An optical system of a large aperture half-frame fixed focus lens
By optimizing the lens combination design of the large-aperture APS-C prime lens, the problem of insufficient image quality was solved, achieving high image quality and stable imaging effects.
Patent Information
- Application Number
- CN202610380960.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-03-26
- Publication Date
- 2026-06-26
AI Technical Summary
The image quality of existing large-aperture APS-C prime lenses needs improvement, especially since aberrations fluctuate significantly when in focus, affecting image quality.
Design an optical system for a large-aperture APS-C fixed-focus lens, with a first objective lens group, a second objective lens group, and a third objective lens group arranged along the optical axis. The refraction and convergence of light are optimized by the positive and negative optical powers of the lens groups and the ratio of the combined focal length. The second objective lens group moves during the focusing process, while the third objective lens group remains unchanged. The lens groups are combined into a cemented lens for dispersion compensation.
It effectively suppresses spherical aberration, coma, and chromatic aberration, improves image quality, achieves high image quality, and features fast focusing and stable image plane.
Smart Images
Figure CN122284059A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of optical lens technology, specifically to an optical system for a large-aperture APS-C fixed-focus lens. Background Technology
[0002] In the field of photography, the 35mm focal length combined with the perspective effect of a half-frame camera is very close to that of the human eye. This natural perspective can realistically reproduce the scene, avoiding the distortion of wide-angle lenses and the spatial compression of telephoto lenses. The scene is an important means to set off the characters, tell a story, and express emotions. The F1.2 large aperture can meet the needs of shooting in low-light environments. At the same time, it can achieve a soft background blur through shallow depth of field, creating a dreamy atmosphere and enhancing the sense of layering in the picture. For this reason, its unique advantages have gradually been favored by a large number of photography enthusiasts.
[0003] Large apertures easily introduce aberrations such as spherical aberration and chromatic aberration, affecting image quality. Moreover, the movement of the lens group during focusing can cause aberration fluctuations, affecting image quality. As photography enthusiasts have increasingly higher requirements for image quality, the image quality of current large aperture APS-C prime lenses needs to be improved. Therefore, it is necessary to design an optical system for large aperture APS-C prime lenses to improve the above-mentioned problems. Summary of the Invention
[0004] In view of the shortcomings of the existing technology, the purpose of this invention is to provide an optical system for a large aperture APS-C fixed-focus lens, which solves the problem that the imaging quality of current large aperture APS-C fixed-focus lenses needs to be improved.
[0005] To achieve the above objectives, the present invention provides the following technical solution: An optical system for a large aperture APS-C fixed-focus lens, wherein a first objective lens group, a second objective lens group and a third objective lens group are arranged sequentially from the object side to the image side along the optical axis, and an aperture stop is provided in the first objective lens group. During the focusing process, the second objective lens group moves along the optical axis to the object side, while the positions of the first objective lens group, the aperture stop, and the third objective lens group relative to the image plane remain unchanged. The optical system satisfies the following condition: 1.18≤|FGR1 / F|≤1.32 1.426≤|FGR2 / F|≤1.734 1.012≤|FGR3 / F|≤1.328 Wherein, FGR1 is the total focal length of the first objective lens group, FGR2 is the total focal length of the second objective lens group, FGR3 is the total focal length of the third objective lens group, and F is the total focal length of the optical system.
[0006] Preferably, the first objective lens group includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, an aperture stop, a sixth lens, a seventh lens, and an eighth lens, with the aperture stop located between the seventh lens and the eighth lens; The second objective lens group includes a ninth lens; The third objective lens group includes the tenth lens, the eleventh lens, the twelfth lens, the thirteenth lens, the fourteenth lens, and the fifteenth lens.
[0007] Preferably, both the first lens and the eighth lens are positive lenses, and the first lens and the eighth lens satisfy the following condition: 1.215≤Ф8 / Ф1≤1.426 Where Ф1 is the optical power of the first lens and Ф8 is the optical power of the eighth lens.
