Zoom fisheye lens and camera and video camera using same

Abstract

The zoom fisheye lens comprises a first lens group G1 with negative diopter and a second lens group G2 with positive diopter in sequence from an object side to an image plane side, the first lens group G1 is divided into two parts, the object side is a front part G1a with negative diopter, the second lens group G2 is a rear part G1a with positive diopter, and the object side is a rear part G1a with negative diopter. The object side of the aperture stop is a front part G2a with negative diopter, the image surface side of the aperture stop is a rear part G1b with negative diopter, the second lens group is divided into two parts, the aperture is arranged in the second lens group, the object side of the aperture stop is a front part G2a, and the image surface side of the aperture is a rear part G2b; the distance between the first lens G1 and the second lens group G2 is changed to realize zooming, and when an object is from infinity to a close distance, the rear part G1b of the G1 of the first lens group moves towards the object side to realize focusing. The zoom fisheye lens provided by the utility model has the advantages of miniaturization, high performance, simple structure, excellent performance and large aperture.

Description

TECHNICAL FIELD

[0001] The utility model relates to a zoom fisheye lens with a field of view angle of about 180 degrees, which can be widely applied to digital camera lenses, camera lenses, unmanned aerial vehicle cameras, especially to interchangeable lenses on a mirrorless body. BACKGROUND

[0002] At present, there are many fisheye lenses with an angle of 180 degrees, including full-circle fisheye lenses or diagonal fisheye lenses, but most of them are fixed-focus fisheye lenses, which are difficult to realize both the circular fisheye effect like an inscribed circle in an image field and the diagonal fisheye lens effect covering the entire image field on one body. To realize these two effects, a zoom fisheye lens must be used. The known Japanese Patent No. 2020-166234 has four lens groups, negative, negative, positive, and positive, from the object side. During zooming, the four lens groups move according to a certain ratio to change the focal length. The focusing group is set on the third group. Although this can realize a full-circle fisheye lens with an inscribed circle at the wide-angle end and a diagonal fisheye lens covering the entire image field at the telephoto end, the structure is too complex, with a total of four zooms, making the mechanical mechanism design difficult and the manufacturing cost high. At the same time, the aperture can only reach F4, which is relatively dark, and this is not a perfect solution.

[0003] The known Japanese Patent No. 2022-155067 also has four lens groups, negative, negative, positive, and positive, from the object side. During zooming, the four lens groups move according to a certain ratio to change the focal length. The focusing group is set on the third group. Although this can also realize a full-circle fisheye lens with an inscribed circle at the wide-angle end and a diagonal fisheye lens covering the entire image field at the telephoto end, the structure is also too complex, with a total of four zooms. At the same time, many aspherical lenses are used, making it difficult to control the cost, and the mechanical mechanism design is difficult, the manufacturing cost is high, and this is not a perfect solution, still with many problems. CONTENT OF THE UTILITY MODEL

[0004] In order to overcome the above-mentioned problems of the known zoom fisheye lens, which cannot achieve a low-cost, simple structure, easy mass production, and large-aperture zoom fisheye lens effect with an aperture of F2.8, the utility model provides a small, high-performance, simple structure, excellent performance, and large-aperture zoom fisheye lens.

[0005] To achieve the above-mentioned purpose, the technical solution of the utility model is as follows: the zoom fisheye lens includes a first lens group G1 with negative refractive power and a second lens group G2 with positive refractive power, from the object side to the image side.

[0006] The aperture Stop is set inside the second lens group G2.

[0007] Further, the first lens group G1 is divided into two parts, a front part G1 a with negative refractive power on the object side and a rear part G1 b with negative refractive power on the image side, and when the object moves from infinity to a close distance, the rear part G1 b of the first lens group G1 moves toward the object side to achieve focusing.

[0008] Further, the front part G1 a is composed of at least two negative lenses and one negative-positive cemented lens.

[0009] Further, the lens satisfies the conditions (1), (2), and (3):

[0010] 0.3≤|F1 / F2|≤0.8 (1)

[0011] 0.1≤|Fw / F1 a|≤0.6 (2)

[0012] 0.3≤|F1 a / F1 b|≤0.9 (3)

[0013] wherein,

[0014] Fw: focal length of the entire optical system at the wide angle end in the state of infinity;

[0015] F1: focal length of the first lens group G1;

[0016] F2: focal length of the second lens group G2;

[0017] F1 a: focal length of the front part G1 a of the first lens group G1;

[0018] F1 b: focal length of the rear part G1 b of the first lens group G1.

[0019] If the lower limit of the condition 0.3≤|F1 / F2|≤0.8 (1) is exceeded, the refractive power of the first lens group G1 is too strong, and it is easy to achieve a 180-degree angle of view, but because the refractive power is too strong, various aberrations are difficult to correct, and it is difficult to achieve a high-performance zoom fisheye lens. If the upper limit of the condition (1) is exceeded, although high performance is easy to achieve, because the refractive power of the first group G1 is too weak, it becomes large to achieve a 180-degree angle of view, and because the refractive power is too weak, it is difficult to achieve a zoom of more than 1.5 times, and the moving amount also becomes large, and it is difficult to control the volume.

