An optical system for a large-aperture full-frame prime lens
By designing three objective lens groups and optimizing the optical power ratio of the lens combination, the aberration problem of large-aperture full-frame fixed-focus lenses was solved, achieving high-quality imaging.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- CHENGDU WEIZHENG DIGITAL TECH CO LTD
- Filing Date
- 2025-07-28
- Publication Date
- 2026-07-03
AI Technical Summary
The image quality of existing large-aperture full-frame prime lenses needs improvement, especially since aberration fluctuations and spherical aberration and chromatic aberration introduced by aperture affect image quality.
It adopts a three-objective lens design, in which the first objective lens group is fixed, the second objective lens group is floating for focusing, and the third objective lens group balances aberrations. By using the positive and negative optical power ratio of the lens groups and the dispersion compensation of the cemented lens, combined with high refractive index materials and aspherical lenses, light refraction and convergence are optimized.
It effectively suppresses spherical aberration, coma, and chromatic aberration, improves edge image quality on full-frame cameras, ensures stable focusing, corrects image plane curvature and edge distortion, and enhances lens image quality.
Smart Images
Figure CN224457127U_ABST
Abstract
Description
Technical Field
[0001] This utility model belongs to the field of optical lens technology and relates to an optical system for a large aperture full-frame fixed-focus lens. Background Technology
[0002] In the field of photography, an 85mm focal length closely approximates human vision, presenting natural portrait proportions and making it ideal for shooting half-body and full-body portraits. The large F1.4 aperture provides a shallow depth of field, allowing ample light intake to meet the needs of low-light shooting, highlighting the subject, blurring the background, creating a dreamlike atmosphere, and enhancing the sense of depth in the image. For these reasons, its unique advantages have gradually gained favor among photography enthusiasts.
[0003] As photography enthusiasts demand increasingly higher image quality, the image quality of large-aperture full-frame prime lenses currently needs improvement. This is because large apertures easily introduce aberrations such as spherical aberration and chromatic aberration, affecting image quality. Furthermore, the movement of the lens elements during focusing can cause aberration fluctuations, impacting image quality. Summary of the Invention
[0004] The purpose of this invention is to provide an optical system for a large-aperture full-frame fixed-focus lens, which solves the problem that the imaging quality of current large-aperture full-frame fixed-focus lenses needs to be improved.
[0005] The technical solution adopted in this utility model is as follows:
[0006] An optical system for a large-aperture full-frame fixed-focus lens includes a first objective lens group G1, a second objective lens group G2, and a third objective lens group G3. The first objective lens group G1, the second objective lens group G2, and the third objective lens group G3 are arranged sequentially from the object side to the image side along the optical axis, and the radial stop is located in the first objective lens group.
[0007] During the focusing process, the second objective group G2 moves along the optical axis to the image side, while the positions of the first objective group G1, the aperture stop, and the third objective group G3 relative to the image plane remain unchanged.
[0008] The optical system satisfies the following condition:
[0009] 0.87≤FG1 / F≤1.25
[0010] 0.62≤|FG2 / F|≤0.98,
[0011] 0.7≤FG3 / F≤1.2;
[0012] Wherein, FG1 represents the total focal length of the first objective lens group, FG2 represents the total focal length of the second objective lens group, FG3 represents the total focal length of the third objective lens group, and F represents the total focal length of the optical system.
[0013] Furthermore, the first objective lens group includes: a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, an aperture stop STP, and a seventh lens, wherein the third lens and the fourth lens form a first cemented lens;
[0014] The second objective lens group includes an eighth lens;
[0015] The third lens group includes: the ninth lens, the tenth lens, the eleventh lens, the twelfth lens, the thirteenth lens, the fourteenth lens, and the fifteenth lens. The eleventh lens (11), the twelfth lens (12), the thirteenth lens (13), and the fourteenth lens (14) together form the second cemented lens.
[0016] Except for the aperture stop, all the lenses are made of optical glass.
