Zoom lens
阅读说明：本技术 一种变焦镜头 (Zoom lens ) 是由 朱光春 于 2019-12-23 设计创作，主要内容包括：本发明实施例公开了一种变焦镜头。该变焦镜头包括沿光轴从物方到像方依次排列的前固定组、变倍组、补偿组、光阑以及后固定组,变倍组、补偿组和光阑在变焦时沿光轴往复移动；前固定组包括正光焦度的第一透镜,变倍组包括从物方到像方排列的负光焦度的第二透镜和负光焦度的第三透镜,补偿组包括正光焦度的第四透镜,后固定组包括从物方到像方依次排列的负光焦度的第五透镜、负光焦度的第六透镜和正光焦度的第七透镜。本发明实施例的技术方案,可以实现15×连续变焦,且具有主动消热差功能,可以满足镜头在-40℃～60℃宽温度范围内稳定成像,其短焦具有更大的通光孔径,使得短焦成像效果更好,使成像具有高的对比度、画面更加清晰。(The embodiment of the invention discloses a zoom lens. The zoom lens comprises 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 in a reciprocating manner along the optical axis during 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 which are arranged from the object space to the 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. The technical scheme of the embodiment of the invention can realize 15 multiplied by continuous zooming, has the function of actively eliminating the heat difference, can meet the requirement of stable imaging of the lens in a wide temperature range of-40-60 ℃, has larger clear aperture for short focus, has better short focus imaging effect, and ensures that the imaging has high contrast and the image is clearer.)
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;
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.
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；
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.
5. The zoom lens according to claim 1, wherein 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.
6. The zoom lens according to claim 1, wherein 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.
7. The zoom lens of claim 1, wherein 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.
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；
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.
9. The zoom lens according to claim 1, wherein 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.
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.
Technical Field
The embodiment of the invention relates to an optical lens technology, in particular 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 multiplied by, the caliber of the first lens is very large, the processing difficulty is large, the cost is high, and finally the problems of large quality of the whole lens, inconvenience in installation and carrying and the like are caused.
Disclosure of Invention
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 along an optical axis from an object side to an image side, wherein the zoom group, the compensation group, and the diaphragm reciprocate along the optical axis during 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.
According to the zoom lens provided by the embodiment of the invention, the zoom lens realizes the 15 multiplied continuous zooming through the reciprocating movement of the zoom group and the compensation group along the optical axis; in the zooming process, the diaphragm moves along the optical axis, and the relative aperture sizes are different at different focal length positions, so that the F number change of the lens is realized. Compared with the traditional constant F number, the wide angle has higher light transmission amount, the focal length of the lens can be continuously changed and the target object is not lost in the process of searching the target from the wide angle to accurately positioning the long focus, the caliber of the first lens can be reduced by more than 25 percent relative to the structural caliber of the constant F number, and the short focus has larger light transmission aperture, so that the short focus imaging effect is better, the imaging has high contrast and the image is clearer; through reasonably setting the matching relationship between the structures of the lenses and the focal power, the zoom lens has the function of actively eliminating the thermal difference, can stably image the lens within a wide temperature range of-40 ℃ to 60 ℃, and can be used in an environment with large temperature change.
Drawings
Fig. 1 is a schematic structural diagram of a zoom lens according to 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 an MTF curve of a modulation transfer function 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 the embodiment of the present invention;
FIG. 5 is a schematic view of curvature of field with a wide angle of view of the zoom lens according to the 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 diagram of an MTF curve of the zoom lens in a middle focus state according to the 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 the embodiment of the present invention;
FIG. 9 is a schematic diagram illustrating 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 diagram of an MTF curve of the zoom lens in a telephoto state according to the 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 the embodiment of the present invention;
FIG. 13 is a schematic view of distortion of curvature of field of the zoom lens in a telephoto state according to the 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 description of the embodiments of the present invention are used in the angle shown in 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 meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
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 according to an embodiment of the present invention includes a front fixed
It can be understood that, in this embodiment, each lens may 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
According to the technical scheme of the embodiment, the zoom lens can realize 15-times continuous zooming through the reciprocating movement of the zoom group and the compensation group along the optical axis; in the zooming process, the diaphragm moves along the optical axis, and the relative aperture sizes are different at different focal length positions, so that the F number change of the lens is realized. Compared with the traditional constant F number, the wide angle has higher light transmission amount, the focal length of the lens can be continuously changed and the target object is not lost in the process of searching the target from the wide angle to accurately positioning the long focus, the caliber of the first lens can be reduced by more than 25 percent relative to the structural caliber of the constant F number, and the short focus has larger light transmission aperture, so that the short focus imaging effect is better, the imaging has high contrast and the image is clearer; through reasonably setting the matching relationship between the structures of the lenses and the focal power, the zoom lens has the function of actively eliminating the thermal difference, can stably image the lens within a wide temperature range of-40 ℃ to 60 ℃, and can be used in an environment with large temperature change.
