WO2020125383A1

WO2020125383A1 - Lens and terminal device

Info

Publication number: WO2020125383A1
Application number: PCT/CN2019/122306
Authority: WO
Inventors: 卢建龙
Original assignee: 华为技术有限公司
Priority date: 2018-12-21
Filing date: 2019-12-02
Publication date: 2020-06-25
Also published as: CN109581626A

Abstract

Disclosed are a lens and a terminal device, relating to the technical field of lens. The lens comprises a lens assembly; the lens assembly comprises a first lens (1), a second lens (2), a third lens (3) and a fourth lens (4) arranged in sequence from the object side to the image side. The object side (11) of the first lens (1) is a convex surface. The relative illumination (RI) of the lens assembly and the biquadrate cos4(HFOV) of a cosine value at a half viewing angle of the lens assembly satisfy: RI/cos 4(HFOV)≥1. The effective focal length (f) of the lens assembly and the entrance pupil diameter (EPD) of the lens assembly satisfy: f/EPD≤1.3.

Description

Lens and terminal equipment

This application requires the priority of the Chinese patent application submitted to the State Intellectual Property Office of China on December 21, 2018, with the application number 201811596170.5 and the invention titled "a lens and terminal device", the entire content of which is incorporated by reference in this application in.

Technical field

This application relates to the field of lens technology, in particular to a lens and terminal equipment.

Background technique

With the continuous development of mobile devices such as mobile phones, the application of lens modules is becoming more and more diverse. Camera lenses are not limited to functions such as photographing and camera shooting. Near-infrared lenses for 3D modeling, face recognition, motion recognition and other functions are also rapidly developing. Among them, the lens is a key component of the lens module, and its performance is important Sex is increasingly prominent.

In near-infrared applications, especially the time-of-flight (TOF) 3D modeling system in 3D applications, the TOF system needs to obtain the depth information of each point on the measured object, so the brightness of the lens is required very high. And because it is limited to the packaging requirements of portable devices, the control of the lens size is also very strict. At present, the mature lens structure cannot meet the requirements of the TOF system due to its poor depth recognition accuracy.

Summary of the invention

The lens and the terminal device provided by the embodiments of the present application solve the problem of poor accuracy of lens depth recognition in the prior art.

To achieve the above purpose, the embodiments of the present application adopt the following technical solutions:

In a first aspect, the present application provides a lens including a lens group including a first lens, a second lens, a third lens, and a fourth lens arranged in order from the object side to the image side, the first lens The object side is convex, and the relative illuminance RI of the lens group and the cosine of the half field of view (HFOV) of the lens group are the fourth power cos ⁴ (HFOV) satisfying: RI/cos ⁴ (HFOV ) ≥ 1, and the effective focal length f of the lens group and the entrance pupil diameter (EPD) of the lens group satisfy: f/EPD ≤ 1.3.

In the lens provided by the embodiment of the present application, since the fourth power of the cosine value of the half angle of view is a reference standard for whether the relative illuminance of the lens is high, the relative illuminance RI of the lens group and the half angle of view of the lens group in the embodiment of the present application The ratio of the fourth power of the cosine value is greater than or equal to 1, so the relative illuminance of the lens group is greater than or equal to the reference standard, the relative illuminance of the lens group is larger, so that the brightness of the lens is higher, thereby increasing the depth of the lens structure Recognition accuracy. And because the effective focal length f of the lens group and the entrance pupil diameter EPD of the lens group satisfy: f/EPD≤1.3, the aperture value of the lens group is made smaller and the aperture is larger, so that sufficient light flux can be ensured to improve Identify accuracy and increase signal-to-noise ratio. In addition, since the object side surface of the first lens is convex, it focuses first when light enters the first lens, which helps to reduce the aperture of the rear lens and achieve miniaturization. Therefore, the lens provided by the embodiment of the present application can take into account the requirements of the TOF system on the lens illumination and aperture value on the premise of ensuring the miniaturization of the lens, thereby meeting the depth recognition accuracy requirements of the TOF system.

In a possible implementation manner, the effective focal length f of the lens group, the effective focal length f1 of the first lens, and the effective focal length f2 of the second lens satisfy: 0≤|f/f1|+|f/f2|≤0.5. Thus, not only can the lens be miniaturized, but also a larger viewing angle and a larger aperture can be achieved.

In a possible implementation, the image side of the fourth lens is provided with an imaging surface, the effective focal length f of the lens group and the diagonal length of the effective pixel area on the imaging surface 2*Imh(Image)high meet: f/(2*Imh )≤0.635. Thus, a larger angle of view can be realized.

