CN218767553U - Zoom lens and imaging device - Google Patents

Abstract

The utility model discloses a zoom and imaging device, zoom includes the lens cone, light source and battery of lenses, the battery of lenses includes the fixed group that sets gradually from thing side to picture side, the zoom group, compensation group and image plane, zoom group and compensation group move along the optical axis direction in coordination, the compensation group is used for adjusting the formation of image distance when the zoom of zoom group, fixed group includes first post lens and second free curved surface lens, the light beam that throws the light source through first post lens is plastic in the x direction, the light beam that second free curved surface lens throws first post lens and come is plastic in the y direction, make zoom have stronger plastic effect, can stretch the light of two directions, and compressed the volume to the utmost, and free curved surface's face type degree of freedom is high, can effectively correct the light aberration, increase the definition around the final facula, correct the ability poor with solving current laser lens aberration, it is bulky, the problem that the zoom ratio is not high.

Description

Zoom lens and imaging device

Technical Field

The utility model relates to an optical system designs technical field, in particular to be applied to outdoor monitored control system's zoom and image device.

Background

With the rapid development of night vision zoom lens technology, the field illumination of the zoom lens becomes more and more important, and especially the requirement for infrared light zooming illumination at night is continuously increased. The conventional scheme is that a laser fiber is used as a light source, the adjustment of the angle of the emergent light which is changed can be realized by matching with a zoom lens, and the laser fiber has uniform light spots and clear boundaries. In order to adapt to the illumination of the shot picture to the maximum extent, the shape of the illumination spot is sometimes required to be elliptical or rectangular, however, most of the shapes of the optical fiber ports on the market are circular and square, which means that the laser beam is shaped.

It is common practice to shape the light beam by using a cylindrical lens, and to stretch the light beam in one direction, the originally circular light spot will be elongated into an ellipse, but the aberration of the cylindrical lens is large and only one direction can be shaped. When the total length and the maximum caliber of the lens are limited, the zoom ratio of the lens cannot be limited, so that the existing laser lens has poor aberration correction capability, large volume and low zoom ratio.

SUMMERY OF THE UTILITY MODEL

The main objective of the present invention is to provide a zoom lens, the laser lens aims to solve the technical problems of poor aberration correction capability, large volume and low zoom ratio of the existing laser lens.

To achieve the above object, the present invention provides a zoom lens having an object side and an image side which are relatively disposed along an optical axis direction, the zoom lens comprising:

a lens barrel;

a light source disposed at the object side; and the number of the first and second groups,

the lens group comprises a fixed group, a zoom group, a compensation group and an image plane which are sequentially arranged from the object side to the image side, wherein the fixed group is fixedly arranged on the lens barrel, the zoom group and the compensation group are movably arranged on the lens barrel along the optical axis direction, the zoom group and the compensation group move cooperatively along the optical axis direction, and the compensation group is used for adjusting the imaging distance when the zoom group is zoomed;

the fixed group comprises a first cylindrical lens and a second free-form surface lens which are sequentially arranged from the object side to the image side, the first cylindrical lens is used for shaping the light beam projected by the light source in the x direction, and the second free-form surface lens is used for shaping the light beam projected by the first cylindrical lens in the y direction.

Optionally, the light source is provided as a fiber optic light source.

Optionally, the fixed group has positive optical power, and the first cylindrical lens, the second free-form surface lens, and the fixed group satisfy the following condition:

0.8< -f1x/F1 x <1, and 6.7< -f2x/F1 x <9.0, F2y = F1y;

wherein F1x is the focal length in the x direction of the fixed group, F1y is the focal length in the y direction of the fixed group, F1x is the focal length in the x direction of the first cylindrical lens, F2x is the focal length in the x direction of the second free-form-surface lens, and F2y is the focal length in the y direction of the second free-form-surface lens.

