CN216083254U

CN216083254U - Compact zoom lens

Info

Publication number: CN216083254U
Application number: CN202122793914.6U
Authority: CN
Inventors: 上官秋和; 刘青天; 邓莉芬
Original assignee: Xiamen Leading Optics Co Ltd
Current assignee: Xiamen Leading Optics Co Ltd
Priority date: 2021-11-15
Filing date: 2021-11-15
Publication date: 2022-03-18
Anticipated expiration: 2031-11-15

Abstract

The utility model discloses a compact zoom lens, which comprises a front fixed group, a zoom group, a diaphragm, a rear fixed group and a compensation group, wherein the front fixed group, the zoom group, the diaphragm, the rear fixed group and the compensation group are sequentially arranged from an object side to an image side along an optical axis, the front fixed group has positive diopter, the front fixed group sequentially comprises a first lens, a second lens and a third lens, the zoom group has negative diopter, the zoom group sequentially comprises a fourth lens, a fifth lens and a sixth lens, the rear fixed group has positive diopter, the rear fixed group sequentially comprises a seventh lens, an eighth lens and a ninth lens, the compensation group has positive diopter, and the compensation group sequentially comprises a tenth lens, an eleventh lens, a twelfth lens, a thirteenth lens, a fourteenth lens and a fifteenth lens. The zoom lens has high resolution and good imaging image quality, meets the requirement of realizing high definition of a full focal length, has the total optical length less than 64mm, is compact and small in overall lens volume, does not lose focus in a working environment of-40 ℃ to +80 ℃, and effectively ensures the imaging quality.

Description

Compact zoom lens

Technical Field

The utility model relates to the technical field of optical lenses, in particular to a compact zoom lens.

Background

The zoom lens is a camera lens which can change focal length in a certain range, thereby obtaining different field angles, images with different sizes and different scene ranges. The zoom lens can change a photographing range by varying a focal length without changing a photographing distance, and thus is very advantageous for picture composition. Because one zoom lens can play the role of a plurality of fixed-focus lenses, the number of the carried photographic equipment is reduced and the time for replacing the lenses is saved during traveling.

The existing zoom lens mainly has the following defects: the difference of the resolution of different focal length sections is large, the effect of full-range high definition cannot be achieved from the wide-angle end to the telephoto end, in addition, the number of common lenses of the zoom lens is large, the length of the lens is long, the size of the lens is large, and meanwhile, in a high-temperature and low-temperature environment, the back focus of the lens is large in deviation and easy to defocus.

In view of this, the inventors of the present application invented a compact zoom lens.

SUMMERY OF THE UTILITY MODEL

The utility model aims to provide a compact zoom lens which is small in size, free from defocusing at high and low temperatures and capable of realizing full-focus high definition.

In order to achieve the purpose, the utility model adopts the following technical scheme: a compact zoom lens comprises a front fixed group, a zoom group, a diaphragm, a rear fixed group and a compensation group which are arranged along an optical axis in sequence from an object side to an image side,

the front fixed group has positive diopter, and the front fixed group sequentially comprises a first lens, a second lens and a third lens from the object side to the image side along an optical axis, wherein the first lens has negative diopter, the second lens has positive diopter, and the third lens has positive diopter;

the zoom group has negative diopter, and the zoom group sequentially comprises a fourth lens, a fifth lens and a sixth lens from the object side to the image side along an optical axis, wherein the fourth lens has negative diopter, the fifth lens has negative diopter, and the sixth lens has positive diopter;

the rear fixed group has positive diopter, and the rear fixed group sequentially comprises a seventh lens, an eighth lens and a ninth lens from the object side to the image side along an optical axis, wherein the seventh lens has positive diopter, the eighth lens has negative diopter, and the ninth lens has negative diopter;

the compensation group has a positive diopter, and the compensation group sequentially comprises a tenth lens, an eleventh lens, a twelfth lens, a thirteenth lens, a fourteenth lens and a fifteenth lens along an optical axis from the object side to the image side, wherein the tenth lens has a positive diopter, the eleventh lens has a positive diopter, the twelfth lens has a negative diopter, the thirteenth lens has a positive lens, the fourteenth lens has a positive lens, and the fifteenth lens has a negative diopter.

