A zoom lens system and a measuring device

Abstract

The application provides a zoom lens system and a measuring device. The zoom lens system is sequentially provided with a front fixed lens group with a positive focal length, a zoom lens group with a negative focal length, a compensation lens group with a positive focal length, an aperture stop and a rear fixed lens group with a positive focal length from an object plane to an image plane along an optical axis. The position of the front fixed lens group is invariable. The zoom lens group moves forward and backward along the optical axis, is used for realizing optical zoom of the system and compressing a light ray aperture again so that the light ray enters the compensation lens group. The compensation lens group moves forward and backward along the optical axis, is used for compensating aberration occurring in the optical zoom process. The position of the aperture stop is invariable. The position of the rear fixed lens group is invariable and is used for balancing system aberration. The F number of the system is invariable and the system always maintains good imaging performance in the optical zoom process. The positions of the aperture stop and the rear fixed lens group are invariable in the system, assembly operation is simplified and work efficiency is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical imaging technology, in particular to a zoom lens system and a measuring device. BACKGROUND

[0002] The light intake of an optical lens is determined by the relative aperture. The relative aperture value of a general zoom optical system at long focus is relatively small, which leads to poor imaging quality under weak light conditions and an increase in the exposure time of the system. In order to ensure that the lens can clearly image under different light conditions, the zoom lens should have a relatively large relative aperture at all focal lengths. However, as the relative aperture increases, the aberration also increases, so the imaging quality of the lens cannot be guaranteed. Most zoom lenses increase vignetting by blocking a part of the imaging light beam of the off-axis field of view, thereby reducing the aperture of the light beam participating in the imaging of the off-axis field of view to obtain better imaging quality. However, vignetting can cause the relative luminance of the zoom lens to be uneven, resulting in a phenomenon that the imaging of the off-axis field of view is darker. At the same time, in order to simplify the zoom mechanism, the position of the aperture stop is generally fixed between the compensation group and the rear fixed group of the lens, which leads to a large optical distortion of the lens at short focus.

[0003] It is difficult to find a zoom lens with excellent imaging quality in the market that meets the requirements of a large zoom ratio, a high relative luminance of the full field of view, a large relative aperture in the full focal range, and a small maximum optical distortion.

[0004] Chinese patent CN 117572612 B discloses a zoom lens system and a camera. The zoom lens system is sequentially provided with a first lens group, a second lens group, an aperture stop, a third lens group, a fourth lens group, and a photosensitive element from the object side to the image side. The relative position of the aperture stop and the third lens group is fixed, and the second lens group, the third lens group, and the fourth lens group can move forward and backward along the optical axis for zooming. The focal length of the zoom lens system changes between 10.3-106.3 mm. The zoom lens system has a wide-angle end aperture F number of 1.05 and a long-focus end aperture F number of 3.5, realizing a zoom lens system with a small size and a large aperture. The patent achieves imaging at different focal lengths by moving the second lens group, the third lens group, and the fourth lens group forward and backward along the optical axis, which requires configuring corresponding motion structures for any moving lens group. At the same time, the F number changes at different focal lengths, which cannot guarantee the same quality of imaging at the long-focus end and the wide-angle end.

[0005] A zoom lens is disclosed in Chinese patent CN 106772964 B, which has an optical system including 20 spherical glass lenses and 1 diaphragm, and sequentially forms a front fixed group with positive focal power, a variable group with negative focal power, a compensation group with positive focal power, and a rear fixed group with positive focal power along the light incident direction. The zoom lens uses 20 spherical lenses, and through reasonable arrangement of the elements and selection of appropriate materials, achieves a 50 times zoom ratio of focal length from 750 mm to 15 mm, and an optical index requirement of 350 mm long focal length. The F number of the zoom lens changes in the range of 4.78-10.54, wherein the F number is 4.78 when the focal length is 15 mm, and the F number is 10.54 when the focal length is 750 mm. Similarly, the F number changes at different focal lengths, which cannot guarantee the same quality of imaging at the long focal end and the wide angle end; and the F number of the patent is large, and the relative aperture is small, which cannot guarantee excellent imaging quality. SUMMARY

[0006] The present application provides a zoom lens system and a measuring device, which at least solve one of the above technical problems.

