CN114236781B

CN114236781B - Optical lens

Info

Publication number: CN114236781B
Application number: CN202210183457.5A
Authority: CN
Inventors: 曾昊杰; 于笑枝; 章彬炜
Original assignee: Jiangxi Lianyi Optics Co Ltd
Current assignee: Hefei Lianchuang Optical Co ltd
Priority date: 2022-02-28
Filing date: 2022-02-28
Publication date: 2022-07-19
Anticipated expiration: 2042-02-28
Also published as: CN114236781A

Abstract

The invention discloses an optical lens, which comprises the following components in sequence from an object side to an imaging surface along an optical axis: a first lens having a power, an object side surface of the first lens being concave at a paraxial region and an image side surface of the first lens being convex at a paraxial region; a second lens having a negative optical power, the second lens having a convex object-side surface and a concave image-side surface at a paraxial region; and the object side surface and the image side surface of the third lens are convex surfaces. The optical lens has the advantages of wide visual angle, large aperture and high infrared imaging quality.

Description

Optical lens

Technical Field

The invention relates to the technical field of imaging lenses, in particular to an optical lens.

Background

In recent years, three-dimensional depth recognition technology is rapidly developed, and meanwhile, a ToF (Time of Flight) stereoscopic depth-sensing lens with three-dimensional space sensing capability opens a new future of depth information. The ToF technology can be divided into a DToF technology and an IToF technology according to a distance measuring principle, the DToF technology is a direct Time-of-Flight technology, and the DToF technology has higher precision, shorter distance measuring Time, strong anti-interference capability and relatively simple calibration compared with the IToF technology, so that the DToF optical lens is widely concerned and applied in various industries, such as human face recognition, AR augmented reality pictures, unmanned high-precision high-speed information transmission, military and commercial unmanned aerial vehicle laser radar, infrared detection and other industries.

The DToF optical lens can receive optical information carried by infrared light, and the optical information is transmitted to a specific chip to be subjected to photoelectric conversion, so that the information transmitted in the infrared light is interpreted, and the photoelectric information conversion is realized; since the DToF lens has the most marked function of measuring data information such as depth of field, the DToF lens is required to have the characteristics of wide viewing angle, large aperture, high resolution, infrared imaging and the like so as to meet the requirement of accurate measurement of distance information. However, the existing DToF lens cannot meet these requirements at the same time.

Disclosure of Invention

Therefore, an object of the present invention is to provide an optical lens for solving the above technical problems.

The embodiment of the invention implements the above object by the following technical scheme.

The invention provides an optical lens, which sequentially comprises the following components from an object side to an imaging surface along an optical axis: a first lens having a power, an object side surface of the first lens being concave at a paraxial region and an image side surface of the first lens being convex at a paraxial region; a second lens having a negative optical power, the second lens having a convex object-side surface and a concave image-side surface at a paraxial region; and the object side surface and the image side surface of the third lens are convex surfaces.

Compared with the prior art, the optical lens provided by the invention adopts three lenses with specific shapes and focal powers, and through reasonable arrangement of the diaphragm and the surface types of the lenses, the optical lens meets the high-quality image resolving capability, has the characteristics of wide visual angle, large aperture and high infrared imaging quality, and can better meet the imaging requirement of imaging equipment adopting the DToF technology.

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 diagram of an optical lens according to a first embodiment of the present invention;

FIG. 2 is a astigmatic chart of an optical lens according to a first embodiment of the present invention;

FIG. 3 is a graph illustrating f-theta distortion of an optical lens according to a first embodiment of the present invention;

FIG. 4 is a graph illustrating relative illumination of an optical lens according to a first embodiment of the present invention;

FIG. 5 is a diagram illustrating an optical lens assembly according to a second embodiment of the present invention;

FIG. 6 is an astigmatism graph of an optical lens according to a second embodiment of the present invention;

FIG. 7 is a graph showing the f-theta distortion of an optical lens according to a second embodiment of the present invention;

FIG. 8 is a graph illustrating relative illumination of an optical lens according to a second embodiment of the present invention;

FIG. 9 is a schematic structural diagram of an optical lens assembly according to a third embodiment of the present invention;

FIG. 10 is an astigmatism graph of an optical lens of a third embodiment of the invention;

fig. 11 is a graph showing f-theta distortion of an optical lens according to a third embodiment of the present invention;

fig. 12 is a graph illustrating relative illuminance of an optical lens according to a third embodiment of the present invention.

