CN210924091U

CN210924091U - Zoom lens

Info

Publication number: CN210924091U
Application number: CN201922339970.5U
Authority: CN
Inventors: 朱光春
Original assignee: Ningbo Sunny Infrared Technologies Co Ltd
Current assignee: Ningbo Sunny Infrared Technologies Co Ltd
Priority date: 2019-12-23
Filing date: 2019-12-23
Publication date: 2020-07-03
Anticipated expiration: 2029-12-23

Abstract

The embodiment of the utility model discloses a zoom lens includes along the preceding fixed group that the optical axis arranged in proper order from the object space to the image space, the group of becoming doubly, the compensation group, diaphragm and back fixed group, become doubly the group, compensation group and diaphragm along the optical axis reciprocating motion when zooming, preceding fixed group includes the first lens of positive focal power, become doubly the group and include the second lens of the negative focal power and the third lens of negative focal power of arranging from the object space to the image space, the compensation group includes the fourth lens of positive focal power, back fixed group includes the fifth lens of the negative focal power of arranging in proper order from the object space to the image space, the sixth lens of negative focal power and the seventh lens of positive focal power.

Description

Zoom lens

Technical Field

The embodiment of the utility model provides a relate to optical lens technique, especially relate to a zoom lens.

Background

With the continuous development of infrared technology, the market demand for long-wave infrared lenses is higher and higher, and multiple fields of view and continuous zoom lenses are generally needed to realize the long-wave infrared lenses in the field of infrared security monitoring and some large-scene application fields at present. The continuous zooming has the functions of large-scale searching and accurate positioning of a small visual field, so that the target is not lost in the zooming process, the imaging is stable, and the like, and the method is widely applied to large-scene application occasions such as border invasion prevention, port monitoring, forest fire prevention, road safety and the like.

At present, common continuous zoom lenses in the market mostly adopt a constant F number structure, so that the zoom ratio of the continuous zoom lens exceeds more than 10 ×, the caliber of a first lens of the continuous zoom lens is very large, the processing difficulty is large, the cost is high, and finally the problems of large overall lens quality, inconvenience in installation and carrying and the like are caused.

SUMMERY OF THE UTILITY MODEL

In order to solve the above problem, an embodiment of the present invention provides a zoom lens, including a front fixed group, a zoom group, a compensation group, a diaphragm, and a rear fixed group, which are sequentially arranged from an object side to an image side along an optical axis, wherein the zoom group, the compensation group, and the diaphragm reciprocate along the optical axis when zooming;

the front fixed group comprises a first lens with positive focal power, the zoom group comprises a second lens with negative focal power and a third lens with negative focal power, the second lens and the third lens are arranged from an object space to an image space, the compensation group comprises a fourth lens with positive focal power, and the rear fixed group comprises a fifth lens with negative focal power, a sixth lens with negative focal power and a seventh lens with positive focal power, which are sequentially arranged from the object space to the image space.

Optionally, the surfaces of the first lens to the seventh lens include at least one diffractive surface and at least one aspheric surface.

Optionally, the first lens is a meniscus lens with at least one surface being a diffraction surface and a convex surface facing the object side; the second lens is a meniscus lens with at least one aspheric surface and a convex surface facing the object side; the third lens is a meniscus lens with at least one aspheric surface and a convex surface facing the object side; at least one surface of the fourth lens is an aspherical surface; the fifth lens is a meniscus lens of which at least one surface is an aspheric surface and a concave surface faces the object side; the sixth lens is a meniscus lens with at least one aspheric surface and a convex surface facing the object side; the seventh lens is a meniscus lens with at least one aspheric surface and a convex surface facing the object side.

Optionally, the zoom lens satisfies:

0.3<ft·(n-1)/(FNO·R1)<1.5；

0.05<fs·(n-1)/(FNO·R1)<0.3；

wherein ft represents a focal length of the zoom lens in a telephoto state; fs represents a focal length of the zoom lens in a short focus state; n represents a refractive index of the first lens; FNO represents the aperture F number of the zoom lens; r1 denotes a radius of curvature of a surface of the first lens facing the image side.

Optionally, the front fixed group satisfies:

0.2<|f1/ft|<1.5；

where f1 denotes a focal length of the first lens, and ft denotes a focal length when the zoom lens is in a telephoto state.