[0008] Preferably, the fourth and sixth lenses are both negative lenses, and the fifth and seventh lenses are both positive lenses, belonging to the category of biconvex lenses. The fourth and fifth lenses form a first cemented lens, and the sixth and seventh lenses form a second cemented lens, satisfying the following condition: 1.952<|ФGR1 / Ф45|<|ФGR1 / Ф67|<2.143 0.953 < |Ф45 / Ф67| < 1.214 Wherein ФGR1 is the optical power of the first objective lens group, Ф45 is the optical power of the first cemented lens composed of the fourth and fifth lenses, and Ф67 is the optical power of the second cemented lens composed of the sixth and seventh lenses.
[0009] Preferably, the third lens is a positive lens, specifically a meniscus lens, with the centers of both spheres located on the image side, satisfying the following condition: 0.254 < |ФGR1 / Ф3| < 0.362 Where ФGR1 is the optical power of the first objective lens group, and Ф3 is the optical power of the third lens.
[0010] Preferably, the second lens is a negative lens, belonging to a biconcave lens, and satisfies the following condition: 1.024 < |ФGR1 / Ф2| < 1.265 Where ФGR1 is the optical power of the first objective lens group and Ф2 is the optical power of the second lens.
[0011] Preferably, the ninth lens is a negative lens, belonging to the biconcave lens category, and satisfies the following condition: 0.523|Ф / Ф9|<0.687 Where Ф is the total optical power of the optical system, and Ф9 is the optical power of the ninth lens.
[0012] Preferably, the tenth lens, twelfth lens, and thirteenth lens are all positive lenses, satisfying the following condition: 1.487 <N12<N10<N13<1.9537 17.47 <V13<V10<V12<81.613 Wherein N10 is the refractive index of the material of the tenth lens relative to D light, N12 is the refractive index of the material of the twelfth lens relative to D light, and N13 is the refractive index of the material of the thirteenth lens relative to D light; V10 is the Abbe number of the material of the tenth lens relative to D light, V12 is the Abbe number of the material of the twelfth lens relative to D light, and V13 is the Abbe number of the material of the thirteenth lens relative to D light.
[0013] Preferably, the eleventh, fourteenth, and fifteenth lenses are all negative lenses, the eleventh and fifteenth lenses are biconcave lenses, and the fifteenth lens is aspherical, satisfying the following condition: 1.624 <N14<N11<N15<2.0007 25.471 <V11<V15<V14<34.465 Wherein N11 is the refractive index of the material of the eleventh lens relative to D light, N14 is the refractive index of the material of the fourteenth lens relative to D light, and N15 is the refractive index of the material of the fifteenth lens relative to D light. V11 is the Abbe number of the material of the eleventh lens relative to D light, V14 is the Abbe number of the material of the fourteenth lens relative to D light, and V15 is the Abbe number of the material of the fifteenth lens relative to D light.
[0014] Preferably, the tenth lens, the eleventh lens, and the twelfth lens form the third cemented lens, satisfying the following condition: 1.741 < |ФGR3 / Ф101112| < 1.862 Wherein ФGR3 is the optical power of the third objective lens group, and Ф101112 is the optical power of the third cemented lens composed of the tenth lens, the eleventh lens, and the twelfth lens.
[0015] Compared with the prior art, the beneficial effects of the present invention are: 1. The optical system of the large aperture APS-C fixed-focus lens of the present invention optimizes the refraction and convergence of light, balances aberrations, and improves 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.
[0016] 2. This invention utilizes a collaborative design of three objective lens groups: the first objective lens group is fixed to handle the main optical power, the second objective lens group is used for floating focus, and the third objective lens group balances aberrations, effectively suppressing spherical aberration, coma, and chromatic aberration at a large aperture of F1.2.
[0017] 3. The dispersion compensation design of the first cemented lens composed of the fourth and fifth lenses, the second cemented lens composed of the sixth and seventh lenses, and the third cemented lens composed of the tenth, eleventh, and twelfth lenses in the first objective lens group of the present invention significantly reduces magnification chromatic aberration and improves edge image quality.