Detailed Description

In order to make the objects, features and advantages of the present invention more comprehensible, embodiments accompanying figures are described in detail below. Several embodiments of the invention are shown in the drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. Like reference numerals refer to like elements throughout the specification.

The present invention provides an optical lens, sequentially including, from an object side to an image plane along an optical axis: the device comprises a first lens, a diaphragm, a second lens, a third lens and an infrared filter.

Wherein the first lens has a focal power, the object-side surface of the first lens is concave at a paraxial region, and the image-side surface of the first lens is convex at the paraxial region;

the second lens has negative focal power, the object side surface of the second lens is a convex surface, and the image side surface of the second lens is a concave surface at a paraxial region;

the third lens has positive focal power, and the object-side surface and the image-side surface of the third lens are both convex surfaces.

In some embodiments, the optical lens satisfies the following conditional expression:

2.5<TTL/IH <3.5；（1）

wherein, TTL represents the optical total length of the optical lens, and IH represents the half-image height of the optical lens. The ratio of the focal length to the total optical length of the optical lens can be reasonably controlled by satisfying the conditional expression (1), and the optical total length of the optical lens can be shortened.

f/EPD<1.2；（2）

where f denotes a focal length of the optical lens, and EPD denotes an entrance pupil diameter of the optical lens. When the conditional expression (2) is satisfied, the optical lens can be ensured to have the characteristic of a large aperture, so that the luminous flux of the lens is large enough, and the optical lens is ensured to have good imaging quality under a dark environment.

0.35<BFL/TTL<0.5；（3）

and BFL represents the distance from the image side surface of the third lens to the imaging surface on the optical axis, and TTL represents the total optical length of the optical lens. The condition formula (3) is met, so that the shooting quality of the optical lens can be well guaranteed, and the shot infrared light signal is clearer; meanwhile, the back focal length of the optical lens can be reasonably controlled, the miniaturization of the lens is guaranteed, meanwhile, enough back focal space is reserved, and the interference when the lens and a chip module are assembled is reduced.

0.7<DM32/DM11<0.95；（4）

where DM11 denotes the effective aperture of the object-side surface of the first lens, and DM32 denotes the effective aperture of the image-side surface of the third lens. The optical lens meets the conditional expression (4), can ensure that the field angle of the side of an object is increased, and simultaneously realizes the small size of the head of the optical lens, is beneficial to reducing the windowing area of a screen, and realizes the miniaturization of the lens.

4<|f1/f|<10；（5）

-2<R1/f<0；（6）

where f denotes a focal length of the optical lens, f1 denotes a focal length of the first lens, and R1 denotes a radius of curvature of an object side surface of the first lens. Satisfy conditional expressions (5) and (6), can rationally control the focus and the face type of first lens, reduce the aberration correction degree of difficulty of big visual field angle, be favorable to improving the relative illuminance of off-axis visual field.

0.25<CT1/DM11<0.45；（7）

-0.1<SAG11/DM11<0；（8）

where CT1 represents the center thickness of the first lens, DM11 represents the effective aperture of the object side of the first lens, and SAG11 represents the sagittal height of the object side of the first lens at the effective aperture. Satisfy conditional expressions (7) and (8), can rationally control the face type of first lens, reduce the processing degree of difficulty of first lens, be favorable to improving the production yield.

-5<f1/f2<3；（9）

-6<f2/f3<-2；（10）

where f1 denotes a focal length of the first lens, f2 denotes a focal length of the second lens, and f3 denotes a focal length of the third lens. The optical lens meets the conditional expressions (9) and (10), can reasonably distribute the focal length of each lens, is beneficial to correcting spherical aberration and reducing the correction difficulty of high-grade aberration, and has high-quality resolving power.

