Zoom fisheye lens and camera and video camera using same

Abstract

The invention relates to a zoom fisheye lens and a camera and a video camera applying the same, the zoom fisheye lens sequentially comprises a first lens group G1 with negative diopter and a second lens group G2 with positive diopter 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 image plane side is a rear part G1b with negative diopter, and the second lens group G2 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 invention has the advantages of miniaturization, high performance, simple structure, excellent performance and large aperture.

Description

Technical Field

[0001] The invention discloses a zoom fisheye lens with a field of view of about 180 degrees, which can be widely applied to digital camera lenses, video camera lenses, and drone cameras, and is particularly applicable to exchange lenses on mirrorless cameras. Background Art

[0002] At present, there are many known fisheye lenses with a picture angle of 180 degrees, including full-circle fisheye lenses or diagonal fisheye lenses, but most of them are fixed-focus fisheye lenses. It is difficult to achieve both a circular fisheye effect like an inscribed circle in the image field and a diagonal fisheye lens effect covering the entire image field on one body. To achieve these two effects, a zoom fisheye lens must be used. Currently, the well-known Japanese patent No. 2020-166234, starting from the object side, consists of four lens groups: negative, negative, positive, and positive. When zooming, the four lens groups move in a certain proportion to achieve focal length changes, and the focusing group is set on the third group. Although the full-circle fisheye lens in the inscribed circle mode at the wide-angle end and the diagonal fisheye lens effect of fully covering the image field at the telephoto end can be achieved, the structure is too complicated, with a total of 4 groups of zoom, the mechanical mechanism design is difficult, the manufacturing cost is high, and the aperture can only reach F4, which is relatively dark and not a perfect solution.

[0003] There is also the well-known Japanese Patent Application No. 2022-155067, which starts from the object side and consists of four lens groups: negative, negative, positive, and positive. When zooming, the four lens groups move in a certain proportion to achieve focal length changes, and the focusing group is set on the third group. Although it can also achieve the full-circle fisheye lens in the inscribed circle mode at the wide-angle end and the diagonal fisheye lens effect with full coverage of the image field at the telephoto end, the structure is also too complicated, with a total of four groups of zoom and multiple aspherical lenses. The cost is difficult to control, the mechanical mechanism design is difficult, and the manufacturing cost is high. It is not a very perfect solution and there are still many problems. Summary of the invention

[0004] In order to overcome the problem that the above-mentioned known zoom fisheye lens cannot achieve low cost, simple structure and easy mass production, and cannot achieve the effect of a large aperture zoom fisheye lens with an aperture of F2.8, the present invention will provide a miniaturized, high-performance, simple structure, excellent performance, and large aperture zoom fisheye lens.

[0005] To achieve the above object, the technical solution of the present invention is: a zoom fisheye lens, which includes, from the object side to the image side, a first lens group G1 with negative refractive power and a second lens group G2 with positive refractive power;

[0006] Aperture Stop is disposed inside the second lens group G2.

[0007] Furthermore, the first lens group G1 is divided into two parts, a front part G1a with negative refractive power on the object side and a rear part G1b with negative refractive power on the image side. When the object moves from infinity to a close distance, the rear part G1b of the first lens group G1 moves toward the object side to achieve focusing.

[0008] Furthermore, the front portion G1a consists of at least two negative lenses and one negative-positive composite lens.

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

[0010] 0.3≤|F1 / F2|≤0.8 (1)

[0011] 0.1≤|Fw / F1a|≤0.6 (2)

[0012] 0.3≤|F1 a / F1 b|≤0.9 (3)

[0013] in,

[0014] Fw: focal length of the entire optical system at the wide-angle end at 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 portion G1 a of the first lens group G1;

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

[0019] If the lower limit of the conditional expression 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 viewing angle. However, because the refractive power is too strong, it is difficult to correct various aberrations, and it is difficult to achieve a high-performance zoom fisheye lens. If the upper limit of the conditional expression (1) is exceeded, although high performance is easy to achieve, because the refractive power of the first lens group G1 is too weak, the 180-degree viewing angle will become too large. At the same time, because the refractive power is too weak, the movement amount will also become large to achieve a zoom of more than 1.5 times, and the volume control will be more difficult.

