CN116560044B

CN116560044B - Optical lens

Info

Publication number: CN116560044B
Application number: CN202310846170.0A
Authority: CN
Inventors: 谢雨辰; 徐丽丽; 章彬炜
Original assignee: Jiangxi Lianyi Optics Co Ltd
Current assignee: Jiangxi Lianyi Optics Co Ltd
Priority date: 2023-07-11
Filing date: 2023-07-11
Publication date: 2023-10-27
Anticipated expiration: 2043-07-11
Also published as: CN116560044A

Abstract

The invention discloses an optical lens, which sequentially comprises the following components from an object plane to an imaging plane along an optical axis: a flat glass without optical power, a first lens with negative optical power, the object side surface of which is concave at a paraxial region, and the image side surface of which is concave; a diaphragm; a second lens having positive optical power; a third lens element with positive refractive power having a convex object-side surface at a paraxial region and at least one inflection point, and a convex image-side surface; a filter having no optical power; the optical lens satisfies the following conditional expression: 170 < f2/f3 < 220; wherein f2 represents an effective focal length of the second lens, and f3 represents an effective focal length of the third lens. The optical lens provided by the invention adopts three aspheric lenses with focal power, so that the optical lens has good optical performance, and at the same time, the optical lens has the advantages of at least super-large field angle, small volume and small distortion.

Description

Optical lens

Technical Field

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

Background

With the continuous development of mobile information technology, portable electronic devices such as mobile phones are also developing toward ultra-thin, full-screen, ultra-high definition imaging, and the like. With the popularity of the concept of full-screen, the technology of fingerprint identification under the screen has been developed, and because the optical fingerprint identification system under the screen has the advantages of small volume and short total length, the system is widely applied to various full-screen mobile phones, and meanwhile, the performance requirement on an optical lens used in fingerprint identification under the screen is also higher and higher. However, in the prior art, the optical lens used in the fingerprint identification under the screen has the problems of low imaging quality, large distortion and longer total length, and cannot meet the requirements of customers on thinner machine bodies and more accurate identification.

Disclosure of Invention

Based on the above, the present invention aims to provide an optical lens, which has at least the advantages of large field angle, small volume, small distortion, etc.

The embodiment of the invention realizes the aim through the following technical scheme.

The invention provides an optical lens, which sequentially comprises from an object side to an imaging surface along an optical axis: a sheet glass; a first lens element with negative refractive power having a concave object-side surface and a concave image-side surface at a paraxial region; a diaphragm; a second lens having positive optical power; the object side surface of the third lens is convex at a paraxial region and at least has one inflection point, and the image side surface of the third lens is convex; a light filter; the optical lens satisfies the following conditional expression: 170 < f2/f3 < 220; wherein f2 represents an effective focal length of the second lens, and f3 represents an effective focal length of the third lens.

Compared with the prior art, the optical lens provided by the invention has the characteristics of large field angle, small volume and small distortion by reasonably distributing the thickness and the focal power of the three lenses and reasonably controlling the surface shape of each lens.

Drawings

Fig. 1 is a schematic structural diagram of an optical lens according to a first embodiment of the present invention.

Fig. 2 is a graph showing a field curvature of an optical lens according to a first embodiment of the present invention.

Fig. 3 is an optical distortion graph of an optical lens according to a first embodiment of the present invention.

Fig. 4 is a graph showing the relative illuminance of the optical lens in the first embodiment of the present invention.

Fig. 5 is a schematic structural diagram of an optical lens according to a second embodiment of the present invention.

Fig. 6 is a graph showing a field curvature of an optical lens according to a second embodiment of the present invention.

Fig. 7 is an optical distortion graph of an optical lens according to a second embodiment of the present invention.

Fig. 8 is a graph of relative illuminance of an optical lens in a second embodiment of the present invention.

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

Fig. 10 is a graph showing a field curvature of an optical lens according to a third embodiment of the present invention.

Fig. 11 is an optical distortion graph of an optical lens according to a third embodiment of the present invention.