[0017] Furthermore, both the first lens and the second lens are meniscus lenses, with the centers of spheres on both sides of the meniscus lens located on the image side, and the first lens and the second lens satisfy the following condition:
[0018] 1.12≤Ф2 / Ф1≤1.47
[0019] Where Ф1 is the optical power of the first lens and Ф2 is the optical power of the first lens.
[0020] Furthermore, the third lens is a meniscus lens, with the centers of both spheres located on the image side;
[0021] The fourth lens is a meniscus negative lens, with the center of gravity of both surfaces on the image side;
[0022] The third and fourth lenses form a cemented lens, which effectively compensates for the chromatic aberration of the first objective lens group and satisfies the following condition:
[0023] 0.97≤|Ф34 / Ф|≤1.34
[0024] Where Ф34 is the combined optical power of the third and fourth lenses, and Ф is the total optical power of the system.
[0025] Furthermore, the fifth lens is a biconcave lens with negative optical power.
[0026] Furthermore, both the sixth and seventh lenses are biconvex lenses and both have positive optical power;
[0027] The sixth and seventh lenses are located on either side of the aperture stop and satisfy the following condition:
[0028] 1.51 <N6<N7,
[0029] Where N6 is the D-index of the sixth lens and N7 is the D-index of the seventh lens.
[0030] Furthermore, the eighth lens is a biconcave lens that moves along the optical axis to the image side during focusing, and satisfies the following condition:
[0031] 0.63 < |Ф8 / Ф| < 0.89
[0032] Where Ф8 is the optical power of the eighth lens, and Ф is the total optical power of the system.
[0033] Furthermore, the ninth, eleventh, and thirteenth lenses are all biconvex lenses and satisfy the following condition:
[0034] Ф<Ф11<Ф13<Ф9,
[0035] Wherein, Ф9 is the optical power of the ninth lens, Ф11 is the optical power of the eleventh lens, Ф13 is the optical power of the thirteenth lens, and Ф is the total optical power of the system.
[0036] Furthermore, the tenth lens is a meniscus negative lens, with the centers of both spheres located on the image side; the twelfth lens is a biconcave lens; the fourteenth lens is a biconcave lens; and the following conditions are satisfied:
[0037] 0.004 < Ф14 < Ф10 < Ф12 < 0.021
[0038] Wherein, Ф10 is the optical power of the ninth lens, Ф12 is the optical power of the twelfth lens, and Ф14 is the optical power of the fourteenth lens.
[0039] Furthermore, the fifteenth lens is an aspherical lens and satisfies the following condition:
[0040] |SAG151|>|SAG152|,
[0041] Wherein, SAG151 is the sagitta at the object-side aperture of the fifteenth lens, and SAG152 is the sagitta at the image-side aperture of the fifteenth lens.
[0042] In summary, due to the adoption of the above technical solution, the beneficial effects of this utility model are:
[0043] 1. The optical system of a large aperture full-frame fixed-focus lens of this utility model achieves the purpose of optimizing the refraction and convergence of light, balancing aberrations and improving image quality by setting the positive and negative optical power of each lens group and the ratio between the composite focal length of each lens group and the composite focal length of the entire lens, thereby enabling the lens to achieve higher image quality.
[0044] 2. This utility model, through the coordinated design of three objective lens groups, with G1 fixedly bearing the main optical power, G2 floating for focusing, and G3 balancing aberrations, effectively suppresses spherical aberration, coma, and chromatic aberration at a large aperture of F1.4;
[0045] 3. The dispersion compensation design of the cemented lenses (third and fourth lenses) in the first objective lens group G1 of this utility model, combined with the high refractive index materials of the sixth and seventh lenses (N6>1.51, N7>N6), significantly reduces magnification chromatic aberration and improves the edge image quality of the full frame.
