CN210626759U

CN210626759U - Optical imaging lens

Info

Publication number: CN210626759U
Application number: CN201921261257.7U
Authority: CN
Inventors: 郑毅; 池鸿洲
Original assignee: Xiamen Leading Optics Co Ltd
Current assignee: Xiamen Leading Optics Co Ltd
Priority date: 2019-08-06
Filing date: 2019-08-06
Publication date: 2020-05-26
Anticipated expiration: 2029-08-06

Abstract

The utility model relates to a camera lens technical field. The utility model discloses an optical imaging lens, which comprises a first lens, a second lens and a third lens from an object side to an image side along an optical axis, wherein the first lens is a convex-concave lens with negative refractive index; the second lens is a convex-concave or plano-concave lens with negative refractive index, and the third lens is a biconvex or plano-convex lens with positive refraction; the fourth lens is a concave-convex lens, and both the object side surface and the image side surface of the fourth lens are aspheric surfaces; the fifth lens is a biconvex or plano-convex lens with positive refraction; the sixth lens element has a negative refractive index, and an object-side surface of the sixth lens element is concave. The utility model has the advantages of large light transmission, short total length, high resolution, high contrast and good imaging quality.

Description

Optical imaging lens

Technical Field

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

Background

With the continuous progress of science and technology, in recent years, the optical imaging lens is rapidly developed and widely applied to various fields such as smart phones, tablet computers, video conferences, vehicle-mounted monitoring, security monitoring and the like, so that the requirement on the optical imaging lens is higher and higher. However, in the TOF (time of flight) lens currently on the market, the light flux of the TOF lens does not reach the ideal light flux required by the application; the distortion control is poor, and a large amount of pixel loss is caused by distortion correction; the high-resolution TOF lens is large in overall size and falls away from market requirements; in order to realize large light transmission, the relative illumination of the edge field of view is greatly sacrificed, the illumination change is large, and the increasing requirements of consumers cannot be met.

Disclosure of Invention

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

In order to achieve the above object, the utility model adopts the following technical scheme: an optical imaging lens sequentially comprises a first lens, a second lens, a third lens, a fourth lens, a fifth lens and a sixth lens from an object side to an image side along an optical axis; the first lens element to the sixth lens element respectively comprise an object side surface facing the object side and allowing the imaging light to pass and an image side surface facing the image side and allowing the imaging light to pass;

the first lens element with negative refractive index has a convex object-side surface and a concave image-side surface;

the second lens element with negative refractive index has a convex or flat object-side surface and a concave image-side surface;

the third lens element with positive refractive index has a convex object-side surface and a convex image-side surface; or the object side surface of the third lens is a convex surface and the image side surface of the third lens is a plane; or the object side surface of the third lens is a plane and the image side surface of the third lens is a convex surface;

the object side surface of the fourth lens is a concave surface, and the image side surface of the fourth lens is a convex surface; the object side surface and the image side surface of the fourth lens are both aspheric surfaces;

the fifth lens element with positive refractive index has a convex object-side surface and a convex image-side surface; or the object side surface of the fifth lens is a convex surface and the image side surface of the fifth lens is a plane; or the object side surface of the fifth lens is a plane and the image side surface of the fifth lens is a convex surface;

the sixth lens element with negative refractive index has a concave object-side surface;

the optical imaging lens has only the six lenses with the refractive indexes.

Further, the lens further comprises a diaphragm, and the diaphragm is arranged between the third lens and the fourth lens.

Further, the optical imaging lens satisfies: nd3>1.8, nd5> nd6, wherein nd3 is the refractive index of the third lens at the d line, nd5 is the refractive index of the fifth lens at the d line, and nd6 is the refractive index of the sixth lens at the d line.

Further, the optical imaging lens satisfies: nd1 is more than or equal to 1.51 and less than or equal to nd2, nd4 is more than or equal to 1.68 and less than or equal to nd3 and less than or equal to 2.1, nd6 is more than or equal to 1.49 and less than or equal to nd5 and less than or equal to 2.1, wherein nd1-nd6 are refractive indexes of the first lens to the sixth lens in a d line respectively.