On the basis of the above technical solution, optionally, the surfaces of the
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
Exemplarily, table 1 shows optical parameter design values 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
In this case, the
Fig. 2 is a schematic structural diagram of a zoom lens in a wide-angle state according to an embodiment of the present invention, fig. 3 is a schematic diagram of an MTF curve of a modulation transfer function of the zoom lens in the wide-angle state according to the embodiment of the present invention, fig. 4 is a schematic diagram of a scattered spot of the zoom lens in the wide-angle state according to the embodiment of the present invention, and fig. 5 is a schematic diagram of a field curvature distortion of the zoom lens in the wide-angle state according to the embodiment of the present invention.
Exemplarily, table 2 shows optical parameter design values of each lens of a zoom lens in a mid-focus state according to an embodiment of the present invention:
TABLE 2 zoom lens design values for each lens in mid-focus
Number of noodles
Surface type
Radius (mm)
Spacing (mm)
Material
Caliber (mm)
1
Spherical surface
279.275
14
100
2
Diffraction surface
490.161
114.58
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
55.52
36.2
7
Spherical surface
716.392
6.5
Single crystal germanium
35.5
8
Aspherical surface
-366.693
64.89
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
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
infinity
1
Single crystal germanium
16
infinity
1
IMA
Plane surface
infinity
In this case, the
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 MTF curve of the zoom lens in the middle focus state according to the embodiment of the present invention, fig. 8 is a schematic diagram of a scattered spot of the zoom lens in the middle focus state according to the embodiment of the present invention, and fig. 9 is a schematic diagram of a field curvature distortion of the zoom lens in the middle focus state according to the embodiment of the present invention.
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
In this case, the
Fig. 10 is a schematic structural diagram of a zoom lens in a telephoto state according to an embodiment of the present invention, fig. 11 is a schematic MTF curve of the zoom lens in the telephoto state according to the embodiment of the present invention, fig. 12 is a schematic diagram of a scattered spot of the zoom lens in the telephoto state according to the embodiment of the present invention, and fig. 13 is a schematic diagram of a field curvature distortion of the zoom lens in the telephoto state according to the embodiment of the present invention.
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
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
0.2<|f1/ft|<1.5；
where f1 denotes a focal length of the
Optionally, the
0.01<|f23/ft|<0.3；
where f23 is the combined focal length of the
Optionally, the
0.1<|f4/ft|<0.6；
where f4 denotes the focal length of the
Optionally, the rear fixed
0.3<|f56/ft|<1.2；
0.05<|f7/ft|<0.4；
where f56 denotes a combined focal length of the
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
Alternatively, referring to fig. 2, 6 and 10, the
Move along the optical axis through
Optionally, the
In the embodiment, through the combined optical structure of the single crystal germanium glass and the chalcogenide glass material, 15 multiplied by continuous zooming is realized, the active athermal function is realized, stable imaging of the lens in a wide temperature range of-40-60 ℃ can be met, the lens can be used in an environment with large temperature change, and through 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 is to be noted that the foregoing is only illustrative of the preferred embodiments of the present invention and the technical principles employed. 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 by the above embodiments, the present invention is not limited to the above embodiments, and may include other equivalent embodiments without departing from the spirit of the present invention, and the scope of the present invention is determined by the scope of the appended claims.
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