[0007] To achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0008] A zoom lens system, which is sequentially provided with a front fixed lens group with positive focal length, a variable lens group with negative focal length, a compensation lens group with positive focal length, an aperture diaphragm, and a rear fixed lens group with positive focal length from an object plane to an image plane along an optical axis direction;

[0009] The position of the front fixed lens group is unchanged; the variable lens group moves forward and backward along the optical axis direction, and is used to realize optical zoom of the system and compress the light aperture again so that the light enters the compensation lens group; the compensation lens group moves forward and backward along the optical axis direction, and is used to compensate for aberration occurring in the optical zoom process; the position distance of the aperture diaphragm is unchanged; the position of the rear fixed lens group is unchanged, and is used to balance the system aberration so that the visible light is imaged on the image plane;

[0010] At any focal length, the total length of the zoom lens system from the front surface of the front fixed lens group to the rear surface of the rear fixed lens group is unchanged, and the F number is unchanged; when the focal length of the zoom lens system changes from 18 mm to 180 mm, the spacing between the front fixed lens group and the variable lens group changes in the range of 10.1 mm-211.6 mm; the spacing between the variable lens group and the compensation lens group changes in the range of 0.1 mm-228.3 mm; and the spacing between the compensation lens group and the aperture diaphragm changes in the range of 1.1 mm-27.9 mm.

[0011] Further, the front fixed lens group comprises, in sequence from the object plane to the image plane, a first lens, a second lens and a third lens; the first lens is a biconvex lens with negative focal length, the second lens is a biconcave lens with negative focal length, and the third lens is a biconvex lens with positive focal length; the first lens and the second lens form a first cemented lens group.

[0012] Further, the variable lens group comprises, in sequence from the object plane to the image plane, a fourth lens, a fifth lens and a sixth lens; the fourth lens is a positive meniscus lens with negative focal length, the fifth lens is a biconcave lens with positive focal length, and the sixth lens is a positive meniscus lens with negative focal length; the fifth lens and the sixth lens form a second cemented lens group.

[0013] Further, the compensation lens group comprises, in sequence from the object plane to the image plane, a seventh lens, an eighth lens and a ninth lens; the seventh lens is a positive biconvex lens with negative focal length, the eighth lens is a positive meniscus lens with positive focal length, and the ninth lens is a positive meniscus lens with negative focal length; the eighth lens and the ninth lens form a third cemented lens group.

[0014] Further, the rear fixed lens group comprises, in sequence from the object plane to the image plane, a tenth lens, an eleventh lens, a twelfth lens, a thirteenth lens and a fourteenth lens; the tenth lens is a negative meniscus lens with negative focal length, the eleventh lens is a negative meniscus lens with positive focal length, the twelfth lens is a positive biconvex lens with positive focal length, the thirteenth lens is a biconvex lens with positive focal length, and the fourteenth lens is a biconcave lens with negative focal length; the tenth lens and the eleventh lens form a fourth cemented lens group, and the thirteenth lens and the fourteenth lens form a fifth cemented lens group.

[0015] Further, all the lenses in the front fixed lens group, the variable lens group, the compensation lens group and the rear fixed lens group are spherical lenses.

[0016] Further, the zoom lens system has a zoom ratio of fmax / fmin=10, the minimum focal length of the zoom lens system is fmin, and the maximum focal length of the zoom lens system is fmax.

[0017] Further, a protective glass is further arranged at a position 0.1mm away from the rear surface of the rear fixed lens group.

[0018] In another aspect, the present application further provides a measuring device comprising the zoom lens system as described above.

[0019] The present application has the following advantages:

[0020] The application discloses a zoom lens system, wherein a front fixed lens group with positive focal length, a zoom lens group with negative focal length, a compensation lens group with positive focal length, an aperture stop and a rear fixed lens group with positive focal length are sequentially arranged along the light incident direction.

[0021] In the application, the full field of view of the object side is 25 degrees at short focus, and the full field of view of the object side is 2.5 degrees at long focus, the target contrast of 100 line pairs is greater than 0.5 at all focal lengths, a 5-micron pixel camera is adapted, the relative luminance at all focal lengths is greater than 0.95, the maximum optical distortion is less than or equal to 2%, and good imaging performance is achieved.

[0022] In the application, the positions of the front fixed lens group, the aperture stop and the rear fixed lens group are unchanged during the optical zooming process, the corresponding motion structure of the optical elements does not need to be designed in the actual application scene, the assembly operation is simplified, the manufacturing cost is reduced, and the work efficiency is improved.

