A long-focus optical lens with a three-lens group structure

Abstract

The application discloses a long-focus optical lens with a three-lens group structure, which comprises a first lens group, a variable diaphragm, a seventh lens and a second lens group in sequence along the light path in the light incidence direction; the seventh lens moves along the optical axis direction of the light path to adjust the focal length of the long-focus optical lens; the optical power of the first lens group and the optical power of the second lens group are both positive; the optical power of the seventh lens is negative; the refractive index of the seventh lens is greater than 1.7 and less than 1.8. The application can be widely applied to the technical field of long-focus optical lenses.

Description

Technical Field

[0001] This application relates to the field of telephoto optical lens technology, and in particular to a telephoto optical lens with a three-lens group structure. Background Technology

[0002] Against the backdrop of rapid socio-economic development, the demand for film and television creation and self-media content continues to rise, and video application scenarios are constantly increasing. Consequently, the industry's requirements for lens performance and technical parameters are also rising, especially for autofocus telephoto lenses. Currently, autofocus telephoto video lenses generally suffer from drawbacks such as low resolution, small aperture, significant distortion, and large chromatic aberration, failing to meet the high demands of the autofocus telephoto cinema shooting market. Therefore, there are still technical problems that need to be solved in this area. Summary of the Invention

[0003] The purpose of this application is to at least partially solve one of the technical problems existing in the prior art.

[0004] Therefore, one objective of this application is to provide a telephoto optical lens with a three-lens group structure, which can improve the problems of low resolution, small aperture, large distortion and large chromatic aberration.

[0005] To achieve the above-mentioned technical objectives, the technical solution adopted in the embodiments of this application includes: a telephoto optical lens with a three-lens group structure, wherein the telephoto optical lens with the three-lens group structure includes:

[0006] The optical path, along the direction of light incidence, includes, in sequence, a first lens group, a variable aperture, a seventh lens, and a second lens group;

[0007] The seventh lens moves along the optical axis in the optical path to adjust the focal length of the telephoto lens with the three-lens group structure. The optical power of the first lens group and the second lens group are both positive; the optical power of the seventh lens is negative; the focusing range of the seventh lens is 0-17mm; and the refractive index of the seventh lens is greater than 1.7 and less than 1.8.

[0008] In addition, a telephoto optical lens with a three-lens group structure according to the above embodiments of the present invention may also have the following additional technical features:

[0009] Furthermore, in this embodiment of the application, the first lens group includes, in sequence, a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and a sixth lens along the incident direction of the light rays; wherein, the refractive index of the second lens and the fifth lens is both greater than 1.4 and less than 1.5.

[0010] Furthermore, in this embodiment, the second lens and the third lens are configured as cemented doublet lenses.

[0011] Furthermore, in the embodiments of this application, the Abbe numbers of the first lens, the third lens, the fourth lens, and the sixth lens are all greater than 20 and less than 30.

[0012] Furthermore, in this embodiment of the application, the second lens group sequentially includes an eighth lens, a ninth lens, a tenth lens, an eleventh lens, a twelfth lens, a thirteenth lens, a fourteenth lens, a fifteenth lens, and a sixteenth lens along the incident direction of the light rays; wherein, the Abbe number of the ninth lens is greater than 80 and less than 90.

[0013] Furthermore, in this embodiment of the application, the Abbe number of the eleventh lens is greater than 80 and less than 90.

[0014] Furthermore, in this embodiment of the application, the fourteenth lens and the fifteenth lens are configured as cemented doublet lenses.

[0015] Furthermore, in this embodiment of the application, the total optical length of the telephoto lens with the three-lens group structure is greater than 145 mm and less than 150 mm.

[0016] The advantages and beneficial effects of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application:

[0017] The telephoto lens with a three-lens-group structure of this application includes, in sequence along the incident light direction, a first lens group, a variable aperture, a seventh lens, and a second lens group. The parameters of the three-lens-group telephoto lens are set as follows: the optical power of the first lens group and the second lens group are both positive; the optical power of the seventh lens is negative; and the refractive index of the seventh lens is greater than 1.7 and less than 1.8.