[0020] If the lower limit of the conditional expression 0.1≤|Fw / F1a|≤0.6(2) is exceeded, the refractive power of the front part G1a of the first lens group G1 is too weak, the light convergence ability at the edge is weakened, the volume of the entire optical system is difficult to control, and the diameter of the lens at the front end will be very large. If the upper limit of the conditional expression (2) is exceeded, although the volume of the first lens group can be effectively controlled, the angle of the edge light emitted from the first group will be too large, so that the final exit pupil distance is too close, the angle of the edge light emitted to the edge is too large, and the vignetting will be very 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 half G1b of the first lens group G1 is too weak, the movement of the focus group is too large, the close-up capability is weak, or the refractive power of the front part G1a is too strong, which makes it difficult to control various aberrations and achieve high performance. If the upper limit of the conditional expression (3) is exceeded, the refractive power of the front part G1a of the first lens group G1 is too weak, which is beneficial for correcting aberrations, but it is very difficult to design a miniaturized lens, resulting in a large volume.

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

[0023] 10≤Lt / Fw≤18 (4)

[0024] 0.1≤|F1 / F1b|≤0.5 (5)

[0025] in,

[0026] Lt: The length of the entire optical system at the telephoto end.

[0027] If the lower limit of the conditional expression 10≤Lt / Fw≤18(4) is exceeded, the length of the telephoto end is very short. Although miniaturization is very advantageous, the structure is too compact because it is too short, making the mechanism design and 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 part G1b of the first lens group G1 is too weak, so the movement of the focus group will become large, the close-up performance will be very weak, and it will be not conducive to close-range focusing; if the upper limit of the conditional expression (5) is exceeded, the refractive power of the rear part G1b of the first lens group G1 is very strong. Although the focus movement is very small, it is conducive to close-range shooting, but because the refractive power is too strong, various aberrations are difficult to correct, and high performance is difficult.

[0029] Furthermore, the front and rear portions of the second lens group G2 are both positive refractive power lens groups, the object side of the aperture Stop is the front portion G2a of the second lens group, and the image side of the aperture Stop is the rear portion G2b of the second lens group G2.

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

[0031] 0.6≤F2 / F2a≤0.95 (6)

[0032] 0.3≤F2a / F2b≤1 (7)

[0033] in,

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

[0035] F2b: focal length of the rear portion G2b of the second lens group G2.

[0036] If the lower limit of the conditional expression 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 cause the light emission angle at the edge to be too large, which will inevitably cause the illumination at the edge to be too dark, which is not conducive to the brightness uniformity of the entire picture. If the upper limit of the conditional expression (6) is exceeded, the refractive power of the rear part G2b of the second lens group G2 is enhanced, so that the light emission angle at the edge will be very gentle, which is conducive to the brightness uniformity of the entire picture. The refractive power of the first lens group G1 is also enhanced, and the aberration of the entire optical system will increase significantly, making it difficult to achieve high-performance design requirements.

[0037] If the lower limit of the conditional expression 0.3≤F2a / F2b≤1(7) is exceeded, the refractive power of the rear part G2b of the second lens group G2 is too weak, the light emission angle at the outermost edge will be large, and the illumination at the outermost edge will be very dark, resulting in uneven brightness of the entire picture and large dark angles; if the upper limit of the conditional expression (7) is exceeded, the refractive power of the rear part G2b of the second lens group G2 is enhanced, so that the light emission angle at the outermost edge will be very gentle, which is conducive to uniform brightness of the entire picture. At the same time, the refractive power of the first lens group G1 is enhanced, and the aberration of the entire optical system will increase significantly, making it difficult to achieve high-performance design requirements.

[0038] The invention also provides a camera having the zoom fisheye lens.

[0039] The invention also provides a camera having the zoom fisheye lens.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] The invention provides a small-sized, high-performance, simple-structured, excellent-performance, large-aperture zoom fisheye lens with an aperture of F2.8. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 is an optical structure diagram of Embodiment 1 of the present invention;

[0043] Figure 2 The spherical aberration, field curvature aberration, distortion aberration and chromatic aberration of magnification at infinity and close distance of Example 1;

[0044] Figure 3 is an optical structure diagram of Embodiment 2 of the present invention;

[0045] Figure 4 These are the spherical aberration, field curvature, distortion, and lateral chromatic aberration at infinity and close distances in Example 2. DETAILED DESCRIPTION

[0046] The present invention is further described below in conjunction with the accompanying drawings and embodiments. The present invention includes but is not limited to the following embodiments.