-5<f2/f<-2；（11）

1<R3/R4<4；（12）

where f denotes a focal length of the optical lens, f2 denotes a focal length of the second lens, R3 denotes a radius of curvature of an object-side surface of the second lens, and R4 denotes a radius of curvature of an image-side surface of the second lens. Satisfy conditional expressions (11) and (12), can rationally control the focus and the face type of second lens, make the second lens have suitable negative focal power, can effectively slow down the degree of turning of light, be favorable to improving optical lens's relative illuminance.

2<(CT1+CT3)/CT2<3；（13）

0.1<CT12/CT23<0.3；（14）

where CT1 denotes a center thickness of the first lens, CT2 denotes a center thickness of the second lens, CT3 denotes a center thickness of the third lens, CT12 denotes a distance of separation of the first lens and the second lens on the optical axis, and CT23 denotes a distance of separation of the second lens and the third lens on the optical axis. Satisfying the conditional expressions (13) and (14), the central thickness of each lens and the spacing distance between the lenses can be reasonably distributed, the light distribution can be adjusted, the compactness and miniaturization of the optical lens structure can be realized, and the reduction of the sensitivity of the optical lens can be facilitated.

0.5<f3/f<1.2；（15）

-3<R5/R6<0；（16）

where f3 denotes a focal length of the third lens, f denotes a focal length of the optical lens, R5 denotes a radius of curvature of an object side surface of the third lens, and R6 denotes a radius of curvature of an image side surface of the third lens. The focal length and the surface type of the third lens can be reasonably controlled by satisfying the conditional expressions (15) and (16), thereby being beneficial to shortening the total length of the optical lens and realizing the miniaturization of the optical lens.

In one embodiment, the first lens, the second lens and the third lens may all be aspheric lenses, or may be a mixture of aspheric lenses and spherical lenses. The aspheric lens can effectively reduce the number of lenses, correct aberration and provide better optical performance.

The invention is further illustrated below by means of a number of examples. In various embodiments, the thickness, the curvature radius, and the material selection of each lens in the optical lens are different, and the specific differences can be referred to in the parameter tables of the various embodiments. The following examples are only preferred embodiments of the present invention, but the embodiments of the present invention are not limited by the following examples, and any other changes, substitutions, combinations or simplifications which do not depart from the gist of the present invention should be construed as being equivalent replacements within the scope of the present invention.

In each embodiment of the present invention, when the lens is an aspherical lens, the surface shape of the aspherical lens satisfies the following equation:

wherein z is the distance rise from the aspheric surface vertex at the position of height h along the optical axis direction, c is the paraxial curvature of the surface, and k is conic coefficient, A_2iThe coefficient of the aspheric surface type of the 2 i-th order.

First embodiment

Referring to fig. 1, a schematic structural diagram of an optical lens 100 according to a first embodiment of the present invention is shown, where the optical lens 100 includes, in order from an object side to an image plane S9: a first lens L1, an aperture stop ST, a second lens L2, a third lens L3, and an infrared filter G1.

The first lens L1 has positive optical power, the first lens ' object-side surface S1 is concave at the paraxial region and has a point of inflection, the first lens ' image-side surface S2 is convex at the paraxial region, and the first lens ' object-side surface S1 and image-side surface S2 have points of inflection;

the second lens element L2 has negative power, the object-side surface S3 of the second lens element is convex, the image-side surface S4 of the second lens element is concave at the paraxial region, and the image-side surface S4 of the second lens element has a point of inflection;

the third lens L3 has positive power, and the object-side surface S5 of the third lens is a convex surface, and the image-side surface S6 of the third lens is a convex surface.

The first lens L1, the second lens L2 and the third lens L3 are all plastic aspheric lenses.

The object side of the infrared filter G1 is S7, and the image side is S8.

