A high-performance long focal length continuous zoom lens

Abstract

The present invention relates to a zoom lens, specifically to a high-performance long focal length continuous zoom lens, which solves the technical problems of complex mechanical structure and high processing difficulty of existing zoom lenses. The continuous zoom lens provided by the present invention includes a front fixed group, a zoom group, a compensation group, and a rear fixed group arranged in sequence from the object side to the image side. The rear fixed group includes a rear fixed group I, a rear fixed group II, and a rear fixed group III arranged in sequence from the object side to the image side. Among them, the zoom group makes a linear motion between the front fixed group and the compensation group to achieve zooming, and the compensation group makes a non-linear motion between the zoom group and the rear fixed group to compensate for the change in the axial position of the image plane during the zooming process. The present invention adopts a 6-group 20-lens structure, and the lenses used in each lens group are all spherical mirrors, which has good processability. The zoom group makes a linear motion to achieve zooming, the compensation group makes a non-linear motion to achieve image plane stability, with a large magnification, a large field of view, low distortion, and good imaging quality.

Description

Technical Field

[0001] The present invention relates to a zoom lens, and more particularly to a high-performance long-focus continuous zoom lens. Background Art

[0002] High-performance long-focus continuous zoom lenses have a wide range of applications in commercial surveillance, digital video, medical diagnosis, public security investigation, border surveillance, forest fire prevention and other fields. In addition to requiring a large field of view, a stable image plane, and good imaging quality, they also require a large magnification, a long focal length, low distortion, a compact structure, and functions of focusing, zooming, and dimming. Generally, it is required that the imaging range Φ≥32mm, within a 0.8 field of view, at a spatial frequency of 50 lp / mm, the MTF≥0.25, the magnification is generally 20 times, the long focal length is not less than 1 meter, the distortion of the short focal length <2%, and the distortion of the long focal length <0.5%.

[0003] Current high-performance long-focus continuous zoom lenses usually include a front fixed group, a zoom group, a compensation group, and a rear fixed group. Generally, non-linear movements of the zoom group and the compensation group are used, or a combination of multi-group linkage and other methods are used to achieve zooming. And multiple groups of high-order aspherical lenses are used in the lens group to correct aberrations to obtain better imaging quality. However, the disadvantages of such long-focus continuous zoom lenses are that the mechanical structure is complex, the processing requirements are relatively high, and the processing, detection, and alignment of visible high-order aspherical lenses are difficult, and the processability is poor. Summary of the Invention

[0004] The object of the present invention is to solve the technical problems of the existing long-focus continuous zoom lens, such as complex mechanical structure, high processing difficulty requirements, and large detection and alignment difficulties, and to provide a high-performance long-focus continuous zoom lens.

[0005] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] A high-performance long-focus continuous zoom lens, comprising a front fixed group 1, a zoom group 2, a compensation group 3, and a rear fixed group 4 arranged in sequence from the object side to the image side, characterized in that:

[0007] The front fixed group 1, the zoom group 2, the compensation group 3, and the rear fixed group 4 all adopt spherical mirrors, and the spherical mirrors have good processability;

[0008] The position of the front fixed group 1 is fixed, and it is used for chromatic aberration and spherical aberration correction, as well as auxiliary correction of off-axis aberrations;

[0009] The zoom group 2 moves linearly between the front fixed group 1 and the compensation group 3 to achieve zooming and simultaneously assist in correcting the remaining aberrations of the front fixed group 1; the zoom group 2 includes a fifth lens 21 with positive optical power, a sixth lens 22 with negative optical power, a seventh lens 23 with negative optical power, and an eighth lens 24 with positive optical power, which are arranged in sequence from the object side to the image side; the seventh lens 23 and the eighth lens 24 form a first cemented lens; the zoom group 2 realizes continuous zooming by linearly adjusting the optical interval;