Optionally, the focal power of the first cylindrical lens is positive, and the object-side surface of the first cylindrical lens is a convex surface, and the image-side surface of the first cylindrical lens is a convex surface;

the focal power of the second free-form surface lens is positive, the object side surface of the second free-form surface lens is a concave surface, and the image side surface of the second free-form surface lens is a convex surface.

Optionally, a surface shape of an object side surface of the second free-form-surface lens satisfies the following condition:

wherein, c _x Radius of curvature in the x direction, c _y Radius of curvature in the y-direction, k _x Conic coefficient, k, in the x direction _y The conic coefficient in the y-direction.

Optionally, the focal power of the zoom group is negative, the zoom group includes a third biconcave lens and a fourth biconcave lens that are sequentially disposed from the object side to the image side, the third biconcave lens and the fourth biconcave lens are both spherical lenses, and the third biconcave lens, the fourth biconcave lens and the zoom group satisfy the following conditions:

1.9-woven fabric f3/F2<2.7, and 2.1-woven fabric f4/F2<2.9;

wherein F2 is a focal length of the variable power group, F3 is a focal length of the third biconcave lens, and F4 is a focal length of the fourth biconcave lens.

Optionally, the focal powers of the third biconcave lens and the fourth biconcave lens are both negative, and the object-side surface and the image-side surface of the third biconcave lens and the fourth biconcave lens are both concave.

Optionally, the optical power of the compensation group is positive, the compensation group includes a fifth meniscus lens, a sixth meniscus lens and a seventh biconvex lens, which are sequentially disposed from the object side to the image side, the fifth meniscus lens, the sixth meniscus lens and the seventh biconvex lens are all spherical lenses, and the fifth meniscus lens, the sixth meniscus lens, the seventh biconvex lens and the compensation group satisfy the following conditions:

2.7< -f5/F3 <3.8, and 2.7< -f6/F3 <3.6, and 2.2< -f7/F3 <3.0;

wherein F3 is a focal length of the compensation group, F5 is a focal length of the fifth meniscus lens, F6 is a focal length of the sixth meniscus lens, and F7 is a focal length of the seventh biconvex lens.

Optionally, the focal power of the fifth meniscus lens is positive, and the object-side surface of the fifth meniscus lens is a concave surface and the image-side surface thereof is a convex surface;

the focal power of the sixth meniscus lens is positive, the object side surface of the sixth meniscus lens is a concave surface, and the image side surface of the sixth meniscus lens is a convex surface;

the focal power of the seventh biconvex lens is positive, the object-side surface of the seventh biconvex lens is a convex surface, and the image-side surface of the seventh biconvex lens is a convex surface.

An imaging device comprising the zoom lens according to the above technical solution.

The utility model provides an among the technical scheme, fixed group fixed mounting in the lens cone, the variable power group with compensation group along optical axis direction movably install in the lens cone, fixed group includes certainly the object side extremely first cylinder lens and the second free-form surface lens that the image side set gradually, first cylinder lens with the second free-form surface lens are used for focusing and the plastic with the light beam of incidenting for the light beam plastic is the light beam of required shape facula, the variable power group is used for zooming, the compensation group is used for adjusting the formation of image distance when the variable power group becomes doubly the variable power group follow optical axis direction moves in coordination, so that zoom lens is by zoom lens to the telephoto end, and the compensation group receives external force drive along the optical axis do with the position of variable power group, formation of image wavelength, formation of image object distance correspond move focus, make zoom lens keep in zoom lens in the formation of image clarity, through first cylinder lens will the light beam that the light source was thrown is on the x direction, the second free-form lens will first cylinder lens come the light beam of the displacement focus that the variable power group is focused on the optical axis direction, make the zoom lens carry out the high light beam of the high-form of image aberration, the high-angle of the high-adjustable power lens, the high-angle aberration of the light beam, the high-adjustable aberration of the high-adjustable power lens is corrected light beam, and the high-adjustable lens is the high-adjustable optical aberration, and the high-adjustable lens is improved the high-adjustable optical aberration, and the high-power lens is improved.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly described below, 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 the structures shown in the drawings without creative efforts.