The infrared filter G1 can effectively filter out other light rays except infrared rays, and the optical lens can have higher resolving power in an infrared band.

The parameters related to each lens in the optical lens 100 provided in this embodiment are shown in table 1.

TABLE 1

The surface shape coefficients of the aspherical surfaces of the optical lens 100 in the present embodiment are shown in table 2.

TABLE 2

In the present embodiment, graphs of astigmatism, f-theta distortion, and relative illuminance of the optical lens 100 are shown in fig. 2, 3, and 4, respectively.

The curvature degrees of the meridional image plane and the sagittal image plane are indicated by the field curvature curve of fig. 2, in which the abscissa indicates the amount of displacement (unit: mm) and the ordinate indicates the angle of view (unit: degree). It can be seen from fig. 2 that both the meridional and sagittal field curvatures at different wavelengths are within ± 0.3mm, indicating that astigmatism is well corrected.

Fig. 3 shows distortion amounts corresponding to different image heights on an imaging plane, where the abscissa is f- θ distortion amount and the ordinate is field angle (unit: degree). As can be seen from fig. 3, the distortion of the present embodiment is within 8%, indicating that the f- θ distortion is well corrected.

Fig. 4 shows relative illumination corresponding to different image heights on the imaging surface, in which the abscissa is the field angle (unit: degree) and the ordinate is the relative illumination, and it can be seen from fig. 4 that the relative illumination of the lens at the maximum field of view is above 60%, and the relative illumination of the peripheral field of view is also high, which indicates that the relative illumination of the optical lens 100 is improved well.

Second embodiment

Referring to fig. 5, a schematic structural diagram of an optical lens 200 provided in the present embodiment is shown, the optical lens 200 in the present embodiment has a structure substantially the same as that of the optical lens 100 in the first embodiment, and the difference is that: the first lens has negative focal power, and the curvature radius, the lens thickness and the distance of each lens are different.

Table 3 shows relevant parameters of each lens of the optical lens 200 provided in this embodiment.

TABLE 3

The surface shape coefficients of the aspherical surfaces of the optical lens 200 in the present embodiment are shown in table 4.

TABLE 4

In the present embodiment, graphs of astigmatism, distortion, and relative illuminance of the optical lens 200 are shown in fig. 6, 7, and 8, respectively. As can be seen from fig. 6, the meridional field curvature and the sagittal field curvature of different wavelengths are both within ± 0.5mm, which indicates that the astigmatism of the optical lens 200 is well corrected. As can be seen from fig. 7, the f-theta distortion of the present embodiment is within 10%, indicating that the f-theta distortion is well corrected. As can be seen from fig. 8, the relative illumination of the lens at the maximum field of view reaches more than 55%, and the relative illumination of the peripheral field of view is also higher, which indicates that the relative illumination of the optical lens 200 is improved well.

Third embodiment

Referring to fig. 9, a schematic structural diagram of an optical lens 300 according to the present embodiment is shown, where the optical lens 300 according to the present embodiment has a structure substantially the same as that of the optical lens 100 according to the first embodiment, and the difference is that curvature radii, lens thicknesses, and pitches of the lenses are different.

The parameters related to each lens of the optical lens 300 provided in this embodiment are shown in table 5.

TABLE 5

The surface shape coefficients of the respective aspherical surfaces of the optical lens 300 in the present embodiment are shown in table 6.

TABLE 6

Graphs of astigmatism, distortion, and relative illuminance of the optical lens 300 are shown in fig. 10, 11, and 12, respectively. As can be seen from fig. 10, the meridional field curvature and the sagittal field curvature of different wavelengths are both within ± 0.4mm, indicating that astigmatism is well corrected. As can be seen from fig. 11, the f- θ distortion of the present embodiment is within 8%, indicating that the distortion is well corrected. As can be seen from fig. 12, the relative illuminance of the lens at the maximum field of view reaches more than 60%, and the relative illuminance of the peripheral field of view is also higher, which indicates that the relative illuminance of the optical lens 300 is improved well.