[0046] 4. In this invention, only the second objective lens group G2 (eighth lens) moves during focusing, effectively reducing the weight of the focusing group and making focusing faster; the focal length ratio of G2 (|FG2 / F|∈[0.62,0.98]) and the optical power condition (0.63<|Ф8 / Ф|<0.89) ensure the stability of the image plane during focusing;
[0047] 5. In this invention, the center of the sphere of the meniscus lens (first and second lenses) faces the image side and the optical power ratio Ф2 / Ф1∈[1.12,1.47] effectively corrects the astigmatism caused by the large aperture;
[0048] 6. In this utility model, the ninth, eleventh, and thirteenth lenses (biconvex) and the tenth, twelfth, and fourteenth lenses (negative lenses) are arranged in an alternating "positive-negative-positive" pattern, which, together with the aspherical surface of the fifteenth lens (|SAG151|>|SAG152|), accurately corrects image plane curvature and edge distortion. Attached Figure Description
[0049] To more clearly illustrate the technical solutions of the embodiments of this utility model, the drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this utility model and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort, wherein:
[0050] Figure 1 This is a schematic diagram of the optical system structure of this utility model;
[0051] Figure 2 This is a schematic diagram of field curvature distortion when focusing at infinity in Embodiment 1 of this utility model;
[0052] Figure 3 This is a schematic diagram of the axial chromatic aberration when focusing at infinity in Embodiment 1 of this utility model;
[0053] Figure 4 This is a schematic diagram of the field curvature distortion in Embodiment 1 of this utility model at a focal length of 0.8m;
[0054] Figure 5 This is a schematic diagram of the axial color difference in Embodiment 1 of this utility model when focusing at 0.8m. Detailed Implementation
[0055] To make the objectives, technical solutions, and advantages of this utility model clearer, the present utility model will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only for explaining the present utility model and are not intended to limit the present utility model; that is, the described embodiments are only some embodiments of the present utility model, and not all embodiments. The components of the embodiments of the present utility model described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.
[0056] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.
[0057] It should be noted that relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.
[0058] The features and performance of this utility model will be further described in detail below with reference to the embodiments.
[0059] Example 1:
[0060] like Figures 1-5 As shown, the preferred embodiment of this utility model provides an optical system for a large-aperture full-frame fixed-focus lens, including a first objective lens group G1, a second objective lens group G2, and a third objective lens group G3. The first objective lens group G1, the second objective lens group G2, and the third objective lens group G3 are arranged sequentially from the object side to the image side along the optical axis, and the radial stop is located in the first objective lens group.
[0061] During the focusing process, the second objective group G2 moves along the optical axis to the image side, while the positions of the first objective group G1, the aperture stop, and the third objective group G3 relative to the image plane remain unchanged.
[0062] The optical system satisfies the following condition:
[0063] 0.87≤FG1 / F≤1.25
[0064] 0.62≤|FG2 / F|≤0.98,
[0065] 0.7≤FG3 / F≤1.2;
[0066] Wherein, FG1 represents the total focal length of the first objective lens group, FG2 represents the total focal length of the second objective lens group, FG3 represents the total focal length of the third objective lens group, and F represents the total focal length of the optical system.
[0067] The first objective lens group G1 includes: a first lens 1, a second lens 2, a third lens 3, a fourth lens 4, a fifth lens 5, a sixth lens 6, an aperture stop STP, and a seventh lens 7. The third lens 3 and the fourth lens 4 form a first cemented lens.
[0068] The second objective lens group G2 includes an eighth lens 8;
[0069] The third lens group G3 includes: a ninth lens 9, a tenth lens 10, an eleventh lens 11, a twelfth lens 12, a thirteenth lens 13, a fourteenth lens 14, and a fifteenth lens 15. The eleventh lens (11), the twelfth lens (12), the thirteenth lens (13), and the fourteenth lens (14) form the second cemented lens. The first cemented lens is a cemented doublet lens, and the second cemented lens is a cemented quadruplet lens.
[0070] Except for the aperture stop, all the lenses are made of optical glass.