[0020] If the lower limit of the conditional expression 0.1≤|Fw / F1a|≤0.6 (2) is exceeded, the refractive power of the front portion G1a of the first lens group G1 is too weak, the marginal ray convergence ability is weakened, the entire optical system volume is difficult to control, and the front lens diameter is large. If the upper limit of the conditional expression (2) is exceeded, the first lens group volume can be effectively controlled, but the marginal ray angle from the first group is too large, so that the final exit pupil distance is too close, the marginal ray is emitted to the edge at a large angle, and the dark corner is serious.

[0021] If the lower limit of the conditional expression 0.3≤|F1a / F1b|≤0.9 (3) is exceeded, the refractive power of the rear portion G1b of the first lens group G1 is too weak, the focusing group movement is too large, the close-up ability is weak, or the refractive power of the front portion G1a is too strong, which makes it difficult to control various aberrations and difficult to achieve high performance. If the upper limit of the conditional expression (3) is exceeded, the refractive power of the front portion G1a of the first lens group G1 is too weak, which is beneficial to correcting aberrations, but miniaturization design is very difficult, resulting in a large volume.

[0022] Further, the first lens group G1 satisfies the conditional expressions (4) and (5):

[0023] 10≤Lt / Fw≤18 (4)

[0024] 0.1≤|F1 / F1b|≤0.5 (5)

[0025] wherein,

[0026] Lt: Length of the entire optical system in the telephoto end state.

[0027] If the lower limit of the conditional expression 10≤Lt / Fw≤18 (4) is exceeded, the length in the telephoto end is short, which is beneficial to miniaturization, but because it is too short, the structure is too compact, which makes the mechanism design difficult and the manufacturing difficult. If the upper limit of the conditional expression (4) is exceeded, the volume will be large and miniaturization will be difficult.

[0028] If the lower limit of the conditional expression 0.1≤|F1 / F1b|≤0.5 (5) is exceeded, the refractive power of the rear portion G1b of the first lens group G1 is too weak, so that the focusing group movement will be large and the close-up performance will be weak, which is not conducive to close-up focusing. If the upper limit of the conditional expression (5) is exceeded, the refractive power of the rear portion G1b of the first lens group G1 is too strong, which is beneficial to close-up shooting because the focusing movement is small, but because the refractive power is too strong, various aberrations are difficult to correct, and high performance is difficult.

[0029] Further, the second lens group G2 is positive lens group in front and back, the object side of the stop is the front part G2a of the second lens group, and the image side of the stop is the back part G2b of the second lens group G2.

[0030] Further, the second lens group G1 satisfies the conditions (6) and (7):

[0031] 0.6≤F2 / F2a≤0.95 (6)

[0032] 0.3≤F2a / F2b≤1 (7)

[0033] Wherein,

[0034] F2a: focal length of the front part G2a of the second lens group G2;

[0035] F2b: focal length of the back part G2b of the second lens group G2.

[0036] If the lower limit of the condition 0.6≤F2 / F2a≤0.95 (6) is exceeded, the refractive power of the front part G2a of the second lens group G2 is too weak, which will result in too large exit angle of the marginal light, and inevitably result in too dark illumination of the edge, which is not conducive to the brightness uniformity of the whole picture.

[0037] If the lower limit of the condition 0.3≤F2a / F2b≤1 (7) is exceeded, the refractive power of the back part G2b of the second lens group G2 is too weak, the exit angle of the marginal light is very large, the illumination of the marginal edge is very dark, which results in uneven brightness of the whole picture and large dark angle.

[0038] The utility model also provides a camera with the zoom fisheye lens.

[0039] The utility model also provides a camera with the zoom fisheye lens.

[0040] Compared with the prior art, the utility model has the following beneficial effects:

[0041] This invention provides a miniaturized, high-performance, simple-structured, and high-performance large-aperture zoom fisheye lens with an aperture of F2.8. Attached Figure Description

[0042] Figure 1 This is an optical structure diagram of Embodiment 1 of this utility model;

[0043] Figure 2 These are the spherical aberrations, field curvature aberrations, distortion aberrations, and magnification chromatic aberrations at infinity and near distance in Example 1.

[0044] Figure 3 This is an optical structure diagram of Embodiment 2 of this utility model;

[0045] Figure 4 These are the spherical aberrations, field curvature aberrations, distortion aberrations, and magnification chromatic aberrations at infinity and near distance in Example 2. Detailed Implementation

[0046] The present invention will be further described below with reference to the accompanying drawings and embodiments. The present invention includes, but is not limited to, the following embodiments.

