Internal focusing type photographic lens

Abstract

The utility model discloses an internal focusing type photographic lens. A first lens group with positive focal power, an aperture diaphragm, a second lens group with positive focal power and a third lens group with positive focal power are sequentially arranged from an object side; in the focusing process from infinity to the nearest end object distance, the second lens group moves towards the object end along with the optical axis, and the first lens group and the third lens group are fixed relative to the image plane. According to the whole device, various aberrations can be fully reduced, excellent imaging can be achieved in a full view field, the focusing lens is light in weight, and the breathing effect is effectively restrained.

Description

Technical Field

[0001] The utility model belongs to the technical field of optical lenses, and particularly relates to an internally focusing photographic lens. Background Art

[0002] An internally focusing photographic lens is a lens design in which, during focusing, the front group elements of the lens remain stationary while certain group elements inside the lens move to adjust the focal length.

[0003] In recent years, digital still cameras, digital mirrorless cameras, etc. that use solid-state imaging devices (such as CCD "charge-coupled device" and CMOS "complementary metal oxide semiconductor") have rapidly spread. The spread of such digital cameras has led to a higher demand for high-performance imaging lenses corresponding to high pixel counts. In particular, in recent years, such demand has been increasing not only for zoom lenses but also for single-focus lenses with a fixed focal length. The current market far from meets the growing demand. Summary of the Utility Model

[0004] Aiming at the deficiencies of the prior art, the purpose of the utility model is to provide an internally focusing photographic lens, which solves the above-mentioned technical problems existing in the prior art.

[0005] The purpose of the utility model can be achieved by the following technical solutions:

[0006] An internally focusing photographic lens, sequentially arranged from the object side: a first lens group with positive optical power, an aperture stop, a second lens group with positive optical power, and a third lens group with positive optical power;

[0007] During the focusing process from infinity to the closest object distance, the second lens group moves axially towards the object end, and the first lens group and the third lens group are fixed relative to the image plane.

[0008] Further, the first lens group is composed of a first negative lens, a second positive lens, a third positive lens, a fourth positive lens, and a fifth negative lens, sequentially arranged from the object side;

[0009] Wherein the fourth positive lens and the fifth negative lens form a first cemented lens group.

[0010] Further, the second lens group is composed of a sixth negative lens and a seventh positive lens;

[0011] And the following conditional expressions are satisfied:

[0012] -4 < F2a / F2 < -2.1;

[0013] 0 < F2b / F2 < 1;

[0014] Wherein: F2a is the focal length of the sixth negative lens, F2b is the focal length of the seventh positive lens, and F2 is the total focal length of the second lens group.

[0015] Further, the third lens group is composed of an eighth positive lens, a ninth negative lens, and a tenth positive lens sequentially arranged from the object side;

[0016] Wherein the eighth positive lens and the ninth negative lens are combined to form a second cemented lens group.

[0017] Further, the first lens group satisfies the following conditional formula:

[0018] 1 < F1 / F < 4;

[0019] The second lens group satisfies the following conditional formula:

[0020] 0.5 < F2 / F < 2;

[0021] Wherein: F is the total focal length of the lens, F1 represents the combined focal length of the first lens group, and F2 represents the combined focal length of the second lens group.

[0022] Further, the second cemented lens group of the third lens group and the tenth positive lens satisfy the following conditional formula:

[0023] -1.7 < F3b / F3a < 0;

[0024] Wherein: F3a is the combined focal length of the second doublet lens, and F3b is the focal length of the tenth positive lens.

[0025] Advantages of the present utility model:

[0026] 1. The present device realizes an imaging lens with a large aperture, but can fully reduce various aberrations, enabling excellent imaging in the entire field of view, lightening the focusing lens, and effectively suppressing the breathing effect.

[0027] 2. The fixed-focus lens adopted by the present device should be a high-performance large-aperture lens with a maximum aperture of F / 1.8, and it needs to be portable and have excellent imaging.

[0028] 3. The present device also suppresses the breathing effect, making the change in the field of view extremely small when using the video shooting mode, and greatly improving the user experience. Description of the Drawings

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art.

[0030] Figure 1 It is a schematic diagram of the lens structure of the imaging lens according to the embodiment of the present utility model;

[0031] Figure 2 It is a graphical illustration of an embodiment of the present utility model at infinite focus (INF), showing the chromatic aberration diagram of the imaging lens according to the embodiment;

[0032] Figure 3 It is a graphical illustration of an embodiment of the present utility model at infinite focus (INF), showing the astigmatism distortion diagram of the imaging lens according to the embodiment;

[0033] Figure 4 In the graphical illustration of an embodiment of the present utility model, F, d, and C respectively represent the spherical aberration of visible light wavelengths of 486 nm, 587.6 nm, and 656 nm;

[0034] Figure 5 In the graphical illustration of an embodiment of the present utility model, T and S respectively represent the meridional field curvature and sagittal field curvature at the visible light wavelength of 587.6 nm. Detailed implementation manners

[0035] Next, the technical solutions in the embodiments of the present utility model will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present utility model. Based on the embodiments in the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present utility model.