[0018] 4. In this invention, only the ninth lens in the second objective lens group moves during focusing, effectively reducing the weight of the focusing group and making focusing faster. The focal ratio (|D6 / Ф6|∈[1.69,1.85]) and optical power condition (1.426<|Ф / Ф9|<1.734) of the second objective lens group ensure the stability of the image plane during focusing. 5. The fifteenth lens in the third objective lens group of this invention is designed as an aspherical lens, which can effectively compensate for system field curvature and distortion.
[0019] 6. The cemented lens design composed of the fourth lens, the fifth lens, the sixth lens, and the seventh lens in this invention, wherein the fifth lens and the seventh lens are made of the same material, can achieve the effect of achromatic correction. Attached Figure Description
[0020] Figure 1 This is a schematic diagram of the optical system structure of the large aperture APS-C fixed-focus lens of the present invention; Figure 2 This is a schematic diagram of the field curvature distortion when focusing at infinity according to the present invention; Figure 3 This is a schematic diagram of axial chromatic aberration during infinity focusing according to the present invention; Figure 4 This is a schematic diagram of the field curvature distortion of the present invention at a focusing depth of 0.35m; Figure 5 This is a schematic diagram of the axial color difference when the focus is at 0.35m according to the present invention.
[0021] In the diagram: GR1, first objective lens group; GR2, second objective lens group; GR3, third objective lens group; G1, first lens; G2, second lens; G3, third lens; G4, fourth lens; G5, fifth lens; G6, sixth lens; G7, seventh lens; G8, eighth lens; G9, ninth lens; G10, tenth lens; G11, eleventh lens; G12, twelfth lens; G13, thirteenth lens; G14, fourteenth lens; G15, fifteenth lens. Detailed Implementation
[0022] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention. Example
[0023] Please see Figures 1-5 This embodiment provides an optical system for a large aperture APS-C fixed-focus lens. The optical system has a first objective lens group GR1, a second objective lens group GR2 and a third objective lens group GR3 arranged sequentially from the object side to the image side along the optical axis. An aperture stop is provided in the first objective lens group GR1. During the focusing process, the second objective group GR2 moves along the optical axis to the object side, while the positions of the first objective group GR1, the aperture stop, and the third objective group GR3 relative to the image plane remain unchanged. The optical system satisfies the following condition: 1.18≤|FGR1 / F|≤1.32 1.426≤|FGR2 / F|≤1.734 1.012≤|FGR3 / F|≤1.328 Wherein, FGR1 is the total focal length of the first objective lens group GR1, FGR2 is the total focal length of the second objective lens group GR2, FGR3 is the total focal length of the third objective lens group GR3, and F is the total focal length of the optical system.
[0024] In this embodiment, the first objective lens group GR1 includes a first lens G1, a second lens G2, a third lens G3, a fourth lens G4, a fifth lens G5, an aperture stop, a sixth lens G6, a seventh lens G7, and an eighth lens G8, with the aperture stop located between the seventh lens G7 and the eighth lens G8. The second objective group GR2 includes the ninth lens G9; The third objective group GR3 includes the tenth lens G10, the eleventh lens G11, the twelfth lens G12, the thirteenth lens G13, the fourteenth lens G14, and the fifteenth lens G15.
[0025] In this embodiment, both the first lens G1 and the eighth lens G8 are positive lenses, and the first lens G1 and the eighth lens G8 satisfy the following condition: 1.215≤Ф8 / Ф1≤1.426 Where Ф1 is the optical power of the first lens G1, and Ф8 is the optical power of the eighth lens G8.
[0026] In this embodiment, the fourth lens G4 and the sixth lens G6 are both negative lenses, and the fifth lens G5 and the seventh lens G7 are both positive lenses, belonging to the biconvex lens category. The fourth lens G4 and the fifth lens G5 form the first cemented lens, and the sixth lens G6 and the seventh lens G7 form the second cemented lens, satisfying the following condition: 1.952<|ФGR1 / Ф45|<|ФGR1 / Ф67|<2.143 0.953 < |Ф45 / Ф67| < 1.214 Wherein ФGR1 is the optical power of the first objective lens group GR1, Ф45 is the optical power of the first cemented lens composed of the fourth lens G4 and the fifth lens G5, and Ф67 is the optical power of the second cemented lens composed of the sixth lens G6 and the seventh lens G7.