Further, the image side surface of the first lens and the object side surface of the second lens are mutually glued.

Further, the image side surface of the fifth lens and the object side surface of the sixth lens are mutually glued.

Further, the optical imaging lens satisfies: TTL is less than 26mm, wherein TTL is the distance between the object side surface of the first lens and an imaging surface on the optical axis.

Further, the optical imaging lens satisfies: 8mm < ALG <10mm, where ALG is the sum of the air gaps on the optical axis from the first lens to the imaging surface.

Further, the optical imaging lens satisfies: 12mm < ALT <13mm, where ALT is a sum of six lens thicknesses of the first lens to the sixth lens on the optical axis.

Further, the optical imaging lens satisfies: 1.2< ALT/ALG <1.6, where ALG is a sum of air gaps of the first lens to an image plane on the optical axis, and ALT is a sum of six lens thicknesses of the first lens to the sixth lens on the optical axis.

The utility model has the advantages of:

the utility model has large light transmission (the f-number FNO reaches below 1.2), and the identification range is enlarged; the optical transfer function is well controlled and high in resolution; distortion is low, and the situation that pixel loss is serious under the condition of correcting distortion is reduced; the total length of the system is short; the relative illumination is controlled, so that the uniformity of the relative illumination under the condition of large light transmission is ensured; and the design yield is high (aiming at the existing conventional TOF sensor, the design yield reaches more than 95%).

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 first MTF graph at 850nm according to a first embodiment of the present invention;

FIG. 3 is a graph II of MTF at 850nm according to the first embodiment of the present invention;

fig. 4 is a graph of MTF at 940nm according to the first embodiment of the present invention;

FIG. 5 is a graph of the defocus curve at 840-860nm in the first embodiment of the present invention;

fig. 6 is a schematic view of curvature of field and distortion according to a first embodiment of the present invention;

fig. 7 is a graph of relative illuminance of the first embodiment of the present invention;

fig. 8 is a schematic structural view of a second embodiment of the present invention;

FIG. 9 is a graph I of MTF at 850nm according to embodiment II of the present invention;

FIG. 10 is a second MTF plot at 850nm according to second embodiment of the present invention;

fig. 11 is a graph of MTF at 940nm according to a second embodiment of the present invention;

FIG. 12 is a graph showing the defocus curve at 840-860nm in the second embodiment of the present invention;

fig. 13 is a schematic view of curvature of field and distortion according to a second embodiment of the present invention;

fig. 14 is a graph showing a relative illuminance curve according to the second embodiment of the present invention;

fig. 15 is a schematic structural view of a third embodiment of the present invention;

FIG. 16 is a first MTF plot at 850nm according to a third embodiment of the present invention;

FIG. 17 is a graph II of MTF at 850nm according to the third embodiment of the present invention;

FIG. 18 is a graph showing the defocus curve at 840-860nm in the third embodiment of the present invention;

fig. 19 is a schematic view of curvature of field and distortion according to a third embodiment of the present invention;

fig. 20 is a graph showing a relative illuminance curve of a third embodiment of the present invention;

fig. 21 is a schematic structural view of a fourth embodiment of the present invention;

fig. 22 is a graph i of MTF at 850nm according to the fourth embodiment of the present invention;

fig. 23 is a graph two of MTF at 850nm according to example four of the present invention;

FIG. 24 is a graph showing the defocus curve at 840-860nm of the fourth embodiment of the present invention;

fig. 25 is a schematic view of curvature of field and distortion according to a fourth embodiment of the present invention;

fig. 26 is a graph showing a relative illuminance curve of a fourth embodiment of the present invention;

fig. 27 is a schematic structural diagram of a fifth embodiment of the present invention;

fig. 28 is a graph i of MTF at 940nm according to embodiment v of the present invention;

fig. 29 is a graph two of MTF at 940nm according to embodiment v of the present invention;

fig. 30 is a 940nm defocus graph of embodiment five of the present invention;

fig. 31 is a schematic view of curvature of field and distortion according to an embodiment of the present invention;

fig. 32 is a contrast graph of a fifth embodiment of the present invention;