[0010] The compensation group 3 moves non-linearly between the zoom group 2 and the rear fixed group 4 to compensate for the change in the axial position of the image plane during the zooming process of the zoom group 2 and simultaneously assist in correcting the remaining aberrations of the zoom group 2; the compensation group 3 includes a ninth lens 31 with positive optical power, a tenth lens 32 with negative optical power, an eleventh lens 33 with positive optical power, and a twelfth lens 34 with positive optical power, which are arranged in sequence from the object side to the image side; the tenth lens 32 and the eleventh lens 33 form a second cemented lens; the compensation group 3 realizes the compensation of the image plane by non-linearly adjusting the change in the optical interval to ensure the stability of the image plane; the specific non-linear motion of the compensation group 3 is theoretically calculated according to the imaging characteristics of the system, generally a smooth curve motion;

[0011] The position of the rear fixed group 4 is fixed and includes a rear fixed group I 5, a rear fixed group II 6, and a rear fixed group III 7, which are arranged in sequence from the object side to the image side; the compensation group 3 moves non-linearly between the zoom group 2 and the rear fixed group I 5;

[0012] The rear fixed group I 5 is used to correct the remaining aberrations of the compensation group, and the remaining aberrations include spherical aberration, chromatic aberration, coma, astigmatism, field curvature, and distortion, etc.;

[0013] The rear fixed group II 6 is used to correct the remaining aberrations of the rear fixed group I 5;

[0014] The rear fixed group III 7 is used to correct the field curvature to improve the imaging quality.

[0015] Further, the front fixed group 1 includes a first lens 11 with negative optical power, a second lens 12 with positive optical power, a third lens 13 with negative optical power, and a fourth lens 14 with positive optical power, which are arranged in sequence from the object side to the image side.

[0016] Further, the rear fixed group I 5 includes a thirteenth lens 51 with negative optical power, a fourteenth lens 52 with positive optical power, a fifteenth lens 53 with negative optical power, a sixteenth lens 54 with positive optical power, and a seventeenth lens 55 with negative optical power, which are arranged in sequence from the object side to the image side.

[0017] Further, the rear fixed group II 6 includes an eighteenth lens 61 with positive optical power and a nineteenth lens 62 with negative optical power, which are arranged in sequence from the object side to the image side;

[0018] The eighteenth lens 61 and the nineteenth lens 62 form a third cemented lens.

[0019] Further, the rear fixed group III 7 includes a twentieth lens 71 with positive optical power.

[0020] Further, it further includes an aperture stop located between the rear fixed group I 5 and the compensation group 3;

[0021] The aperture stop is located in front of the first lens of the rear fixed group I 5 and is in close contact with the first lens of the rear fixed group I 5. The aperture stop is used to achieve light regulation;

[0022] The compensation group 3 makes a non-linear movement between the zoom group 2 and the aperture stop.

[0023] Further, the distance between the fourth lens 14 and the fifth lens 21 is 2.8 mm to 281.1 mm.

[0024] Further, the distance between the eighth lens 24 and the ninth lens 31 is 2 mm to 419.5 mm.

[0025] Further, the distance between the twelfth lens 34 and the aperture stop is 1 mm to 140.2 mm.

[0026] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0027] The high-performance long-focus continuous zoom lens provided by the present invention uses spherical lenses, which has good processability; the zoom group makes a linear movement to achieve zooming, the compensation group makes a non-linear movement to achieve image plane stability, with a large magnification, a large field of view, low distortion, and good imaging quality, and can meet the actual use requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is the short-focus state optical path diagram of the embodiment of the high-performance long-focus continuous zoom lens of the present invention;

[0029] Figure 2 It is the medium-focus state optical path diagram of the embodiment of the high-performance long-focus continuous zoom lens of the present invention;

[0030] Figure 3 It is the long-focus state optical path diagram of the embodiment of the high-performance long-focus continuous zoom lens of the present invention;

[0031] Figure 4It is the MTF curve graph of the short - focus state of the embodiment of the high - performance long - focal - length continuous zoom lens of the present invention at a spatial frequency of 50 lp / mm;

[0032] Figure 5 It is the MTF curve graph of the medium - focus state of the embodiment of the high - performance long - focal - length continuous zoom lens of the present invention at a spatial frequency of 50 lp / mm;