[0027] In this embodiment, the third lens G3 is a positive lens, specifically a meniscus lens, with the centers of both spheres located on the image side, satisfying the following condition: 0.254 < |ФGR1 / Ф3| < 0.362 Where ФGR1 is the optical power of the first objective lens group GR1, and Ф3 is the optical power of the third lens G3.
[0028] In this embodiment, the second lens G2 is a negative lens, belonging to a biconcave lens, and satisfies the following condition: 1.024 < |ФGR1 / Ф2| < 1.265 Where ФGR1 is the optical power of the first objective lens group GR1, and Ф2 is the optical power of the second lens G2.
[0029] In this embodiment, the ninth lens G9 is a negative lens, belonging to the biconcave lens category, and satisfies the following condition: 0.523|Ф / Ф9|<0.687 Where Ф represents the total optical power of the optical system, and Ф9 represents the optical power of the ninth lens G9.
[0030] In this embodiment, the tenth lens G10, the twelfth lens G12, and the thirteenth lens G13 are all positive lenses, satisfying the following condition: 1.487 <N12<N10<N13<1.9537 17.47 <V13<V10<V12<81.613 Where N10 is the refractive index of the material of the tenth lens G10 relative to D light, N12 is the refractive index of the material of the twelfth lens G12 relative to D light, and N13 is the refractive index of the material of the thirteenth lens G13 relative to D light. V10 is the Abbe number of the material of the tenth lens G10 relative to D light, V12 is the Abbe number of the material of the twelfth lens G12 relative to D light, and V13 is the Abbe number of the material of the thirteenth lens G13 relative to D light.
[0031] In this embodiment, the eleventh lens G11, the fourteenth lens G14, and the fifteenth lens G15 are all negative lenses. The eleventh lens G11 and the fifteenth lens G15 are biconcave lenses, and the fifteenth lens G15 is an aspherical surface, satisfying the following condition: 1.624 <N14<N11<N15<2.0007 25.471 <V11<V15<V14<34.465 Where N11 is the refractive index of the material of the eleventh lens G11 relative to D light, N14 is the refractive index of the material of the fourteenth lens G14 relative to D light, and N15 is the refractive index of the material of the fifteenth lens G15 relative to D light. V11 is the Abbe number of the material of the eleventh lens G11 relative to D light, V14 is the Abbe number of the material of the fourteenth lens G14 relative to D light, and V15 is the Abbe number of the material of the fifteenth lens G15 relative to D light.
[0032] In this embodiment, the tenth lens G10, the eleventh lens G11, and the twelfth lens G12 form the third cemented lens, satisfying the following condition: 1.741 < |ФGR3 / Ф101112| < 1.862 Where ФGR3 is the optical power of the third objective lens group GR3, and Ф101112 is the optical power of the third cemented lens composed of the tenth lens G10, the eleventh lens G11, and the twelfth lens G12.
[0033] Combination Figures 1-5 As shown, the optical system provided in this embodiment of the invention can achieve good imaging quality and realize high-performance design.