fig. 33 is a table of values of relevant important parameters according to five embodiments 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 discloses an optical imaging lens, which comprises a first lens, a second lens, a third lens, a fourth lens, a fifth lens and a sixth lens from an object side to an image side along an optical axis in sequence; the first lens element to the sixth lens element respectively comprise an object side surface facing the object side and allowing the imaging light to pass and an image side surface facing the image side and allowing the imaging light to pass;

the first lens element with negative refractive index has a convex object-side surface and a concave image-side surface; the second lens element with negative refractive index has a convex or flat object-side surface and a concave image-side surface; the first lens and the second lens are negative lenses, the aberration compensation amount of the fourth lens, the fifth lens and the sixth lens is reduced, the focal power of each lens is reduced, the primary amount of aberration (especially coma aberration and distortion) is reduced, and the high-order amount thereof can also be reduced.

The third lens element with positive refractive index has a convex object-side surface and a convex image-side surface; or the object side surface of the third lens is a convex surface and the image side surface of the third lens is a plane; or the object side surface of the third lens is a plane and the image side surface of the third lens is a convex surface. The third lens is similar to a drum lens, aberration compensation is performed, and the power distribution can be greatly reduced or the total length of the system can be greatly reduced.

The object side surface of the fourth lens is a concave surface, and the image side surface of the fourth lens is a convex surface; the object side surface and the image side surface of the fourth lens are both aspheric surfaces; the high-grade spherical aberration and coma aberration can be improved, the relative aperture is improved, meanwhile, the effective diameter of the aspheric surface can be reduced as much as possible, the total length of the system is shortened, and the cost of the system is reduced.

The fifth lens element with positive refractive index has a convex object-side surface and a convex image-side surface; or the object side surface of the fifth lens is a convex surface and the image side surface of the fifth lens is a plane; or the object side surface of the fifth lens is a plane and the image side surface of the fifth lens is a convex surface; the sixth lens element with negative refractive index has a concave object-side surface; the fifth lens and the sixth lens are combined to correct aberration.

The optical imaging lens has only the six lenses, the utility model adopts six lenses, and has large light transmission through the arrangement design of the refractive index and the concave-convex curved surface of each lens; the optical transfer function is well controlled and high in resolution; distortion is low, and the situation that pixel loss is serious under the condition of correcting distortion is reduced; the total length of the system is short; the relative illumination is controlled, so that the uniformity of the relative illumination under the condition of large light transmission is ensured; and the design yield is high.

Preferably, the optical diaphragm is arranged between the third lens and the fourth lens, so that the whole structure is inclined to be a symmetrical structure, and the optimization and improvement of distortion and coma aberration are facilitated. The distance between the diaphragm and the front and rear lenses is enlarged, and the aperture of the lenses is reduced.

Preferably, the optical imaging lens satisfies: nd3>1.8, nd5> nd6, wherein nd3 is the refractive index of the third lens at d line, nd5 is the refractive index of the fifth lens at d line, and nd6 is the refractive index of the sixth lens at d line, so that chromatic aberration is further corrected, assembly conditions are improved, and the product yield is improved.

More preferably, the optical imaging lens satisfies: nd1 is more than or equal to 1.51 and less than or equal to nd2, nd4 is more than or equal to 1.68 and less than or equal to nd3 and less than or equal to 2.1, nd6 is more than or equal to 1.49 and less than or equal to nd5 and less than or equal to 2.1, wherein nd1-nd6 are refractive indexes of the first lens to the sixth lens in a d line respectively, and the system performance is further improved.

Preferably, the image side surface of the first lens and the object side surface of the second lens are mutually glued, so that the process stability is better, and the product yield is improved.

Preferably, the image side surface of the fifth lens and the object side surface of the sixth lens are mutually glued, so that the field curvature of the system is reduced, the assembly condition is improved, and the product yield is improved.

Preferably, the optical imaging lens satisfies: TTL is less than 26mm, wherein TTL is the distance between the object side surface of the first lens and an imaging surface on an optical axis, and the total system length of the optical imaging lens is further shortened.

