim 1, wherein the fourth lens has a convex object-side surface near the optical axis; the image side surface is concave at the paraxial axis.

5. The optical imaging system of claim 1, wherein at least one of the object-side surface and the image-side surface of the fourth lens is provided with at least one inflection point.

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

0.8<tan(FOV/2)<1.0；

wherein the FOV is a maximum field angle of the optical imaging system.

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

FNO≤1.6；

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

8. The optical imaging system of claim 7, wherein the optical imaging system satisfies the following conditional expression:

FNO≤1.3；

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

9. The optical imaging system of claim 1, wherein the optical imaging system satisfies the following conditional expression:

19<Vd1<25；

19<Vd2<25；

19<Vd3<25；

19<Vd4<25；

10. The optical imaging system of claim 1, wherein the optical imaging system satisfies the following conditional expression:

0.5<CT2/CT3<1.5；

11. The optical imaging system of claim 1, wherein the optical imaging system satisfies the following conditional expression:

0<R5/R6<2.2；

12. The optical imaging system of claim 1, wherein the optical imaging system satisfies the following conditional expression:

0.18<R7/R8<1.1；

13. The optical imaging system of claim 1, wherein the optical imaging system satisfies the following conditional expression:

0.4<R10/f<0.8；

14. The optical imaging system of any of claims 1-13, wherein the optical imaging system satisfies the following conditional expression:

-1<f1/f23<0.5；

15. An image capturing apparatus, comprising:

the optical imaging system of any one of claims 1-14; and

16. An electronic device, comprising:

an apparatus main body; and

the image capturing device as claimed in claim 15, wherein the image capturing device is mounted on the main body of the apparatus.