Fig. 1 is a schematic cross-sectional structure diagram of a zoom lens provided by the present invention;

FIG. 2 is a schematic view of the light source of FIG. 1;

fig. 3 is a schematic structural view of the zoom lens of fig. 1 at a wide-angle end;

FIG. 4 is a schematic structural diagram of the zoom lens of FIG. 1 at intermediate magnification;

FIG. 5 is a schematic structural diagram of the zoom lens of FIG. 1 at the telephoto end;

FIG. 6 is a schematic diagram of incoherent irradiance at the wide-angle end of the zoom lens of FIG. 3;

FIG. 7 is a schematic view of incoherent irradiance at the wide-angle end of the zoom lens of FIG. 4;

FIG. 8 is a schematic diagram of incoherent irradiance at intermediate magnification for the zoom lens of FIG. 5.

The reference numbers illustrate:

the objects, features and advantages of the present invention will be further described with reference to the accompanying drawings.

Detailed Description

The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative efforts belong to the protection scope of the present invention.

It should be noted that, if the present invention relates to a directional indication, the directional indication is only used to explain the relative position relationship between the components, the motion situation, etc. in a specific posture, and if the specific posture is changed, the directional indication is changed accordingly.

In addition, if there is a description relating to "first", "second", etc. in the embodiments of the present invention, the description of "first", "second", etc. is for descriptive purposes only and is not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In addition, the meaning of "and/or" appearing throughout includes three juxtapositions, exemplified by "A and/or B" including either A or B or both A and B. Moreover, the technical solutions in the embodiments may be combined with each other, but it must be based on the realization of those skilled in the art, and when the technical solutions are contradictory or cannot be realized, the combination of the technical solutions should not be considered to exist, and is not within the protection scope of the present invention.

With the rapid development of night vision zoom lens technology, the field illumination of the zoom lens becomes more and more important, and especially the requirement for infrared light zooming illumination at night is continuously increased. The conventional scheme is that a laser fiber is used as a light source, the adjustment of the angle of the emergent light which is changed can be realized by matching with a zoom lens, and the laser fiber has uniform light spots and clear boundaries. In order to adapt to the illumination of the shot picture to the maximum extent, the shape of the illumination spot is sometimes required to be elliptical or rectangular, however, most of the shapes of the optical fiber ports on the market are circular and square, which means that the laser beam is shaped. It is common practice to shape the light beam by using a cylindrical lens, and to stretch the light beam in one direction, the originally circular spot will be elongated into an elliptical shape, but the aberration of the cylindrical lens is large and the shaping can be performed only in one direction. When the total length and the maximum caliber of the lens are limited, the zoom ratio of the lens cannot be limited, so that the existing laser lens has poor aberration correction capability, large volume and low zoom ratio.

The utility model provides a zoom lens aims at improving the technical problem that current laser lens's aberration correction ability is poor, bulky, the zoom ratio is not high, please refer to fig. 1-8, the attached drawing shows to be the zoom lens's concrete embodiment.

Fig. 1 to 8 illustrate a zoom lens according to a first embodiment of the present invention.

Referring to fig. 1 to 5, the zoom lens has an object side and an image side which are opposite to each other along an optical axis direction, and includes a lens barrel (not shown), a light source 10 and a lens group, the light source 10 is disposed on the object side, the lens group includes a fixed group 20, a variable magnification group 30, a compensation group 40 and an image plane which are sequentially disposed from the object side to the image side, wherein the fixed group 20 is fixedly mounted on the lens barrel, the variable magnification group 30 and the compensation group 40 are movably mounted on the lens barrel along the optical axis direction, the variable magnification group 30 and the compensation group 40 cooperatively move along the optical axis direction, and the compensation group 40 is configured to adjust an imaging distance when the variable magnification group 30 is zoomed; the fixed group 20 includes a first cylindrical lens 1 and a second free-form surface lens 2 arranged in order from the object side to the image side, the first cylindrical lens 1 is configured to shape the light beam projected by the light source 10 in the x direction, and the second free-form surface lens 2 is configured to shape the light beam projected by the first cylindrical lens 1 in the y direction.

