All-glass fisheye lens

Abstract

The application discloses a kind of all-glass fisheye lenses, including first lens, second lens, third lens, fourth lens, fifth lens, aperture diaphragm, sixth lens, seventh lens, eighth lens, optical filter sequentially arranged from object side to image side along optical axis, the first lens to eighth lens are glass spherical lens, wherein, the seventh lens and eighth lens are glued components.The application adopts eight glass spherical lenses, simple structure, low processing difficulty, realizes F2.4 large aperture, 240 ° field of view, total length is less than 20 mm and 3.45 mm image plane diameter.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of optical lenses, and particularly relates to a full-glass fisheye lens. BACKGROUND

[0002] The fisheye lens is named because its front end is like a fish eye, its focal length is extremely short, and its field of view angle is as high as 180 degrees or more. Due to the advantage of the super-large field of view angle, a real picture can accommodate more and wider scenes, and can meet the picture shooting of some large scene range, so it is widely used in the camera shooting field such as sports cameras, unmanned aerial vehicle cameras, panoramic monitoring, etc.

[0003] At present, the field of view angle of the fisheye lens on the market is mostly between 180-220 degrees, and plastic aspherical or glass aspherical lenses are used to realize a larger aperture and higher resolution. However, there is almost no scheme that can realize a field of view angle greater than 220 degrees. For example, a fisheye lens is disclosed in Chinese Patent No. CN209433111U, which comprises first to eighth lenses from the object side to the image side along an optical axis; the first lens is a convex-concave lens with negative refractive power; the second lens is a convex-concave lens with negative refractive power; the third lens is a convex-concave lens with negative refractive power; the fourth lens is a convex-convex lens with positive refractive power; the fifth lens is a plano-convex lens with positive refractive power; the sixth lens is a convex-concave lens with negative refractive power; the seventh lens is a convex-convex lens with positive refractive power; the eighth lens is a convex-concave lens with negative refractive power; the fisheye lens more satisfies nd1>1.9, wherein nd1 is the refractive index of the first lens at the d line; the fisheye lens has a field of view angle of 195 degrees. And a fisheye lens system is disclosed in Chinese Patent No. CN112817120A. The fisheye lens system comprises, from the object side to the image side along the optical axis, a negative first lens with a convex object surface and a concave image surface, a negative second lens with a convex object surface and a concave image surface, a negative third lens with a convex object surface and a concave image surface, a positive fourth lens with a convex object surface and a convex image surface, a negative fifth lens with a concave object surface and a concave image surface, a positive sixth lens with a convex object surface and a convex image surface, a positive seventh lens with a convex object surface and a convex image surface, a positive eighth lens with a convex object surface and a convex image surface, and a negative ninth lens with a concave object surface and a concave image surface. Thus, a super-pixel fisheye lens with a field of view angle of 195 degrees, an optical total length of less than 22 mm, and a resolution of up to 12 million pixels is provided, which can fully meet the application requirements of 4K.

[0004] Adopting plastic aspherical surface can effectively improve the resolution of the lens and reduce the processing cost of the lens, but the high and low temperature resistance of the plastic aspherical surface is poor, and the performance is not stable; the optical material of the glass aspherical surface lens is more, which helps to improve the imaging quality of the lens more, and the performance of the glass aspherical surface lens is stable, but the processing cost of the glass aspherical surface lens is higher.

[0005] Therefore, there is almost no fisheye lens on the market that can achieve a 240° field of view, an F2.4 aperture, a 3.45mm image surface diameter, and an eight-piece all-glass lens structure. Therefore, it is urgent to develop an all-glass fisheye lens with a 240° field of view, an F2.4 aperture, and a 3.45mm image surface diameter to fill the market gap. SUMMARY

[0006] The purpose of the present application is to provide an all-glass fisheye lens which realizes a 240° field of view, an F2.4 maximum aperture, a 3.45mm image surface diameter and a total length less than 20mm.