Further, each of the first to fifteenth lenses includes an object side surface facing the object side and passing the image light, and an image side surface facing the image side and passing the image light,

the object side surface of the first lens is a convex surface, and the image side surface of the first lens is a concave surface;

the object side surface of the second lens is a convex surface, and the image side surface of the second lens is a convex surface;

the object side surface of the third lens is a convex surface, and the image side surface of the third lens is a concave surface;

the object side surface of the fourth lens is a concave surface, and the image side surface of the fourth lens is a concave surface;

the object side surface of the fifth lens is a concave surface, and the image side surface of the fifth lens is a concave surface;

the object side surface of the sixth lens is a convex surface, and the image side surface of the sixth lens is a concave surface;

the object side surface of the seventh lens is a convex surface, and the image side surface of the seventh lens is a convex surface;

the object side surface of the eighth lens is a concave surface, and the image side surface of the eighth lens is a convex surface;

the object side surface of the ninth lens is a concave surface, and the image side surface of the ninth lens is a convex surface;

the object side surface of the tenth lens is a convex surface, and the image side surface of the tenth lens is a concave surface;

the object side surface of the eleventh lens is a convex surface, and the image side surface of the eleventh lens is a convex surface;

the object side surface of the twelfth lens is a concave surface, and the image side surface of the twelfth lens is a concave surface;

the object side surface of the thirteenth lens is a convex surface, and the image side surface of the thirteenth lens is a convex surface;

the object side surface of the fourteenth lens is a convex surface, and the image side surface of the fourteenth lens is a concave surface;

the object side surface of the fifteenth lens is a concave surface, and the image side surface of the fifteenth lens is a convex surface.

Further, the variable magnification group satisfies: -0.6< f (G2)/fw < -1.3, wherein f (G2) is the focal length of the variable power group, and fw is the focal length of the lens at the wide-angle end.

Further, the rear fixed group satisfies: 0.8< f (G3)/ft <1.3, where f (G3) is the focal length of the rear fixed group and ft is the focal length of the lens at the telephoto end.

Further, the first lens satisfies: nd1 > 1.75, where nd1 is the refractive index of the first lens.

Further, the first lens and the third lens satisfy: -0.6< f1/f3< -1.3, wherein f1 is the focal length of the first lens and f3 is the focal length of the third lens.

Further, the image-side surface of the second lens element is cemented with the object-side surface of the third lens element, the image-side surface of the fifth lens element is cemented with the object-side surface of the sixth lens element, the image-side surface of the eighth lens element is cemented with the object-side surface of the ninth lens element, the image-side surface of the twelfth lens element is cemented with the object-side surface of the thirteenth lens element,

the fifth lens and the sixth lens satisfy: vd5-Vd6 is more than 30, wherein Vd5 is the Abbe coefficient of the fifth lens, and Vd6 is the Abbe coefficient of the sixth lens;

the eighth lens and the ninth lens satisfy: vd8-Vd9 is more than 30, wherein Vd8 is the Abbe coefficient of the eighth lens, and Vd9 is the Abbe coefficient of the ninth lens;

the twelfth lens and the thirteenth lens satisfy: vd13-Vd12 > 20, wherein Vd12 is the Abbe number of the twelfth lens, and Vd13 is the Abbe number of the thirteenth lens.

Further, the eleventh lens is an aspherical lens.

Further, the seventh lens is a positive lens, and the temperature coefficient of refractive index of the seventh lens is less than-2 x 10E-6 at a temperature range of-40 ℃ to 80 ℃.

Further, the thirteenth lens is a positive lens, and the temperature coefficient of refractive index of the thirteenth lens is less than-2 x 10E-6 at a temperature range of-40 ℃ to 80 ℃.

After the technical scheme is adopted, the utility model has the following advantages:

the zoom lens has high resolution and good imaging image quality, meets the requirement of realizing full-focus high definition, can continuously change the magnification within 8-32 mm, has the wide-angle of more than 70 degrees and the total optical length of less than 64mm, thereby ensuring that the whole lens is compact and small in volume and is light and convenient; in addition, the zoom lens does not lose focus in a working environment of-40 ℃ to +80 ℃, and the imaging quality is effectively ensured.