It should be noted that the zoom group 30 and the compensation group 40 can be driven by an external force to move along the optical axis direction, where the external force may be driven by a driving motor, or may be manually adjusted without limitation.

It should be noted that an included angle from an upper ray to a lower ray of the light ray emitted is defined as a divergence angle. The divergence angle can be changed by the cooperative motion of the variable power group 30 and the compensation group 40, when the variable power group 30 is close to the T end which is the telephoto end of the light source 10, the zoom lens has the largest focal length and the smallest divergence angle, and when the variable power group 30 is close to the image plane and moves towards the W end which is the wide angle end, the focal length of the zoom lens gradually decreases and the divergence angle gradually increases.

In the technical solution provided in the present invention, the fixing unit 20 is fixedly installed in the lens barrel, the variable power unit 30 and the compensation unit 40 are movably installed in the lens barrel along the optical axis direction, the fixing unit 20 includes a first cylindrical lens 1 and a second free-form-surface lens 2 sequentially arranged from the object side to the image side, the first cylindrical lens 1 and the second free-form-surface lens 2 are used for focusing and shaping the incident light beam, so that the light beam is shaped into a light beam with a light spot of a desired shape, the variable power unit 30 is used for zooming, the compensation unit 40 is used for adjusting the imaging distance when the variable power unit 30 is varied in power, the variable power unit 30 and the compensation unit 40 cooperatively move along the optical axis direction, so that the zoom lens is zoomed from a wide-angle end to a telephoto end, and the compensation group 40 is driven by an external force to move and focus along the optical axis corresponding to the position, the imaging wavelength and the imaging object distance of the zoom lens group 30, so that the zoom lens keeps the imaging surface clear in the zooming process, the light beam projected by the light source 10 is shaped in the x direction through the first cylindrical lens 1, and the light beam projected by the first cylindrical lens 1 is shaped in the y direction through the second free-form surface lens 2, so that the zoom lens has a strong shaping effect, can stretch light in two directions, maximally compresses the volume, has a high surface type freedom of a free-form surface, can effectively correct light aberration, and increases the definition around a final light spot, so as to solve the problems of poor aberration correction capability, large volume and low zoom ratio of the existing laser lens.

Specifically, in the present embodiment, the light source 10 is provided as a fiber optic light source 10. Because the light intensity distribution of the end face of the optical fiber is uniform and the boundary is clear, the imaged light spot is also uniform and the boundary is clear. More specifically, the optical fiber port model of the optical fiber light source 10 is set to SMA905, the port diameter of the optical fiber end is 0.28mm, the numerical aperture NA =0.22, the light beam emitted by the optical fiber light source 10 passes through the lens group, so that the light beam finally transmits to the light spot on the image plane as an amplified elliptical light spot, the uniformity reaches more than 90%, and the boundary is clear.

Specifically, in the present embodiment, the optical power of the fixed group 20 is positive, and the first cylindrical lens 1, the second free-form-surface lens 2, and the fixed group 20 satisfy the following condition: 0.8-sj [ F1x/F1x ] <1, and 6.7-f2x/F1 x <9.0, F2y = F1y; wherein F1x is the focal length in the x direction of the fixed group 20, F1y is the focal length in the y direction of the fixed group 20, F1x is the focal length in the x direction of the first cylindrical lens 1, F2x is the focal length in the 2x direction of the second free-form-surface lens, and F2y is the focal length in the 2y direction of the second free-form-surface lens. It should be noted that the optical power is equal to the difference between the convergence of the image-side beam and the convergence of the object-side beam, which characterizes the ability of the optical system to deflect the rays.