[0047] Example 1: Figure 1 As shown, from the object side to the image 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 object side is a front part G1a with negative refractive power, and the image side is a rear part G1b with negative refractive power. The second lens group is divided into two parts, the aperture is arranged inside the second lens group, the object side of the aperture stop is the front part G2a, and the image side of the aperture is the rear part G2b; the interval between the first lens G1 and the second lens group G2 changes to achieve zooming, and when the object is from infinity to a close distance, the rear part G1b of the first lens group G1 moves toward the object side to achieve focusing.

[0048] The spherical aberration, field curvature aberration, distortion aberration and chromatic aberration of magnification at infinity and close distance of Example 1 are as follows: Figure 2 shown.

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

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

[0051] D (mm): the distance between lenses and the thickness of lenses;

[0052] Nd: refractive index of each glass at d line;

[0053] Vd: Abbe number of glass;

[0054] Focal length: 8.4640~14.8033;

[0055] FNO: 2.85~2.85;

[0056] Half-screen angle ω: 90.1°~90.1°.

[0057]

[0058]

[0059]

[0060] Embodiment 2: From the object side to the image side, it includes, in sequence, 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, a front part G1a with negative refractive power on the object side and a rear part G1b with negative refractive power on the image side. The second lens group is divided into two parts, the aperture is arranged inside the second lens group, the object side of the aperture stop is the front part G2a, and the image side of the aperture is the rear part G2b. Zooming is achieved by changing the interval between the first lens G1 and the second lens group G2. When the object moves from infinity to a close distance, the rear part G1b of the first lens group G1 moves toward the object side to achieve focusing.

[0061] The spherical aberration, field curvature aberration, distortion aberration and chromatic aberration of magnification at infinity and close distance of Example 2 are as follows: Figure 4 shown.

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

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

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

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

[0066] Vd: Abbe number of glass;

[0067] Focal length: 5.5085~9.7014;

[0068] FNO: 2.85~2.85;

[0069] Half-screen angle ω: 90.1°~90.1°.

[0070]

[0071]

[0072]

[0073] Conditional summary table:

[0074]

[0075] The zoom fisheye lens provided by any of the above embodiments can be applied to cameras and camcorders.

[0076] The above contents are merely examples and explanations of the structure of the present invention. The technicians in this technical field may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the structure of the invention or exceed the scope defined by the claims, they should all fall within the protection scope of the present invention.

Claims

1. A zoom fisheye lens, characterized in that: The lens group 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. Aperture Stop is disposed inside the second lens group G2.

2. The zoom fisheye lens according to claim 1, characterized in that: The first lens group G1 is divided into two parts, a front part G1a with negative refractive power on the object side and a rear part G1b with negative refractive power on the image side. When the object moves from infinity to a close distance, the rear part G1b of the first lens group G1 moves toward the object side to achieve focusing.

3. The zoom fisheye lens according to claim 2, characterized in that: The front part G1a is composed of at least two negative lenses and one negative-positive cemented lens.

4. The zoom fisheye lens according to claim 2, characterized in that: The lens satisfies the following conditions (1), (2), and (3): 0.3≤|F1 / F2|≤0.8 (1) 0.1≤|Fw / F1a|≤0.6 (2) 0.3≤|F1 a / F1 b|≤0.9 (3) in, Fw: focal length of the entire optical system at the wide-angle end at infinity; 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 portion G1 a of the first lens group G1; F1 b: focal length of the rear portion G1 b of the first lens group G1.

5. The zoom fisheye lens according to claim 4, characterized in that: The first lens group G1 satisfies the following conditions (4) and (5): 10≤Lt / Fw≤18 (4) 0.1≤|F1 / F1 b|≤0.5 (5) in, Lt: The length of the entire optical system at the telephoto end.

6. The zoom fisheye lens according to claim 4, characterized in that: The front and rear portions of the second lens group G2 are both positive refractive power lens groups. The object side of the aperture Stop is the front portion G2a of the second lens group, and the image side of the aperture Stop is the rear portion G2b of the second lens group G2.

7. The zoom fisheye lens according to claim 6, characterized in that: The second lens group G1 satisfies the following conditions (6) and (7): 0.6≤F2 / F2a≤0.95 (6) 0.3≤F2a / F2b≤1 (7) in, F2a: focal length of the front portion G2a of the second lens group G2; F2b: focal length of the rear portion G2b of the second lens group G2.

8. A camera having the zoom fisheye lens according to any one of claims 1 to 7.

9. A camera having the zoom fisheye lens according to any one of claims 1 to 7.

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