[0036] As Figures 1-5 shown, an embodiment of the present utility model provides an internally focusing photographic lens, which is sequentially arranged from the object side: a first lens group GR1 with positive optical power, an aperture stop STP, a second lens group GR2 with positive optical power, and a third lens group GR3 with positive optical power.

[0037] During the focusing process from infinity to the closest object distance, the second lens group GR2 moves axially towards the object end, and the first lens group GR1 and the third lens group GR3 are fixed relative to the image plane.

[0038] At this time, the first lens group GR1 satisfies the following conditional formula:

[0039] 1 < F1 / F < 4;

[0040] The second lens group GR2 satisfies the following conditional formula:

[0041] 0.5 < F2 / F < 2;

[0042] Wherein, F is the total focal length of the lens, F1 represents the combined focal length of the first lens group GR1, and F2 represents the combined focal length of the second lens group GR2.

[0043] The above two conditional expressions define the focal length ranges of the first lens group GR1 and the second lens group GR2 of the lens. Among them, the focal length range of the first lens group GR1 determines that the total length of the lens is relatively short, and the focal length range of the second lens group GR2 greatly reduces the breathing effect of the lens.

[0044] The first lens group GR1 is composed of a first negative lens G1, a second positive lens G2, a third positive lens G3, a fourth positive lens G4, and a fifth negative lens G5 arranged in sequence from the object side;

[0045] Among them, the fourth positive lens G4 and the fifth negative lens G5 form a first cemented lens group.

[0046] The second lens group GR2 is composed of a sixth negative lens G6 and a seventh positive lens G7;

[0047] And the following conditional expressions are satisfied:

[0048] -4 < F2a / F2 < -2.1; 0 < F2b / F2 < 1;

[0049] Where: F2a is the focal length of the sixth negative lens G6, F2b is the focal length of the seventh positive lens G7, and F2 is the total focal length of the second lens group GR2.

[0050] At this time, the power distribution of different lenses within the second lens group GR2 is determined, and this distribution can effectively correct the aberration of the lens group, greatly optimizing the overall imaging of the lens.

[0051] The third lens group GR3 is composed of an eighth positive lens G8, a ninth negative lens G9, and a tenth positive lens G10 arranged in sequence from the object side;

[0052] Among them, the eighth positive lens G8 and the ninth negative lens G9 form a second cemented lens group.

[0053] The second cemented lens group of the third lens group GR3 and the tenth positive lens G10 satisfy the following conditional expressions:

[0054] -1.7 < F3b / F3a < 0;

[0055] Where: F3a is the combined focal length of the second doublet lens, and F3b is the focal length of the tenth positive lens G10.

[0056] At this time, the power positive and negative distribution of each lens within the third lens group GR3 is the eighth positive lens G8, the ninth negative lens G9, and the tenth positive lens G10. This distribution scheme can effectively correct the chromatic aberration of the third lens group GR3. The conditional expressions further limit the specific focal length ranges of each lens group within the third lens group GR3. This range enables good correction of other aberrations within the third lens group GR3.

[0057] The above design of the optical powers of the lenses of the present utility model for the internal focusing type compact lens realizes a large aperture, but can fully reduce various aberrations, enabling excellent imaging in the entire field of view, making the focusing lens lightweight, and effectively suppressing the breathing effect. In order to more clearly understand the present utility model, the following are the specific data and aberration drawings of the embodiments.

[0058] Based on the attached drawings, the imaging lens of the present utility model will be described in detail. In the lens data, the refractive index and Abbe number are the values for the d-line. Among them, in the optical lens-related data, the unit of length is mm, and its unit will be omitted from display.