Specifically, in this embodiment, the focal power of the first cylindrical lens 1 is positive, and the object-side surface of the first cylindrical lens 1 is a convex surface and the image-side surface thereof is a convex surface; the focal power of the second free-form surface lens 2 is positive, and the object-side surface of the second free-form surface lens 2 is a concave surface, and the image-side surface thereof is a convex surface.

Specifically, since the object-side surface of the second free-form-surface lens 2 is a free-form surface, in order to allow the free-form surface to be transported in a desired transport direction, the surface shape of the object-side surface of the second free-form-surface lens 2 satisfies the following condition:

wherein, c _x Is the radius of curvature in the X direction, i.e. c _x ＝1/Rx，c _y Is the radius of curvature in the Y direction, i.e. c _y ＝1/Ry，k _x Conic coefficient of X direction, k _y The conic coefficient in the Y direction.

Specifically, in this embodiment, the optical power of the variable power group 30 is negative, the variable power group 30 includes a third biconcave lens 3 and a fourth biconcave lens 4 which are arranged in order from the object side to the image side, the third biconcave lens 3 and the fourth biconcave lens 4 are both spherical lenses, and the third biconcave lens 3, the fourth biconcave lens 4 and the variable power group 30 satisfy the following conditions: 1.9-woven fabric f3/F2<2.7, and 2.1-woven fabric f4/F2<2.9; wherein F2 is a focal length of the variable power group 30, F3 is a focal length of the third biconcave lens 3, and F4 is a focal length of the fourth biconcave lens 4.

Specifically, in the present embodiment, the optical powers of the third biconcave lens 3 and the fourth biconcave lens 4 are both negative, and the object-side surface and the image-side surface of the third biconcave lens 3 and the fourth biconcave lens 4 are both concave.

Specifically, the power of the compensation group 40 is positive in this embodiment, the compensation group 40 includes a fifth meniscus lens 5, a sixth meniscus lens 6 and a seventh biconvex lens 7 which are sequentially disposed from the object side to the image side, the fifth meniscus lens 5, the sixth meniscus lens 6 and the seventh biconvex lens 7 are all spherical lenses, and the fifth meniscus lens 5, the sixth meniscus lens 6, the seventh biconvex lens 7 and the compensation group 40 satisfy the following conditions: 2.7-t-F5/F3 <3.8, and 2.7-t-F6/F3 <3.6, and 2.2-t-F7/F3 <3.0; wherein F3 is a focal length of the compensation group 40, F5 is a focal length of the fifth meniscus lens 5, F6 is a focal length of the sixth meniscus lens 6, and F7 is a focal length of the seventh biconvex lens 7.

Specifically, in the present embodiment, the optical power of the fifth meniscus lens 5 is positive, and the object-side surface of the fifth meniscus lens 5 is a concave surface and the image-side surface thereof is a convex surface; the focal power of the sixth meniscus lens 6 is positive, and the object-side surface of the sixth meniscus lens 6 is a concave surface and the image-side surface thereof is a convex surface; the focal power of the seventh biconvex lens 7 is positive, and the object-side surface of the seventh biconvex lens 7 is a convex surface, and the image-side surface thereof is a convex surface. Effectively correcting the distortion.

So, through optical parameter, the material of each lens of reasonable design, thereby realize zoom need not focus again and guarantee that the resolution is clear in extreme environment, the system fully considers the variable quantity that various lens material refracting index, high low temperature of Abbe number match the face type and air space's variable quantity, has realized the positive negative collocation of each key element variable quantity of high low temperature and humidity, guarantees the synchronization and the clarity of image plane in high low temperature and the different humidity environment. By reasonably distributing the focal power of the lenses, adjusting the shape and the material collocation of the glass, the chromatic aberration and the secondary spectrum are effectively reduced, and the spherical aberration, the coma aberration, the astigmatism and the like on each lens are compensated and offset, so that the effect of clear imaging is achieved. By adopting the spherical lens, on the premise of ensuring the image quality and reliability, the cost is reduced, the assembly sensitivity is lower, and the yield of finished products is improved.