In a possible implementation manner, the curvature radius R31 of the object side of the third lens and the curvature radius R32 of the image side of the third lens satisfy: 0≤(R31+R32)/(R31-R32)≤10. Thereby, the curvature radius of the object side and the image side of the third lens can be within a reasonable range, which can not only ensure the processability of the third lens, but also make the object side and the image side of the third lens satisfy the incident of each field of view The incidence angle of the third lens is required to meet the spherical aberration requirements of the imaging system.

In a possible implementation manner, the refractive index N1 of the material of the first lens, the Abbe number V2 of the material of the second lens, and the Abbe number of the material of the third lens are V3, satisfying: N1*(V3-V2)≥20. As a result, the degree of dispersion and the refractive index of the lens can be taken into account, so that the aberration of the lens group can be improved, and the angle of view can be increased to increase the recognition range.

In a possible implementation, the refractive index of the third lens material N3≥1.58. Thereby, the aberration of the lens group can be improved, and better resolution can be achieved.

In a possible implementation manner, the curvature radius R41 of the object side of the fourth lens and the system focal length f can satisfy: (R41/f)≥(1/2.5). In this way, it is possible to ensure that the lens has good manufacturability in processing and manufacturing while satisfying the effective focal length of the lens group, and reduce processing difficulty.

In a possible implementation manner, the image side of the first lens is concave, and both the object side and the image side of the first lens are aspherical. Aspheric lenses can improve aberrations, thereby improving imaging quality.

In a possible implementation manner, the first lens has negative power, and the second lens, third lens, and fourth lens all have positive power. Such setting is beneficial for adjusting the optical path, shortening the optical path length, and realizing a larger angle of view while ensuring the miniaturization of the lens.

In a possible implementation manner, the object side and/or the image side of the second lens have an inflection point, and the object side and the image side of the second lens are both aspherical. The inflection point of the second lens is helpful to balance the light aberrations at different apertures, to achieve a larger aperture, and at the same time to achieve higher illumination at the edges.

In a possible implementation manner, the object side of the third lens is concave, the image side of the third lens is convex, and the object side and image side of the third lens are both aspherical. Aspheric lenses can improve aberrations, thereby improving imaging quality.

In a possible implementation manner, the object side and/or the image side of the fourth lens have an inflection point, and the object side and the image side of the fourth lens are both aspherical. The inflection point on the fourth lens is beneficial to achieve less distortion and at the same time achieve higher illumination at the edges.

In a possible implementation manner, an aperture stop is provided between the first lens and the second lens. The aperture diaphragm can effectively improve the imaging quality of the lens.

In a possible implementation manner, a filter is provided between the imaging surface and the fourth lens, so that light of a desired wavelength can be selected to filter out interference light to improve imaging quality.

In a second aspect, an embodiment of the present application further provides a terminal device, which includes the lens described in any of the foregoing embodiments.

In a possible implementation manner of the second aspect, the terminal device includes a TOF system, the TOF system includes a laser emitting module and a laser receiving module, the laser receiving module includes the lens and the sensor, and the laser emitting module is used to target An object emits an optical signal, and the lens is used to receive the optical signal reflected by the target object and deliver the optical signal to the sensor after focusing.

The terminal device provided by the embodiment of the present application adopts the lens described in any of the above embodiments, so it can meet the requirements of the TOF system for the lens illumination and aperture value on the premise of ensuring the miniaturization of the lens, so as to meet the The TOF system's depth recognition accuracy requirements. The terminal can realize 3D modeling, face recognition, motion recognition and other functions.

BRIEF DESCRIPTION

1 is a schematic structural diagram of a lens according to a specific embodiment of the application;

2 is a schematic diagram of the optical path of a lens according to a specific embodiment of the application;

3 is a distortion curve diagram of a lens according to a specific embodiment of the application;

FIG. 4 is a spherical aberration curve diagram of a lens of a specific embodiment of the present application;

FIG. 5 is a graph of relative illuminance of a lens according to a specific embodiment of the application;

6 is a schematic structural diagram of a lens according to a second embodiment of this application;

7 is a distortion curve diagram of a lens of a specific embodiment of the present application;

8 is a spherical aberration curve diagram of a lens of a specific embodiment 2 of the present application;

9 is a graph of the relative illuminance curve of the second lens of the specific embodiment of the present application;

10 is a schematic structural diagram of a third lens according to a specific embodiment of the application;

FIG. 11 is a distortion curve diagram of a third lens of a specific embodiment of this application;

FIG. 12 is a spherical aberration curve diagram of a third lens of a specific embodiment of this application;

13 is a graph of the relative illuminance curve of the third lens of the specific embodiment of the present application;

14 is a schematic structural diagram of a fourth lens according to a specific embodiment of the application;

15 is a distortion curve diagram of a fourth lens of a specific embodiment of this application;