[0034] As a preferred embodiment of the technical solution, the parameters of the optical system of the large aperture APS-C fixed focal length lens embodiment are shown in Tables 1, 2, 3, and 4. Table 1 shows the radius of curvature, thickness, refractive index, and Abbe number of each lens in the optical system within the scope of the embodiments; 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 its adjacent surface 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. Table 1 Parameters of each lens Face number radius of curvature Thickness / Gap Refractive index Abbe number 1 60.513 4.868 1.9460 17.9420 2 -1139.191 2.258 3 -1644.553 1.300 1.5168 64.1987 4 19.774 3.104 5 81.338 2.872 1.8040 46.5745 6 256.88 3.579 7 -26.237 1.791 1.6477 33.8403 8 39.737 7.631 1.8040 46.5745 9 -28.303 2.568 10 -23.016 1.200 1.8467 23.7845 11 Infinite 6.359 1.8040 46.5745 12 -35.6 1.300 13 Infinite 1.800 14 80.19 6.450 1.8040 46.5745 15 -64.928 D1 16 -290.372 1.200 1.5168 64.1987 17 30.518 D2 18 30.819 10.768 1.6936 49.1938 19 -25.083 1.200 1.7408 27.7601 20 22.349 7.313 1.4970 81.6054 21 -195.418 0.100 22 32.934 5.850 1.9460 17.9420 23 -102.724 0.100 24 106.099 1.000 1.6477 33.8880 25 22.698 4.631 26* -132.304 2.000 1.9537 32.2762 27* -985.04 Table 2 Parameters of Aspherical Lenses 26 27 K 93.31004 87.37665 A2 0 0 A4 -5.9068697e-06 1.1863127e-05 A6 3.5876698e-08 -6.0814386e-08 A8 -3.5329518e-10 1.8441533e-09 A10 2.6569858e-12 -2.1364607e-11 A12 -1.1788456e-15 1.3265833e-13 A14 -1.5174556e-17 -3.2683296e-16 A16 0 0 Table 3 shows the position of the second objective lens group GR2 when focusing at different shooting distances, corresponding to D1 and D2 in Table 1: Table 3 Conjugate distance Infinity 0.35m D1 1 8.4906 D2 8.5094 0.9812 The physical parameters of the optical system of the large-aperture APS-C fixed-focus lens in this embodiment are shown in Table 4: Table 4 focal length 34.43 Relative aperture F# 1.2 2w field of view 44.53° Overall optical length 107.5 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.
[0035] The above embodiments are preferred implementations of the present invention. In addition, the present invention can be implemented in other ways. Any obvious substitutions without departing from the concept of the present technical solution are within the protection scope of the present invention.
Claims
1. An optical system for a large-aperture APS-C fixed-focus lens, characterized in that, The optical system is provided with a first objective lens group (GR1), a second objective lens group (GR2) and a third objective lens group (GR3) arranged sequentially from the object side to the image side along the optical axis. The first objective lens group (GR1) is provided with an aperture stop. During the focusing process, the second objective lens group (GR2) moves along the optical axis to the object side, while the positions of the first objective lens group (GR1), the aperture stop, and the third objective lens group (GR3) relative to the image plane remain unchanged. The optical system satisfies the following condition: 1.18≤|FGR1 / F|≤1.32 1.426≤|FGR2 / F|≤1.734 1.012≤|FGR3 / F|≤1.328 Wherein, FGR1 is the total focal length of the first objective lens group (GR1), FGR2 is the total focal length of the second objective lens group (GR2), FGR3 is the total focal length of the third objective lens group (GR3), and F is the total focal length of the optical system.
2. The optical system of a large aperture APS-C fixed-focus lens according to claim 1, characterized in that, The first objective lens group (GR1) includes a first lens (G1), a second lens (G2), a third lens (G3), a fourth lens (G4), a fifth lens (G5), an aperture stop, a sixth lens (G6), a seventh lens (G7), and an eighth lens (G8), with the aperture stop located between the seventh lens (G7) and the eighth lens (G8). The second objective lens group (GR2) includes a ninth lens (G9); The third objective lens group (GR3) includes the tenth lens (G10), the eleventh lens (G11), the twelfth lens (G12), the thirteenth lens (G13), the fourteenth lens (G14), and the fifteenth lens (G15).
3. The optical system of a large aperture APS-C fixed-focus lens according to claim 2, characterized in that, Both the first lens (G1) and the eighth lens (G8) are positive lenses, and both satisfy the following condition: 1.215≤Ф8 / Ф1≤1.426 Where Ф1 is the optical power of the first lens (G1) and Ф8 is the optical power of the eighth lens (G8).