Preferably, the optical imaging lens satisfies: the thickness of the first lens is 8mm < ALG <10mm, wherein ALG is the sum of air gaps between the first lens and an imaging surface on the optical axis, so that the system length of the optical imaging lens is further shortened, the processing and the manufacturing are easy, and the system configuration is optimized.

Preferably, the optical imaging lens satisfies: 12mm < ALT <13mm, where ALT is the sum of the thicknesses of the six lenses on the optical axis of the first lens to the sixth lens, so as to further shorten the system length of the optical imaging lens, and facilitate manufacturing and optimizing the system configuration.

Preferably, the optical imaging lens satisfies: 1.2< ALT/ALG <1.6, where ALG is the sum of air gaps between the first lens and the imaging plane on the optical axis, and ALT is the sum of six lens thicknesses between the first lens and the sixth lens on the optical axis, so as to further shorten the system length of the optical imaging lens, and facilitate manufacturing and optimizing the system configuration.

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

Example one

As shown in fig. 1, an optical imaging lens includes, in order along an optical axis I, a first lens 1, a second lens 2, a third lens 3, a stop 7, a fourth lens 4, a fifth lens 5, a sixth lens 6, a flat glass 8, and an image plane 9 from an object side a1 to an image side a 2; the first lens element 1 to the sixth lens element 6 each include an object-side surface facing the object side a1 and passing the imaging light rays, and an image-side surface facing the image side a2 and passing the imaging light rays.

The first lens element 1 has a negative refractive index, the object-side surface 11 of the first lens element 1 is convex, and the image-side surface 12 of the first lens element 1 is concave.

The second lens element 2 has a negative refractive index, and an object-side surface 21 of the second lens element 2 is convex and an image-side surface 22 of the second lens element 2 is concave. Of course, in other embodiments, the object side 21 of the second lens 2 may also be planar.

The third lens element 3 has a positive refractive index, and an object-side surface 31 of the third lens element 3 is convex and an image-side surface 32 of the third lens element 3 is convex. Of course, in other embodiments, the third lens element 3 may have a convex object-side surface 31 and a flat image-side surface 32; or the object side 31 is planar and the image side 32 is convex.

The fourth lens element 4 with positive refractive index has a concave object-side surface 41 of the fourth lens element 4 and a convex image-side surface 42 of the fourth lens element 4; the object-side surface 41 and the image-side surface 42 of the fourth lens element 4 are both aspheric.

The fifth lens element 5 has positive refractive index, the object-side surface 51 of the fifth lens element 5 is convex, and the image-side surface 52 of the fifth lens element 5 is convex. Of course, in other embodiments, the fifth lens element 5 may have a convex object-side surface 51 and a flat image-side surface 52; or the object side 51 is planar and the image side 52 is convex.

The sixth lens element 6 has a negative refractive index, and an object-side surface 61 of the sixth lens element 6 is concave and an image-side surface 62 of the sixth lens element 6 is concave. Of course, in other embodiments, the image-side surface 62 of the sixth lens element 6 may be a plane or a convex surface.

In this embodiment, the image-side surface 52 of the fifth lens element 5 and the object-side surface 61 of the sixth lens element 6 are cemented to each other.

In the present embodiment, the diaphragm 7 is preferably disposed between the third lens 3 and the fourth lens 4, but is not limited thereto.

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

Table 1-1 detailed optical data for example one

In this embodiment, the object-side surface 41 and the image-side surface 42 of the third lens element 4 are defined by the following aspheric curve formula:

wherein:

z: depth of the aspheric surface (the vertical distance between a point on the aspheric surface that is y from the optical axis and a tangent plane tangent to the vertex on the optical axis of the aspheric surface);

c: curvature of aspheric vertex (the vertex curvature);

k: cone coefficient (Conic Constant);

radial distance (radial distance);

r_n: normalized radius (normalysis radius (NRADIUS));

u：r/r_n；

a_m: mth order Q^conCoefficient of performance(is the m^thQ^concoefficient)；

Q_m ^con: mth order Q^conPolynomial (the m)^thQ^conpolynomial)；

For details of parameters of each aspheric surface, please refer to the following table:

surface of	41	42
			K＝	1.37E+00	-3.99E-01
a₄＝	-1.85E-03	-1.76E-04
			a₆＝	2.47E-04	5.72E-06
a₈＝	-5.18E-05	5.61E-06
			a₁₀＝	3.96E-06	-7.23E-07
a₁₂＝	8.47E-08	4.44E-08
			a₁₄＝	-1.00E-08	-8.00E-10
a₁₆＝	0.00E+00	0.00E+00

Please refer to fig. 33 for values of the conditional expressions according to this embodiment.

