CN211236422U

CN211236422U - Optical lens

Info

Publication number: CN211236422U
Application number: CN202020127401.4U
Authority: CN
Inventors: 郑毅; 李志鹏
Original assignee: Xiamen Leading Optics Co Ltd
Current assignee: Xiamen Leading Optics Co Ltd
Priority date: 2020-01-19
Filing date: 2020-01-19
Publication date: 2020-08-11
Anticipated expiration: 2030-01-19

Abstract

The utility model discloses an optical lens, which comprises a first lens, a second lens, a third lens and a fourth lens from an object side to an image side in sequence; the first lens has positive diopter, and has an object side surface facing to the object side and an image side surface facing to the image side, wherein the object side surface is a convex surface, and the image side surface is a concave surface or a plane; the second lens element has positive diopter, and has an object-side surface facing the object side and an image-side surface facing the image side, wherein the object-side surface is convex, and the image-side surface is concave or planar; the third lens element with positive refractive power has an object-side surface facing the object side and an image-side surface facing the image side, wherein the object-side surface is a concave surface or a plane, and the image-side surface is a convex surface; the fourth lens element has negative refractive power, and has an object-side surface facing the object side and an image-side surface facing the image side, wherein the object-side surface is concave and the image-side surface is convex. The utility model provides an identification lens adopts miniaturized lightweight design, can satisfy VCM drive requirement, realizes the quick discernment of big object distance scope.

Description

Optical lens

Technical Field

The utility model belongs to the technical field of the camera lens, specifically relate to an optical lens.

Background

With the rapid development of science and technology, smart phones are continuously updated, and the traditional identity recognition mode cannot meet the new requirements of people on information safety, so that the easy-to-use and highly reliable biometric recognition technology is highly valued by people. However, in practical application, the potential safety hazard of the fingerprint identification, face identification and other biological identification technologies is found, the iris identification technology has the unique characteristics of protectiveness, high stability, high anti-counterfeiting performance and the like, the defects of the biological identification are well overcome, and the iris identification technology has high research value and wide application prospect in the biological identification field. The iris recognition technology is applied to mobile terminals such as mobile phones and the like, which is necessary for rapid development of science and technology and research of people. In the iris recognition technology, the acquisition of an iris image is the first step and also the key step, and the acquisition directly influences the quality of the image and the accuracy of recognition.

The iris identification lens commonly used in the market at present adopts a mode of reducing light transmission to obtain the depth of field, the resolution ratio contrast is unsatisfactory, the external dimension and the weight of the lens cannot meet the driving requirement of a Voice Coil Motor (VCM), the VCM cannot be used for quick focusing, and even the lens has small light transmission aperture, low resolution and low illumination. Therefore, the utility model provides a new optical lens.

SUMMERY OF THE UTILITY MODEL

An object of the utility model is to provide an optical lens is used for solving the above-mentioned technical problem who exists.

In order to achieve the above object, the utility model adopts the following technical scheme: an optical lens is provided, which comprises a first lens, a second lens, a third lens and a fourth lens from an object side to an image side in sequence;

the first lens has positive diopter, and has an object side surface facing to the object side and an image side surface facing to the image side, wherein the object side surface is a convex surface, and the image side surface is a concave surface or a plane;

the second lens element has positive diopter, and has an object-side surface facing the object side and an image-side surface facing the image side, wherein the object-side surface is convex, and the image-side surface is concave or planar;

the third lens element with positive refractive power has an object-side surface facing the object side and an image-side surface facing the image side, wherein the object-side surface is a concave surface or a plane, and the image-side surface is a convex surface;

the fourth lens element has negative refractive power, and has an object-side surface facing the object side and an image-side surface facing the image side, wherein the object-side surface is concave and the image-side surface is convex.

Further, the optical lens further satisfies: 1.7 ≦ nd1, where nd1 is the refractive index of the first lens.

Further, the optical lens further satisfies: 1.7 ≦ nd2, where nd2 is the refractive index of the second lens.

Further, the optical lens further satisfies: nd1 is comparable to nd2 in size.