4. The optical system of a large-aperture APS-C fixed-focus lens according to claim 2, characterized in that, The fourth lens (G4) and the sixth lens (G6) are both negative lenses, and the fifth lens (G5) and the seventh lens (G7) are both positive lenses, belonging to the biconvex lens category. The fourth lens (G4) and the fifth lens (G5) form the first cemented lens, and the sixth lens (G6) and the seventh lens (G7) form the second cemented lens, satisfying the following condition: 1.952<|ФGR1 / Ф45|<|ФGR1 / Ф67|<2.143 0.953 < |Ф45 / Ф67| < 1.214 Wherein ФGR1 is the optical power of the first objective lens group (GR1), Ф45 is the optical power of the first cemented lens composed of the fourth lens (G4) and the fifth lens (G5), and Ф67 is the optical power of the second cemented lens composed of the sixth lens (G6) and the seventh lens (G7).
5. The optical system of a large aperture APS-C fixed-focus lens according to claim 2, characterized in that, The third lens (G3) is a positive lens, specifically a meniscus lens, with the centers of both spheres located on the image side, satisfying the following condition: 0.254 < |ФGR1 / Ф3| < 0.362 Wherein ФGR1 is the optical power of the first objective lens group (GR1), and Ф3 is the optical power of the third lens (G3).
6. The optical system of a large-aperture APS-C fixed-focus lens according to claim 2, characterized in that, The second lens (G2) is a negative lens, belonging to the biconcave lens category, and satisfies the following condition: 1.024 < |ФGR1 / Ф2| < 1.265 Where ФGR1 is the optical power of the first objective lens group (GR1), and Ф2 is the optical power of the second lens (G2).
7. The optical system of a large-aperture APS-C fixed-focus lens according to claim 2, characterized in that, The ninth lens (G9) is a negative lens, belonging to the biconcave lens category, and satisfies the following condition: 0.523|Ф / Ф9|<0.687 Where Ф is the total optical power of the optical system, and Ф9 is the optical power of the ninth lens (G9).
8. The optical system of a large-aperture APS-C fixed-focus lens according to claim 2, characterized in that, The tenth lens (G10), twelfth lens (G12), and thirteenth lens (G13) are all positive lenses, satisfying the following condition: 1.487 <N12<N10<N13<1.9537 17.47 <V13<V10<V12<81.613 Wherein N10 is the refractive index of the material of the tenth lens (G10) relative to D light, N12 is the refractive index of the material of the twelfth lens (G12) relative to D light, and N13 is the refractive index of the material of the thirteenth lens (G13) relative to D light. V10 is the Abbe number of the material of the tenth lens (G10) relative to D light, V12 is the Abbe number of the material of the twelfth lens (G12) relative to D light, and V13 is the Abbe number of the material of the thirteenth lens (G13) relative to D light.
9. The optical system of a large aperture APS-C fixed-focus lens according to claim 2, characterized in that, The eleventh lens (G11), fourteenth lens (G14), and fifteenth lens (G15) are all negative lenses. The eleventh lens (G11) and fifteenth lens (G15) are biconcave lenses. The fifteenth lens (G15) is aspherical and satisfies the following condition: 1.624 <N14<N11<N15<2.0007 25.471 <V11<V15<V14<34.465 Wherein N11 is the refractive index of the material of the eleventh lens (G11) relative to D light, N14 is the refractive index of the material of the fourteenth lens (G14) relative to D light, and N15 is the refractive index of the material of the fifteenth lens (G15) relative to D light. V11 is the Abbe number of the material of the eleventh lens (G11) relative to D light, V14 is the Abbe number of the material of the fourteenth lens (G14) relative to D light, and V15 is the Abbe number of the material of the fifteenth lens (G15) relative to D light.
10. The optical system of a large aperture APS-C fixed-focus lens according to claim 2, characterized in that, The tenth lens (G10), the eleventh lens (G11), and the twelfth lens (G12) together form the third cemented lens, satisfying the following condition: 1.741 < |ФGR3 / Ф101112| < 1.862 Wherein ФGR3 is the optical power of the third objective lens group (GR3), and Ф101112 is the optical power of the third cemented lens composed of the tenth lens (G10), the eleventh lens (G11), and the twelfth lens (G12).