[0023] In the application, all the lenses are spherical lenses, the processing is facilitated, and the system cost is reduced. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 Fig. 1 is a structural schematic diagram of the zoom lens system of the application;

[0025] Figure 2 Fig. 2 is a structural comparison diagram of the zoom lens system of the application at different focal lengths;

[0026] Figure 3 Fig. 3 is an MTF curve diagram of the system shown in Fig. 1; Figure 2 Fig. 4 is a distortion curve diagram of the system shown in Fig. 1;

[0027] Figure 4 Fig. 5 is an image plane luminance diagram of the system shown in Fig. 1; Figure 2 Fig. 6 is an MTF curve diagram of the system shown in Fig. 2;

[0028] Figure 5 Fig. 7 is a distortion curve diagram of the system shown in Fig. 2; Figure 2 Fig. 8 is an image plane luminance diagram of the system shown in Fig. 2;

[0029] Figure 6 Fig. 9 is an MTF curve diagram of the system shown in Fig. 3; Figure 2 Fig. 10 is a distortion curve diagram of the system shown in Fig. 3;

[0030] Figure 7 Fig. 11 is an image plane luminance diagram of the system shown in Fig. 3; Figure 2 Fig. 12 is an MTF curve diagram of the system shown in Fig. 4;

[0031] Figure 8 Fig. 13 is a distortion curve diagram of the system shown in Fig. 4; Figure 2b. The image plane illuminance plot for the system shown in c. The MTF plot for the system shown in

[0032] Figure 9 is Figure 2 c. The MTF plot for the system shown in

[0033] Figure 10 is Figure 2 c. The distortion plot for the system shown in

[0034] Figure 11 is Figure 2 c. The image plane illuminance plot for the system shown in

[0035] Figure 12 is Figure 2 d. The MTF plot for the system shown in

[0036] Figure 13 is Figure 2 d. The distortion plot for the system shown in

[0037] Figure 14 is Figure 2 d. The image plane illuminance plot for the system shown in

[0038] Figure 15 is Figure 2 e. The MTF plot for the system shown in

[0039] Figure 16 is Figure 2 e. The distortion plot for the system shown in

[0040] Figure 17 is Figure 2 e. The image plane illuminance plot for the system shown in

[0041] Figure 18 is a cam curve plot for the zoom lens system of the present invention.

[0042] wherein 1 - first cemented lens group; 2 - third lens; 3 - fourth lens; 4 - second cemented lens group; 5 - seventh lens; 6 - third cemented lens group; 7 - fourth cemented lens group; 8 - twelfth lens; 9 - fifth cemented lens group; 10 - aperture stop. DETAILED DESCRIPTION

[0043] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some but not all of the embodiments of the present application.

[0044] As Figure 1As shown, the embodiment of the present application proposes a zoom lens system. The system is sequentially provided with a front fixed lens group with positive focal length, a variable zoom lens group with negative focal length, a compensation lens group with positive focal length, an aperture stop 10 and a rear fixed lens group with positive focal length from the object plane to the image plane along the optical axis.

[0045] Wherein, the position of the front fixed lens group is unchanged, which is used to collect the light emitted from the object plane in the field of view and compress the light aperture, so that the light enters the variable zoom lens group. The variable zoom lens group moves forward and backward along the optical axis, which is used to realize the optical zoom of the system and compress the light aperture again, so that the light enters the compensation lens group. The compensation lens group moves forward and backward along the optical axis, which is used to compensate the aberration in the process of optical zoom. The distance between the aperture stop 10 and the rear fixed lens group is unchanged. The position of the rear fixed lens group is unchanged, which is used to balance the aberration of the system, so that the visible light is imaged on the image plane.

[0046] In the embodiment, the total length of the zoom lens system from the front surface of the front fixed lens group to the rear surface of the rear fixed lens group is unchanged at any focal length, and the F number is unchanged. When the focal length of the zoom lens system changes from 18mm to 180mm, the distance between the front fixed lens group and the variable zoom lens group changes in the range of 10.1mm-211.6mm; the distance between the variable zoom lens group and the compensation lens group changes in the range of 0.1mm-228.3mm; the distance between the compensation lens group and the aperture stop 10 changes in the range of 1.1mm-27.9mm.

[0047] The zoom ratio of the zoom lens system is fmax / fmin=10, the minimum focal length of the zoom lens system is fmin, and the maximum focal length of the zoom lens system is fmax.

[0048] In the front fixed lens group, the variable zoom lens group, the compensation lens group and the rear fixed lens group, all the lenses are spherical lenses.

