Photographic large-aperture optical lens

Abstract

The invention discloses a photographing large-aperture optical lens, which relates to the technical field of optical lenses and comprises a first lens group, a second lens group, a third lens group, a fourth lens group and a fifth lens group which are sequentially arranged from an object side to an image side along an optical axis, the first lens group has negative focal power, the second lens group has positive focal power, the third lens group has positive focal power, the fourth lens group has negative focal power, and the fifth lens group has positive focal power; the lens group satisfies the following conditional expressions:-3.5 < = F1 / F < =-1, 3.0 < = F2 / F < = 4.0, 6.5 < = F3 / F < = 10.0,-3.5 < = F4 / F < =-1.0, and 0.8 < = F5 / F < = 2.5. According to the photographing large-aperture optical lens, on the premise that the same optical performance is met, the used aperture is larger, the number of the lenses is small, and the cost is low.

Description

Technical Field

[0001] The present invention relates to the technical field of optical lenses, and in particular to a large aperture optical lens for photography. Background Art

[0002] Some existing large-aperture optical lenses for photography have a lens group structure with a large number of lenses and high costs. After reducing the number of lenses, the performance is poor at large apertures and the resolution is low.

[0003] For example, in the document with publication number US2018031813A1, the disclosed embodiments three and four have high costs under similar performance, while in the document with publication number US2022001542A1, multiple embodiments have small apertures under similar parameters and high costs. Summary of the invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention provides a large aperture optical lens for photography, which, under the premise of satisfying the same optical performance, uses a larger aperture, fewer lenses and lower costs.

[0005] A large aperture optical lens for photography according to an embodiment of the present invention comprises a first lens group, a second lens group, a third lens group, a fourth lens group and a fifth lens group arranged in sequence from the object side to the image side along the optical axis; The first lens group has negative optical power, the second lens group has positive optical power, the third lens group has positive optical power, the fourth lens group has negative optical power, and the fifth lens group has positive optical power; The fourth lens group includes at least one aspherical lens, and the fifth lens group includes at least one aspherical lens; The first lens group, the second lens group, the third lens group, the fourth lens group and the fifth lens group respectively satisfy the following conditional expressions: -3.5≤F1 / F≤-1, 3.0≤F2 / F≤4.0, 6.5≤F3 / F≤10.0, -3.5≤F4 / F≤-1.0, 0.8≤F5 / F≤2.5, in, F1: focal length of the first lens group; F2: focal length of the second lens group; F3: focal length of the third lens group; F4: focal length of the fourth lens group; F5: focal length of the fifth lens group; F: is the focal length of the large aperture optical lens for photography.

[0006] The large aperture optical lens for photography according to the embodiment of the present invention has at least the following beneficial effects: the first lens group satisfies the conditional formula and has appropriate refractive power, which will not increase the refractive power of the second lens group, and the off-axis aberration is easy to balance and correct, and the aperture of the first lens group can be controlled to avoid the large size of the entire lens; the second lens group satisfies the conditional formula, which can reduce the burden of axial aberration correction at the rear end, has better performance under large aperture, and the off-axis aberration is easy to balance and correct; the third lens group satisfies the conditional formula and has appropriate refractive power, so that the light height changes little during the focusing process of the fourth lens group at different object distances, reducing the aberration correction burden of the focusing group; the fourth lens group is used as the focusing group, the fourth lens group satisfies the conditional formula, the light angle changes moderately, and has an appropriate focus displacement, which is beneficial to controlling the aperture of the first lens group and preventing the lens volume from increasing; the fifth lens group satisfies the conditional formula, also has appropriate refractive power, and is beneficial to controlling off-axis aberrations.

[0007] According to some embodiments of the present invention, the first lens group includes three lenses, and the first lens group includes at least one lens that satisfies the following conditional formula: Nd≥1.8, Wherein, Nd is the refractive index of the lens material when transmitting light with a wavelength of 587.56 nm.