16 is a spherical aberration curve diagram of a fourth lens of a specific embodiment of this application;

17 is a graph of the relative illuminance curve of the fourth lens of the specific embodiment of the present application;

18 is a schematic structural diagram of a fifth lens according to a specific embodiment of the application;

FIG. 19 is a distortion curve diagram of a fifth lens according to a specific embodiment of this application;

20 is a spherical aberration curve diagram of a fifth lens according to a specific embodiment of the application;

21 is a graph of relative illuminance curves of a fifth lens according to a specific embodiment of the application;

22 is a schematic structural diagram of a terminal device according to an embodiment of the present application.

detailed description

The embodiments of the present application relate to a lens and a terminal device provided with the lens. The terminal device may be a mobile phone, a mobile computer, a handheld game machine, a tablet computer, or the like.

The following briefly describes the concepts involved in the above embodiments:

Lens: It is a component that uses the refraction principle of the lens to make the scene light pass through the lens to form a clear image on the focusing plane.

Optical power: equal to the difference between the beam convergence of the image side and the beam convergence of the object side, which characterizes the ability of the optical system to deflect light.

Aperture value: the ratio of the total focal length of the lens to the diameter of the entrance pupil.

Radius of curvature: Curvature is a value used to indicate the degree of curvature of a curve at a certain point. The greater the curvature, the greater the degree of curvature of the curve, and the reciprocal of the curvature is the radius of curvature.

Contrast: refers to the ratio of the edge illumination of the image plane to the center illumination.

Distortion: For an ideal optical system, the magnification is constant on a pair of conjugate object image planes. But for the actual optical system, it has this property only when the field of view is small. When the field of view is large, the magnification of the image will vary with the field of view, causing the image to lose similarity to the object. This imaging defect that deforms the image is called distortion.

Spherical aberration: Spherical aberration is caused by the difference in the ability of the central and peripheral regions of the lens to converge the beam. The far-axis beam is refracted much more than the paraxial beam when passing through the lens, so the beam scattered by the same object point does not intersect at a point after passing through the lens, but becomes a diffuse circular spot on the lens phase plane . As a result, the imaging becomes blurred, and this imaging defect is spherical aberration.

Aperture diaphragm: The diaphragm with the smallest incident aperture angle is called the aperture diaphragm.

Entrance pupil: Corresponding to the exit pupil, the conjugate image of the aperture stop in the object space is called the "entrance pupil". The position and diameter of the entrance pupil represent the position and diameter of the incident beam.

Half field of view (HFOV): refers to the half of the maximum angle that the lens can shoot.

Object side: The surface closest to the real object on the lens is the object side.

Image side: The surface closest to the imaging plane on the lens is the image side.

Effective focal length: the distance from the main plane of the optical system to the corresponding focal point.

As shown in FIGS. 1 and 2, an embodiment of the present application provides a lens including a lens group including a first lens 1, a second lens 2, and a third lens arranged in order from the object side to the image side 3 and the fourth lens 4, the object side surface 11 of the first lens 1 is a convex surface, the relative illuminance RI of the lens group and the fourth order of the cosine value of the half field of view (HFOV) of the lens group The square cos ⁴ (HFOV) satisfies: RI/cos ⁴ (HFOV) ≥ 1, and the effective focal length f of the lens group and the entrance pupil diameter EPD of the lens group satisfy: f/EPD ≤ 1.3.

In the lens provided by the embodiment of the present application, since the fourth power of the cosine value of the half angle of view is a reference standard for whether the relative illuminance of the lens is high, the relative illuminance RI of the lens group and the half angle of view of the lens group in the embodiment of the present application The ratio of the fourth power of the cosine value is greater than or equal to 1, so the relative illuminance of the lens group is greater than or equal to the reference standard, the relative illuminance of the lens group is larger, so that the brightness of the lens is higher, thereby increasing the depth of the lens structure Recognition accuracy. And because the effective focal length f of the lens group and the entrance pupil diameter EPD of the lens group satisfy: f/EPD≤1.3, the aperture value of the lens group is made smaller and the aperture is larger, so that sufficient light flux can be ensured to improve Imaging quality and recognition accuracy, increase signal-to-noise ratio. In addition, since the object side surface 11 of the first lens 1 is a convex surface, when the light enters the first lens 1, it is focused first, which is conducive to reducing the aperture of the rear lens and achieving miniaturization. Therefore, the lens provided by the embodiment of the present application can take into account the requirements of the TOF system on the lens illumination and aperture value on the premise of ensuring the miniaturization of the lens, thereby meeting the depth recognition accuracy requirements of the TOF system.