Table 7 shows the optical characteristics corresponding to the above three embodiments, which mainly include the focal length F, F #, total optical length TTL, and field angle FOV, and the values corresponding to each conditional expression.

TABLE 7

In summary, the optical lens provided by the embodiments of the present invention has at least the following advantages:

(1) the optical lens provided by the invention adopts three aspheric lenses with specific focal power and specific surface shape collocation, so that the wide-angle-of-view and miniaturization balance of the lens is better realized, and the structure is more compact and the volume is smaller while the large field angle is met.

(2) The optical lens provided by the invention has the advantages of wide visual angle, large aperture (aperture can reach 1.1), short total length, small distortion, high infrared imaging quality and the like while meeting the high-quality resolution capability, and can better meet the requirements of the DToF lens.

In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean 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, the schematic representations of the terms used above 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.

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

Claims

1. An optical lens assembly, comprising three lenses in sequence from an object side to an image plane along an optical axis:

a first lens having a power, an object side surface of the first lens being concave at a paraxial region and an image side surface of the first lens being convex at a paraxial region;

a second lens having a negative optical power, the second lens having a convex object-side surface and a concave image-side surface at a paraxial region;

a third lens having a positive optical power, the third lens having convex object and image side surfaces;

the optical lens satisfies the following conditional expression:

4<|f1/f|<10；

-2<R1/f<0；

where f denotes a focal length of the optical lens, f1 denotes a focal length of the first lens, and R1 denotes a radius of curvature of an object side surface of the first lens.

2. An optical lens according to claim 1, characterized in that the optical lens satisfies the following conditional expression:

2.5<TTL/IH <3.5；

wherein, TTL represents the optical total length of the optical lens, and IH represents the half-image height of the optical lens.

3. An optical lens according to claim 1, characterized in that the optical lens satisfies the following conditional expression:

f/EPD<1.2；

where f denotes a focal length of the optical lens, and EPD denotes an entrance pupil diameter of the optical lens.

4. An optical lens according to claim 1, characterized in that the optical lens satisfies the following conditional expression:

0.35<BFL/TTL<0.5；

and BFL represents the distance from the image side surface of the third lens to the imaging surface on the optical axis, and TTL represents the total optical length of the optical lens.

5. An optical lens according to claim 1, characterized in that the optical lens satisfies the following conditional expression:

0.7<DM32/DM11<0.95；

wherein DM11 represents an effective aperture of an object side surface of the first lens, and DM32 represents an effective aperture of an image side surface of the third lens.

6. An optical lens according to claim 1, characterized in that the optical lens satisfies the following conditional expression:

-5<f1/f2<3；

-6<f2/f3<-2；

wherein f1 denotes a focal length of the first lens, f2 denotes a focal length of the second lens, and f3 denotes a focal length of the third lens.

7. An optical lens according to claim 1, characterized in that the optical lens satisfies the following conditional expression:

-5<f2/f<-2；

1<R3/R4<4；

where f denotes a focal length of the optical lens, f2 denotes a focal length of the second lens, R3 denotes a radius of curvature of an object-side surface of the second lens, and R4 denotes a radius of curvature of an image-side surface of the second lens.

8. An optical lens according to claim 1, characterized in that the optical lens satisfies the following conditional expression:

2<(CT1+CT3)/CT2<3；

0.1<CT12/CT23<0.3；

wherein CT1 represents a center thickness of the first lens, CT2 represents a center thickness of the second lens, CT3 represents a center thickness of the third lens, CT12 represents a distance of separation of the first lens and the second lens on an optical axis, and CT23 represents a distance of separation of the second lens and the third lens on the optical axis.

9. An optical lens according to claim 1, characterized in that the optical lens satisfies the following conditional expression:

0.5<f3/f<1.2；

-3<R5/R6<0；

where f3 denotes a focal length of the third lens, f denotes a focal length of the optical lens, R5 denotes a radius of curvature of an object-side surface of the third lens, and R6 denotes a radius of curvature of an image-side surface of the third lens.