[0007] To solve the above technical problems, the technical solution adopted by the present application is:

[0008] An all-glass fisheye lens, comprising a first lens, a second lens, a third lens, a fourth lens, a fifth lens, an aperture stop, a sixth lens, a seventh lens, an eighth lens and a filter arranged in order along the optical axis from the object side to the image side, wherein the first lens to the eighth lens are glass spherical lenses, and the seventh lens and the eighth lens are a cemented assembly.

[0009] Further, along the optical axis direction from the object side to the image side, the first lens is a convex-concave negative power meniscus lens, the second lens is a convex-concave negative power meniscus lens, the third lens is a double-convex positive power lens, the fourth lens is a double-concave negative power lens, the fifth lens is a double-convex positive power lens, the sixth lens is a concave-convex positive power lens, the seventh lens is a double-convex positive power lens, and the eighth lens is a concave-convex negative power lens.

[0010] Further, the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the seventh lens and the eighth lens respectively satisfy the following conditional expressions with the entire lens:

[0011] -7.0 < f1 / f < -5.0;

[0012] -4.0 < f2 / f < -3.0;

[0013] 5.0 < f3 / f < 6.0;

[0014] -4.0 < f4 / f < -3.0;

[0015] 3.0 < f5 / f < 4.0;

[0016] 12.5 < f6 / f < 13.5;

[0017] 2.0 < f7 / f < 3.0;

[0018] -6.0 < f8 / f < -5.0;

[0019] wherein f is the focal length of the whole lens, f1, f2, f3, f4, f5, f6, f7, f8 respectively correspond to the focal length of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the seventh lens and the eighth lens.

[0020] Further, the seventh lens and the eighth lens are cemented to form a cemented lens, and the cemented lens and the whole lens satisfy the following conditional expression:

[0021] 4.0 < f e / f < 5.0;

[0022] wherein f e is the focal length of the cemented lens.

[0023] Still further, the focal length, the refractive index and the curvature radius of the first lens to the eighth lens satisfy the following conditions:

[0024] -7<f1<-5 1.8<n1<1.9 10<R1<15 3<R2<4 -4<f2<-3 1.8<n2<1.9 20<R3<25 2.5<R4<3 5.5<f3<6.5 1.8<n3<1.95 25<R5<35 -10<R6<-5 -4<f4<-3 1.4<n4<1.5 -5<R7<-3 3<R8<5 3.5<f5<4.5 1.6<n5<1.75 4.5<R9<6 -6.5<R10<-4.5 14<f6<15 1.4<n6<1.5 -8<R11<-6.5 -4.5<R12<-3 2<f7<3 1.5<n7<1.65 3<R13<5 -3<R14<-2 -6<f8<-5 2.0<n8<2.15 -3<R15<-2 -7<R16<-4.5

[0025] In the above table, "f" is the focal length, "n" is the refractive index, "R" is the curvature radius, and "-" indicates that the direction is negative;

[0026] wherein f1 to f8 respectively correspond to the focal length of the first lens to the eighth lens; n1 to n8 respectively correspond to the refractive index of the first lens to the eighth lens; R1, R3, R5, R7, R9, R11, R13, R15 respectively correspond to the curvature radius of the first to eighth lenses close to the object side surface, and R2, R4, R6, R8, R10, R12, R14, R16 respectively correspond to the curvature radius of the first to eighth lenses away from the object side surface.

[0027] Still further, the interval between the lenses satisfies the following conditions:

[0028] 2.65 < D1 < 2.75;

[0029] 1.2 < D2 < 1.25;

[0030] 0.3 < D3 < 0.5;

[0031] 0.15 < D4 < 0.25;

[0032] 2.0 < D5 < 2.5;

[0033] 0.25 < D6 < 0.35;

[0034] Wherein, D1 is the interval of the first lens and the second lens, D2 is the interval of the second lens and the third lens, D3 is the interval of the third lens and the fourth lens, D4 is the interval of the fourth lens and the fifth lens, D5 is the interval of the fifth lens and the sixth lens, and D6 is the interval of the sixth lens and the seventh lens.

[0035] The full-glass fisheye lens provided by the application has a field of view FOV≥240°.