In order to achieve a large aperture, the effective focal length f of the lens group, the effective focal length f1 of the first lens 1 and the effective focal length f2 of the second lens 2 can satisfy: 0≤|f/f1|+|f/f2|≤0.5. The longer the effective focal length f1 of the first lens 1 and the effective focal length f2 of the second lens 2, the smaller the power of the lens group, the larger the angle of view, and the larger the aperture. However, in order to take into account the requirements of lens miniaturization and the cooperation relationship between the lenses, the effective focal length f of the lens group, the effective focal length f1 of the first lens 1 and the effective focal length f2 of the second lens 2 satisfy the above relationship, which can guarantee the lens Miniaturization can achieve a larger viewing angle and a larger aperture.

As shown in FIG. 1, the image side of the fourth lens 4 has an imaging surface 5. In order to further realize a large angle of view, the effective focal length f of the lens group and the effective pixel area on the imaging surface 5 can be diagonally 2*Imh Satisfaction: f/(2*Imh)≤0.635. Thereby achieving a larger angle of view. It should be noted that the imaging surface 5 is the surface of the film or the light-receiving surface of the sensor.

In some embodiments, the curvature radius R31 of the object side surface 31 of the third lens 3 and the curvature radius R32 of the image side surface 32 of the third lens 3 satisfy: 0≦(R31+R32)/(R31-R32)≦10. Thereby, the curvature radius of the object side 31 and the image side of the third lens 3 can be within a reasonable range, which can not only ensure the processability of the third lens 3, but also make the object side 31 and the image side of the third lens 3 Satisfying the angle of incidence of each field of view into the third lens 3 to meet the spherical aberration requirements of the imaging system.

In some embodiments, the refractive index N1 of the material of the first lens 1, the Abbe number V2 of the material of the second lens 2 and the Abbe number of the material of the third lens 3 are V3 satisfying: N1*(V3-V2)≥ 20. Among them, the Abbe number is the dispersion coefficient of the lens material, which is used to characterize the degree of dispersion of light passing through the lens. The larger the Abbe number, the smaller the dispersion and the clearer the imaging. The higher the refractive index of the lens material, the stronger the ability to refract the incident light. Therefore, if the refractive index N1 of the material of the first lens 1 and the Abbe number V2 of the material of the second lens 2 and the Abbe number of the material of the third lens 3 are V3 satisfy the above relationship, the degree of dispersion and the refractive index of the lens can be taken into account , Which can improve the aberration of the lens group, while increasing the angle of view and improving the recognition range. Optionally, the refractive index N3 of the material of the third lens 3 is ≥ 1.58, which can improve the aberration of the lens group and achieve better resolution.

Among them, the curvature radius R41 of the object side surface 41 of the fourth lens 4 and the system focal length f can satisfy: (R41/f)≥(1/2.5). In this way, it is possible to ensure that the lens has good manufacturability in processing and manufacturing while satisfying the effective focal length of the lens group, and reduce processing difficulty.

In a possible implementation, as shown in FIG. 1, the object side surface 11 of the first lens 1 is convex, and the image side surface 12 of the first lens 1 is concave; the object side 21 of the second lens 2 is convex, the second The image side 22 of the lens 2 is concave; the object side 31 of the third lens 3 is concave, and the image side 32 of the third lens 3 is convex; the object side 41 of the fourth lens 4 is convex, and the image side 42 of the fourth lens 4 It is concave. It should be noted that the above-mentioned definition of the convex surface and the concave surface is the definition of the paraxial region of each surface, that is, the region near the main optical axis O.

The first lens 1, the second lens 2, the third lens 3, and the fourth lens 4 in the lens group all have optical power. The optical power is used to characterize the deflection ability of the optical system to the incident light. The larger the absolute value of the optical power, the greater the deflection ability. Therefore, the first lens 1, the second lens 2, the third lens 3, and the fourth lens 4 all have a deflection effect on the incident light, thereby facilitating adjustment of the angle of view of the lens to the required value of the TOF system.

Wherein, the first lens 1 may have positive power or negative power, the second lens 2 may have positive power or negative power, the third lens 3 may have positive power or negative power, and the fourth lens 4 may have positive power or negative power, which is not limited herein. A positive power value means that the optical system deflects incident parallel light beams parallel to the optical axis. A negative power value means that the optical system deflects incident parallel light beams parallel to the optical axis. of. In a possible implementation, the first lens 1 has negative power, and the second lens 2, the third lens 3, and the fourth lens 4 all have positive power. Such setting is beneficial for adjusting the optical path, shortening the optical path length, and realizing a larger angle of view while ensuring the miniaturization of the lens.