Optionally, the variable magnification group satisfies:

0.01<|f23/ft|<0.3；

where f23 is a combined focal length of the second lens and the third lens, and ft denotes a focal length when the zoom lens is in a telephoto state.

Optionally, the compensation group satisfies:

0.1<|f4/ft|<0.6；

where f4 denotes a focal length of the fourth lens, ft denotes a focal length when the zoom lens is in a telephoto state.

Optionally, the rear fixed group satisfies:

0.3<|f56/ft|<1.2；

0.05<|f7/ft|<0.4；

where f56 denotes a combined focal length of the fifth lens and the sixth lens, f7 denotes a focal length of the seventh lens, and ft is a focal length when the zoom lens is in a telephoto state.

Optionally, the zoom lens satisfies:

0.05<|BFL/ft|<0.2；

BFL represents the distance from an axial point of the seventh lens towards the image side to the image surface, and ft represents the focal length of the zoom lens in a long-focus state.

Optionally, the diaphragm is disposed between the fourth lens and the fifth lens, and the diaphragm moves along the optical axis along with the fourth lens when the zoom lens zooms.

Optionally, the first lens, the second lens, the third lens, the fourth lens, the sixth lens and the seventh lens are all single-crystal germanium glass lenses, and the fifth lens is a chalcogenide glass lens.

The embodiment of the utility model provides a zoom lens, through zoom group and compensation group along optical axis reciprocating motion, realize zoom lens's 15 × continuous zooming, in-process zooms, the diaphragm moves along the optical axis, in different focal length positions, relative aperture size is different, thereby realize the F number change of camera lens, compare with traditional invariable F number, the wide angle has higher light flux, the camera lens is in from wide angle search target to the accurate positioning process of telephoto, the focus can continuous variation and guarantee the target object is not lost, and first lens can reduce more than 25% for invariable F number structure bore, and its short burnt has bigger light flux aperture, make short burnt image forming effect better, make formation of image have high contrast, the picture clearer, through the collocation relation between the structure of reasonable setting individual lens and the focal power, make zoom lens have the heat difference function of initiatively disappearing, can satisfy the camera lens and form images in-40 ℃ -60 ℃ wide temperature range stability, make the camera lens can use in the great environment of temperature variation.

Drawings

Fig. 1 is a schematic structural diagram of a zoom lens provided in an embodiment of the present invention;

fig. 2 is a schematic structural diagram of a zoom lens according to an embodiment of the present invention in a wide angle state;

fig. 3 is a schematic diagram of a modulation transfer function MTF curve of a zoom lens in a wide angle state according to an embodiment of the present invention;

fig. 4 is a schematic diagram of a diffuse spot of the zoom lens in a wide-angle state according to an embodiment of the present invention;

fig. 5 is a schematic view illustrating curvature of field of a zoom lens in a wide angle state according to an embodiment of the present invention;

fig. 6 is a schematic structural diagram of a zoom lens in a middle focus state according to an embodiment of the present invention;

fig. 7 is a schematic view of an MTF curve of a zoom lens in a middle focus state according to an embodiment of the present invention;

fig. 8 is a schematic diagram of a diffuse spot of the zoom lens in a middle focus state according to an embodiment of the present invention;

fig. 9 is a schematic view of curvature of field distortion of a zoom lens in a middle focus state according to an embodiment of the present invention;

fig. 10 is a schematic structural diagram of a zoom lens according to an embodiment of the present invention in a telephoto state;

fig. 11 is a schematic view of an MTF curve of a zoom lens in a telephoto state according to an embodiment of the present invention;

fig. 12 is a schematic diagram of a diffuse spot of the zoom lens in a telephoto state according to an embodiment of the present invention;

fig. 13 is a field curvature distortion schematic diagram of a zoom lens in a telephoto state according to an embodiment of the present invention.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting of the invention. It should be further noted that, for the convenience of description, only some of the structures related to the present invention are shown in the drawings, not all of the structures.

The terminology used in the embodiments of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. It should be noted that the terms "upper", "lower", "left", "right", and the like used in the embodiments of the present invention are described in terms of the drawings, and should not be construed as limiting the embodiments of the present invention. In addition, in this context, it is also to be understood that when an element is referred to as being "on" or "under" another element, it can be directly formed on "or" under "the other element or be indirectly formed on" or "under" the other element through an intermediate element. The terms "first," "second," and the like, are used for descriptive purposes only and not for purposes of limitation, and do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. The specific meaning of the above terms in the present invention can be understood according to specific situations by those skilled in the art.