[0036] Compared with the prior art, the full-glass fisheye lens provided by the application has the beneficial effects that: in order to ensure the stability of the optical system, the full-glass optical structure is formed by using eight glass spherical lenses, the lenses are reasonably arranged, and the optical material is selected, so that the imaging quality is good, the 240° field of view, the F2.4 maximum aperture, the 3.45mm image surface diameter and the total length less than 20mm and other indexes can be realized, the full-glass spherical lens structure is simple in structure and low in processing difficulty, and the problems that the existing fisheye lens on the market has a field of view of only 180-220° which is not large enough, and the performance of the glass-plastic hybrid fisheye lens is not stable or the cost is high are solved. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 is a schematic diagram of an optical system of the full-glass fisheye lens provided in Embodiment 1;

[0038] Figure 2 is an MTF curve diagram of the full-glass fisheye lens provided in Embodiment 1;

[0039] Figure 3 is a point column diagram of the full-glass fisheye lens provided in Embodiment 1;

[0040] Figure 4 is a schematic diagram of an optical system of the full-glass fisheye lens provided in Embodiment 2;

[0041] Figure 5 is an MTF curve diagram of the full-glass fisheye lens provided in Embodiment 2;

[0042] Figure 6 is a point column diagram of the full-glass fisheye lens provided in Embodiment 2. DETAILED DESCRIPTION

[0043] In order to make the above features and advantages of the application more obvious and easy to understand, the following embodiments are described in detail below, and the detailed description is made below with reference to the accompanying drawings.

[0044] As Figure 1 and Figure 2As shown, the two all-glass fisheye lenses provided by Example 1 and Example 2 respectively include, in order along the optical axis from the object side to the image side, a first lens 1, a second lens 2, a third lens 3, a fourth lens 4, a fifth lens 5, an aperture stop 11, a sixth lens 6, a seventh lens 7, an eighth lens 8, a filter 9, and an imaging surface 10. The first lens 1 to the eighth lens 8 are all glass spherical lenses, wherein the seventh lens 7 and the eighth lens 8 are a cemented lens assembly.

[0045] Further, along the optical axis direction from the object side to the image side, the first lens 1 is a convex-concave negative power meniscus lens, the second lens 2 is a convex-concave negative power meniscus lens, the third lens 3 is a double-convex positive power lens, the fourth lens 4 is a double-concave negative power lens, the fifth lens 5 is a double-convex positive power lens, the sixth lens 6 is a concave-convex positive power lens, the seventh lens 7 is a double-convex positive power lens, and the eighth lens 8 is a concave-convex negative power lens.

[0046] Further, the first lens 1, the second lens 2, the third lens 3, the fourth lens 4, the fifth lens 5, the sixth lens 6, the seventh lens 7, and the eighth lens 8 respectively satisfy the following conditional expressions with the entire lens:

[0047] -7.0 < f1 / f < -5.0;

[0048] -4.0 < f2 / f < -3.0;

[0049] 5.0 < f3 / f < 6.0;

[0050] -4.0 < f4 / f < -3.0;

[0051] 3.0 < f5 / f < 4.0;

[0052] 12.5 < f6 / f < 13.5;

[0053] 2.0 < f7 / f < 3.0;

[0054] -6.0 < f8 / f < -5.0;

[0055] wherein f is the focal length of the entire lens, and f1, f2, f3, f4, f5, f6, f7, and f8 respectively correspond to the focal lengths of the first lens 1, the second lens 2, the third lens 3, the fourth lens 4, the fifth lens 5, the sixth lens 6, the seventh lens 7, and the eighth lens 8.

[0056] Further, the seventh lens 7 and the eighth lens 8 are cemented to form a cemented lens, and the cemented lens and the entire lens satisfy the following conditional expressions:

[0057] 4.0 < f e / f < 5.0;

[0058] wherein fe The focal length of the glued lens.