Further, the optical lens further satisfies: nd3 is not less than 1.5 and not more than nd4 is not less than 2.1, nd3 is not less than 1.5 and not more than nd5 is not less than 2.1, wherein nd3 is the refractive index of the third lens, nd4 is the refractive index of the fourth lens, and nd5 is the refractive index of the fifth lens.

Further, the optical lens further satisfies: nd4 is more than or equal to nd1 is more than or equal to nd 3.

Further, the optical lens further satisfies: nd5 is more than or equal to nd1 is more than or equal to nd 3.

Further, the optical lens further satisfies: TTL is less than EFL, wherein TTL is the distance between the first lens and the imaging surface on the optical axis, and EFL is the distance between the lens center of the first lens and the focal point.

The utility model has the advantages of:

the utility model adopts four lenses, and has the advantages of enlarging the light transmission of the system, improving the diffraction limit and the resolution ratio by correspondingly designing each lens; various infrared spectrum designs can achieve good image quality by selecting proper optical filters according to light supplement conditions; the size is small, the weight is light (can be less than 1.5g), the VCM driving requirement can be met, VCM is used for quickly focusing, and the quick identification of a large object distance range is realized; the position of the diaphragm is insensitive, the position of the diaphragm is freely selected, the diaphragm can be arranged in front, and a liquid lens is matched, so that the large object distance range can be quickly identified; the telephoto structure is complicated, the total length of the system is effectively shortened, and the aperture of the lens is effectively reduced under the condition that the diaphragm is arranged in front.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.

Fig. 1 is a schematic structural diagram of a first embodiment of the present invention;

FIG. 2 is a graph of MTF at 400mm object distance and at 850nm infrared (160lp/mm) according to an embodiment I of the present invention;

FIG. 3 is a graph of MTF at 300mm object distance and 850nm infrared (160lp/mm) according to the first embodiment of the present invention;

FIG. 4 is an MTF plot of object distance 650mm and infrared 850nm (160lp/mm) according to the first embodiment of the present invention;

FIG. 5 is a graph of MTF at 400mm object distance and 940nm infrared (160lp/mm) according to an embodiment of the present invention;

fig. 6 is a graph of infrared 850nm defocus curve of the first embodiment of the present invention;

fig. 7 is a field curve/distortion diagram according to a first embodiment of the present invention;

fig. 8 is a graph of relative illuminance of the first embodiment of the present invention;

fig. 9 is a schematic structural view of a second embodiment of the present invention;

FIG. 10 is a graph of MTF at 400mm object distance and at 850nm infrared (160lp/mm) according to the second embodiment of the present invention;

FIG. 11 is a graph of MTF at 300mm object distance and 850nm infrared (160lp/mm) according to the second embodiment of the present invention;

FIG. 12 is an MTF plot of object distance 650mm and infrared 850nm (160lp/mm) for example two of the present invention;

FIG. 13 is a graph of MTF at 400mm object distance and 940nm infrared (160lp/mm) according to the second embodiment of the present invention;

fig. 14 is a graph of infrared 850nm defocus curve of the second embodiment of the present invention;

fig. 15 is a field curve/distortion diagram of the second embodiment of the present invention;

fig. 16 is a graph showing a relative illuminance curve according to the second embodiment of the present invention;

fig. 17 is a schematic structural view of a third embodiment of the present invention;

FIG. 18 is a graph of MTF at 400mm object distance and at 850nm infrared (160lp/mm) according to the third embodiment of the present invention;

FIG. 19 is a graph of MTF at 300mm object distance and 850nm infrared (160lp/mm) according to the third embodiment of the present invention;

FIG. 20 is an MTF plot of object distance 650mm and infrared 850nm (160lp/mm) for inventive example III;

FIG. 21 is a graph of MTF at 400mm object distance and 940nm infrared (160lp/mm) according to a third embodiment of the present invention;

fig. 22 is a graph of infrared 850nm defocus curve of the third embodiment of the present invention;

fig. 23 is a field curve/distortion diagram of the third embodiment of the present invention;

fig. 24 is a graph showing a relative illuminance curve of a third embodiment of the present invention;

fig. 25 is a schematic structural diagram of a fourth embodiment of the present invention;