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

Detailed Description

In order that the invention may be readily understood, a more complete description of the invention will be rendered by reference to the appended drawings. Several embodiments of the invention are presented in the figures. 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 invention provides an optical lens, which sequentially comprises from an object side to an imaging surface along an optical axis: plate glass, a first lens, a diaphragm, a second lens, a third lens and an optical filter.

The first lens has negative focal power, the object side surface of the first lens is a concave surface at a paraxial region, and the image side surface of the first lens is a concave surface; the second lens has positive focal power, the object side surface of the second lens is convex at a paraxial region, and the image side surface of the second lens is concave at the paraxial region; the third lens has positive focal power, the object side surface of the third lens is a convex surface at the paraxial region, and the image side surface of the third lens is a convex surface; meanwhile, the first lens, the second lens and the third lens are all plastic aspherical lenses.

In some embodiments, the radius of curvature R22 of the second lens image-side surface and the radius of curvature R31 of the third lens object-side surface satisfy: R22/R31 is more than 3.0 and less than 7.0. The invention can lead the optical lens to have the characteristics of large angle of view, small volume and small distortion through specific surface shape collocation and reasonable focal power distribution and simultaneously meets the range.

In some embodiments, the center thickness CT1 of the first lens and the air separation CT12 of the first lens and the second lens on the optical axis satisfy: CT1/CT12 is more than 1.0 and less than 2.0. The above range is satisfied, and the relationship between the center thickness of the first lens and the interval between the first lens and the second lens is reasonably distributed, so that the total length of the optical lens is reduced, and the miniaturization of the optical lens is realized.

In some embodiments, the effective focal length f1 of the first lens and the effective focal length f of the optical lens satisfy: -3.0 < f1/f < -1.0. The range is satisfied, and the focal length of the first lens is reasonably controlled, so that the incident angle of light entering the diaphragm is reduced, the angle of view and object height of the optical lens are increased, and the identification range of the optical lens is enlarged.

In some embodiments, the radius of curvature R11 of the first lens object-side surface and the radius of curvature R32 of the third lens image-side surface satisfy: R11/R32 is more than 0.3 and less than 0.7. The optical lens system meets the above range, and is beneficial to controlling the focal length of the optical lens and reducing the optical distortion of the optical lens by reasonably controlling the curvature radiuses of the object side surface of the first lens and the image side surface of the third lens.

In some embodiments, the effective focal length f2 of the second lens and the effective focal length f of the optical lens satisfy: 190 < f2/f < 240; the effective focal length f2 of the second lens and the effective focal length f3 of the third lens satisfy: 170 < f2/f3 < 220. The spherical aberration correction method has the advantages that the spherical aberration of the central view field of the optical lens is corrected by reasonably controlling the focal lengths of the second lens and the third lens, and the imaging quality of the optical lens is improved.

In some embodiments, the center thickness CT2 of the second lens and the air separation CT23 of the second lens and the third lens on the optical axis satisfy: CT2/CT23 is more than 12.0 and less than 18.0; the center thickness CT2 of the second lens and the center thickness CT3 of the third lens satisfy: CT2/CT3 is more than 1.0 and less than 1.5. The central thicknesses of the second lens and the third lens are reasonably controlled to meet the range, so that the second lens and the third lens are compact in distribution, aberration of the optical lens is corrected, and imaging quality is improved.

In some embodiments, the sum of the center thickness CT1 of the first lens, the center thickness CT2 of the second lens, and the center thickness CT3 of the third lens and the distance TTL between the object side surface of the first lens and the imaging surface on the optical axis satisfy: 0.48 < (CT1+CT2+CT3)/TTL < 0.58. The above range is satisfied, and the ratio of the thicknesses of the first lens, the second lens and the third lens in the total optical length is reasonably controlled, so that the distribution of the lenses is more compact, the total optical length of the optical lens is reduced, and the miniaturization of the optical lens is realized.