Specifically, an inflection point may be formed on the object side 21 and/or image side of the second lens 2, as shown in FIG. 1, at least one inflection point 211 is formed on the object side 21 of the second lens 2, the image of the second lens 2 At least one inflection point 221 is formed on the side surface 22, and the inflection point of the second lens 2 is beneficial to balance light aberrations at different apertures, achieve a larger aperture, and at the same time facilitate higher illumination at the edges. Similarly, an inflection point may also be formed on the object side 41 and/or image side of the fourth lens 4, as shown in FIG. 1, at least one inflection point 411 is formed on the object side 41 of the fourth lens 4, the image of the fourth lens 4 At least one inflection point 421 is formed on the side surface 42, and the inflection point on the fourth lens 4 is beneficial to achieve less distortion and at the same time achieve higher illumination at the edge.

As shown in FIG. 1, an aperture stop 6 can be provided between the first lens 1 and the second lens 2, and the aperture stop 6 can effectively improve the imaging quality of the lens. It should be noted that the aperture stop 6 can also be disposed at other positions, such as the object side of the first lens 1, between the second lens 2 and the third lens 3, between the third lens 3 and the fourth lens 4, etc. , Not limited here.

In addition, as shown in FIG. 1, a filter 7 can also be provided between the imaging surface 5 and the fourth lens 4, so that light of a desired wavelength can be selected to filter out interference light to improve imaging quality.

Alternatively, both the object side 11 and the image side of the first lens 1 may be aspherical. Similarly, one or more of the object side 21 and the image side of the second lens 2, the object side 31 and the image side of the third lens 3, and the object side 41 and the image side of the fourth lens 4 may also be Aspherical. Aspheric surfaces are surfaces where the curvature changes, and spherical surfaces are surfaces where the curvature is constant. Aspheric lenses can improve aberrations, thereby improving imaging quality.

Specifically, the surface parameter of each aspheric surface can be expressed by the following equation:

Where x is the abscissa of the point on the aspheric surface, h is the ordinate of the point on the aspheric surface, c is the curvature of the aspheric surface at the optical center (that is, the intersection of the lens and the optical axis), and k is the preset conic coefficient, Ai is the aspheric coefficient of order i.

The specific embodiments of several lenses are listed below with reference to the drawings. It should be noted that the aspheric surface parameters of the lenses in the following embodiments all conform to the above equations. The shape of the spherical or aspheric surface shown in the drawings is only It is a schematic representation, that is, the shape of a spherical surface or aspherical surface is not limited to the shape shown in the drawings.

Specific example one

FIG. 1 is a schematic diagram of a lens structure of a specific embodiment 1. As shown in FIG. 1, the lens includes a first lens 1 and a second lens 2 arranged in sequence along the main optical axis O from the object to the imaging surface 5 , The third lens 3 and the fourth lens 4, an aperture stop can be set between the first lens 1 and the second lens 2, the specific parameters of each lens are given in Table 1, and the cones on the surface of each lens are given in Table 2 Coefficient k and aspheric coefficient Ai (i=4, 6, 8, 10, 12, 14, 16, 18, 20).

It can be seen from Table 1, |f/f1|+|f/f2|=0.43, f/(2*Imh)=0.61, (L3R1+L3R2)/(L3R1-L3R2)=1.92, L4R1/f=1/1.83 , RI/cos ⁴ (HFOV)=1.27. Therefore, the lens of the specific embodiment 1 meets the limited range of the parameters of the lens group in this application. The lens group of the specific embodiment 1 can take into account the requirements of the TOF system for the lens illuminance and aperture value on the premise of ensuring the miniaturization of the lens, thereby To meet the depth recognition accuracy requirements of the TOF system.

FIG. 3 shows the distortion curve of the lens of the first embodiment. The abscissa of FIG. 3 represents the distortion (which may be the ratio of the actual image height on the imaging surface 5 to the ideal image height as a percentage), and the ordinate represents the image height. It can be seen from Fig. 3 that the optical distortion is controlled within the range of 0 to 2%.

FIG. 4 shows the spherical aberration curve of the lens of the first embodiment. The abscissa of FIG. 4 is the intersection point of light rays incident on the same object point at different angles and the optical axis. The ordinate is the normalized height of the incident light at the entrance pupil. It can be seen from Fig. 4 that the spherical aberration is controlled within a relatively small range. It should be noted that the normalized height refers to a dimensionless ratio value obtained by normalizing the height of each incident ray at the entrance pupil. That is to say, the maximum value of the height is 1, and the remaining height values are expressed by the proportional relationship with the maximum value. Normalization is a way of simplifying calculations, that is, dimensional expressions are transformed into non-dimensional expressions and transformed into scalar quantities.