FIG. 26 is a graph of MTF at 400mm object distance and at 850nm infrared (160lp/mm) according to example four of the present invention;

FIG. 27 is a graph of MTF at 300mm object distance and at 850nm infrared (160lp/mm) according to example four of the present invention;

FIG. 28 is an MTF plot of object distance 650mm and infrared 850nm (160lp/mm) for inventive example four;

fig. 29 is a graph of infrared 850nm defocus curve of the fourth embodiment of the present invention;

fig. 30 is a field curve/distortion diagram of the fourth embodiment of the present invention;

fig. 31 is a graph showing a relative illuminance curve of a fourth embodiment of the present invention.

Detailed Description

To further illustrate the embodiments, the present invention provides the accompanying drawings. The accompanying drawings, which are incorporated in and constitute a part of this disclosure, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the embodiments. With these references, one of ordinary skill in the art will appreciate other possible embodiments and advantages of the present invention. Elements in the figures are not drawn to scale and like reference numerals are generally used to indicate like elements.

The present invention will now be further described with reference to the accompanying drawings and detailed description.

The term "a lens element having positive refractive index (or negative refractive index)" means that the paraxial refractive index of the lens element calculated by Gaussian optics theory is positive (or negative). The term "object-side (or image-side) of a lens" is defined as the specific range of imaging light rays passing through the lens surface. The determination of the surface shape of the lens can be performed by the judgment method of a person skilled in the art, i.e., by the sign of the curvature radius (abbreviated as R value). The R value may be commonly used in optical design software, such as Zemax or CodeV. The R value is also commonly found in lens data sheets (lens data sheets) of optical design software. When the R value is positive, the object side is judged to be a convex surface; and when the R value is negative, judging that the object side surface is a concave surface. On the contrary, regarding the image side surface, when the R value is positive, the image side surface is judged to be a concave surface; when the R value is negative, the image side surface is judged to be convex.

The utility model provides an optical lens, which comprises a first lens, a second lens, a diaphragm (with flexible position), a third lens and a fourth lens from an object side to an image side in sequence;

Preferably, the position of the diaphragm is flexible, and a front diaphragm or a middle diaphragm can be selected, so that the adaptability of the lens is further improved.

More preferably, the first and second lenses are meniscus positive lenses, the object-side surface is convex, the image-side surface is concave or planar, the first lens is made of a high refractive index material to perform pre-refraction on the optical path, and in order to reduce the amount of aberration compensation of the rear group, the front group can be further split, so as to reduce the optical power of each lens, reduce the primary amount of aberration (especially coma aberration and distortion), and also reduce the high-order amount thereof.

Preferably, the third lens element is a plano-convex lens element or a positive meniscus lens element, the object side surface is a concave surface or a flat surface, and the image side surface is a convex surface, receiving the front set of input light rays, providing positive spherical aberration, and canceling negative spherical aberration of the last negative meniscus lens element.

Preferably, the fourth lens is a meniscus negative lens, bears the negative group action of a telephoto structure, and forms a new negative group with any front lens, so that the purpose of compressing the total length of the lens is realized. A fifth lens can be added to form a combined sheet with the fourth lens group, so that the negative group effect of a telephoto structure is born, and the optimization under the non-monochromatic light condition is increased. Meanwhile, most of the commonly used sensors for optical application are monochromatic sensors with large chief ray incidence angles, the side facing the object is a concave surface, and the side facing the object is a final lens in a convex surface shape, so that the larger chief ray incidence angle and the smaller lens aperture are realized, and the miniaturization is realized.

Preferably, the refractive indices of the four lenses respectively satisfy: the first lens and the second lens are more than or equal to 1.7 and less than or equal to nd1 and approximately equal to nd 2; the third lens, the fourth lens (the fifth lens), 1.5 nd3 nd4(nd5) nd 2.1, wherein the adjustment based on chromatic aberration optimization can be further limited to nd4(nd5) nd1 nd2 nd 3.

The optical imaging lens of the present invention will be described in detail with reference to specific embodiments.

Implement one

As shown in fig. 1, an optical lens includes, in order along an optical axis I, a first lens 1, a second lens 2, a stop, a third lens 4, a fourth lens 5, a protective glass 6, and an image plane 7 from an object side a1 to an image side a 2.