In some embodiments, the radius of curvature R22 of the second lens image-side surface and the radius of curvature R32 of the third lens image-side surface satisfy: -2.0 < R22/R32 < -0.5. The above range is satisfied, and by reasonably controlling the curvature radius of the second lens image side surface and the third lens image side surface, the coma aberration of each view field can be corrected, and the resolution of the optical lens can be improved.

In some embodiments, the effective focal length f3 of the third lens and the effective focal length f of the optical lens satisfy: 0.5 < f3/f < 1.1. The focal length of the third lens is reasonably controlled to be favorable for correcting the vertical axis aberration of the central view field of the optical lens and improving the imaging quality of the optical lens.

In some embodiments, the radius of curvature R31 of the third lens object-side surface and the radius of curvature R32 of the third lens image-side surface satisfy: -0.3 < R31/R32 < -0.1. The curvature radius of the second lens image side surface and the curvature radius of the third lens image side surface are reasonably controlled, so that field curves of various fields of view can be corrected respectively, and the resolution of the optical lens can be improved.

In some embodiments, the distance TTL on the optical axis from the object side surface of the first lens element to the image plane and the distance FFL on the optical axis from the image side surface of the third lens element to the image plane satisfy: 2.5 < TTL/FFL < 3.2. The range is satisfied, and the ratio of the optical back focus in the total optical length is reasonably controlled, so that the risk of interference between a mechanism and a lens is reduced, and the mechanism design of a product is facilitated.

In some embodiments, the radius of curvature R12 of the image side of the first lens and the radius of curvature R21 of the object side of the second lens satisfy: R12/R21 is more than 0.8 and less than 2.4; the sagittal height SAG12 of the first lens image side and the sagittal height SAG21 of the second lens object side satisfy: 20 < SAG12/SAG21 < 70. The range is met, the surface shapes of the first lens and the second lens are reasonably distributed, so that light rays are converged, the total length of the optical lens is reduced, and the miniaturization of the optical lens is realized.

In some embodiments, the center thickness CT1 of the first lens and the center thickness CT3 of the third lens satisfy: CT1/CT3 is more than 0.6 and less than 1.3. The above range is satisfied, and the relationship between the center thicknesses of the first lens and the third lens is reasonably controlled, so that the total length of the optical lens is reduced, and the miniaturization of the optical lens is realized.

In some embodiments, the sagittal height SAG22 of the second lens image side and the sagittal height SAG31 of the third lens object side satisfy: SAG22/SAG31 < 20.0; the sagittal height SAG31 of the third lens object-side surface and the sagittal height SAG32 of the third lens image-side surface satisfy: 0.05 < SAG31/SAG32 < 0.20. The range is satisfied, the sagittal heights of the second lens and the third lens are reasonably distributed, so that the distortion of the peripheral view field is corrected, the optical distortion of the optical lens is reduced, and the imaging quality is improved.

In various embodiments of the present invention, when an aspherical lens is used as the lens, the surface shape of the aspherical lens satisfies the following equation:

；

where z is the distance sagittal height from the aspherical surface vertex when the aspherical surface is at a position of height h along the optical axis direction, c is the paraxial curvature of the surface, k is the conic coefficient conic, A _2i The aspherical surface profile coefficient of the 2 i-th order.

The invention is further illustrated in the following examples. In various embodiments, the thickness, radius of curvature, and material selection portion of each lens in the optical lens may vary, and for specific differences, reference may be made to the parameter tables of the various embodiments. The following examples are merely preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the following examples, and any other changes, substitutions, combinations or simplifications that do not depart from the gist of the present invention are intended to be equivalent substitutes within the scope of the present invention.

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 imaging surface S11 along an optical axis: a plate glass G1, a first lens L1, a stop ST, a second lens L2, a third lens L3, and a filter G2.