Specifically, the imaging surface may be understood as a surface of the photosensitive chip facing the object side, that is, a surface of an image pickup element such as a CCD or a CMOS, and it may be understood that light rays carrying subject information may sequentially pass through the fixed group 20, the variable magnification group 30, and the compensation group 40 and finally form an image on the imaging surface.

Specifically, in the present embodiment, the parameters of the zoom lens are as follows:

a wide-angle end focal length fw =0.687mm, a telephoto end focal length ft =81.36mm; diaphragm number Fno at wide angle end _w =2.22, telescope stop Fno _T =2.22; wide-angle end horizontal field angle FOVH _w =20 °, telescopic half field angle FOVH _T =0.15 °; the optical distortion ranges between-1% and 3.5%; the total optical length TTL =90mm of the zoom lens.

Specifically, in this embodiment, the refractive index, the radius of curvature, and the thickness interval of the lens material are shown in the following table:

TABLE 1 parameters of the lenses

In this embodiment, please refer to fig. 3 to 5, which are schematic structural diagrams of the zoom lens at a wide-angle end, a middle magnification, and a telephoto end, respectively; the intermediate magnification is understood to be a schematic position diagram of each lens group in the zoom lens when the zoom lens is between the wide-angle end and the telephoto end.

Fig. 6 to 8 show schematic diagrams of incoherent irradiance at the wide-angle end, at the intermediate magnification, and at the telephoto end, respectively.

As can be seen from the above diagrams, the zoom lens according to the present embodiment can obtain good corrections of spherical aberration, curvature of field, and distortion at the intermediate magnification, the wide-angle end, and the telephoto end, respectively, thereby obtaining sharp imaging.

To sum up, the zoom lens of the present invention adopts three groups of positive and negative structures, wherein one of the fixed group 20, one zoom group 30 and one compensation group 40, along with the corresponding movement of the zoom group 30, the focal length changes, the compensation group 40 is used for focusing, the focal length can be changed between the WIDE angle end 0.687mmmm and the telephoto end 81.36mm, the WIDE angle end (WIDE) shooting angle level >20 °, the WIDE angle end and the telephoto end optical distortion is within-1% -3.5%, the optical total length is controlled within 90mm, and the zoom lens has the advantages of small volume, good optical effect and large zoom ratio; and 5 glass spherical lenses are contained in the zoom lens, so that good optical performance is fully ensured.

Furthermore, the utility model also provides an imaging device, imaging device includes above-mentioned technical scheme zoom. The specific structure of the zoom lens refers to the above embodiments, and since the zoom lens of the imaging device adopts all the technical solutions of all the above embodiments, at least all the beneficial effects brought by the technical solutions of the above embodiments are achieved, and no further description is given here.

The aforesaid only is the optional embodiment of the utility model discloses a to not consequently restrict the patent scope of the utility model, all be in the utility model discloses a under the utility model conceiving, utilize the equivalent structure transform that the content of the description and the attached drawing was done, or direct/indirect application all is included in other relevant technical field the utility model discloses a patent protection within range.

Claims (10)

1. A zoom lens having an object side and an image side which are oppositely disposed in an optical axis direction, comprising:

a lens barrel;

the light source is arranged on the object side; and (c) a second step of,

the lens group comprises a fixed group, a zoom group, a compensation group and an image plane which are sequentially arranged from the object side to the image side, wherein the fixed group is fixedly arranged on the lens barrel, the zoom group and the compensation group are movably arranged on the lens barrel along the optical axis direction, the zoom group and the compensation group move cooperatively along the optical axis direction, and the compensation group is used for adjusting the imaging distance when the zoom group is zoomed;

the fixed group comprises a first cylindrical lens and a second free-form surface lens which are sequentially arranged from the object side to the image side, the first cylindrical lens is used for shaping the light beam projected by the light source in the x direction, and the second free-form surface lens is used for shaping the light beam projected by the first cylindrical lens in the y direction.