Drawings

Fig. 1 is a wide-angle end structure diagram of a variable magnification lens in embodiment 1 of the present invention;

fig. 2 is a structure diagram of a telescopic end of a zoom lens in embodiment 1 of the present invention;

fig. 3 is a wide-angle end MTF graph of the zoom lens in visible light in embodiment 1 of the present invention;

fig. 4 is a telephoto end MTF graph of the zoom lens in visible light according to embodiment 1 of the present invention;

fig. 5 is a structure view of a wide-angle end of a variable magnification lens in embodiment 2 of the present invention;

fig. 6 is a structure diagram of a telescopic end of a zoom lens in embodiment 2 of the present invention;

fig. 7 is a wide-angle end MTF graph of the zoom lens in visible light in embodiment 2 of the present invention;

fig. 8 is a telephoto end MTF graph of the zoom lens in visible light according to embodiment 2 of the present invention;

fig. 9 is a wide-angle end structure diagram of a variable magnification lens in embodiment 3 of the present invention;

fig. 10 is a structure view of a telephoto end of the zoom lens in embodiment 3 of the present invention;

fig. 11 is a wide-angle end MTF graph of the zoom lens in visible light in embodiment 3 of the present invention;

fig. 12 is a chart of MTF at the telephoto end of the zoom lens in visible light according to embodiment 3 of the present invention.

Description of reference numerals:

1. a first lens; 2. a second lens; 3. a third lens; 4. a fourth lens; 5. a fifth lens; 6. a sixth lens; 7. a seventh lens; 8. an eighth lens; 9. a ninth lens; 10. a tenth lens; 11. an eleventh lens; 12. a twelfth lens; 13. a thirteenth lens; 14. a fourteenth lens; 15. a fifteenth lens element; 16. and (4) a diaphragm.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the utility model and are not intended to limit the utility model.

In the present invention, it should be noted that the terms "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. are all based on the orientation or positional relationship shown in the drawings, and are only for convenience of describing the present invention and simplifying the description, but do not indicate or imply that the apparatus or element of the present invention must have a specific orientation, and thus, should not be construed as limiting the present invention.

As used herein, the term "a lens element having a positive refractive index (or a negative refractive index)" means that the paraxial refractive index of the lens element calculated by Gaussian optics 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 a compact zoom lens, which comprises a front fixed group, a zoom group, a diaphragm 16, a rear fixed group and a compensation group which are sequentially arranged along an optical axis from an object side to an image side, wherein the positions of the front fixed group and the rear fixed group are fixed, the zoom group can move along the optical axis direction to adjust the focal length of the lens, the compensation group can move along the optical axis direction to compensate the offset of the image surface position of the lens in the zooming process,

the front fixed group has positive diopter, and the front fixed group sequentially comprises a first lens 1, a second lens 2 and a third lens 3 along an optical axis from an object side to an image side, wherein the first lens 1 has negative diopter, the second lens 2 has positive diopter, and the third lens 3 has positive diopter;

the zoom group has negative diopter, and the zoom group sequentially comprises a fourth lens 4, a fifth lens 5 and a sixth lens 6 along an optical axis from the object side to the image side, wherein the fourth lens 4 has negative diopter, the fifth lens 5 has negative diopter, and the sixth lens 6 has positive diopter;

the rear fixed group has a positive diopter, and the rear fixed group sequentially comprises a seventh lens 7, an eighth lens 8 and a ninth lens 9 along an optical axis from the object side to the image side, wherein the seventh lens 7 has a positive diopter, the eighth lens 8 has a negative diopter, and the ninth lens 9 has a negative diopter;

the compensation group has a positive refractive power, and the compensation group sequentially includes a tenth lens 10, an eleventh lens 11, a twelfth lens 12, a thirteenth lens 13, a fourteenth lens 14 and a fifteenth lens 15 along an optical axis from an object side to an image side, wherein the tenth lens 10 has the positive refractive power, the eleventh lens 11 has the positive refractive power, the twelfth lens 12 has the negative refractive power, the thirteenth lens 13 has the positive lens, the fourteenth lens 14 has the positive lens, and the fifteenth lens 15 has the negative refractive power.