[0071] Both the first lens 1 and the second lens 2 are meniscus lenses, with the centers of the spheres on both sides of the meniscus lens located on the image side, and the first lens 1 and the second lens 2 satisfy the following condition:
[0072] 1.12≤Ф2 / Ф1≤1.47
[0073] Where Ф1 is the optical power of the first lens 1 and Ф2 is the optical power of the first lens 2.
[0074] The third lens 3 is a meniscus lens, with the center of the sphere on both sides located on the image side;
[0075] The fourth lens 4 is a meniscus negative lens, with the center of the sphere on both sides located on the image side;
[0076] The third lens 3 and the fourth lens 4 form a cemented lens, which effectively compensates for the chromatic aberration of the first objective lens group and satisfies the following condition:
[0077] 0.97≤|Ф34 / Ф|≤1.34
[0078] Where Ф34 is the combined optical power of the third lens 3 and the fourth lens 4, and Ф is the total optical power of the system.
[0079] The fifth lens 5 is a biconcave lens with negative optical power.
[0080] Both the sixth lens 6 and the seventh lens 7 are biconvex lenses and both have positive optical power.
[0081] The sixth lens 6 and the seventh lens 7 are located on either side of the aperture stop, and satisfy the following condition:
[0082] 1.51 <N6<N7,
[0083] Wherein, N6 is the D-index of the sixth lens 6, and N7 is the D-index of the seventh lens 7.
[0084] The eighth lens 8 is a biconcave lens that moves along the optical axis to the image side during focusing and satisfies the following condition:
[0085] 0.63 < |Ф8 / Ф| < 0.89
[0086] Where Ф8 is the optical power of the eighth lens 8, and Ф is the total optical power of the system.
[0087] The ninth lens 9, the eleventh lens 11, and the thirteenth lens 13 are all biconvex lenses and satisfy the following condition:
[0088] Ф<Ф11<Ф13<Ф9,
[0089] Wherein, Ф9 is the optical power of the ninth lens 9, Ф11 is the optical power of the eleventh lens 11, Ф13 is the optical power of the thirteenth lens 13, and Ф is the total optical power of the system.
[0090] The tenth lens 10 is a meniscus negative lens, with the centers of both spheres on the image side; the twelfth lens 12 is a biconcave lens; the fourteenth lens 14 is a biconcave lens; and satisfies the following condition:
[0091] 0.004 < Ф14 < Ф10 < Ф12 < 0.021
[0092] Wherein, Ф10 is the optical power of the ninth lens 10, Ф12 is the optical power of the twelfth lens 12, and Ф14 is the optical power of the fourteenth lens 14.
[0093] The fifteenth lens 15 is an aspherical lens and satisfies the following condition:
[0094] |SAG151|>|SAG152|,
[0095] Wherein, SAG151 is the sagitta at the object-side aperture of the fifteenth lens 15, and SAG152 is the sagitta at the image-side aperture of the fifteenth lens 15.
[0096] Figure 2 This is a schematic diagram of field curvature distortion when focusing at infinity in Embodiment 1 of this utility model;
[0097] Figure 3 This is a schematic diagram of the axial chromatic aberration when focusing at infinity in Embodiment 1 of this utility model;
[0098] Figure 4 This is a schematic diagram of the field curvature distortion in Embodiment 1 of this utility model at a focal length of 0.8m;
[0099] Figure 5 This is a schematic diagram of the axial color difference in Embodiment 1 of this utility model when focusing at 0.8m;
[0100] Combination Figures 1-5 As shown, the optical system provided in Embodiment 1 of this utility model can achieve good imaging quality and realize high-performance design.
[0101] Table 1 shows the radius of curvature, thickness, refractive index, and Abbe number of each lens in the optical system within the scope of Example 1; the radius of curvature column shows the radius of curvature of a certain lens, where a positive radius of curvature indicates that the surface is curved towards the object side, and a negative radius of curvature indicates that the surface is curved towards the image side; the thickness column shows the surface spacing on the optical axis between each surface and the surface adjacent to it on the image side; the refractive index column shows the refractive index of a certain lens; and the Abbe number column shows the Abbe number of a certain lens.