FIG. 5 shows the relative illuminance curve of the lens of the first embodiment. The relative illumination (RI) refers to the ratio of the edge illumination of the imaging plane 5 to the center illumination. The center (0, 0) of FIG. 5 is the center of the imaging surface 5 and the brightness is 100%. As it moves toward the edge of the imaging surface 5, the brightness of the edge gradually becomes darker until the brightness becomes approximately 50 at a distance of 1.4 mm from the center %.

It can be seen from FIGS. 3 to 5 that the optical distortion, spherical aberration, and relative illuminance of the lens of the first embodiment can meet the imaging requirements, thereby ensuring good imaging quality.

Specific example two

6 shows the structure of the lens of the second embodiment. As shown in FIG. 6, the lens includes a first lens 1, a second lens 2, and a second lens 2 arranged in sequence along the main optical axis O from the object to the imaging surface 5. The third lens 4 and the fourth lens 4, the specific parameters of each lens are given in Table 3, and the conic coefficient k and the aspheric coefficient Ai (i=4, 6, 8, 10, 12, 14, 16, 18, 20).

It can be seen from Table 3 that |f/f1|+|f/f2|=0.32, f/(2*Imh)=0.6, (L3R1+L3R2)/(L3R1-L3R2)=1.74, L4R1/f=1/1.81 , RI/cos ⁴ (HFOV) = 1.4. Therefore, the lens of the specific embodiment 2 meets the limited range of the parameters of the lens group in this application. The lens group of the specific embodiment 2 can take into account the requirements of the TOF system for the lens illuminance and aperture value on the premise of ensuring the miniaturization of the lens, thereby To meet the depth recognition accuracy requirements of the TOF system.

FIG. 7 shows the distortion curve of the lens of the second embodiment. The abscissa of FIG. 7 represents distortion (which may be the ratio of the actual image height on the imaging surface 5 to the ideal image height as a percentage), and the ordinate represents the image height. It can be seen from FIG. 7 that the optical distortion is controlled within the range of 0 to 2%.

FIG. 8 shows the spherical aberration curve of the lens of the second embodiment. The abscissa of FIG. 8 is the intersection point of light rays incident on the same object point at different angles and the optical axis. The ordinate is the normalized height of the incident light at the entrance pupil. It can be seen from Fig. 8 that the spherical aberration is controlled within a relatively small range.

FIG. 9 shows the relative illuminance curve of the lens of the second embodiment. The relative illumination (RI) refers to the ratio of the edge illumination of the imaging plane 5 to the center illumination. The center (0, 0) in FIG. 9 is the center of the imaging surface 5 and the brightness is 100%. As the image moves toward the edge of the imaging surface 5, the brightness of the edge gradually becomes darker until the brightness becomes approximately 50 at a distance of 1.4 mm from the center %.

As can be seen from FIGS. 7-9, the optical distortion, spherical aberration, and relative illuminance of the lens of the second embodiment can meet imaging requirements, thereby ensuring good imaging quality.

Specific example three

FIG. 10 shows the lens structure of the third embodiment. As shown in FIG. 10, the lens includes a first lens 1, a second lens 2, and a second lens 2 arranged in sequence along the main optical axis O from the object to the imaging surface 5. The third lens 4 and the fourth lens 4, the specific parameters of each lens are given in Table 5, and the conic coefficient k and aspheric coefficient Ai (i=4, 6, 8, 10, 12, 14, 16, 18, 20).

From Table 5, we know that |f/f1|+|f/f2|=0.4, f/(2*Imh)=0.6, (L3R1+L3R2)/(L3R1-L3R2)=2.15, L4R1/f=1/1.81 , RI/cos ⁴ (HFOV)=1.26. Therefore, the lens of the specific embodiment 3 meets the limited range of the parameters of the lens group in this application. The lens group of the specific embodiment 3 can take into account the requirements of the TOF system for the lens illuminance and aperture value on the premise of ensuring the miniaturization of the lens, thereby To meet the depth recognition accuracy requirements of the TOF system.

FIG. 11 shows the distortion curve of the lens of the third embodiment. The abscissa of FIG. 11 represents distortion (which may be the ratio of the actual image height on the imaging surface 5 to the ideal image height as a percentage), and the ordinate represents the image height. It can be seen from FIG. 11 that the optical distortion is controlled in the range of 0 to 2%.

FIG. 12 shows the spherical aberration curve of the lens of the third embodiment. The abscissa of FIG. 12 is the intersection of the light rays incident on the same object point at different angles and the optical axis. The ordinate is the normalized height of the incident light at the entrance pupil. It can be seen from Fig. 12 that the spherical aberration is controlled within a relatively small range.