Fig. 1 is a schematic structural diagram of a zoom lens according to an embodiment of the present invention. Referring to fig. 1, a zoom lens provided in an embodiment of the present invention includes a front fixed group 1, a zoom group 2, a compensation group 3, a diaphragm 4, and a rear fixed group 5, which are sequentially arranged from an object side to an image side along an optical axis, wherein the zoom group 2, the compensation group 3, and the diaphragm 4 reciprocate along the optical axis during zooming; the front fixed group 1 includes a first lens 11 of positive power, the variable power group 2 includes a second lens 21 of negative power and a third lens 22 of negative power arranged from the object side to the image side, the compensation group 3 includes a fourth lens 31 of positive power, and the rear fixed group 5 includes a fifth lens 51 of negative power, a sixth lens 52 of negative power and a seventh lens 53 of positive power arranged in order from the object side to the image side.

It can be understood that, in this embodiment, each lens can be disposed in a lens barrel (not shown in fig. 1), the focal length of the lens is changed by the reciprocal movement of the zoom group 2 along the optical axis, meanwhile, the aberration caused by the reciprocal movement of the zoom group 2 along the optical axis is compensated by the reciprocal movement of the compensation group 3, and the combined movement of the compensation group 3 and the zoom group 2 is realized, the clear imaging is realized during zooming, the deviation of the image plane is reduced during zooming, the F number of the lens can be changed by the movement of the diaphragm 4 at different focal length positions and different relative aperture sizes, and by setting the focal length and the combination relationship between the lenses, in an embodiment of the present invention, the zoom lens is a long-wave infrared continuous zoom lens with a total length of 384mm, the focal length zoom ratio is 15 times, the zoom range is 20mm to 300mm, the F number is 0.88 in the short-focus state and the F number is 1.5 in the long-focus state, and is adapted to 1024 × 768 pixels, and the non-refrigeration detector with a resolution of 14 μm size.

Compared with the traditional constant F number, a wide angle has higher light flux, the focal length of the lens can be continuously changed and a target object is not lost in the process of accurately positioning the lens from a wide angle search target to a long focus, the caliber of a first lens relative to a constant F number structure can be reduced by more than 25%, the short focus has larger light flux, the short focus imaging effect is better, the imaging has high contrast and clearer picture, the zoom lens has an active athermal difference elimination function by reasonably setting the structure of the lenses and the collocation relationship between focal powers, the zoom lens can meet the requirement that the lens can stably image in a wide temperature range of-40 ℃ to 60 ℃, and the lens can be used in an environment with larger temperature change.

On the basis of the above technical solution, optionally, the surfaces of the first lens 11 to the seventh lens 53 include at least one diffraction surface and at least one aspheric surface.

It can be understood that the diffraction surface can change the focal positions of the light rays with different wave bands, can correct chromatic aberration in a long-focus state, and improves imaging quality. The aspheric surface has a better curvature radius characteristic than a spherical surface, has an advantage of improving aberrations such as spherical aberration, and can make a field of view larger and real. The use of the aspherical surface can eliminate aberrations occurring at the time of imaging as much as possible, thereby improving imaging quality.

Optionally, the first lens 11 is a meniscus lens with at least one surface being a diffraction surface and a convex surface facing the object side; the second lens 21 is a meniscus lens with at least one aspheric surface and a convex surface facing the object side; the third lens 22 is a meniscus lens with at least one aspheric surface and a convex surface facing the object side; at least one surface of the fourth lens 31 is an aspherical surface; the fifth lens 51 is a meniscus lens in which at least one surface is aspheric and a concave surface faces the object side; the sixth lens 52 is a meniscus lens in which at least one surface is aspheric and the convex surface faces the object side; the seventh lens 53 is a meniscus lens having at least one aspheric surface and a convex surface facing the object side.