Referring to fig. 2-4, the MTF curve of the present embodiment shows that the optical transfer function is better controlled and has high resolution; see FIG. 5 for confocal infrared 850 nm; the field curvature and distortion diagram are shown in detail in (a) and (B) of fig. 6, and it can be seen that the field curvature and distortion are small; referring to fig. 7, it can be seen that the contrast is high and the uniformity is good.

In this embodiment, the focal length f of the optical imaging lens is 5.3mm, the aperture value FNO is 1.15, and TTL is 24.758 mm.

Example two

As shown in fig. 8, in this embodiment, the surface-type convexo-concave and the refractive index of each lens are the same as those of the first embodiment, and only the optical parameters such as the curvature radius of the surface of each lens and the thickness of the lens are different.

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

TABLE 2-1 detailed optical data for example two

For the detailed data of the parameters of each aspheric surface in this embodiment, refer to the following table:

surface of	41	42
			K＝	1.32E+00	-4.69E-01
a₄＝	-2.18E-03	-5.92E-05
			a₆＝	3.58E-04	-1.77E-05
a₈＝	-6.33E-05	6.91E-06
			a₁₀＝	2.93E-06	-6.57E-07
a₁₂＝	3.52E-07	3.30E-08
			a₁₄＝	-2.00E-08	-5.00E-10
a₁₆＝	0.00E+00	0.00E+00

Referring to fig. 9-11, the MTF curve of the present embodiment shows that the optical transfer function is better controlled and has high resolution; see fig. 12 for confocal infrared 850 nm; the field curvature and distortion diagram are shown in detail in (a) and (B) of fig. 13, and it can be seen that the field curvature and distortion are small; referring to fig. 14, it can be seen that the contrast is high and the uniformity is good.

In this embodiment, the focal length f of the optical imaging lens is 5.3mm, the aperture value FNO is 1.15, and TTL is 24.775 mm.

EXAMPLE III

As shown in fig. 15, the surface-type convexities and concavities and refractive indexes of the lenses of the present embodiment are substantially the same as those of the first embodiment, only the image-side surface 62 of the sixth lens element 6 is a convex surface, and the optical parameters such as the curvature radius of the lens surface and the lens thickness are different, and in the present embodiment, the image-side surface 12 of the first lens element 1 and the object-side surface 21 of the second lens element 2 are cemented with each other, and the fifth lens element 5 and the sixth lens element 6 are not cemented with each other.

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

TABLE 3-1 detailed optical data for EXAMPLE III

surface of	41	42
			K＝	1.55E+00	-5.96E-01
a₄＝	-4.31E-04	-7.13E-06
			a₆＝	5.86E-05	-8.71E-06
a₈＝	-1.73E-06	1.08E-06
			a₁₀＝	4.73E-08	-1.00E-08
a₁₂＝	-9.84E-10	-9.84E-10
			a₁₄＝	5.00E-10	4.00E-11
a₁₆＝	0.00E+00	0.00E+00

Referring to fig. 16 and 17, the MTF curves of the present embodiment show that the optical transfer function is better controlled and has high resolution; see FIG. 18 for confocal infrared 850 nm; the field curvature and distortion diagram are shown in detail in (a) and (B) of fig. 19, and it can be seen that the field curvature and distortion are small; referring to fig. 20, it can be seen that the contrast is high and the uniformity is good.

In this embodiment, the focal length f of the optical imaging lens is 5.3mm, the aperture value FNO is 1.14, and TTL is 24.680 mm.

Example four

As shown in fig. 21, in this embodiment, the surface convexoconcave and the refractive index of each lens element are substantially the same as those of the first embodiment, only the object-side surface 21 of the second lens element 2 is a flat surface, the image-side surface 32 of the third lens element 3 is a flat surface, and the fourth lens element has negative refractive power.