[0018] This application improves the problems of low resolution, small aperture, large distortion, and large chromatic aberration by using a movable negative angle lens positioned between the first lens group and the second lens group, thereby enhancing the practicality of telephoto lenses with a three-lens-group structure. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of a telephoto optical lens with a three-lens group structure in a specific embodiment of the present invention;

[0020] Figure 2 This is a schematic diagram of longitudinal aberration of a telephoto lens with a three-lens-group structure in a specific embodiment of the present invention.

[0021] Figure 3 This is a schematic diagram of the lateral chromatic aberration of a telephoto lens with a three-lens group structure in a specific embodiment of the present invention;

[0022] Figure 4 This is a schematic diagram of the field curvature and distortion of a telephoto lens with a three-lens group structure in a specific embodiment of the present invention;

[0023] Figure 5 This is an MTF defocus curve diagram of a telephoto lens with a three-lens group structure in a specific embodiment of the present invention.

[0024] Figure 6 This is an MTF curve of a telephoto lens with a three-lens group structure in a specific embodiment of the present invention;

[0025] Figure 7 This is a schematic diagram of the relative illumination of a telephoto lens with a three-lens group structure in a specific embodiment of the present invention. Detailed Implementation

[0026] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings, and the principle and process of the telephoto optical lens with a three-lens group structure in the embodiments of the present invention will be explained as follows.

[0027] This application provides a telephoto optical lens with a three-lens-group structure, referring to... Figure 1 The telephoto optical lens with a three-lens structure of this application includes, in sequence along the light incident direction, a first lens group 101, a variable aperture 102, a seventh lens 103, and a second lens group 104.

[0028] The seventh lens 103 moves along the optical axis in the optical path to adjust the focal length of the telephoto lens with the three-lens group structure. The optical power of the first lens group 101 and the second lens group 104 are both positive; the optical power of the seventh lens 103 is negative; and the refractive index of the seventh lens 103 is greater than 1.7 and less than 1.8.

[0029] In addition, a telephoto optical lens with a three-lens group structure according to the above embodiments of the present invention may also have the following additional technical features:

[0030] Furthermore, referring to Figure 1 In this embodiment of the application, the first lens group 101 includes, in sequence along the incident direction of the light, a first lens 1001, a second lens 1002, a third lens 1003, a fourth lens 1004, a fifth lens 1005, and a sixth lens 1006; wherein, the refractive indices of the second lens 1002 and the fifth lens 1005 are both greater than 1.4 and less than 1.5.

[0031] Furthermore, in this embodiment, the second lens 1002 and the third lens 1003 are configured as cemented doublet lenses.

[0032] Furthermore, in the embodiments of this application, the Abbe numbers of the first lens 1001, the third lens 1003, the fourth lens 1004, and the sixth lens 1006 are all greater than 20 and less than 30.

[0033] Furthermore, in this embodiment, the second lens group 104 sequentially includes an eighth lens 1008, a ninth lens 1009, a tenth lens 1010, an eleventh lens 1011, a twelfth lens 1012, a thirteenth lens 1013, a fourteenth lens 1014, a fifteenth lens 1015, and a sixteenth lens 1016 along the light path incident direction; wherein, the Abbe number of the ninth lens 1009 is greater than 80 and less than 90, and the focusing range of the seventh lens 103 is 0-17mm.

[0034] Furthermore, in this embodiment of the application, the Abbe number of the eleventh lens 1011 is greater than 80 and less than 90.

[0035] Furthermore, in this embodiment of the application, the fourteenth lens 1014 and the fifteenth lens 1015 are configured as cemented doublet lenses.

[0036] Furthermore, in the embodiments of this application, the total optical length of the telephoto lens with a three-lens group structure is greater than 145 mm and less than 150 mm.