FIG. 13 shows the relative illuminance curve of the lens of the third embodiment. The relative illumination (RI) refers to the ratio of the edge illumination of the imaging plane 5 to the center illumination. The center (0, 0) of FIG. 13 is the center of the imaging surface 5 and the brightness is 100%. As the image moves toward the edge of the imaging surface 5, the brightness of the edge gradually becomes darker until the brightness becomes approximately 50 at 1.4 mm from the center %.

It can be seen from FIGS. 11 to 13 that the optical distortion, spherical aberration, and relative illuminance of the lens of Embodiment 3 can all meet imaging requirements, thereby ensuring good imaging quality.

Specific embodiment four

FIG. 14 shows a lens structure of a specific embodiment 4. As shown in FIG. 14, the lens includes a first lens 1, a second lens 2, and a second lens 2 arranged in sequence along the main optical axis O from the object to the imaging surface 5. The third lens 4 and the fourth lens 4, the specific parameters of each lens are given in Table 7, and the conic coefficient k and aspheric coefficient Ai (i=4, 6, 8, 10, 12, 14, 16, 18, 20).

From Table 7, we know that |f/f1|+|f/f2|=0.44, f/(2*Imh)=0.6, (L3R1+L3R2)/(L3R1-L3R2)=1.88, L4R1/f=1/1.81 , RI/cos ⁴ (HFOV)=1.37. Therefore, the lens of the specific embodiment 4 meets the limited range of the parameters of the lens group in this application. The lens group of the specific embodiment 4 can take into account the requirements of the TOF system for the lens illuminance and aperture value on the premise of ensuring the miniaturization of the lens, thereby To meet the depth recognition accuracy requirements of the TOF system.

FIG. 15 shows the distortion curve of the lens of the fourth embodiment. The abscissa of FIG. 15 represents distortion (which may be the ratio of the actual image height on the imaging surface 5 to the ideal image height as a percentage), and the ordinate represents the image height. It can be seen from FIG. 15 that the optical distortion is controlled in the range of 0 to 2%.

FIG. 16 shows the spherical aberration curve of the lens of the fourth embodiment. The abscissa of FIG. 16 is the intersection of the light rays incident at different angles on the same object point and the optical axis. The ordinate is the normalized height of the incident light at the entrance pupil. It can be seen from Fig. 16 that the spherical aberration is controlled within a relatively small range.

FIG. 17 shows the relative illuminance curve of the lens of the fourth embodiment. The relative illumination (RI) refers to the ratio of the edge illumination of the imaging plane 5 to the center illumination. The center (0, 0) of FIG. 17 is the center of the imaging surface 5 and the brightness is 100%. As the image moves toward the edge of the imaging surface 5, the brightness of the edge gradually becomes darker until the brightness becomes approximately 50 at 1.4 mm from the center %.

It can be seen from FIGS. 15 to 17 that the optical distortion, spherical aberration, and relative illuminance of the lens of Embodiment 4 can all meet imaging requirements, thereby ensuring good imaging quality.

Specific embodiment five

FIG. 18 shows a lens structure of a specific embodiment 5. As shown in FIG. 18, the lens includes a first lens 1, a second lens 2, and a second lens 2 arranged in sequence along the main optical axis O from the object to the imaging surface 5. For the third lens 4 and the fourth lens 4, the specific parameters of each lens are given in Table 9, and the conic coefficient k and aspheric coefficient Ai (i=4, 6, 8, 10, 12, 14, 16, 18, 20).

From Table 9, we know that |f/f1|+|f/f2|=0.47, f/(2*Imh)=0.6, (L3R1+L3R2)/(L3R1-L3R2)=1.88, L4R1/f=1/1.81 , RI/cos ⁴ (HFOV) = 1.31. Therefore, the lens of the specific embodiment 5 meets the limited range of the parameters of the lens group in this application. The lens group of the specific embodiment 5 can take into account the requirements of the TOF system for the lens illuminance and aperture value on the premise of ensuring the miniaturization of the lens, thereby To meet the depth recognition accuracy requirements of the TOF system.

FIG. 19 shows the distortion curve of the lens of the fifth embodiment. The abscissa of FIG. 19 represents distortion (which may be the ratio of the actual image height on the imaging surface 5 to the ideal image height as a percentage), and the ordinate represents the image height. It can be seen from FIG. 19 that the optical distortion is controlled within the range of 0 to 2%.

FIG. 20 shows the spherical aberration curve of the lens of the fifth embodiment. The abscissa of FIG. 20 is the intersection of light rays incident at different angles on the same object point and the optical axis. The ordinate is the normalized height of the incident light at the entrance pupil. It can be seen from Fig. 20 that the spherical aberration is controlled within a relatively small range.