[0102] Table 1 Parameters of each lens
[0103] Face number radius of curvature thickness Refractive index Abbe number 1 74.792 6.929 1.95906018 17.47243449 2 179.471 0.107 3 86.388 7.633 1.5168 64.19873179 4 470.512 0.107 5 44.795 9.754 1.49699999 81.61283821 6 894.533 1.599 1.95906018 17.47243449 7 40.778 9.840 8 -64.897 1.599 1.74077003 27.7600631 9 57.349 1.162 10 68.308 6.588 1.83481007 42.72517706 11 -116.466 1.599 12 INF 2.985 13 62.881 6.844 1.88299974 39.21820042 14 -762.703 D1 15 573.656 1.599 1.5168 64.19873179 16 38.059 D2 17 32.192 9.541 1.49699999 81.61283821 18 -131.492 0.107 19 83.013 2.964 1.84665713 23.78997194 20 27.613 2.111 21 32.023 10.224 1.5168 64.19873179 22 -24.746 1.066 1.54814001 45.82001118 23 31.398 7.921 1.84665713 23.78997194 24 -62.906 1.066 1.49699999 81.61283821 25 33.212 8.017 26* -82.262 2.452 1.80337004 45.49155657 27* -400.147 15.000 28 INF 2.000 1.5168 64.19873179 29 INF 0.500
[0104] The parameters of the aspherical lenses of the optical system within the scope of Example 1 are shown in Table 2;
[0105] Table 2 Parameters of Aspherical Lenses
[0106] 26 27 k 13.432 5.967 A4 -5.9066900E-05 -5.4465181E-05 A6 2.4596541E-08 7.2425048E-08 A8 3.7186310E-10 8.7340540E-11 A10 -2.5906276E-12 -9.2903373E-13 A12 7.0615355E-15 2.7822229E-15 A14 -2.0516225E-18 -1.7500675E-18
[0107] The position of the second objective lens group when focusing at different shooting distances is shown in Table 3, corresponding to D1 and D2 in Table 1;
[0108] Table 3 Position and status of the second objective lens group
[0109] Conjugate distance Infinity 0.8m D1 3.559 10.114 D2 9.067 2.512
[0110] The physical parameters of the optical system within the scope of Example 1 are shown in Table 4;
[0111] Table 4 Physical parameters of the optical system
[0112] focal length 85.97 Relative aperture F# 1.48 2w field of view 28.3° Overall optical length 134.6
[0113] This invention optimizes light refraction and convergence, reduces aberrations, and improves image quality by setting the positive and negative optical power of each lens group and the ratio between the combined focal length of each lens group and the combined focal length of the entire lens, thereby enabling the lens to achieve higher image quality.
[0114] The above description is only a preferred embodiment of the present utility model and is not intended to limit the scope of protection of the present utility model. Any modifications, equivalent substitutions and improvements made by those skilled in the art within the spirit and principles of the present utility model should be included within the scope of protection of the present utility model.
Claims
1. An optical system of a large aperture full-frame prime lens, characterized by: It includes a first objective lens group G1, a second objective lens group G2, and a third objective lens group G3. The first objective lens group G1, the second objective lens group G2, and the third objective lens group G3 are arranged sequentially from the object side to the image side along the optical axis, and the radial stop is located in the first objective lens group. During the focusing process, the second objective group G2 moves along the optical axis to the image side, while the positions of the first objective group G1, the aperture stop, and the third objective group G3 relative to the image plane remain unchanged. The optical system satisfies the following condition: 0.87≤FG1 / F≤1.25 0.62≤|FG2 / F|≤0.98, 0.7≤FG3 / F≤1.2; Wherein, FG1 represents the total focal length of the first objective lens group, FG2 represents the total focal length of the second objective lens group, FG3 represents the total focal length of the third objective lens group, and F represents the total focal length of the optical system.