Specifically, the object side surface of the plate glass G1 is S1, and the image side surface is S2; the first lens element L1 has negative refractive power, wherein an object-side surface S3 of the first lens element is concave at a paraxial region, and an image-side surface S4 of the first lens element is concave; the second lens element L2 has positive refractive power, wherein an object-side surface S5 of the second lens element is convex at a paraxial region thereof, and an image-side surface S6 of the second lens element is concave at a paraxial region thereof; the third lens element L3 has positive refractive power, wherein an object-side surface S7 thereof is convex at a paraxial region thereof and has at least one inflection point, and an image-side surface S8 thereof is convex; the object side surface of the filter G2 is S9, and the image side surface is S10. The first lens L1, the second lens L2 and the third lens L3 are all plastic aspheric lenses.

The relevant parameters of each lens in the optical lens 100 according to the first embodiment of the present invention are shown in table 1.

TABLE 1

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

TABLE 2

Fig. 2 shows a field curvature curve of the optical lens 100 in this embodiment, which represents field curvature values at different fields of view, and it can be seen from the figure that the field curvature values at each field of view are controlled within ±0.1mm, which indicates that the field curvature of each field of view of the optical lens 100 is well corrected.

Fig. 3 shows optical distortion curves of the optical lens 100 of the present embodiment, which represent distortions at different fields of view on the imaging plane, and it can be seen from the figure that the optical distortion is controlled within ±1.5%, which indicates that the distortion of the optical lens 100 is well corrected.

Fig. 4 shows the relative illuminance curves of the optical lens 100 in this embodiment, which represent the ratio of the illuminance of different fields of view to the illuminance of the central field of view, and it can be seen from the figure that the relative illuminance of the maximum field of view is controlled to be 34% or more, which indicates that the relative illuminance of each field of view of the optical lens 100 is good.

Second embodiment

Referring to fig. 5, a schematic structural diagram of an optical lens 200 according to a second embodiment of the present invention is shown, and the optical lens 200 in this embodiment is substantially the same as the first embodiment, and the differences are shown in tables 3 and 4.

The relevant parameters of each lens in the optical lens 200 according to the second embodiment of the present invention are shown in table 3.

TABLE 3 Table 3

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

TABLE 4 Table 4

In the present embodiment, a field curvature curve, an optical distortion curve, and a relative illuminance curve of the optical lens 200 are shown in fig. 6, 7, and 8, respectively. As can be seen from the figure, the curvature of field is controlled within ±0.2mm, which indicates that the curvature of field of the optical lens 200 is well corrected; the optical distortion is controlled within +/-1.5%, which indicates that the distortion of the optical lens 200 is well corrected; the relative illuminance of the maximum field of view is controlled to 33% or more, indicating that the relative illuminance of each field of view of the optical lens 200 is good.

Third embodiment

Referring to fig. 9, a schematic diagram of an optical lens 300 according to a second embodiment of the present invention is shown, and the optical lens 300 in this embodiment is substantially the same as the first embodiment, and the differences are shown in table 5 and table 6.

The relevant parameters of each lens in the optical lens 300 according to the third embodiment of the present invention are shown in table 5.

TABLE 5

The surface profile coefficients of the aspherical surfaces of the optical lens 300 in this embodiment are shown in table 6.

TABLE 6

In the present embodiment, a field curvature curve, an optical distortion curve, and a relative illuminance curve of the optical lens 300 are shown in fig. 10, 11, and 12, respectively. As can be seen from the figure, the curvature of field is controlled within ±0.2mm, which indicates that the curvature of field of the optical lens 300 is well corrected; the optical distortion is controlled within +/-1.5%, which means that the distortion of the optical lens 300 is well corrected; the relative illuminance of the maximum field of view is controlled to 34% or more, indicating that the relative illuminance of each field of view of the optical lens 300 is good.

Table 7 is an optical characteristic corresponding to the above four embodiments, and mainly includes an effective focal length F, an f#, an optical total length TTL, an object height OH, a maximum field angle FOV, and an image height IH corresponding to the object height OH of the system, and a value corresponding to each of the above conditional expressions.