The first lens element 1 to the fifteenth lens element 15 each include an object-side surface facing the object side and passing the imaging light, and an image-side surface facing the image side and passing the imaging light, wherein,

the object side surface of the first lens 1 is a convex surface, and the image side surface of the first lens is a concave surface;

the object side surface of the second lens element 2 is a convex surface, and the image side surface thereof is a convex surface;

the object side surface of the third lens element 3 is a convex surface, and the image side surface thereof is a concave surface;

the object side surface of the fourth lens 4 is a concave surface, and the image side surface is a concave surface;

the object side surface of the fifth lens 5 is a concave surface, and the image side surface is a concave surface;

the object side surface of the sixth lens element 6 is a convex surface, and the image side surface thereof is a concave surface;

the object side surface of the seventh lens element 7 is a convex surface, and the image side surface thereof is a convex surface;

the object side surface of the eighth lens element 8 is a concave surface, and the image side surface thereof is a convex surface;

the object side surface of the ninth lens element 9 is a concave surface, and the image side surface thereof is a convex surface;

the object side surface of the tenth lens element 10 is a convex surface, and the image side surface thereof is a concave surface;

the object side surface of the eleventh lens element 11 is a convex surface, and the image side surface thereof is a convex surface;

the object side surface of the twelfth lens element 12 is a concave surface, and the image side surface is a concave surface;

the object side surface of the thirteenth lens element 13 is a convex surface, and the image side surface thereof is a convex surface;

the object side surface of the fourteenth lens element 14 is a convex surface, and the image side surface is a concave surface;

the object-side surface of the fifteenth lens element 15 is a concave surface, and the image-side surface thereof is a convex surface.

The zoom group satisfies: -0.6< f (G2)/fw < -1.3, wherein f (G2) is the focal length of the variable power group, and fw is the focal length of the lens at the wide-angle end. Therefore, wide angle can be realized, and the system performance is improved.

The rear fixed group satisfies: 0.8< f (G3)/ft <1.3, where f (G3) is the focal length of the rear fixed group and ft is the focal length of the lens at the telephoto end. Therefore, the total length of the lens can be reduced, the system performance is improved, and the miniaturization and the compactness of the lens are favorably realized.

The first lens 1 satisfies: nd1 > 1.75, where nd1 is the refractive index of the first lens 1. The first lens 1 has a high refractive index, reduces the outer diameter of the lens and is beneficial to realizing the miniaturization and the compactness of the lens.

The first lens 1 and the third lens 3 satisfy: -0.6< f1/f3< -1.3, wherein f1 is the focal length of the first lens 1 and f3 is the focal length of the third lens 3. Therefore, the focal power can be balanced, the high-temperature and low-temperature back focus offset can be controlled, and the defocusing is avoided.

The image-side surface of the second lens element 2 and the object-side surface of the third lens element 3 are cemented to each other, the image-side surface of the fifth lens element 5 and the object-side surface of the sixth lens element 6 are cemented to each other, the image-side surface of the eighth lens element 8 and the object-side surface of the ninth lens element 9 are cemented to each other, and the image-side surface of the twelfth lens element 12 and the object-side surface of the thirteenth lens element 13 are cemented to each other. The fifth lens 5 and the sixth lens 6 satisfy: vd5-Vd6 is more than 30, wherein Vd5 is the Abbe coefficient of the fifth lens 5, and Vd6 is the Abbe coefficient of the sixth lens 6; the eighth lens 8 and the ninth lens 9 satisfy: vd8-Vd9 is more than 30, wherein Vd8 is the Abbe coefficient of the eighth lens 8, and Vd9 is the Abbe coefficient of the ninth lens 9; the twelfth lens 12 and the thirteenth lens 13 satisfy: vd13-Vd12 > 20, wherein Vd12 is the Abbe number of the twelfth lens 12, and Vd13 is the Abbe number of the thirteenth lens 13. The total optical length of the lens can be reduced by gluing the lenses, the miniaturization and the compactness of the lens are favorably realized, and the chromatic aberration can be effectively corrected and the resolution is improved by combining high dispersion and low dispersion among the glued lenses.

The eleventh lens 11 is a glass aspherical lens. The aspheric surface is adopted to improve the resolution, optimize chromatic aberration, greatly shorten the outer diameter and the total length of the system and facilitate the realization of the miniaturization and the compactness of the lens.