2. The optical system of a large-aperture full-frame prime lens according to claim 1, wherein: The first objective lens group G1 includes: a first lens (1), a second lens (2), a third lens (3), a fourth lens (4), a fifth lens (5), a sixth lens (6), an aperture stop STP, and a seventh lens (7). The third lens (3) and the fourth lens (4) form the first cemented lens. The second objective group G2 includes an eighth lens (8); The third objective lens group G3 includes: the ninth lens (9), the tenth lens (10), the eleventh lens (11), the twelfth lens (12), the thirteenth lens (13), the fourteenth lens (14), and the fifteenth lens (15). The eleventh lens (11), the twelfth lens (12), the thirteenth lens (13), and the fourteenth lens (14) together form the second cemented lens.
3. The optical system of a large-aperture full-frame prime lens according to claim 2, wherein: Both the first lens (1) and the second lens (2) are meniscus lenses, with the centers of the spheres on both sides of the meniscus lens on the image side, and the first lens (1) and the second lens (2) satisfy the following condition: 1.12≤Ф2 / Ф1≤1.47 Where Ф1 is the optical power of the first lens (1) and Ф2 is the optical power of the second lens (2).
4. The optical system of a large-aperture full-plate standard lens according to claim 2, wherein: The third lens (3) is a meniscus lens, with the center of the sphere on both sides located on the image side; The fourth lens (4) is a meniscus negative lens, with the center of the sphere on both sides on the image side; The third lens (3) and the fourth lens (4) form a cemented lens, which effectively compensates for the chromatic aberration of the first objective lens group and satisfies the following condition: 0.97≤|Ф34 / Ф|≤1.34 Where Ф34 is the combined optical power of the third lens (3) and the fourth lens (4), and Ф is the total optical power of the system.
5. The optical system of a large-aperture full-plate standard lens according to claim 2, wherein: The fifth lens (5) is a biconcave lens with negative optical power.
6. The optical system of a large-aperture full-plate standard lens according to claim 2, wherein: The sixth lens (6) and the seventh lens (7) are both biconvex lenses and both have positive optical power; The sixth lens (6) and the seventh lens (7) are located on both sides of the aperture stop, and satisfy the following condition: 1.51 <N6<N7, Wherein, N6 is the D-index of the sixth lens (6), and N7 is the D-index of the seventh lens (7).
7. The optical system of a large-aperture full-plate standard lens according to claim 2, wherein: The eighth lens (8) is a biconcave lens that moves along the optical axis to the image side during focusing and satisfies the following condition: 0.63 < |Ф8 / Ф| < 0.89 Where Ф8 is the optical power of the eighth lens (8), and Ф is the total optical power of the system.
8. The optical system of a large-aperture full-plate standard lens according to claim 2, wherein: The ninth lens (9), eleventh lens (11), and thirteenth lens (13) are all biconvex lenses and satisfy the following condition: Ф<Ф11<Ф13<Ф9, Wherein, Ф9 is the optical power of the ninth lens (9), Ф11 is the optical power of the eleventh lens (11), Ф13 is the optical power of the thirteenth lens (13), and Ф is the total optical power of the system.
9. The optical system of a large-aperture full-plate standard lens according to claim 2, wherein: The tenth lens (10) is a meniscus negative lens, with the centers of both spheres on the image side; the twelfth lens (12) is a biconcave lens; the fourteenth lens (14) is a biconcave lens; and satisfies the following condition: 0.004 < Ф14 < Ф10 < Ф12 < 0.021 Wherein, Ф10 is the optical power of the tenth lens (10), Ф12 is the optical power of the twelfth lens (12), and Ф14 is the optical power of the fourteenth lens (14).
10. The optical system of a large-aperture full-plate standard lens according to claim 2, wherein: The fifteenth lens (15) is an aspherical lens and satisfies the following condition: |SAG151|>|SAG152|, Wherein, SAG151 is the sag at the object-side aperture of the fifteenth lens (15), and SAG152 is the sag at the image-side aperture of the fifteenth lens (15).