[0037] This embodiment employs a three-segment optical power layout—front positive, center negative, and rear positive—to enhance the MTF resolution across the entire field of view. The dispersed optical power arrangement reduces individual element curvature, suppressing spherical and coma aberrations. The lens features three sets of cemented doublet achromatic units, paired with Abbe number 20-30 medium-high dispersion lenses and Abbe number 80-90 ultra-low dispersion lenses. Multi-level dispersion matching eliminates various chromatic aberrations and secondary spectral distortion at long focal lengths. A negative focusing lens with a refractive index of 1.7-1.8 further reduces higher-order aberrations. The three optical power segments work together to compensate for field curvature, controlling image plane shift within ±0.05mm. The full-field MTF approaches the diffraction limit, and the center-to-edge resolution is consistently excellent at a high frequency of 60lp / mm.

[0038] This embodiment corrects distortion using a three-segment optical path: front positive, middle negative, and rear positive. A movable negative lens in the middle counteracts the field-of-view magnification deviation of the front and rear positive lenses, while a smooth curved surface weakens higher-order distortion. Stable compensation is provided throughout the 0-17mm focusing range. Multiple lenses in the rear group correct residual distortion, keeping the absolute value of the total field-of-view distortion below 1%.

[0039] Specifically, referring to Table 1, which is a parameter table for each lens in a telephoto lens with a three-lens-group structure according to one embodiment of this application, in Table 1, object planes 1-10 represent all surfaces of the six lenses in the first lens group, and object planes 12 and 13 represent the two surfaces of the seventh lens. As can be seen from Table 1, the refractive index of the seventh lens is preferably 1.713. From the radii of curvature of the two surfaces, object planes 12 and 13, it can be seen that the optical power is negative, and the Abbe number of the seventh lens is preferably 53.832974.

[0040] Face number type radius of curvature thickness Refractive index Abbe number surface Standard sphere infinity infinity 1 Standard sphere 75.124012 9.55 1.84666 23.784497 2 Standard sphere 621.808057 2.550614 3 Standard sphere 54.576179 11.9 1.497 81.612838 4 Standard sphere -641.734658 1.2 1.74077 27.760063 5 Standard sphere 75.194356 5.483578 6 Standard sphere 53.531364 1.2 1.7552 27.530047 7 Standard sphere 33.291838 1.247481 8 Standard sphere 37.391229 11.27 1.4378 94.523389 9 Standard sphere -114.706728 0.999828 1.84666 23.784497 10 Standard sphere -417.233367 1.85381 Aperture Standard sphere infinity 2.580306 12 Standard sphere infinity 1 1.713 53.832974 13 Standard sphere 42.544681 20.355072 14 Standard sphere 30.318203 6.945 1.52307 58.639792 15 Standard sphere -605.83027 0.148624 16 Standard sphere 213.51871 1 1.84666 23.784497 17 Standard sphere 27.577831 3.063717 18 Standard sphere 33.03517 7.16 1.497 81.612838 19 Standard sphere -60.45662 0.149719 20 Standard sphere -399.188809 1 1.72825 28.318797 21 Standard sphere 59.482037 10.123746 22 Standard sphere -27.868276 1 1.497 81.612838 23 Standard sphere 178.876739 0.149033 24 Standard sphere 106.308882 7.264506 2.0033 28.316305 25 Standard sphere -48.309236 0.149637 26 Standard sphere 60.116289 5.1 1.84666 23.784497 27 Standard sphere -505.402597 1 1.618 63.392702 28 Standard sphere 61.850131 8.328738 29 Standard sphere -32.701218 1 1.5928 68.342024 30 Standard sphere -70.574457 19.533382 31 Standard sphere infinity 2.5 1.5168 64.198732 32 Standard sphere infinity 1 Image Standard sphere infinity -

[0041] Table 1

[0042] Figure 2 This is a schematic diagram illustrating the longitudinal aberrations of the telephoto lens with a three-lens-group structure according to this application. Figure 2 In the diagram, the horizontal axis represents the longitudinal aberration shift, and the vertical axis represents the field of view. The vertical spacing between the curves represents the focal shift of the wavelength relative to the reference wavelength; the larger the spacing, the more severe the chromatic aberration.