The first lens element 1 has positive refractive power, and has an object-side surface 11 facing an object side a1 and an image-side surface 12 facing an image side a2, wherein the object-side surface 11 is convex, and the image-side surface 12 is concave, and in some embodiments, the image-side surface may be planar;

the second lens element 2 with positive refractive power has an object-side surface 21 facing the object side a1 and an image-side surface 22 facing the image side a2, wherein the object-side surface 21 is convex, and the image-side surface 22 is concave, and in some embodiments, the image-side surface may be planar;

the third lens element 4 with positive refractive power has an object-side surface 41 facing the object side a1 and an image-side surface 42 facing the image side a2, wherein the object-side surface 41 is concave or planar, and the image-side surface 42 is convex;

the fourth lens element 5 with negative refractive power has an object-side surface 51 facing the object side a1 and an image-side surface 52 facing the image side a2, wherein the object-side surface 51 is concave and the image-side surface 52 is convex.

In the present embodiment, the refractive index nd1 of the first lens 1 is smaller than the refractive index nd2 of the second lens 2, and the refractive index nd3 of the third lens 4 is smaller than the refractive index nd4 of the fourth lens 5.

The detailed optical data of this example is shown in Table 1-1.

The detailed explanation of this embodiment refers to fig. 2-8, in which fig. 2-5 are graphs of diffraction MTF of multiple colors in this embodiment, and different infrared spectrum designs are adopted to observe the imaging contrast of the lens, and good image quality can be achieved by selecting appropriate filters according to the light supplement conditions. In addition, when an automatic focusing module (such as a VCM) is used, the focusing can be realized in a larger object distance range. Fig. 6 is a defocus graph in the first embodiment, in which the horizontal axis represents the focus shift and the peak is at the focal distance, and the imaging quality is significantly reduced but still high as the focus shift changes.

Fig. 7 is a field curve/distortion diagram in the first embodiment, and it can be seen from the diagram that the parameter change, field curve and distortion are not obvious, and fig. 8 is a relative illumination diagram in the first embodiment, and the relative illumination decreases with the enlargement of the field of view, but still remains above 0.8.

In addition, TTL is less than EFL, wherein TTL is the distance between the first lens and the imaging surface on the optical axis, and EFL is the distance between the lens center of the first lens and the focal point. In example one, the TTL is about 14.53mm and the EFL is 15.00 mm.

Example two

As shown in fig. 9, an optical lens includes, in order along an optical axis I, a stop, a first lens 200, a second lens 300, a third lens 400, a fourth lens 500, a protective glass 600, and an image plane 700 from an object side a1 to an image side a 2.

The first lens element 200 with positive refractive power has an object-side surface 201 facing an object side a1 and an image-side surface 202 facing an image side a2, wherein the object-side surface 201 is convex and the image-side surface 202 is concave, and in some embodiments, the image-side surface may be planar;

the second lens element 300 with positive refractive power has an object-side surface 301 facing the object side a1 and an image-side surface 302 facing the image side a2, wherein the object-side surface 301 is convex and the image-side surface 302 is concave, and in some embodiments, the image-side surface may be planar;

the third lens element 400 with positive refractive power has an object-side surface 401 facing to an object side a1 and an image-side surface 402 facing to an image side a2, wherein the object-side surface 401 is concave, in some embodiments, the object-side surface may be flat, and the image-side surface 402 is convex;

the fourth lens element 500 with negative refractive power has an object-side surface 501 facing an object side a1 and an image-side surface 502 facing an image side a2, wherein the object-side surface 501 is concave and the image-side surface 502 is convex.

In the present embodiment, the refractive index nd1 of the first lens 200 is greater than the refractive index nd2 of the second lens 300, and the refractive index nd3 of the third lens 400 is smaller than the refractive index nd4 of the fourth lens 500.

The detailed optical data of this example is shown in Table 2-1.