[0008] According to some embodiments of the present invention, from the object side to the image side, the first lens group sequentially includes a first lens with positive optical power, a second lens with negative optical power, and a third lens with negative optical power.

[0009] According to some embodiments of the present invention, from the object side to the image side, the second lens group sequentially includes a fourth lens having negative optical power, a fifth lens having positive optical power, and a sixth lens having positive optical power.

[0010] According to some embodiments of the present invention, the fourth lens group includes only one lens with positive optical power, and the lens is an aspherical lens.

[0011] According to some embodiments of the present invention, the aspheric curve driving equation of the aspheric lens in the fourth lens group and / or the fifth lens group is as follows: , in, R: is the radius of curvature of the aspheric surface; Y: radial coordinate; K: is the cone coefficient of the quadratic surface; Z: is the sagittal height of the surface along the optical axis; A: 4th order aspheric coefficient; B: 6th order aspheric coefficient; C: 8th order aspheric coefficient; D: is the 10th order aspheric coefficient.

[0012] According to some embodiments of the present invention, the fifth lens group sequentially includes a seventh lens with positive power, an eighth lens with negative power, a ninth lens with positive power, and a tenth lens with negative power.

[0013] According to some embodiments of the present invention, the third lens group includes only one lens with positive optical power.

[0014] According to some embodiments of the present invention, during the focusing process from infinity to close distance on the object side, the fourth lens group moves along the optical axis toward the image side.

[0015] According to some embodiments of the present invention, an aperture stop is provided between the second lens group and the third lens group.

[0016] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The present invention will be further described below with reference to the accompanying drawings and embodiments, wherein: Figure 1 This is a schematic diagram of the lens arrangement structure when the large aperture optical lens for photography according to an embodiment of the present invention is at the Far end; Figure 2 It is a schematic diagram of the lens arrangement structure when the large aperture optical lens for photography according to an embodiment of the present invention is at the Near end; Figure 3 for Figure 1 Spherical aberration diagram of lens position; Figure 4 for Figure 1 Astigmatism field curvature plot for lens position; Figure 5 for Figure 1 Distortion map of lens position; Figure 6 for Figure 1 MTFvsField diagram of the lens position; Figure 7 for Figure 2 Spherical aberration diagram of lens position; Figure 8 for Figure 2 Astigmatism field curvature plot for lens position; Fig. 9 for Figure 2 Distortion map of lens position; Fig.10 for Figure 2 MTFvsField plot for the lens position.

[0018] Figure Number: The first lens group 100 , the second lens group 200 , the third lens group 300 , the fourth lens group 400 , and the fifth lens group 500 . DETAILED DESCRIPTION

[0019] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0020] In the description of the present invention, it should be understood that descriptions involving orientation, such as orientation or positional relationship indicated as up, down, etc., are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0021] In the description of the present invention, "a plurality" means more than two. If there is a description of "first" or "second", it is only used for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0022] In the description of the present invention, unless otherwise clearly defined, terms such as setting, installing, connecting, etc. should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in the present invention based on the specific content of the technical solution.

[0023] Some existing large-aperture optical lenses for photography have a lens group structure with a large number of lenses and high costs. After reducing the number of lenses, the performance is poor at large apertures and the resolution is low.

[0024] For example, in the document with publication number US2018031813A1, the disclosed embodiments three and four have high costs under similar performance, while in the document with publication number US2022001542A1, multiple embodiments have small apertures under similar parameters and high costs.