The seventh lens 7 and the thirteenth lens 13 are both positive lenses, and the temperature coefficients of refractive index (dn/dT) of the seventh lens 7 and the thirteenth lens 13 are both less than-2 x 10E-6 in the temperature range of-40 ℃ to 80 ℃. The temperature coefficient of the refractive index is a negative value, so that the temperature drift can be effectively balanced, and the athermalization of the lens is realized. Among them, materials that meet this requirement are: H-ZPK5/H-FK61 and the like.

The mini infrared imaging lens of the present invention will be described in detail with specific embodiments.

Example 1

Referring to fig. 1 and 2, the present invention discloses a compact zoom lens, including a front fixed group, a zoom group, a diaphragm 16, a rear fixed group and a compensation group, which are sequentially arranged along an optical axis from an object side to an image side, wherein the positions of the front fixed group and the rear fixed group are fixed, the zoom group can move along the optical axis direction to adjust the focal length of the lens, the compensation group can move along the optical axis direction to compensate the shift of the image plane position of the lens during zooming,

In this embodiment, the image-side surface of the second lens element 2 and the object-side surface of the third lens element 3 are cemented to each other, the image-side surface of the fifth lens element 5 and the object-side surface of the sixth lens element 6 are cemented to each other, the image-side surface of the eighth lens element 8 and the object-side surface of the ninth lens element 9 are cemented to each other, and the image-side surface of the twelfth lens element 12 and the object-side surface of the thirteenth lens element 13 are cemented to each other.

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

Table 1-1 detailed optical data for example 1

In this embodiment, the values of the variable parameters are shown in tables 1-2.

Table 1-2 detailed parametric data for example 1

In this embodiment, the eleventh lens element is an aspheric lens element, and both surfaces thereof are aspheric. The equation for the surface curve of an aspherical lens is expressed as follows:

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: the curvature of the 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 (is the m)^thQ^con coefficient)；

Q_m ^con: mth order Q^conPolynomial (the m)^thQ^con polynomial)。

The aspherical surface data in this embodiment are shown in tables 1 to 3.

Tables 1-3 aspheric data for example 1

Number of noodles	S18	S19
			K	4.7	4.3
A4	5.60E-05	8.34E-05
			A6	1.93E-07	-1.61E-06
A8	-1.68E-08	5.22E-08
			A10	1.63E-09	5.52E-10
A12	-1.76E-11	-2.32E-11

In this embodiment, please refer to fig. 3 for the MTF graph at the wide-angle end of the lens under visible light, and please refer to fig. 4 for the MTF graph at the telephoto end, and it can be seen from the graphs that when the spatial frequency of the lens reaches 200lp/mm from the wide-angle end to the telephoto end, the MTF values are all greater than 30%, the imaging quality is good, the resolution of the lens is high, and the full-focus high definition is achieved.

In this embodiment, the back focus offset of the lens in the high and low temperature environment is shown in tables 1 to 4.

Tables 1-4 back focus offset at different temperatures for the lens of example 1

Temperature of

(-40℃)

(-20℃)

(0℃)

(25℃)

(40℃)

(60℃)

(80℃)

Offset of back focus

-0.004mm

-0.0028mm

0.0017mm

0mm

0.0016mm

0.003mm

0.0041mm

As can be seen from the figure, the back focal shift of the lens is within 0.005mm under the environment of-40 ℃ to 80 ℃, the image surface position movement is small, the MTF variation is small, and high-definition image quality can be output at high and low temperatures.

Example 2

As shown in fig. 5 and 6, the present example is different from example 1 mainly in the optical parameters such as the curvature radius of each lens surface and the lens thickness.

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

Table 2-1 detailed optical data for example 2

In this embodiment, the values of the variable parameters are shown in table 2-2.

Table 2-2 detailed parametric data for example 2

In the present embodiment, aspherical surface data of the eleventh lens are shown in tables 2 to 3.

Tables 2-3 aspheric data for example 2

Number of noodles	S19	S20
			K	4.7	4.3
A4	5.60E-05	8.34E-05
			A6	1.93E-07	-1.61E-06
A8	-1.68E-08	5.22E-08
			A10	1.63E-09	5.52E-10
A12	-1.76E-11	-2.32E-11

In this embodiment, please refer to fig. 7 for the MTF graph at the wide-angle end of the lens under visible light, and please refer to fig. 8 for the MTF graph at the telephoto end, and it can be seen from the graphs that when the spatial frequency of the lens reaches 200lp/mm from the wide-angle end to the telephoto end, the MTF values are all greater than 30%, the imaging quality is good, the resolution of the lens is high, and the full-focus high definition is achieved.