[0033] Figure 6 It is the MTF curve graph of the long - focus state of the embodiment of the high - performance long - focal - length continuous zoom lens of the present invention at a spatial frequency of 50 lp / mm;

[0034] Figure 7 It is the distortion curve graph of the short - focus state of the embodiment of the high - performance long - focal - length continuous zoom lens of the present invention;

[0035] Figure 8 It is the distortion curve graph of the medium - focus state of the embodiment of the high - performance long - focal - length continuous zoom lens of the present invention;

[0036] Figure 9 It is the distortion curve graph of the long - focus state of the embodiment of the high - performance long - focal - length continuous zoom lens of the present invention;

[0037] The description of the reference numerals is as follows:

[0038] 1 - front fixed group, 11 first lens, 12 - second lens, 13 - third lens, 14 fourth lens;

[0039] 2 - zoom group, 21 - fifth lens, 22 - sixth lens, 23 seventh lens, 24 - eighth lens;

[0040] 3 - compensation group, 31 - ninth lens, 32 - tenth lens, 33 - eleventh lens, 34 - twelfth lens;

[0041] 4 - rear fixed group;

[0042] 5 - rear fixed group Ⅰ, 51 thirteenth lens, 52 - fourteenth lens, 53 - fifteenth lens, 54 - sixteenth lens, 55 - seventeenth lens;

[0043] 6 - rear fixed group Ⅱ, 61 - eighteenth lens, 62 - nineteenth lens;

[0044] 7 - rear fixed group Ⅲ, 71 - twentieth lens. Detailed implementation manners

[0045] To make the objectives, advantages and features of the present invention clearer, the following further details a high - performance long - focal - length continuous zoom lens proposed by the present invention in combination with the accompanying drawings and specific embodiments.

[0046] In the description of the present invention, it should be noted that the terms "first", "second", etc. are only for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0047] See Figure 1 , Figure 2 , Figure 3 , a high-performance long-focus continuous zoom lens, including a front fixed group 1, a zoom group 2, a compensation group 3, and a rear fixed group 4 arranged in sequence from the object side to the image side. The front fixed group 1, the zoom group 2, the compensation group 3, and the rear fixed group 4 all adopt spherical mirrors.

[0048] The front fixed group 1 is fixed in position and is used for chromatic aberration and spherical aberration correction, as well as auxiliary correction of off-axis aberration, and includes a first lens 11 with negative optical power, a second lens 12 with positive optical power, a third lens 13 with negative optical power, and a fourth lens 14 with positive optical power arranged in sequence from the object side to the image side.

[0049] The zoom group 2 moves linearly between the front fixed group 1 and the compensation group 3, and includes a fifth lens 21 with positive optical power, a sixth lens 22 with negative optical power, a seventh lens 23 with negative optical power, and an eighth lens 24 with positive optical power arranged in sequence from the object side to the image side. Among them, the seventh lens 23 and the eighth lens 24 form a first cemented lens. The zoom group 2 is mainly used to achieve zooming and at the same time assist in correcting the remaining aberrations of the front fixed group 1. The distance between the fourth lens 14 of the front fixed group 1 and the fifth lens 21 of the zoom group 2 is 2.8 mm to 281.1 mm.

[0050] The compensation group 3 moves non-linearly between the zoom group 2 and the rear fixed group 4, and includes a ninth lens 31 with positive optical power, a tenth lens 32 with negative optical power, an eleventh lens 33 with positive optical power, and a twelfth lens 34 with positive optical power arranged in sequence from the object side to the image side. Among them, the tenth lens 32 and the eleventh lens 33 form a second cemented lens. The compensation group 3 is used to compensate for the change in the axial position of the image plane during the zooming process of the zoom group 2 and at the same time assist in correcting the remaining aberrations of the zoom group 2. The distance between the eighth lens 24 of the zoom group 2 and the ninth lens 31 of the compensation group 3 is 2 mm to 419.5 mm.