[0059] Further, the intervals between the lenses satisfy the following conditions:

[0060] 2.65 < D1 < 2.75;

[0061] 1.2 < D2 < 1.25;

[0062] 0.3 < D3 < 0.5;

[0063] 0.15 < D4 < 0.25;

[0064] 2.0 < D5 < 2.5;

[0065] 0.25 < D6 < 0.35;

[0066] wherein D1 is the interval between the first lens 1 and the second lens 2, D2 is the interval between the second lens 2 and the third lens 3, D3 is the interval between the third lens 3 and the fourth lens 4, D4 is the interval between the fourth lens 4 and the fifth lens 5, D5 is the interval between the fifth lens 5 and the sixth lens 6, and D6 is the interval between the sixth lens 6 and the seventh lens 7.

[0067] Embodiment 1

[0068] In embodiment 1, the parameters of the first lens to the eighth lens in the all-glass fisheye lens provided by the embodiment are shown in Table 1. The optical system structure composed of the above lenses achieves the following optical indexes:

[0069] Focal length: f' = 1.087 mm;

[0070] Relative aperture: F = 2.4;

[0071] Field of view: 2w = 240°;

[0072] Imaging circle diameter: 3.45 mm;

[0073] Total length of optical path is less than 20 mm;

[0074] Applicable spectral range: 430-700 nm.

[0075] Table 1 Parameters of the all-glass fisheye lens provided by embodiment 1

[0076]

[0077]

[0078] Wherein, R is the radius of the center of the lens surface, D is the distance from the corresponding optical surface to the next optical surface on the optical axis, nd is the refractive index corresponding to d light (wavelength 587 nm); f is the focal length of the lens. S1 and S2 are the object surface and image surface of the first lens, S3 and S4 are the object surface and image surface of the second lens, S5 and S6 are the object surface and image surface of the third lens, S7 and S8 are the object surface and image surface of the fourth lens, S8 and S9 are the object surface and image surface of the fifth lens, Stop is the surface where the diaphragm is located, S12 and S13 are the object surface and image surface of the sixth lens, S14 and S15 are the object surface and image surface of the seventh lens, S15 and S16 are the object surface and image surface of the eighth lens, S17 and S18 are the object surface and image surface of the filter.

[0079] Figure 2 The MTF curve diagram of the all-glass fisheye lens provided in Example 1 is shown in Figure 1. Figure 2 It can be seen that the central field of view is greater than 0.45 at 300 line pairs, and the edge field of view is greater than 0.2 at 300 line pairs, and the lens has good contrast.

[0080] Figure 3 The spot diagram of the all-glass fisheye lens provided in Example 1 is shown in Figure 2. Figure 3 It can be seen that the central field of view spot diagram diameter is less than 1.8 μm, and the edge field of view spot diagram diameter is less than 3.5 μm, and the lens has high resolution.

[0081] Example 2

[0082] In Example 2, the parameters of the first lens to the eighth lens in the all-glass fisheye lens provided in the embodiment are shown in Table 2, and the optical system structure composed of the above lenses reaches the following optical indicators:

[0083] Focal length: f' = 1.084 mm;

[0084] Relative aperture: F = 2.4;

[0085] Field of view angle: 2w = 240°;

[0086] Imaging circle diameter: 3.45 mm;

[0087] Total length of optical path is less than 20 mm;

[0088] Spectral range: 430-700 nm.

[0089] Table 2 Parameters of the all-glass fisheye lens provided in Example 2

[0090]

[0091] Wherein, R is the radius of the center of the lens surface, D is the distance from the corresponding optical surface to the next optical surface on the optical axis, nd is the refractive index corresponding to d light (wavelength 587nm), f is the focal length of the lens. S1 and S2 are the object surface and image surface of the first lens, S3 and S4 are the object surface and image surface of the second lens, S5 and S6 are the object surface and image surface of the third lens, S7 and S8 are the object surface and image surface of the fourth lens, S8 and S9 are the object surface and image surface of the fifth lens, Stop surface is the surface where the diaphragm is located, S12 and S13 are the object surface and image surface of the sixth lens, S14 and S15 are the object surface and image surface of the seventh lens, S15 and S16 are the object surface and image surface of the eighth lens, S17 and S18 are the object surface and image surface of the filter.