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

TABLE 4-1 detailed optical data for example four

Referring to fig. 22 and 23, the MTF curve of the present embodiment shows that the optical transfer function is better controlled and has high resolution; see fig. 24 for confocal infrared 850 nm; the field curvature and distortion diagram are shown in detail in (a) and (B) of fig. 25, and it can be seen that the field curvature and distortion are small; referring to fig. 26, it can be seen that the contrast is high and the uniformity is good.

In this embodiment, the focal length f of the optical imaging lens is 5.3mm, the aperture value FNO is 1.15, and TTL is 24.062 mm.

EXAMPLE five

As shown in fig. 27, the surface-type convexoconcave shape and the refractive index of each lens element in this embodiment are substantially the same as those of the first embodiment, only the image-side surface 32 of the third lens element 3 is a flat surface, the image-side surface 62 of the sixth lens element 6 is a convex surface, and the optical parameters such as the radius of curvature of the lens surface and the lens thickness are different from each other.

The detailed optical data of this embodiment is shown in Table 5-1.

TABLE 5-1 detailed optical data for EXAMPLE V

Referring to fig. 28 and 29, the MTF curve of the present embodiment shows that the optical transfer function is better controlled and has high resolution; please refer to fig. 30 for infrared 940nm confocal performance; the field curvature and distortion diagram are shown in detail in (a) and (B) of fig. 31, and it can be seen that the field curvature and distortion are small; referring to fig. 32, it can be seen that the contrast is high and the uniformity is good.

In this embodiment, the focal length f of the optical imaging lens is 2.97mm, the aperture value FNO is 1.13, and TTL is 25.990 mm.

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 imaging lens characterized in that: the lens comprises a first lens, a second lens, a third lens, a fourth lens, a fifth lens and a sixth lens in sequence from an object side to an image side along an optical axis; the first lens element to the sixth lens element respectively comprise an object side surface facing the object side and allowing the imaging light to pass and an image side surface facing the image side and allowing the imaging light to pass;

the optical imaging lens only has the six lenses with the refractive indexes; the optical imaging lens satisfies the following conditions: nd3>1.8, nd5> nd6, wherein nd3 is the refractive index of the third lens at the d line, nd5 is the refractive index of the fifth lens at the d line, and nd6 is the refractive index of the sixth lens at the d line.

2. The optical imaging lens according to claim 1, characterized in that: the diaphragm is arranged between the third lens and the fourth lens.

3. The optical imaging lens of claim 1, wherein the optical imaging lens satisfies: nd1 is more than or equal to 1.51 and less than or equal to nd2, nd4 is more than or equal to 1.68 and less than or equal to nd3 and less than or equal to 2.1, nd6 is more than or equal to 1.49 and less than or equal to nd5 and less than or equal to 2.1, wherein nd1-nd6 are refractive indexes of the first lens to the sixth lens in a d line respectively.

4. The optical imaging lens according to claim 1, characterized in that: the image side surface of the first lens and the object side surface of the second lens are mutually glued.

5. The optical imaging lens according to claim 1, characterized in that: the image side surface of the fifth lens and the object side surface of the sixth lens are mutually glued.

6. The optical imaging lens of claim 1, wherein the optical imaging lens satisfies: TTL is less than 26mm, wherein TTL is the distance between the object side surface of the first lens and an imaging surface on the optical axis.

7. The optical imaging lens of claim 1, wherein the optical imaging lens satisfies: 8mm < ALG <10mm, where ALG is the sum of the air gaps on the optical axis from the first lens to the imaging surface.

8. The optical imaging lens of claim 1, wherein the optical imaging lens satisfies: 12mm < ALT <13mm, where ALT is a sum of six lens thicknesses of the first lens to the sixth lens on the optical axis.

9. The optical imaging lens of claim 1, wherein the optical imaging lens satisfies: 1.2< ALT/ALG <1.6, where ALG is a sum of air gaps of the first lens to an image plane on the optical axis, and ALT is a sum of six lens thicknesses of the first lens to the sixth lens on the optical axis.