[0051] The rear fixed group 4 is fixed in position and includes the rear fixed group I 5, the rear fixed group II 6, and the rear fixed group III 7 arranged in sequence from the object side to the image side. The rear fixed group I 5 is used to correct the remaining spherical aberration, chromatic aberration, and some other aberrations of the compensation group 3, and includes the thirteenth lens 51 with negative optical power, the fourteenth lens 52 with positive optical power, the fifteenth lens 53 with negative optical power, the sixteenth lens 54 with positive optical power, and the seventeenth lens 55 with negative optical power arranged in sequence from the object side to the image side. The rear fixed group II 6 is used to correct the remaining aberrations of the rear fixed group I 5, and includes the eighteenth lens 61 with positive optical power and the nineteenth lens 62 with negative optical power arranged in sequence from the object side to the image side. Among them, the eighteenth lens 61 and the nineteenth lens 62 form the third cemented lens. The rear fixed group III 7 is used to correct the field curvature to achieve the purpose of improving the imaging quality, and includes the twentieth lens 71 with positive optical power.

[0052] Meanwhile, an aperture stop is arranged between the rear fixed group I 5 and the compensation group 3. The aperture stop is located in front of the thirteenth lens 51 and is used to achieve light regulation. The distance between the twelfth lens 34 of the compensation group 3 and the aperture stop is 1 mm to 140.2 mm.

[0053] By continuously changing the distance between the fourth lens 14 and the fifth lens 21, the distance between the eighth lens 24 and the ninth lens 31, and the distance between the twelfth lens 34 and the aperture stop, the zooming and compensation of the high-performance long-focus continuous zoom lens of the present invention can be achieved. When the distance between the fourth lens 14 and the fifth lens 21 changes from 2.8 mm to 264.6 mm, the distance between the eighth lens 24 and the ninth lens 31 changes from 419.5 mm to 64.8 mm, and the distance between the twelfth lens 34 and the aperture stop changes from 1 mm to 93.9 mm, the system focal length changes from short focus to medium focus. When the distance between the fourth lens 14 and the fifth lens 21 changes from 264.6 mm to 281.1 mm, the distance between the eighth lens 24 and the ninth lens 31 changes from 64.8 mm to 2 mm, and the distance between the twelfth lens 34 and the aperture stop changes from 93.9 mm to 140.2 mm, the system focal length changes from medium focus to long focus.

[0054] The zoom group 2 and the compensation group 3 respectively achieve continuous zooming and compensation of the optical lens by linearly and non-linearly adjusting the change of the optical interval. Figure 1 、 Figure 2 、 Figure 3As shown, they are respectively the optical path diagrams of the present invention in the short-focus, medium-focus, and long-focus states. The present invention adopts a 6-group and 20-piece structure, and the lens surface shapes are all spherical surfaces, which have good processability. The zoom group 2 makes a linear motion to achieve zooming, and the compensation group 3 makes a non-linear motion to achieve image plane stabilization. It has a relatively large magnification, a relatively large field of view, a relatively low distortion, and good imaging quality. The distance between the first lens 11 and the twentieth lens 71 of the present invention, that is, the total system length is 872 mm, the focal length is 46.7 mm to 1045 mm, the F number is F4 to F10, and the imaging size is Φ32.8 mm, which can meet the actual use requirements. As shown in Table 1, it is the optical element parameter table of the present invention in the short-focus state.

[0055] Table 1

[0056]

[0057]

[0058]

[0059] As Figure 4 、 Figure 5 、 Figure 6 shown, they are respectively the MTF curve diagrams of the high-performance long-focus continuous zoom lens provided by the present invention at a spatial frequency of 50 lp / mm in the short-focus, medium-focus, and long-focus states. As Figure 7 、 Figure 8 、 Figure 9 shown, they are respectively the distortion curve diagrams of the high-performance long-focus continuous zoom lens provided by the present invention at a spatial frequency of 50 lp / mm in the short-focus, medium-focus, and long-focus states. It can be seen that the present invention has good imaging quality, a relatively small distortion in the entire field of view, and can meet the monitoring requirements such as commercial use, border defense, and forest fire prevention.