[0049] The front fixed lens group sequentially includes a first cemented lens group 1 with negative focal length and a third lens 2 with positive focal length from the object plane to the image plane. Wherein, the first cemented lens group 1 is composed of a first lens and a second lens, the first lens is a biconvex lens with negative focal length, and the second lens is a biconcave lens with negative focal length; the third lens 2 is a biconvex lens. The focal length of the first cemented lens group 1 is-1502.8mm, and the focal length of the third lens 2 is 311.3mm.

[0050] The variable magnification lens group sequentially comprises, from the object plane to the image plane, a fourth lens 3 with a negative focal length and a second cemented lens group 4 with a negative focal length. The fourth lens 3 is a positive meniscus lens. The second cemented lens group 4 is composed of a fifth lens and a sixth lens. The fifth lens is a double concave lens with a positive focal length, and the sixth lens is a positive meniscus lens with a negative focal length. The focal length of the fourth lens 3 is -256.5 mm, and the focal length of the second cemented lens group 4 is -117.0 mm.

[0051] The compensation lens group sequentially comprises, from the object plane to the image plane, a seventh lens 5 with a negative focal length and a third cemented lens group 6 with a positive focal length. The seventh lens 5 is a positive biconvex lens. The third cemented lens group 6 is composed of an eighth lens and a ninth lens. The eighth lens is a positive meniscus lens with a positive focal length, and the ninth lens is a positive meniscus lens with a negative focal length. The focal length of the seventh lens 5 is 88 mm, and the focal length of the third cemented lens group 6 is 236.2 mm.

[0052] The rear fixed lens group sequentially comprises, from the object plane to the image plane, a fourth cemented lens group 7 with a positive focal length, a twelfth lens 8 with a positive focal length, and a fifth cemented lens group 9 with a negative focal length. The fourth cemented lens group 7 is composed of a tenth lens and an eleventh lens. The tenth lens is a negative meniscus lens with a negative focal length, and the eleventh lens is a negative meniscus lens with a positive focal length. The twelfth lens 8 is a positive biconvex lens. The fifth cemented lens group 9 is composed of a thirteenth lens and a fourteenth lens. The thirteenth lens is a biconvex lens with a positive focal length, and the fourteenth lens is a double concave lens with a negative focal length. The focal length of the fourth cemented lens group 7 is 1246.8 mm, the focal length of the twelfth lens 8 is 30.5 mm, and the focal length of the fifth cemented lens group 9 is -22.1 mm.

[0053] In this embodiment, the relevant parameters of each lens are shown in Table 1.

[0054] Table 1 Lens parameters

[0055]

[0056] According to the result parameters in Table 1, clear imaging of visible light bands can be achieved when the focal length is 18 mm / 60 mm / 100 mm / 140 mm / 180 mm, as shown in Figure 2 .

[0057] As shown in Figure 2 a, when the focal length is 18 mm, the relative distance between the second lens and the third lens 2 is 10.1 mm, the relative distance between the fourth cemented lens and the fifth lens is 228.3 mm, and the relative distance between the sixth lens and the aperture stop 10 is 1.1 mm.

[0058] Figure 3 is shownFigure 2 a, which shows the modulation transfer function (MTF) curve of the zoom lens system, indicating the system imaging contrast of different spatial frequencies under each field of view. The horizontal axis represents the spatial frequency (unit: lp / mm), and the vertical axis represents the MTF value. As can be seen from the figure, the MTF value of the embodiment is higher than 0.5 at 100 lp / mm, and has good imaging quality.

[0059] Figure 4 It is shown that Figure 2 a, which shows the distortion curve of the zoom lens system, indicating the distortion degree of the system in the visible light band. The horizontal axis is the distortion percentage, and the vertical axis is the field of view (FOV) of the system. As can be seen from the figure, the distortion of the system in the visible light band is less than 2%, and has good imaging quality.

[0060] Figure 5 It is shown that Figure 2 a, which shows the image plane illumination diagram of the zoom lens system, indicating the image plane illumination of each field of view relative to the central field of view. The horizontal axis represents the field of view (FOV) of the zoom lens system, and the vertical axis represents the relative image plane illumination ratio of each field of view to the central field of view. As can be seen from the figure, the ratio of the image plane illumination of the edge field of view to the central field of view of the system is higher than 0.95, which enhances the uniformity of the image plane illumination of the system, so that the system has good imaging quality.