[0025] Reference Figure 1 As shown, a large aperture optical lens for photography according to an embodiment of the present invention comprises a first lens group 100, a second lens group 200, a third lens group 300, a fourth lens group 400 and a fifth lens group 500 which are sequentially arranged from the object side to the image side along the optical axis; The first lens group 100 has negative power, the second lens group 200 has positive power, the third lens group 300 has positive power, the fourth lens group 400 has negative power, and the fifth lens group 500 has positive power; The fourth lens group 400 includes at least one aspherical lens, and the fifth lens group 500 includes at least one aspherical lens; The first lens group 100, the second lens group 200, the third lens group 300, the fourth lens group 400 and the fifth lens group 500 respectively satisfy the following conditional expressions: -3.5≤F1 / F≤-1(1), 3.0≤F2 / F≤4.0(2) 6.5≤F3 / F≤10.0(3) -3.5≤F4 / F≤-1.0(4) 0.8≤F5 / F≤2.5(5) in, F1: is the lens group focal length of the first lens group 100; F2: is the lens group focal length of the second lens group 200; F3: is the lens group focal length of the third lens group 300; F4: is the lens group focal length of the fourth lens group 400; F5: is the lens group focal length of the fifth lens group 500; F: is the focal length of the large aperture optical lens for photography.

[0026] Under the premise of satisfying the same optical performance, the large aperture optical lens for photography that meets the conditional formula has a larger aperture, fewer lenses and lower cost. The first lens group 100 that meets the conditional formula (1) will have a suitable refractive power, which will not increase the refractive power of the second lens group 200, and the off-axis aberration is easy to balance and correct, and the aperture of the first lens group 100 can be controlled to avoid the entire lens being large in size. The second lens group 200 that meets the conditional formula (2) can reduce the burden of on-axis aberration correction at the rear end, and has better performance at a large aperture, and the off-axis aberration is easy to balance and correct. Balance correction; the third lens group 300 satisfies the conditional expression (3) and has a suitable refractive power, so that the light height of the fourth lens group 400 changes little during the focusing process at different object distances, reducing the aberration correction burden of the focusing group; the fourth lens group 400 is used as the focusing group, the fourth lens group 400 satisfies the conditional expression, the light angle changes moderately, and has a suitable focus displacement, which is beneficial to controlling the aperture of the first lens group 100 and preventing the lens volume from increasing; the fifth lens group 500 satisfies the conditional expression, also has a suitable refractive power, and is beneficial to controlling off-axis aberrations.

[0027] More specifically, if the data of the first lens group 100 is less than the lower limit of the conditional expression (1), the refractive power of the first lens group 100 will be reduced, which will lead to an increase in the diameter of the first lens group 100, which is not conducive to the miniaturization of the volume of the first lens group 100. The diameter of the first lens group 100 refers to the size of the largest lens in the lens group. If the data of the first lens group 100 is greater than the upper limit of the conditional expression (1), the refractive power of the first lens group 100 will increase. Although the size of the first lens group 100 can be reduced, the trend of the emitted light of the first lens group 100 will become steeper, which will simultaneously increase the refractive power of the second lens group 200, making it difficult to balance and correct the off-axis aberration.

[0028] If the data of the second lens group 200 is greater than the upper limit of conditional expression (2), the refractive power of the second lens group 200 will decrease, which will lead to a decrease in the refractive power of the first lens group 100, causing the lens diameter of the first lens group 100 to increase, while increasing the correction burden of the rear end axial aberration, and ultimately making it difficult to improve the performance at a large aperture. If the data of the second lens group 200 is less than the lower limit of conditional expression (2), the refractive power of the second lens group 200 will further increase, resulting in a steeper trend of the light passing through the second lens group 200, and it will become difficult to balance and correct the off-axis aberration.

[0029] If the data of the third lens group 300 is greater than the upper limit of the conditional expression (3), the refractive power of the third lens group 300 will be further weakened, which will cause the refractive power of the second lens group 200 to increase, and the light near the object surface will be too steep, making it difficult to correct the on-axis aberration. If the data of the third lens group 300 is less than the lower limit of the conditional expression (3), the refractive power of the third lens group 300 will be further enhanced, which will cause the refractive power of the second lens group 200 to be weakened. At the same time, the aperture of the first lens group 100 will increase, and the emitted light of the third lens group 300 will be steeper. In addition, the height change of the light during the focusing process of the fourth lens group 400 at different object distances will increase, and the aberration correction burden of the focusing group will be increased.