[0060] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the present invention.

Claims

1. A high-performance long-focus continuous zoom lens, comprising a front fixed group (1), a zoom group (2), a compensation group (3) and a rear fixed group (4) arranged in sequence from the object side to the image side. Characterized in that: The front fixed group (1), the zoom group (2), the compensation group (3) and the rear fixed group (4) all adopt spherical lenses; The position of the front fixed group (1) is fixed, used for chromatic aberration and spherical aberration correction, and auxiliary correction of off-axis aberration; the front fixed group (1) includes a first lens (11) with negative optical power, a second lens (12) with positive optical power, a third lens (13) with negative optical power and a fourth lens (14) with positive optical power arranged in sequence from the object side to the image side; The zoom group (2) moves linearly between the front fixed group (1) and the compensation group (3) to achieve zooming, and at the same time assists in correcting the remaining aberrations of the front fixed group (1); the zoom group (2) includes a fifth lens (21) with positive optical power, a sixth lens (22) with negative optical power, a seventh lens (23) with negative optical power and an eighth lens (24) with positive optical power arranged in sequence from the object side to the image side; the seventh lens (23) and the eighth lens (24) form a first cemented lens; The compensation group (3) moves non-linearly between the zoom group (2) and the rear fixed group (4) to compensate for the change in the axial position of the image plane during the zooming process of the zoom group (2), and at the same time assists in correcting the remaining aberrations of the zoom group (2); the compensation group (3) includes a ninth lens (31) with positive optical power, a tenth lens (32) with negative optical power, an eleventh lens (33) with positive optical power and a twelfth lens (34) with positive optical power arranged in sequence from the object side to the image side; the tenth lens (32) and the eleventh lens (33) form a second cemented lens; The position of the rear fixed group (4) is fixed, including a rear fixed group I (5), a rear fixed group II (6) and a rear fixed group III (7) arranged in sequence from the object side to the image side, and the compensation group (3) moves non-linearly between the zoom group (2) and the rear fixed group I (5); The rear fixed group I (5) is used to correct the remaining aberrations of the compensation group (3); the rear fixed group II (6) is used to correct the remaining aberrations of the rear fixed group I (5); the rear fixed group III (7) is used to correct field curvature and improve imaging quality.

2. A high-performance long-focus continuous zoom lens according to claim 1, Characterized in that: The rear fixed group I (5) includes a thirteenth lens (51) with negative optical power, a fourteenth lens (52) with positive optical power, a fifteenth lens (53) with negative optical power, a sixteenth lens (54) with positive optical power and a seventeenth lens (55) with negative optical power arranged in sequence from the object side to the image side.

3. A high-performance long-focus continuous zoom lens according to claim 2, Characterized in that: The rear fixed group II (6) includes an eighteenth lens (61) with positive optical power and a nineteenth lens (62) with negative optical power arranged in sequence from the object side to the image side; The eighteenth lens (61) and the nineteenth lens (62) form a third cemented lens.

4. A high-performance long focal length continuous zoom lens according to claim 3, wherein: The rear fixed group III (7) includes a twentieth lens (71) with a positive optical power.

5. A high-performance long focal length continuous zoom lens according to any one of claims 1-4, wherein: It further includes a diaphragm located between the rear fixed group I (5) and the compensation group (3); The diaphragm is located in front of the rear fixed group I (5) and is in close contact with the first lens of the rear fixed group I (5); The compensation group (3) performs a non-linear movement between the zoom group (2) and the diaphragm.

6. A high-performance long focal length continuous zoom lens according to claim 5, wherein: The distance between the fourth lens (14) and the fifth lens (21) is 2.8 mm to 281.1 mm.

7. A high-performance long focal length continuous zoom lens according to claim 6, wherein: The distance between the eighth lens (24) and the ninth lens (31) is 2 mm to 419.5 mm.

8. A high-performance long focal length continuous zoom lens according to claim 7, wherein: The distance between the twelfth lens (34) and the diaphragm is 1 mm to 140.2 mm.

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