TABLE 7

In summary, the optical lens provided by the invention adopts three aspheric lenses with specific focal power, and the specific surface shape collocation and reasonable focal power distribution are adopted: the FOV of the optical lens reaches more than 120 degrees, the object height reaches 9.56mm, and the fingerprint identification range is wide; meanwhile, the arrangement of three lenses is compact, and the total length of the optical lens is reduced; the optical lens has the advantages of super-large field angle, small volume and small distortion.

In the description of the present specification, a description referring to terms "one embodiment," "some embodiments," "examples," "specific examples," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiments or examples. 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 examples merely represent a few embodiments of the present invention, which are described in more detail and are not to be construed as limiting the scope of the present invention. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the invention, which are all within the scope of the invention. Accordingly, the scope of the invention should be assessed as that of the appended claims.

Claims

1. An optical lens comprising, in order from an object side to an imaging surface along an optical axis: plate glass, a first lens, a diaphragm, a second lens, a third lens and an optical filter;

the first lens is provided with negative focal power, the object side surface of the first lens is a concave surface at a paraxial region, and the image side surface of the first lens is a concave surface;

the second lens has positive optical power;

the third lens has positive focal power, the object side surface of the third lens is convex at a paraxial region and at least has one inflection point, and the image side surface of the third lens is convex;

the optical lens satisfies the following conditional expression:

170＜f2/f3＜220；

wherein f2 represents an effective focal length of the second lens, and f3 represents an effective focal length of the third lens.

2. The optical lens according to claim 1, wherein the optical lens satisfies the following conditional expression:

1.0＜CT1/CT12＜2.0；

wherein CT1 represents the center thickness of the first lens, and CT12 represents the air gap between the first lens and the second lens on the optical axis.

3. The optical lens according to claim 1, wherein the optical lens satisfies the following conditional expression:

-3.0＜f1/f＜ -1.0；

wherein f1 represents an effective focal length of the first lens, and f represents an effective focal length of the optical lens.

4. The optical lens according to claim 1, wherein the optical lens satisfies the following conditional expression:

0.3＜R11/R32＜0.7；

wherein R11 represents a radius of curvature of the first lens object-side surface, and R32 represents a radius of curvature of the third lens image-side surface.

5. The optical lens according to claim 1, wherein the optical lens satisfies the following conditional expression:

3.0＜R22/R31＜7.0；

wherein R22 represents the radius of curvature of the image side surface of the second lens, and R31 represents the radius of curvature of the object side surface of the third lens.

6. The optical lens according to claim 1, wherein the optical lens satisfies the following conditional expression:

12.0＜CT2/CT23＜18.0；

1.0＜CT2/CT3＜1.5；

wherein CT2 represents the center thickness of the second lens, CT23 represents the air space between the second lens and the third lens on the optical axis, and CT3 represents the center thickness of the third lens.

7. The optical lens according to claim 1, wherein the optical lens satisfies the following conditional expression:

0.48＜(CT1+CT2+CT3)/TTL＜0.58；

wherein, CT1 represents the center thickness of the first lens, CT2 represents the center thickness of the second lens, CT3 represents the center thickness of the third lens, and TTL represents the distance from the object side surface of the first lens to the imaging surface on the optical axis.

8. The optical lens according to claim 1, wherein the optical lens satisfies the following conditional expression:

-2.0＜R22/R32＜-0.5；

where R22 represents the radius of curvature of the second lens image-side surface and R32 represents the radius of curvature of the third lens image-side surface.

9. The optical lens according to claim 1, wherein the optical lens satisfies the following conditional expression:

0.5＜f3/f＜1.1；

wherein f3 represents an effective focal length of the third lens, and f represents an effective focal length of the optical lens.

10. The optical lens according to claim 1, wherein the optical lens satisfies the following conditional expression:

2.5＜TTL/FFL＜3.2；

wherein TTL represents the distance between the object side surface of the first lens element and the imaging surface on the optical axis, and FFL represents the distance between the image side surface of the third lens element and the imaging surface on the optical axis.