In this embodiment, the back focus offset of the lens in the high and low temperature environment is shown in tables 2 to 4.

Tables 2-4 back focus offset at different temperatures for the lens of example 2

Temperature of

(-40℃)

(-20℃)

(0℃)

(25℃)

(40℃)

(60℃)

(80℃)

Offset of back focus

-0.0045mm

-0.0031mm

-0.0018mm

0mm

0.0017mm

0.003mm

0.0048mm

Example 3

As shown in fig. 9 and 10, the present example is different from example 1 mainly in the optical parameters such as the curvature radius of each lens surface and the lens thickness.

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

Table 3-1 detailed optical data for example 3

In this embodiment, the values of the variable parameters are shown in table 3-2.

Table 3-2 detailed parametric data for example 3

In the present embodiment, aspherical surface data of the eleventh lens is shown in tables 3 to 3.

Tables 3-3 aspheric data for example 3

In this embodiment, please refer to fig. 11 for the MTF graph at the wide-angle end of the lens under visible light, and please refer to fig. 12 for the MTF graph at the telephoto end, and it can be seen from the graphs that when the spatial frequency of the lens reaches 200lp/mm from the wide-angle end to the telephoto end, the MTF values are all greater than 30%, the imaging quality is good, the resolution of the lens is high, and the full-focus high definition is achieved.

In this embodiment, the back focus offset of the lens in the high and low temperature environment is shown in tables 3 to 4.

Tables 3-4 back focus offset at different temperatures for the lens of example 3

Temperature of

(-40℃)

(-20℃)

(0℃)

(25℃)

(40℃)

(60℃)

(80℃)

Offset of back focus

-0.003mm

-0.002mm

-0.0012mm

0mm

0.0012mm

0.002mm

0.0032mm

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A compact zoom lens characterized in that: comprises a front fixed group, a zoom group, a diaphragm, a rear fixed group and a compensation group which are arranged in sequence from an object side to an image side along an optical axis,

2. A compact zoom lens according to claim 1, wherein: the first lens element to the fifteenth lens element each include an object-side surface facing the object side and passing the imaging light, and an image-side surface facing the image side and passing the imaging light,

3. A compact zoom lens according to claim 1, wherein: the zoom group satisfies: -0.6< f (G2)/fw < -1.3, wherein f (G2) is the focal length of the variable power group, and fw is the focal length of the lens at the wide-angle end.

4. A compact zoom lens according to claim 1, wherein: the rear fixed group satisfies: 0.8< f (G3)/ft <1.3, where f (G3) is the focal length of the rear fixed group and ft is the focal length of the lens at the telephoto end.

5. A compact zoom lens according to claim 1 or 2, wherein: the first lens satisfies: nd1 > 1.75, where nd1 is the refractive index of the first lens.

6. A compact zoom lens according to claim 1 or 2, wherein: the first lens and the third lens satisfy: -0.6< f1/f3< -1.3, wherein f1 is the focal length of the first lens and f3 is the focal length of the third lens.

7. A compact zoom lens according to claim 1 or 2, wherein: an image-side surface of the second lens element is cemented with an object-side surface of the third lens element, an image-side surface of the fifth lens element is cemented with an object-side surface of the sixth lens element, an image-side surface of the eighth lens element is cemented with an object-side surface of the ninth lens element, an image-side surface of the twelfth lens element is cemented with an object-side surface of the thirteenth lens element,

8. A compact zoom lens according to claim 1 or 2, wherein: the eleventh lens is an aspherical lens.

9. A compact zoom lens according to claim 1 or 2, wherein: the seventh lens is a positive lens, and the temperature coefficient of refractive index of the seventh lens is less than-2 x 10E-6 at the temperature range of-40 ℃ to 80 ℃.

10. A compact zoom lens according to claim 1 or 2, wherein: the thirteenth lens is a positive lens, and the temperature coefficient of refractive index of the thirteenth lens is less than-2 x 10E-6 at a temperature range of-40 ℃ to 80 ℃.