[0043] Figure 3 This is a schematic diagram illustrating the lateral chromatic aberration of the telephoto lens with a three-lens-group structure according to this application. Figure 3 In this embodiment, the lateral chromatic aberration of the three-lens group structure is <3.5µm. The chromatic aberration of the three-lens group structure is relatively good.

[0044] Figure 4 The diagram shows the field curvature of the telephoto lens with the three-lens-group structure of this application and the distortion diagram of the telephoto lens: Figure 4 The diagram on the left shows the field curvature of the telephoto lens, where S represents the sagittal and T represents the meridional. A larger S / T separation indicates a larger field curvature. The diagram on the right shows the distortion of the telephoto lens, where the horizontal axis represents the distortion value and the vertical axis represents the field of view. The optical distortion of the three-lens structure in this embodiment is <1µm.

[0045] Figure 5 The image shows the MTF defocus curve of the telephoto lens with the three-lens group structure of this application: the horizontal axis represents the focus offset, and the vertical axis represents the OTF modulus value, which ranges from 0 to 1. A higher OTF value indicates better contrast or sharpness at that spatial frequency. In this embodiment, the peak of the defocus curve for the three-lens group structure is >0.8.

[0046] Figure 6 This is a graph showing the MTF (modulation transfer function) curve of the telephoto optical lens with a three-lens group structure of this application. Figure 6The horizontal axis represents spatial frequency, with larger values ​​indicating higher frequencies (stronger detail resolution). The vertical axis represents the OTF (Optical Frequency Tolerance) value, also known as the MTF (Mean Transformer Frequency) value, ranging from 0 to 1. Higher values ​​indicate stronger contrast or detail reproduction capabilities at that spatial frequency. In this embodiment, the MTF of the three-lens group structure is >0.7 at the center (60 lp / mm) and >0.6 at the edges, indicating high resolution and sharpness, and good image quality.

[0047] Figure 7 This is a schematic diagram of the relative illumination of the telephoto optical lens with a three-lens group structure according to this application. Figure 7 The horizontal axis represents the field of view, and the vertical axis represents the relative illumination. It describes the brightness attenuation of light from the center to the edge of the image (vertical axis). The relative illumination curve of the three-lens structure in this embodiment is >0.3, indicating that there will be no vignetting at the lens edge.

[0048] From the above Figures 2-7 The experimental results show that the optical system of this application has good aberration correction. The optimized three-lens group telephoto lens has advantages such as large aperture, high resolution, small distortion, low chromatic aberration and easy close-up shooting. Moreover, the three-lens group telephoto lens of this application adopts a compact optical structure optimization to reduce the total optical length while meeting the requirements of autofocus.

[0049] In the foregoing description of this specification, the references to terms such as "one embodiment," "another embodiment," or "some embodiments," etc., indicate that a specific feature, structure, material, or characteristic described in connection with an embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0050] Although embodiments of this application have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the claims and their equivalents.

[0051] The above is a detailed description of the preferred embodiments of this application, but this application is not limited to the embodiments described. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of this application, and these equivalent modifications or substitutions are all included within the scope defined by the claims of this application.

Claims

1. A telephoto optical lens with a three-lens group structure, characterized in that, The optical path, along the direction of light incidence, sequentially includes a first lens group, a variable aperture, a seventh lens, and a second lens group. The seventh lens moves along the optical axis to adjust the focal length of the telephoto lens. The optical power of the first lens group and the second lens group are both positive; the optical power of the seventh lens is negative. The first lens group, along the direction of light incidence, sequentially includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and a sixth lens. The second lens group, along the direction of light incidence, sequentially includes an eighth lens, a ninth lens, a tenth lens, an eleventh lens, a twelfth lens, a thirteenth lens, a fourteenth lens, a fifteenth lens, and a sixteenth lens. The telephoto lens contains 16 lenses with optical power. The optical parameters of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the seventh lens, the eighth lens, the ninth lens, the tenth lens, the eleventh lens, the twelfth lens, the thirteenth lens, the fourteenth lens, the fifteenth lens, and the sixteenth lens are shown in the table below. 。

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