[0061] As Figure 2 b, when the focal length is 60mm, the relative distance between the second lens and the third lens 2 is 136.7mm, the relative distance between the fourth cemented lens and the fifth lens is 89.3mm, and the relative distance between the sixth lens and the aperture stop 10 is 13.5mm.

[0062] Figure 6 It is shown that Figure 2 b, which shows the modulation transfer function (MTF) curve of the zoom lens system, indicating the system imaging contrast of different spatial frequencies under each field of view. The horizontal axis represents the spatial frequency (unit: lp / mm), and the vertical axis represents the MTF value. As can be seen from the figure, the MTF value of the embodiment is higher than 0.5 at 100 lp / mm, and has good imaging quality.

[0063] Figure 7 It is shown that Figure 2 b, which shows the distortion curve of the zoom lens system, indicating the distortion degree of the system in the visible light band. The horizontal axis is the distortion percentage, and the vertical axis is the field of view (FOV) of the system. As can be seen from the figure, the distortion of the system in the visible light band is less than 1%, and has good imaging quality.

[0064] Figure 8 It is shown that Figure 2Figure b shows the image plane illuminance diagram of the zoom lens system, representing the image plane illuminance of each field of view relative to the central field of view. The horizontal axis represents the field of view (FOV) of the zoom lens system, and the vertical axis represents the ratio of the relative image plane illuminance of each field of view to the central field of view. As can be seen from the figure, the ratio of the image plane illuminance of the edge fields of view to that of the central field of view is higher than 0.95, enhancing the uniformity of the system's image plane illuminance and resulting in good image quality.

[0065] like Figure 2 As shown in Figure c, when the focal length is 100mm, the relative distance between the second lens and the third lens 2 is 173.0mm, the relative distance between the fourth cemented lens and the fifth lens is 45.6mm, and the relative distance between the sixth lens and the aperture stop 10 is 20.9mm.

[0066] Figure 9 It shows Figure 2 Figure c shows the modulation transfer function (MTF) curve of the zoom lens system, which represents the system imaging contrast at different spatial frequencies in each field of view. The horizontal axis represents the spatial frequency (unit: lp / mm), and the vertical axis represents the MTF value. As can be seen from the figure, the MTF value of this embodiment is higher than 0.55 at 100 lp / mm, indicating good imaging quality.

[0067] Figure 10 It shows Figure 2 The distortion curve of the zoom lens system shown in Figure c represents the degree of distortion of the system in the visible light band. The horizontal axis represents the percentage of distortion, and the vertical axis represents the field of view (FOV) of the system. As can be seen from the figure, the distortion of the system in the visible light band is less than 2%, indicating good image quality.

[0068] Figure 11 It shows Figure 2 Figure c shows the image plane illuminance diagram of the zoom lens system, representing the image plane illuminance of each field of view relative to the central field of view. The horizontal axis represents the field of view (FOV) of the zoom lens system, and the vertical axis represents the ratio of the relative image plane illuminance of each field of view to the central field of view. As can be seen from the figure, the ratio of the image plane illuminance of the edge fields of view to that of the central field of view is higher than 0.95, enhancing the uniformity of the system's image plane illuminance and resulting in good image quality.

[0069] like Figure 2 As shown in d, when the focal length is 140mm, the relative distance between the second lens and the third lens 2 is 194.3mm, the relative distance between the fourth cemented lens and the fifth lens is 19.3mm, and the relative distance between the sixth lens and the aperture stop 10 is 25.9mm.

[0070] Figure 12 It shows Figure 2Figure 8 shows a modulation transfer function (MTF) curve of the zoom lens system shown in Figure 7, which represents the system imaging contrast of different spatial frequencies under each field of view, the horizontal axis represents spatial frequency (unit: lp / mm), and the vertical axis represents MTF value. As can be seen from the figure, the MTF value of the embodiment is higher than 0.6 at 100 lp / mm, and has good imaging quality.