The detailed explanation of this embodiment refers to fig. 10-16, in which fig. 10-13 are graphs of diffraction MTF of multiple colors in this embodiment, and different infrared spectrum designs are adopted to observe the imaging contrast of the lens, and good image quality can be achieved by selecting appropriate filters according to the light supplement conditions. Fig. 14 is a defocus graph in the first embodiment, in which the horizontal axis represents the focus shift and the peak is at the focal distance, and the imaging quality is significantly reduced but still high as the focus shift changes.

Fig. 15 is a field curve/distortion diagram in the first embodiment, and it can be seen from the diagram that the parameter changes, the field curve and the distortion are not obvious, fig. 16 is a relative illuminance diagram in the first embodiment, the relative illuminance decreases with the enlargement of the field of view, however, compared with fig. 1, the relative illuminance drops by 0.8 last, and the difference of the position of the visible diaphragm affects the system light transmission.

In example two, the TTL is about 14.58mm and the EFL is 15.00 mm.

EXAMPLE III

As shown in fig. 17, in an optical lens according to the present embodiment, the order of placing the lenses and the refractive index of each lens are the same as those in the second embodiment, and only optical parameters such as the curvature radius of each lens surface and the lens thickness are different.

The detailed optical data of this embodiment is shown in Table 3-1.

Detailed explanation of the present embodiment referring to fig. 18 to 24, each graph in the third embodiment is compared with the embodiment, and although the refractive index of each lens in the second and third embodiments is the same, when the radius of curvature and the thickness of the lens are slightly changed, for example, the MTF graph in the third embodiment is inferior to that in the second embodiment, distortion is more remarkable, and the like.

In example three, the TTL was about 14.57mm and the EFL was 15.00 mm.

Example four

As shown in fig. 25, an optical lens includes, in order along an optical axis I, a first lens 1000, a second lens 2000, a stop, a third lens 4000, a fourth lens 5000, a fifth lens 6000, a protective glass 7000, and an image plane 8000 from an object side a1 to an image side a 2.

The first lens element 1000 with positive refractive power has an object-side surface 1001 facing an object side a1 and an image-side surface 1002 facing an image side a2, wherein the object-side surface 1001 is convex and the image-side surface 1002 is concave, and in some embodiments, the image-side surface may be planar;

the second lens element 2000 with positive refractive power has an object-side surface 2001 facing an object side a1 and an image-side surface 2002 facing an image side a2, wherein the object-side surface 2001 is convex, and the image-side surface 2002 is concave, and in some embodiments, the image-side surface may be planar;

the third lens element 4000 with positive refractive power has an object-side surface 4001 facing the object side a1 and an image-side surface 4002 facing the image side a2, the object-side surface 4001 is concave, in some embodiments, the object-side surface may be planar, and the image-side surface 4002 is convex;

the fourth lens element 5000 with negative refractive power has an object-side surface 5001 facing to the object side a1 and an image-side surface 5002 facing to the image side a2, wherein the object-side surface 5001 is concave and the image-side surface 5002 is convex;

the fifth lens element 6000 with negative refractive power has an object-side surface 6001 facing the object side a1 and an image-side surface 6002 facing the image side a2, wherein the object-side surface 6001 is concave and the image-side surface 6002 is convex.

In the present embodiment, the refractive index nd1 of the first lens 1000 is slightly smaller than the refractive index nd2 of the second lens 2000, the refractive index nd3 of the third lens 4000 is slightly larger than the refractive index nd4 of the fourth lens 5000, and the refractive index nd5 of the fifth lens 6000 is larger than the refractive index nd4 of the fourth lens 5000.

The detailed optical data of this example is shown in Table 4-1.

Referring to fig. 26 to 31, in the fourth embodiment, since a fifth lens is added on the basis of the first embodiment, the specific graphs can be compared with the first embodiment, for example, the MTF graph is obviously better than the first embodiment, however, the distortion is larger in the fourth embodiment, and the relative illuminance is also worse than that in the first embodiment. Therefore, under the condition that the telephoto structure is complex, the total length of the system can be effectively shortened, and the quality of the lens can be improved.

In example four, the TTL was about 14.18mm and the EFL was 15.02 mm.

Comparing example two with example three, it can be seen that the selection of the lens aperture is significantly reduced when the diaphragm is in the forward position. But if the liquid lens is matched, the quick identification of a large object distance range can be realized.