[0092] Figure 5 The MTF curve diagram of the all-glass fisheye lens in embodiment 2 is shown in FIG. 6. It can be seen from FIG. 6 that the central field of view is greater than 0.45 at 300 line pairs, and the edge field of view is greater than 0.15 at 300 line pairs, so the lens has good contrast. Figure 5

[0093] Figure 6 The point diagram of the all-glass fisheye lens in embodiment 2 is shown in FIG. 7. It can be seen from FIG. 7 that the central field of view point diagram diameter is less than 2.0μm, and the edge field of view point diagram diameter is less than 3.7μm, so the lens has high resolution. Figure 6

[0094] The above only describes the preferred embodiments of the present application, and any equivalent changes and modifications made within the scope of the patent application of the present application shall be included in the scope of the present application.​​

Claims

1. An all-glass fisheye lens characterized by comprising: The all-glass fisheye lens is composed of a first lens, a second lens, a third lens, a fourth lens, a fifth lens, an aperture diaphragm, a sixth lens, a seventh lens, an eighth lens and a filter arranged in order along the optical axis from the object side to the image side, wherein the first lens to the eighth lens are glass spherical lenses, and the seventh lens and the eighth lens are a cemented assembly. From the object side to the image side along the optical axis direction, the first lens is a convex-concave negative power meniscus lens, the second lens is a convex-concave negative power meniscus lens, the third lens is a double-convex positive power lens, the fourth lens is a double-concave negative power lens, the fifth lens is a double-convex positive power lens, the sixth lens is a concave-convex positive power lens, the seventh lens is a double-convex positive power lens, and the eighth lens is a concave-convex negative power lens. The first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the seventh lens and the eighth lens respectively satisfy the following conditional expressions with the whole lens: -7.0 < f1 / f < -5.0; -4.0 < f2 / f < -3.0; 5.0 < f3 / f < 6.0; -4.0 < f4 / f < -3.0; 3.0 < f5 / f < 4.0; 12.5 < f6 / f < 13.5; 2.0 < f7 / f < 3.0; -6.0 < f8 / f < -5.0; wherein f is the focal length of the whole lens, and f1, f2, f3, f4, f5, f6, f7 and f8 respectively correspond to the focal lengths of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the seventh lens and the eighth lens; The seventh lens and the eighth lens are cemented to form a cemented lens, and the cemented lens and the whole lens satisfy the following conditional expressions: 4.0 < f < 5.0 e f < 5.0; wherein f e is the focal length of the cemented lens; The focal lengths, refractive indices and curvature radii of the first lens to the eighth lens satisfy the following conditions: In the above table, "f" is the focal length, "n" is the refractive index, and "R" is the curvature radius, and "-" indicates that the direction is negative; wherein f1 to f8 respectively correspond to the focal lengths of the first lens to the eighth lens; n1 to n8 respectively correspond to the refractive indices of the first lens to the eighth lens; R1, R3, R5, R7, R9, R11, R13 and R15 respectively correspond to the curvature radii of the object side surfaces of the first to eighth lenses; and R2, R4, R6, R8, R10, R12, R14 and R16 respectively correspond to the curvature radii of the image side surfaces of the first to eighth lenses; The intervals between the lenses satisfy the following conditions: 2.65<D1<2.75； 1.2<D2<1.25； 0.3<D3<0.5； 0.15<D4<0.25； 2.0<D5<2.5； 0.25<D6<0.35； wherein D1 is the interval between the first lens and the second lens, D2 is the interval between the second lens and the third lens, D3 is the interval between the third lens and the fourth lens, D4 is the interval between the fourth lens and the fifth lens, D5 is the interval between the fifth lens and the sixth lens, and D6 is the interval between the sixth lens and the seventh lens.

2. The all-glass fisheye lens according to claim 1, characterized in that, The field of view FOV of the all-glass fisheye lens is greater than or equal to 240°.

3. The all-glass fisheye lens according to claim 1, characterized in that, The all-glass fisheye lens has a maximum aperture of F2.4, an image surface diameter of 3.45 mm and a total length less than 20 mm.

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