[0071] Figure 13 Figure 9 shows a distortion curve of the zoom lens system shown in Figure 7, which represents the distortion degree of the system in the visible light band, the horizontal axis is the distortion percentage, and the vertical axis is the field of view (FOV) of the system. As can be seen from the figure, the distortion of the system in the visible light band is less than 1%, and has good imaging quality. Figure 2

[0072] Figure 10 shows a distortion curve of the zoom lens system shown in Figure 7, which represents the distortion degree of the system in the visible light band, the horizontal axis is the distortion percentage, and the vertical axis is the field of view (FOV) of the system. As can be seen from the figure, the distortion of the system in the visible light band is less than 2%, and has good imaging quality. Figure 14 Figure 2 Figure 11 shows an image plane illumination diagram of the zoom lens system shown in Figure 7, which represents the image plane illumination of each field of view relative to the central field of view, the horizontal axis represents the field of view (FOV) of the zoom lens system, and the vertical axis represents the relative image plane illumination ratio of each field of view to the central field of view. As can be seen from the figure, the ratio of the image plane illumination of the edge field of view to the central field of view of the system is higher than 0.95, which enhances the uniformity of the image plane illumination of the system, so that the system has good imaging quality.

[0073] Figure 12 shows a modulation transfer function (MTF) curve of the zoom lens system shown in Figure 11, which represents the system imaging contrast of different spatial frequencies under each field of view, the horizontal axis represents spatial frequency (unit: lp / mm), and the vertical axis represents MTF value. As can be seen from the figure, the MTF value of the embodiment is higher than 0.6 at 100 lp / mm, and has good imaging quality. Figure 2 e, the relative distance between the second lens and the third lens 2 is 211.5 mm when the focal length is 180 mm, the relative distance between the fourth cemented lens and the fifth lens is 0.1 mm, and the relative distance between the sixth lens and the aperture stop 10 is 27.9 mm.

[0074] Figure 15 Figure 23 shows a distortion curve of the zoom lens system shown in Figure 22, which represents the distortion degree of the system in the visible light band, the horizontal axis is the distortion percentage, and the vertical axis is the field of view (FOV) of the system. As can be seen from the figure, the distortion of the system in the visible light band is less than 2%, and has good imaging quality. Figure 2 e, the relative distance between the second lens and the third lens 2 is 211.5 mm when the focal length is 180 mm, the relative distance between the fourth cemented lens and the fifth lens is 0.1 mm, and the relative distance between the sixth lens and the aperture stop 10 is 27.9 mm.

[0075] Figure 16 Figure 25 shows a distortion curve of the zoom lens system shown in Figure 24, which represents the distortion degree of the system in the visible light band, the horizontal axis is the distortion percentage, and the vertical axis is the field of view (FOV) of the system. As can be seen from the figure, the distortion of the system in the visible light band is less than 2%, and has good imaging quality. Figure 2

[0076] Figure 27 shows a distortion curve of the zoom lens system shown in Figure 26, which represents the distortion degree of the system in the visible light band, the horizontal axis is the distortion percentage, and the vertical axis is the field of view (FOV) of the system. As can be seen from the figure, the distortion of the system in the visible light band is less than 2%, and has good imaging quality. Figure 17 Figure 2 ​​Fig. 6 shows the image plane illumination diagram of the zoom lens system of Fig. 1, which shows the image plane illumination of each field of view relative to the central field of view, the horizontal axis represents the view angle (FOV) of the zoom lens system, and the vertical axis represents the relative image plane illumination ratio of each field of view to the central field of view. It can be seen from the figure that the ratio of the image plane illumination of the edge field of view to the central field of view of the system is higher than 0.95, which enhances the uniformity of the image plane illumination of the system, so that the system has good imaging quality.

[0077] In summary, the focal length changes from 18 mm to 180 mm, and the distance between the second lens and the aperture stop is 239.5 mm. That is, the total length of the optical zoom system is constant during the optical zooming process.

[0078] The zoom system is to move two or more lens groups in the system, so as to change the combined focal length and keep the last image plane position unchanged, so that the system obtains a continuous clear image during zooming. In order to measure the practicability of the zoom lens system described in the present application, based on the working principle of the zoom system, the motion curves of the variable magnification lens group and the compensation lens group are counted, and the cam curve of the zoom lens system is obtained. The horizontal coordinate of the cam curve is the sampling point number, and the vertical coordinate is the moving distance. As shown in Fig. 7, during the optical zooming process, the variable magnification lens group makes linear motion, and the compensation lens group makes nonlinear motion, and the motion curve of the compensation lens group is smooth, so that the system has high machinability. Figure 18

[0079] Preferably, on the basis of the above, the zoom lens system further comprises: a protective glass arranged at a distance of 0.1 mm from the rear surface of the rear fixed lens group, to protect the above optical elements.