[0059] Table 1

[0060] Surface shape Radius Thickness Refractive index Abbe number si ri di nd vd 0 STANDARD Infinity Infinity 1 Spherical surface -40.113 1.26 1.580 40.90 2 Spherical surface 28.689 3.45 3 Spherical surface 34.67 4.77 1.910 35.20 4 Spherical surface -58.25 0.2 5 Spherical surface 21.31 3.15 1.900 31.30 6 Spherical surface 38.582 0.2 7 Spherical surface 22.36 4.95 1.697 55.50 8 Spherical surface -39.834 1 1.805 25.40 9 Spherical surface 12.269 4.52 10 Aperture Infinity D1 12 Spherical surface -11.368 3.87 1.517 64.20 13 Spherical surface -14.165 0.2 14 Spherical surface 84.696 4.33 1.835 42.70 15 Spherical surface -39.246 D2 16 Spherical surface -47.408 3.35 1.804 46.50 17 Spherical surface -25.31 1.35 1.847 23.70 18 Spherical surface -71.318 0.2 19 Spherical surface 124.568 2.4 1.883 40.79 20 Spherical surface -627.243 12 21 Spherical surface Infinity 2.5 1.517 64.20 22 Spherical surface Infinity 1 23 Image plane (IMA) Infinity

[0061] Among them: The various numerical data of the optical system are: f = 35.8 mm, Fno = 1.8, 2w = 44.9°.

[0062] In Table 1, "si" represents the surface number; "Ri" is the radius of curvature; "di" is the on-axis surface distance between the i-th surface and the (i + 1)-th surface; "nd" is the refractive index; "vd" is the Abbe number; "Fno." is the F-number; "ω" is the semi-field angle. Regarding the surface number, "ASP" indicates that the surface is an aspherical surface, and regarding the radius of curvature, "Infinity" and "∞" indicate that the surface is a plane. "IMG" represents the imaging surface.

[0063] Table 2

[0064]

[0065] At this time, in Table 2, due to the lens focusing type, the position of the second lens group will move back and forth at different object distances. INF is the infinite object distance, X20 is the object distance of 696.9 mm, and MOD is the closest focusing object distance of 305.000 mm. D1 and D2 are the intervals between the focusing lens group and the front and rear lenses respectively. These two intervals will change at different object distances to achieve a clear focusing effect.

[0066] The refractive index and Abbe number are the refractive index and Abbe number for the d-line (wavelength 587.6 nm).

[0067] Table 3

[0068] Conditional expression Embodiment 1 1 < F1 / F < 4 1.936 2 0.5 < F2 / F < 2 0.934 3 -4 < F2a / F2 < -2.1 -3.030 4 0 < F2b / F2 < 1 0.468 5 -1.7 < F3b / F3a < 0 -0.759

[0069] The above has shown and described the basic principles, main features and advantages of the present utility model. Those skilled in the art should understand that the present utility model is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principles of the present utility model. Without departing from the spirit and scope of the present utility model, the present utility model will have various changes and improvements, and these changes and improvements all fall within the scope of the present utility model claimed.

Claims

1. An internal focus camera lens, characterized in that: Arranged in order from the object side: a first lens group (GR1) having positive refractive power, an aperture stop, a second lens group (GR2) having positive refractive power, and a third lens group (GR3) having positive refractive power; During the focusing process from infinity to the closest object distance, the second lens group (GR2) moves along the optical axis toward the object end, and the first lens group (GR1) and the third lens group (GR3) are fixed relative to the image plane; The second lens group (GR2) is composed of a sixth negative lens (G6) and a seventh positive lens (G7); And satisfy the following conditions: -4 <F2a / F2<-2.1; 0 <F2b / F2<1; Wherein: F2a is the focal length of the sixth negative lens (G6), F2b is the focal length of the seventh positive lens (G7), and F2 is the total focal length of the second lens group (GR2); The first lens group (GR1) satisfies the following conditional formula: 1 <F1 / F<4; The second lens group (GR2) satisfies the following condition: 0.5 <F2 / F<2; Wherein: F is the total focal length of the lens, F1 represents the composite focal length of the first lens group (GR1), and F2 represents the composite focal length of the second lens group (GR2).

2. The internal focus camera lens according to claim 1, wherein: The first lens group (GR1) is composed of a first negative lens (G1), a second positive lens (G2), a third positive lens (G3), a fourth positive lens (G4), and a fifth negative lens (G5) arranged in sequence from the object side; The fourth positive lens (G4) and the fifth negative lens (G5) are combined into a first cemented lens group.

3. The internal focus camera lens according to claim 1, wherein: The third lens group (GR3) is composed of an eighth positive lens (G8), a ninth negative lens (G9), and a tenth positive lens (G10) arranged in sequence from the object side; The eighth positive lens (G8) and the ninth negative lens (G9) are combined into a second cemented lens group.

4. The internal focus camera lens according to claim 3, wherein: The second cemented lens group of the third lens group (GR3) and the tenth positive lens (G10) satisfy the following conditional formula: -1.7 <F3b / F3a<0; Wherein: F3a is the combined focal length of the second double cemented lens, and F3b is the focal length of the tenth positive lens (G10).

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