[0047] Example 1: As Figure 1 As shown, from the object side to the image plane side, it includes a first lens group G1 with negative refractive power and a second lens group G2 with positive refractive power. The first lens group G1 is divided into two parts: the front part G1a with negative refractive power on the object side and the rear part G1b with negative refractive power on the image plane side. The second lens group is also divided into two parts, with the aperture set inside the second lens group. The object side of the aperture stop is the front part G2a, and the image plane side of the aperture is the rear part G2b. The zoom is achieved by changing the interval between the first lens G1 and the second lens group G2. When the object moves from infinity to near, the rear part G1b of the first lens group G1 moves towards the object side to achieve focus.

[0048] Spherical aberration, field curvature aberration, distortion aberration, and magnification chromatic aberration at infinity and near distance in Example 1 are as follows: Figure 2 As shown.

[0049] The data for Example 1 are as follows.

[0050] R(mm): Radius of curvature of each surface;

[0051] D (mm): Spacing between lenses and lens thickness;

[0052] Nd: The refractive index of each glass along the d-line;

[0053] Vd: Abbe number of glass;

[0054] Focal length: 8.4640~14.8033;

[0055] FNO: 2.85~2.85;

[0056] Half angle of view ω: 90.1°~90.1°.

[0057]

[0058]

[0059]

[0060] Example 2: from object side to image side in turn includes a first lens group G1 of negative refractive power, a second lens group G2 of positive refractive power, the first lens group G1 is divided into two parts, the object side is a front part G1 a of negative refractive power, the image side is a rear part G1 b of negative refractive power, the second lens group is divided into two parts, the aperture is set inside the second lens group, the object side of the aperture stop is a front part G2a, and the image side of the aperture is a rear part G2b; the interval between the first lens G1 and the second lens group G2 changes to realize zooming, and when the object is from infinity to close range, the rear part G1 b of the first lens group G1 moves to the object side to realize focusing.

[0061] The spherical aberration, field curvature aberration, distortion aberration and magnification chromatic aberration of Example 2 at infinity and close range are shown in Table 2. Figure 4

[0062] The data of Example 2 are as follows:

[0063] R (mm): the radius of curvature of each surface;

[0064] D (mm): the interval between lenses and the thickness of lenses;

[0065] Nd: the refractive index of each glass at d line;

[0066] Vd: the Abbe number of the glass;

[0067] Focal length: 5.5085~9.7014;

[0068] FNO: 2.85~2.85;

[0069] Half angle of view ω: 90.1°~90.1°.

[0070]

[0071]

[0072]

[0073] Conditional expression summary table: ​

[0074]

[0075] Any of the above embodiments can be used in cameras and video cameras.

[0076] The above is only an example and description of the structure of the utility model, and those skilled in the art can make various modifications or supplements to the described specific embodiments or use similar ways to replace them, as long as they do not deviate from the structure of the utility model or exceed the scope defined by the present claims, which shall belong to the protection scope of the utility model.

Claims

1. A zoom fisheye lens, characterized in that, From the object side to the image plane side, the lens group consists of a first lens group G1 with negative refractive power and a second lens group G2 with positive refractive power. The aperture stop is located inside the second lens group G2; The first lens group G1 is divided into two parts: the front part G1a with negative refractive power on the object side and the rear part G1b with negative refractive power on the image plane side. When the object moves from infinity to near distance, the rear part G1b of the first lens group G1 moves towards the object side to achieve focusing. The front part G1 a consists of at least two negative lenses and one negative-positive cemented lens, and the lens satisfies conditions (1), (2), and (3): 0.3≤|F1 / F2|≤0.8 (1) 0.1≤|Fw / F1 a|≤0.6 (2) 0.3≤|F1 a / F1 b|≤0.9 (3) in, Fw: At infinity, the focal length of the entire optical system at the wide-angle end; F1: Focal length of the first lens group G1; F2: Focal length of the second lens group G2; F1 a: Focal length of the front part G1 a of the first lens group G1; F1 b: Focal length of the rear portion G1 b of the first lens group G1; The first lens group G1 satisfies conditions (4) and (5): 10≤Lt / Fw≤18 (4) 0.1≤|F1 / F1b|≤0.5 (5) in, Lt: The length of the entire optical system in the telephoto end position; The second lens group G2 has positive diopter lenses at both the front and back. The object side of the aperture Stop is the front part G2a of the second lens group, and the image plane side of the aperture Stop is the rear part G2b of the second lens group G2. The second lens group G2 satisfies conditions (6) and (7): 0.6≤F2 / F2a≤0.95 (6) 0.3≤F2a / F2b≤1 (7) in, F2a: The focal length of the front part G2a of the second lens group G2; F2b: The focal length of the rear portion G2b of the second lens group G2.

2. A camera having the zoom fisheye lens of claim 1.

3. A camera having the zoom fisheye lens of claim 1.

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