Exemplarily, table 1 shows design values of optical parameters of each lens of a zoom lens in a wide angle state (short focus):

TABLE 1 design values of lenses of zoom lens in wide-angle state

Number of noodles	Surface type	Radius (mm)	Spacing (mm)	Material	Caliber (mm)
						1	Spherical surface	279.275	14	Single crystal germanium	100
2	Diffraction surface	490.161	40.73		97.3
						3	Aspherical surface	294.382	6	Single crystal germanium	42
4	Spherical surface	232.12	4		39.4
						5	Spherical surface	174.00	5.5	Single crystal germanium	39
6	Aspherical surface	76.077	183.76		36.2
						7	Spherical surface	716.392	6.5	Single crystal germanium	35.5
8	Aspherical surface	-366.693	10.5		35.5
						9	Aspherical surface	-126.663	5.5	Chalcogenide glass	33.4
10	Spherical surface	-140.01	9.72		35.5
						11	Spherical surface	285.8	4.5	Single crystal germanium	36
12	Aspherical surface	219.206	53.68		34.6
						13	Spherical surface	56.885	7	Single crystal germanium	32.5
14	Aspherical surface	83.47	29.97		30
						15	Spherical surface	infinity		1	Single crystal germanium
16	Spherical surface	infinity		1
						IMA	Plane surface	infinity

In this case, the surface number 1 indicates the front surface of the first lens element 11 close to the object side, and so on, the surface numbers 15 and 16 indicate lens cover glasses, and IMA indicates an image surface.

Exemplarily, what fig. 2 shows is that the utility model provides a zoom is in wide angle state's schematic structure diagram, what fig. 3 shows is the utility model discloses the zoom is in wide angle state's modulation transfer function MTF curve schematic diagram that the embodiment provides, what fig. 4 shows is the utility model discloses the zoom is in wide angle state's diffuse spot diagram that the embodiment provides, what fig. 5 shows is the utility model provides a zoom is in wide angle state's field curvature distortion schematic diagram.

Exemplarily, table 2 shows optical parameter design values of each lens of the zoom lens in a middle focus state, according to an embodiment of the present invention:

TABLE 2 zoom lens design values for each lens in mid-focus

Exemplarily, what fig. 6 shows is the structural schematic diagram that a zoom lens provided by the utility model is in the middle of the focus state, what fig. 7 shows is the utility model provides a zoom lens is in the MTF curve schematic diagram of the middle of the focus state, what fig. 8 shows is that the utility model provides a zoom lens is in the diffuse spot schematic diagram of the middle of the focus state, what fig. 9 shows is the utility model provides a zoom lens is in the field curvature distortion schematic diagram of the middle of the focus state.

Exemplarily, table 3 shows optical parameter design values of each lens of a zoom lens in a telephoto state, according to an embodiment of the present invention:

TABLE 3 design values of each lens in telephoto state for zoom lens

Exemplarily, what fig. 10 shows is the structural schematic diagram that a zoom lens provided by the utility model is in the long burnt state, what fig. 11 shows is the utility model provides a zoom lens is in the MTF curve schematic diagram of long burnt state, what fig. 12 shows is the utility model provides a zoom lens is in the diffuse spot schematic diagram of long burnt state, what fig. 13 shows is the utility model provides a zoom lens is in the field curvature distortion schematic diagram of long burnt state.

Optionally, the present embodiment provides a zoom lens satisfying:

0.3<ft·(n-1)/(FNO·R1)<1.5；

0.05<fs·(n-1)/(FNO·R1)<0.3；

wherein ft represents a focal length of the zoom lens in the telephoto state; fs represents a focal length of the zoom lens in a short focus state; n represents a refractive index of the first lens 11; FNO denotes the aperture F number of the zoom lens; r1 denotes a radius of curvature of a surface of the first lens 11 facing the image side.

The zoom lens provided by the embodiment is suitable for an infrared band, wherein n represents the refractive index of the first lens at a central wavelength of 10 μm, the maximum value of ft is 300mm, the minimum value of fs is 20mm, the maximum value of F is 0.88, and the minimum value is 1.5.

Optionally, the front fixed group 1 satisfies:

0.2<|f1/ft|<1.5；

where f1 denotes a focal length of the first lens 11, and ft denotes a focal length when the zoom lens is in the telephoto state.

Optionally, the variable magnification group 2 satisfies:

0.01<|f23/ft|<0.3；

where f23 is the combined focal length of the second lens 21 and the third lens 22, and ft denotes the focal length when the zoom lens is in the telephoto state.

Optionally, the compensation group 3 satisfies:

0.1<|f4/ft|<0.6；

where f4 denotes the focal length of the fourth lens 31, ft the zoom lens is in the telephoto state.