2. The zoom lens of claim 1, wherein the light source is provided as a fiber optic light source.

3. The zoom lens according to claim 1, wherein the fixed group has positive optical power, and the first cylindrical lens, the second free-form surface lens, and the fixed group satisfy the following condition:

0.8< -f1x/F1 x <1, and 6.7< -f2x/F1 x <9.0, F2y = F1y;

wherein F1x is the focal length in the x direction of the fixed group, F1y is the focal length in the y direction of the fixed group, F1x is the focal length in the x direction of the first cylindrical lens, F2x is the focal length in the x direction of the second free-form-surface lens, and F2y is the focal length in the y direction of the second free-form-surface lens.

4. The zoom lens of claim 3, wherein the optical power of the first cylindrical lens is positive, and the object-side surface of the first cylindrical lens is convex and the image-side surface thereof is convex;

the focal power of the second free-form surface lens is positive, the object side surface of the second free-form surface lens is a concave surface, and the image side surface of the second free-form surface lens is a convex surface.

5. The zoom lens according to claim 4, wherein a surface shape of an object side surface of the second free-form-surface lens satisfies a condition:

wherein, c _x Radius of curvature in the x direction, c _y Radius of curvature in y direction, k _x Conic coefficient of x direction, k _y The conic coefficient in the y-direction.

6. The zoom lens according to claim 1, wherein an optical power of the variable power group is negative, the variable power group includes a third biconcave lens and a fourth biconcave lens which are arranged in order from the object side to the image side, the third biconcave lens and the fourth biconcave lens are each a spherical lens, and the third biconcave lens, the fourth biconcave lens and the variable power group satisfy the following condition:

1.9-woven fabric f3/F2<2.7, and 2.1-woven fabric f4/F2<2.9;

wherein F2 is a focal length of the variable power group, F3 is a focal length of the third biconcave lens, and F4 is a focal length of the fourth biconcave lens.

7. The zoom lens of claim 6, wherein the optical powers of the third biconcave lens and the fourth biconcave lens are both negative, and the object-side surface and the image-side surface of the third biconcave lens and the fourth biconcave lens are also both concave.

8. The zoom lens of claim 1, wherein an optical power of the compensation group is positive, the compensation group includes a fifth meniscus lens, a sixth meniscus lens, and a seventh double convex lens disposed in this order from the object side to the image side, the fifth meniscus lens, the sixth meniscus lens, and the seventh double convex lens are all spherical lenses, and the fifth meniscus lens, the sixth meniscus lens, the seventh double convex lens, and the compensation group satisfy the following condition:

2.7-t-F5/F3 <3.8, and 2.7-t-F6/F3 <3.6, and 2.2-t-F7/F3 <3.0;

wherein F3 is a focal length of the compensation group, F5 is a focal length of the fifth meniscus lens, F6 is a focal length of the sixth meniscus lens, and F7 is a focal length of the seventh biconvex lens.

9. The zoom lens of claim 8, wherein the optical power of the fifth meniscus lens is positive, and the object-side surface of the fifth meniscus lens is concave and the image-side surface thereof is convex;

the focal power of the sixth meniscus lens is positive, the object side surface of the sixth meniscus lens is a concave surface, and the image side surface of the sixth meniscus lens is a convex surface;

the focal power of the seventh biconvex lens is positive, the object-side surface of the seventh biconvex lens is a convex surface, and the image-side surface of the seventh biconvex lens is a convex surface.

10. An imaging apparatus characterized by comprising the zoom lens according to any one of claims 1 to 9.

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