[0080] On the other hand, the present application also proposes a measuring device comprising the above zoom lens system.

[0081] The technical features of the above embodiments can be combined in any way. In order to make the description concise, not all possible combinations of the technical features in the above embodiments are described, but as long as the combinations of the technical features do not exist contradictions, they should be considered as the scope of the present application.

[0082] The above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacements for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.​

Claims

1. A zoom lens system, characterized in that, Along the optical axis from the object plane to the image plane, there are sequentially arranged a front fixed lens group with a positive focal length, a zoom lens group with a negative focal length, a compensation lens group with a positive focal length, an aperture stop, and a rear fixed lens group with a positive focal length. In this system, the position of the front fixed lens group remains unchanged; the zoom lens group moves back and forth along the optical axis to achieve optical zoom of the system and compress the light aperture again so that light can enter the compensation lens group; the compensation lens group moves back and forth along the optical axis to compensate for aberrations that occur during optical zoom; the position and distance of the aperture stop remain unchanged; and the position of the rear fixed lens group remains unchanged to balance system aberrations so that visible light can be imaged on the image plane. At any focal length, the total length of the zoom lens system from the front surface of the front fixed lens group to the rear surface of the rear fixed lens group remains constant, and the F-number remains constant. When the focal length of the zoom lens system changes from 18mm to 180mm, the distance between the front fixed lens group and the zoom lens group varies from 10.1mm to 211.6mm; the distance between the zoom lens group and the compensation lens group varies from 0.1mm to 228.3mm; and the distance between the compensation lens group and the aperture stop varies from 1.1mm to 27.9mm. From the object plane to the image plane, the front fixed lens group consists of a first lens, a second lens, and a third lens, with the first and second lenses forming a first cemented lens group; the zoom lens group consists of a fourth lens, a fifth lens, and a sixth lens, with the fifth and sixth lenses forming a second cemented lens group; the compensation lens group consists of a seventh lens, an eighth lens, and a ninth lens, with the eighth and ninth lenses forming a third cemented lens group; the rear fixed lens group consists of a tenth lens, an eleventh lens, a twelfth lens, a thirteenth lens, and a fourteenth lens, with the tenth and eleventh lenses forming a fourth cemented lens group, and the thirteenth and fourteenth lenses forming a fifth cemented lens group; wherein, the lenses with negative focal lengths are: the first lens, the second lens, the fourth lens, the sixth lens, the seventh lens, the ninth lens, the tenth lens, and the fourteenth lens; and the lenses with positive focal lengths are: the third lens, the fifth lens, the eighth lens, the eleventh lens, the twelfth lens, and the thirteenth lens.

2. The zoom lens system according to claim 1, characterized in that, In the aforementioned front fixed lens group, the first lens is a biconvex lens with a negative focal length, the second lens is a biconcave lens with a negative focal length, and the third lens is a biconvex lens with a positive focal length.

3. The zoom lens system according to claim 1, characterized in that, In the zoom lens group, the fourth lens is a positive meniscus lens with a negative focal length, the fifth lens is a biconcave lens with a positive focal length, and the sixth lens is a positive meniscus lens with a negative focal length.

4. The zoom lens system according to claim 1, characterized in that, In the compensation lens group, the seventh lens is a positive biconvex lens with a negative focal length, the eighth lens is a positive meniscus lens with a positive focal length, and the ninth lens is a positive meniscus lens with a negative focal length.

5. The zoom lens system according to claim 1, characterized in that, In the rear fixed lens group, the tenth lens is a negative meniscus lens with a negative focal length, the eleventh lens is a negative meniscus lens with a positive focal length, the twelfth lens is a positive biconvex lens with a positive focal length, the thirteenth lens is a biconvex lens with a positive focal length, and the fourteenth lens is a biconcave lens with a negative focal length.

6. The zoom lens system according to claim 1, characterized in that, All lenses in the front fixed lens group, zoom lens group, compensation lens group, and rear fixed lens group are spherical lenses.

7. The zoom lens system according to claim 1, characterized in that, The zoom ratio of the zoom lens system is fmax / fmin = 10, the minimum focal length of the zoom lens system is fmin, and the maximum focal length of the zoom lens system is fmax.

8. The zoom lens system according to claim 1, characterized in that, Also includes: A protective glass is also provided at a distance of 0.1 mm from the rear surface of the rear fixed lens group.

9. A measuring device, characterized in that, Includes the zoom lens system as described in any one of claims 1-8.

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