FIG. 21 shows the relative illuminance curve of the lens of the fifth embodiment. The relative illumination (RI) refers to the ratio of the edge illumination of the imaging plane 5 to the center illumination. The center (0,0) of FIG. 21 is the center of the imaging surface 5 and the brightness is 100%. As the image moves toward the edge of the imaging surface 5, the brightness of the edge gradually becomes darker until the brightness becomes approximately 50 at a distance of 1.4 mm from the center %.

As can be seen from FIGS. 19-21, the optical distortion, spherical aberration, and relative illuminance of the lens of Embodiment 5 can all meet imaging requirements, thereby ensuring good imaging quality.

On the other hand, an embodiment of the present application further provides a terminal device, which includes the lens described in any of the foregoing embodiments.

In a possible implementation, as shown in FIG. 22, the terminal device 100 may further include a TOF system, the TOF system includes a laser emitting module 101 and a laser receiving module, and the laser receiving module includes the lens 102 and a sensor 103. The laser emitting module 101 is used to emit an optical signal to a target, and the lens 102 is used to receive the optical signal reflected by the target and deliver the optical signal to the sensor 103 after focusing. The sensor 103 may be a photosensitive sensor, such as a charge-coupled device (English: Charge-coupled Device, abbreviated as CCD), a complementary metal oxide semiconductor (English: Complementary Metal-Oxide-Semiconductor, abbreviated as CMOS) photosensitive device, and the like.

It should be noted that, the terminal device provided by the embodiment of the present application may be a mobile phone, a tablet computer, a notebook computer, a video camera, an in-vehicle computer, or the like. The embodiment of the present invention does not specifically limit the specific form of the terminal.

The above are only the specific embodiments of the present invention, but the scope of protection of the present invention is not limited to this. Any person skilled in the art can easily think of changes or replacements within the technical scope disclosed by the present invention. It should be covered by the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

A lens, characterized by comprising a lens group including a first lens, a second lens, a third lens and a fourth lens arranged in order from the object side to the image side, the object side of the first lens Is a convex surface, the relative illuminance RI of the lens group and the fourth power cos 4 (HFOV) of the half-angle cosine value of the lens group satisfy: RI/cos 4 (HFOV) ≥ 1, and the effective focal length of the lens group f and the entrance pupil diameter EPD of the lens group satisfy: f/EPD≤1.3.
The lens according to claim 1, wherein the effective focal length f of the lens group, the effective focal length f1 of the first lens, and the effective focal length f2 of the second lens satisfy: 0≤|f/f1| +|f/f2|≤0.5.
The lens according to claim 1 or 2, wherein an image plane is provided on the image side of the fourth lens, an effective focal length f of the lens group and an effective pixel area diagonal length 2 on the image plane *Imh satisfies: f/(2*Imh)≤0.635.
The lens according to any one of claims 1 to 3, wherein a radius of curvature R31 of the object side of the third lens and a radius of curvature R32 of the image side of the third lens satisfy: 0≤(R31 +R32)/(R31-R32)≤10.
The lens according to any one of claims 1 to 4, wherein the material refractive index of the first lens N1, the Abbe number V2 of the material of the second lens, and the material of the third lens The Abbe number of V3 satisfies: N1*(V3-V2)≥20.
The lens according to any one of claims 1 to 5, wherein the radius of curvature R41 of the object side of the fourth lens and the system focal length f satisfy: (R41/f)≥(1/2.5).
The lens according to any one of claims 1 to 6, wherein the material refractive index of the third lens is N3≥1.58.
The lens according to any one of claims 1 to 7, wherein the image side of the first lens is concave, and both the object side and the image side of the first lens are aspherical.
The lens according to any one of claims 1-8, wherein the first lens has negative power, and the second lens, third lens, and fourth lens all have positive power.
The lens according to any one of claims 1-9, wherein the object side and/or the image side of the second lens have an inflection point, and the object side and the image side of the second lens are both aspherical .
The lens according to any one of claims 1 to 10, wherein the object side of the third lens is concave, the image side of the third lens is convex, and the object side of the third lens is The sides of the image are all aspherical.
The lens according to any one of claims 1 to 11, wherein the object side and/or the image side of the fourth lens have an inflection point, and the object side and the image side of the fourth lens are both aspherical .
The lens according to any one of claims 1-12, wherein an aperture stop is provided between the first lens and the second lens.
A terminal device is characterized by comprising a lens, the lens being the lens of any one of claims 1-13.
The terminal device according to claim 14, wherein the terminal device includes a TOF system, the TOF system includes a laser emitting module and a laser receiving module, the laser receiving module includes the lens and the sensor, the laser The transmitting module is used to transmit an optical signal to the target, and the lens is used to receive the optical signal reflected by the target and deliver the optical signal to the sensor after focusing.