Referring to table 5, table 5 is a table of values of each important parameter of the four embodiments of the present invention, wherein T1 is the central thickness of the first lens on the optical axis; t2 is the central thickness of the second lens on the optical axis; t3 is the central thickness of the third lens on the optical axis; t4 is the central thickness of the fourth lens on the optical axis; t5 is the central thickness of the fifth lens on the optical axis; g12 is an air gap on the optical axis from the first lens to the second lens; g23 is an air gap on the optical axis from the second lens to the third lens; g34 is an air gap on the optical axis between the third lens and the fourth lens; g45 is an air gap on the optical axis between the fourth lens and the fifth lens; gstop is the sum of the air gaps before and after the diaphragm; ALT is the sum of the thicknesses of the lenses of the set on the optical axis.

Table 5 each important parameter table of four embodiments of the present invention

	Example 1	Example 2	Example 3	Example 4
					T1	1.058	1.233	1.241	1.786
T2	1.585	1.626	1.616	1.535
					T3	1.628	2.123	2.113	1.018
T4	0.948	0.764	0.766	1.701
					T5	0.000	0.000	0.000	1.000
G12	0.080	0.100	0.100	0.137
					G23	3.223	2.882	2.906	2.310
G34	0.694	0.491	0.490	0.428
					G45	0.000	0.000	0.000	0.000
Gstop	3.223	0.050	0.050	2.310
					ALT	5.219	5.746	5.736	7.040
ALG	3.997	3.473	3.496	2.876
					TTL	14.526	14.576	14.572	14.181
ALT/ALG	1.306	1.655	1.641	2.448
					ndL1	1.805	1.805	1.805	1.728
ndL2	1.596	1.596	1.596	1.785
					ndL3	1.517	1.517	1.517	1.540
ndL4	2.001	2.001	2.001	1.572
					ndL5				2.001
ΦL1	0.049	0.053	0.053	0.057
					ΦL2	0.040	0.033	0.032	0.062
ΦL3	0.061	0.077	0.077	0.028
					ΦL4	-0.118	-0.140	-0.139	0.146
ΦL5				-0.215
					ΦL4/5	-0.118	-0.140	-0.139	-0.121
Phi front group	0.091	0.090	0.090	0.115
					Phi rear group	-0.060	-0.064	-0.063	-0.101
Φ(ALL)	0.067	0.067	0.067	0.067

While the invention has been particularly shown and described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

1. An optical lens assembly includes, in order from an object side to an image side, a first lens element, a second lens element, a third lens element, and a fourth lens element;

2. An optical lens according to claim 1, characterized in that it further satisfies: 1.7 ≦ nd1, where nd1 is the refractive index of the first lens.

3. An optical lens according to claim 1, characterized in that it further satisfies: 1.7 ≦ nd2, where nd2 is the refractive index of the second lens.

4. An optical lens according to claim 2 or 3, characterized in that it further satisfies: nd1 is comparable to nd2 in size.

5. An optical lens according to claim 1, characterized in that it further satisfies: nd3 is not less than 1.5 and not more than nd4 is not less than 2.1, nd3 is not less than 1.5 and not more than nd5 is not less than 2.1, wherein nd3 is the refractive index of the third lens, nd4 is the refractive index of the fourth lens, and nd5 is the refractive index of the fifth lens.

6. An optical lens according to claim 1, characterized in that it further satisfies: nd4 is more than or equal to nd1 is more than or equal to nd3, wherein nd1 is the refractive index of the first lens, nd3 is the refractive index of the third lens, and nd4 is the refractive index of the fourth lens.

7. An optical lens according to claim 1, characterized in that it further satisfies: nd5 is more than or equal to nd1 is more than or equal to nd3, wherein nd1 is the refractive index of the first lens, nd3 is the refractive index of the third lens, and nd5 is the refractive index of the fourth lens.

8. An optical lens according to claim 1, characterized in that it further satisfies: TTL is less than EFL, wherein TTL is the distance between the object side surface of the first lens and the imaging surface on the optical axis, and EFL is the distance between the lens center of the first lens and the focal point.