[0030] Preferably, an aperture stop 600 is provided between the second lens group 200 and the third lens group 300 .

[0031] In some embodiments, the fourth lens group 400 is used as a focusing group. If the data of the fourth lens group 400 is greater than the upper limit of the conditional expression (4), the refractive power of the fourth lens group 400 will be further increased. Although the displacement of the fourth lens group 400 will be reduced during the change of the object distance, the angle change of the light will be more drastic, that is, the sensitivity will be increased, and the difficulty of correcting the off-axis aberration of the fifth lens group 500 will be increased. If the data of the fourth lens group 400 is less than the lower limit of the conditional expression (4), the refractive power of the fourth lens group 400 will be further reduced. The displacement of the fourth lens group 400 will be increased during the change of the object distance, and the aperture of the first lens group 100 will be increased, which is not conducive to the miniaturization of the lens.

[0032] If the data of the fifth lens group 500 is greater than the upper limit of conditional expression (5), the refractive power of the fifth lens group 500 will be further weakened. Although the off-axis aberration can be well balanced, it will lead to a higher light height, which will increase the aperture of the first lens group 100 at the front end, which is not conducive to the miniaturization of the lens. If the data of the fifth lens group 500 is less than the lower limit of conditional expression (5), the refractive power of the fifth lens group 500 will be further increased, which will aggravate the asymmetry of the off-axis light with respect to the main light and increase the off-axis aberration.

[0033] Further, it can be understood that the first lens group 100 includes three lenses, and the first lens group 100 includes at least one lens that satisfies the following conditional formula: Nd ≥ 1.8 (6), Wherein, Nd is the refractive index of the lens material when transmitting light with a wavelength of 587.56 nm.

[0034] If the data of the first lens group 100 is less than the lower limit of conditional expression (6), the refractive power of the first lens group 100 will be reduced. In order to make the data of the first lens group 100 meet conditional expression (1), it is necessary to increase the number of lenses of the first lens group 100. At the same time, the aperture of the first lens group 100 will also increase, which is not conducive to the miniaturization of the lens.

[0035] It can be understood that, from the object side to the image side, the first lens group 100 sequentially includes a first lens having positive optical power, a second lens having negative optical power, and a third lens having negative optical power.

[0036] It can be understood that, from the object side to the image side, the second lens group 200 sequentially includes a fourth lens having negative optical power, a fifth lens having positive optical power, and a sixth lens having positive optical power.

[0037] It can be understood that the fourth lens group 400 includes only one lens with positive refractive power, and is an aspherical lens.

[0038] The fourth lens group 400 is used as a focusing group, and only one lens is used, so it is light in weight and can improve the focusing speed. Preferably, during the focusing process from infinity to close distance on the object side, the fourth lens group 400 moves along the optical axis toward the image side.

[0039] It can be understood that the aspheric curve driving equation of the aspheric lens in the fourth lens group 400 and / or the fifth lens group 500 is as follows: (7), in, R: is the radius of curvature of the aspheric surface; Y: radial coordinate; K: is the cone coefficient of the quadratic surface; Z: is the sagittal height of the surface along the optical axis; A: 4th order aspheric coefficient; B: 6th order aspheric coefficient; C: 8th order aspheric coefficient; D: is the 10th order aspheric coefficient.

[0040] It can be understood that, from the object side to the image side, the fifth lens group 500 sequentially includes a seventh lens with positive power, an eighth lens with negative power, a ninth lens with positive power and a tenth lens with negative power.

[0041] It should be understood that the naming rules of the first to tenth lenses described above are for distinguishing each lens, rather than limiting the position order of the lenses. For example, the eighth lens does not mean that the lens can only be set at the eighth position of the entire lens.

[0042] It can be understood that the third lens group 300 includes only one lens with positive refractive power.