Optionally, the rear fixed group 5 satisfies:

0.3<|f56/ft|<1.2；

0.05<|f7/ft|<0.4；

where f56 denotes a combined focal length of the fifth lens 51 and the sixth lens 52, f7 denotes a focal length of the seventh lens 53, and ft is a focal length when the zoom lens is in a telephoto state.

Optionally, the zoom lens provided by this embodiment satisfies:

0.05<|BFL/ft|<0.2；

where BFL denotes a distance from an on-axis point of the seventh lens 53 toward the image side to the image plane, and ft denotes a focal length when the zoom lens is in a telephoto state.

Alternatively, referring to fig. 2, 6 and 10, the stop 4 is disposed between the fourth lens 31 and the fifth lens 51, and the stop 4 moves along the optical axis with the fourth lens 31 when the zoom lens zooms.

Move along the optical axis through diaphragm 4, in different focal length positions, relative aperture size is different to realize that zoom's F number changes, compare with the invariable F number of tradition, the wide angle has higher light flux, makes the formation of image have high contrast, the picture is more clear.

Optionally, the first lens 11, the second lens 21, the third lens 22, the fourth lens 31, the sixth lens 52, and the seventh lens 53 are all single-crystal germanium glass lenses, and the fifth lens 51 is a chalcogenide glass lens.

In the embodiment, through the combined optical structure of the single crystal germanium glass and the chalcogenide glass material, 15 × continuous zooming is realized, the active athermal function is realized, stable imaging of the lens in a wide temperature range of-40 ℃ to 60 ℃ can be met, the lens can be used in an environment with large temperature change, and by designing the fifth lens to be the chalcogenide glass lens, a precise die pressing process can be used in mass production, so that the cost is greatly reduced.

It should be noted that the foregoing is only a preferred embodiment of the present invention and the technical principles applied. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, but is capable of various obvious changes, rearrangements and substitutions as will now become apparent to those skilled in the art without departing from the scope of the invention. Therefore, although the present invention has been described in greater detail with reference to the above embodiments, the present invention is not limited to the above embodiments, and may include other equivalent embodiments without departing from the scope of the present invention.

Claims

1. A zoom lens is characterized by comprising a front fixed group, a zoom group, a compensation group, a diaphragm and a rear fixed group which are sequentially arranged from an object side to an image side along an optical axis, wherein the zoom group, the compensation group and the diaphragm move back and forth along the optical axis during zooming;

2. The zoom lens according to claim 1, wherein surfaces of the first lens to the seventh lens include at least one diffraction surface and at least one aspherical surface.

3. The zoom lens according to claim 2, wherein the first lens is a meniscus lens having at least one surface that is a diffraction surface and a convex surface facing the object side; the second lens is a meniscus lens with at least one aspheric surface and a convex surface facing the object side; the third lens is a meniscus lens with at least one aspheric surface and a convex surface facing the object side; at least one surface of the fourth lens is an aspherical surface; the fifth lens is a meniscus lens of which at least one surface is an aspheric surface and a concave surface faces the object side; the sixth lens is a meniscus lens with at least one aspheric surface and a convex surface facing the object side; the seventh lens is a meniscus lens with at least one aspheric surface and a convex surface facing the object side.

4. The zoom lens according to claim 1, wherein the zoom lens satisfies:

0.3<ft·(n-1)/(FNO·R1)<1.5；

0.05<fs·(n-1)/(FNO·R1)<0.3；

5. The zoom lens according to claim 1, wherein the front fixed group satisfies:

0.2<|f1/ft|<1.5；

6. The zoom lens according to claim 1, wherein the variable magnification group satisfies:

0.01<|f23/ft|<0.3；

7. The zoom lens of claim 1, wherein the compensation group satisfies:

0.1<|f4/ft|<0.6；

8. The zoom lens of claim 1, wherein the rear fixed group satisfies:

0.3<|f56/ft|<1.2；

0.05<|f7/ft|<0.4；

9. The zoom lens according to claim 1, wherein the zoom lens satisfies:

0.05<|BFL/ft|<0.2；

10. The zoom lens of claim 1, wherein the stop is disposed between the fourth lens and the fifth lens, and wherein the stop moves along the optical axis with the fourth lens when the zoom lens is zoomed.

11. The zoom lens according to any one of claims 1 to 10, wherein the first lens, the second lens, the third lens, the fourth lens, the sixth lens, and the seventh lens are all single-crystal germanium glass lenses, and the fifth lens is a chalcogenide glass lens.