[0043] Embodiment 1: The parameters of the large aperture optical lens for photography of this embodiment are as follows: EFL: 18mm; Fno: 1.2; 2ω: 66.0°; Among them, EFL is the effective focal length of the optical lens, Fno is the aperture, and 2ω is the field of view.

[0044] F1 / F=-2.1, satisfies conditional formula (1); F2 / F=3.4, satisfies conditional formula (2); F3 / F=2.9, satisfies conditional formula (3); F4 / F=-2.3, satisfies conditional formula (4); F5 / F=1.5, satisfies conditional formula (5); Nd =1.92(G1L1), satisfies conditional formula (6).

[0045] It should be understood that in the lens structure shown in the accompanying drawings, the first lens group 100 is also recorded as G1, the second lens group 200 is also recorded as G2, the third lens group 300 is also recorded as G3, the fourth lens group 400 is also recorded as G4, and the fifth lens group 500 is also recorded as G5. In the entire lens, the order of lens arrangement from the object side to the image side is L1 for the first lens, L2 for the second lens, and Ln for the nth lens in this order. For example, lens G3L7 refers to the 7th lens, and the lens belongs to the third lens group 300. Among them, the aperture stop 600 is recorded as ST0, the image plane is recorded as IMA, and the protective glass is recorded as CG. Therefore, in Example 1, the Nd of the first lens of the first lens group 100 is selected as 1.92.

[0046] The parameters of the large aperture optical lens for photography of this embodiment also satisfy the contents of Table 1, Table 2 and Table 3.

[0047] Table 1 Parameters of the large aperture optical lens for photography of Example 1

[0048] In Table 1, Image is the image side; Radius is the radius of curvature of each surface; Thickness is the distance between each lens and the thickness of the lens; Nd is the refractive index of each glass of d line; Vd is the Abbe number of the glass; ASP indicates that the surface is aspherical.

[0049] Table 2 Focusing interval parameters of the large aperture optical lens for photography in Example 1

[0050] In Table 2, FAR stands for far side, that is, the lens focuses on far view; NEAR stands for near side, that is, the lens focuses on near view.

[0051] Table 3 Aspherical lens parameters of the large aperture optical lens for photography of Example 1

[0052] In Table 3, R is the radius of curvature of the aspheric surface; K is the conic coefficient of the quadratic surface; A is the 4th-order aspheric coefficient; B is the 6th-order aspheric coefficient; C is the 8th-order aspheric coefficient; and D is the 10th-order aspheric coefficient.

[0053] Among them, -2.221198E-05 refers to -2.221198×10 -5 , and the same applies to the rest.

[0054] The lens arrangement structure of the large aperture optical lens for photography of Example 1 can be referred to Figure 1 and Figure 2 As shown. And Figure 3 , Figure 4 , Figure 5The spherical aberration, astigmatism field curvature, and distortion diagram of the photographic large aperture optical lens of Example 1 at the Far end are shown; Figure 6 The MTFvsField diagram of Example 1 at the Far end is shown. Figure 7 , Figure 8 , Fig. 9 The spherical aberration, astigmatism field curvature, and distortion diagram of Example 1 at the Near end are shown; Fig.10 The MTFvsField diagram of Example 1 at the Near end is shown.

[0055] In Example 1, the fourth lens group 400 moves along the optical axis to achieve focusing of the object distance from the Far end to the Near end, and the fourth lens group 400 includes only one lens, which is light in weight and has a relatively short focusing formation, and can meet the fast focusing of the lens and the focusing process is quiet. Each lens group of Example 1 meets the conditional formula, has a reasonable optical power distribution, and can achieve high resolution using only 12 lenses, and the lens is small in size and high in performance.

[0056] It is important to understand that Figure 1 In the lens, the first lens group 100 is also recorded as G1, the second lens group 200 is also recorded as G2, the third lens group 300 is also recorded as G3, the fourth lens group 400 is also recorded as G4, and the fifth lens group 500 is also recorded as G5. In the entire lens, the order of the lenses from the object side to the image side is L1 for the first lens, L2 for the second lens, and Ln for the nth lens in this order. For example, lens G3L7 refers to the 7th lens, and the lens belongs to the third lens group 300. Among them, the aperture stop 600 is recorded as ST0, the image plane is recorded as IMA, and the protective glass is recorded as CG.

[0057] The embodiments of the present invention are described in detail above with reference to the accompanying drawings, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge scope of ordinary technicians in the relevant technical field without departing from the purpose of the present invention.

Claims

1. A large aperture optical lens for photography, characterized in that: include: A first lens group (100), a second lens group (200), a third lens group (300), a fourth lens group (400) and a fifth lens group (500) are arranged in sequence from the object side to the image side along the optical axis; The first lens group (100) has negative optical power, the second lens group (200) has positive optical power, the third lens group (300) has positive optical power, the fourth lens group (400) has negative optical power, and the fifth lens group (500) has positive optical power; The fourth lens group (400) includes at least one aspherical lens, and the fifth lens group (500) includes at least one aspherical lens; The first lens group (100), the second lens group (200), the third lens group (300), the fourth lens group (400) and the fifth lens group (500) respectively satisfy the following conditional expressions: -3.5≤F1 / F≤-1, 3.0≤F2 / F≤4.0, 6.5≤F3 / F≤10.0, -3.5≤F4 / F≤-1.0, 0.8≤F5 / F≤2.5, in, F1: is the focal length of the first lens group (100); F2: is the focal length of the second lens group (200); F3: is the focal length of the third lens group (300); F4: is the focal length of the fourth lens group (400); F5: is the focal length of the fifth lens group (500); F: is the focal length of the large aperture optical lens for photography.

2. The large aperture optical lens for photography according to claim 1, characterized in that: The first lens group (100) comprises three lenses, and at least one lens in the first lens group (100) satisfies the following conditional formula: Nd≥1.8, Wherein, Nd is the refractive index of the lens material when transmitting light with a wavelength of 587.56 nm.

3. The large aperture optical lens for photography according to claim 2, characterized in that: From the object side to the image side, the first lens group (100) comprises, in sequence, a first lens having positive optical power, a second lens having negative optical power, and a third lens having negative optical power.

4. The large aperture optical lens for photography according to claim 1, characterized in that: From the object side to the image side, the second lens group (200) comprises, in sequence, a fourth lens having negative focal power, a fifth lens having positive focal power, and a sixth lens having positive focal power.

5. The large aperture optical lens for photography according to claim 1, characterized in that: The fourth lens group (400) includes only one lens with positive optical power, and is an aspherical lens.

6. The large aperture optical lens for photography according to claim 4, characterized in that: The aspheric curve driving equation of the aspheric lens in the fourth lens group (400) and / or the fifth lens group (500) is as follows: ， in, R: is the radius of curvature of the aspheric surface; Y: radial coordinate; K: is the cone coefficient of the quadratic surface; Z: is the sagittal height of the surface along the optical axis; A: 4th order aspheric coefficient; B: 6th order aspheric coefficient; C: 8th order aspheric coefficient; D: is the 10th order aspheric coefficient.

7. The large aperture optical lens for photography according to claim 1, characterized in that: From the object side to the image side, the fifth lens group (500) comprises, in sequence, a seventh lens having positive focal power, an eighth lens having negative focal power, a ninth lens having positive focal power, and a tenth lens having negative focal power.

8. The large aperture optical lens for photography according to claim 1, characterized in that: The third lens group (300) comprises only one lens with positive optical power.

9. The large aperture optical lens for photography according to claim 1, characterized in that: During the focusing process from infinity to close distance on the object side, the fourth lens group (400) moves along the optical axis toward the image side.

10. The large aperture optical lens for photography according to claim 1, characterized in that: An aperture stop (600) is provided between the second lens group (200) and the third lens group (300).

Images