A fish-eye lens and an imaging device

Abstract

The present invention relates to the field of optical imaging technology, and in particular to a fisheye lens and imaging equipment, wherein the fisheye lens comprises, in order from the object side to the image side along the optical axis, a first lens, a second lens, a stop, a third lens, a fourth lens, a fifth lens, a sixth lens and a filter, wherein the first lens is a glass lens, with a convex surface on the object side and a concave surface on the image side, and has negative optical focal length; the second lens has a concave surface on the object side and a convex surface on the image side, and has negative optical focal length; the third and fourth lenses are both biconvex lenses, both have positive optical focal length; the fifth lens is a biconcave lens, with negative optical focal length; the sixth lens has a convex surface on both the object and image side, and has positive optical focal length; the fourth lens and the fifth lens are glued together, and have negative optical focal length; the lens solves the problems of scratch resistance, high development cost and insufficient image height, and embodies the advantages of scratch resistance, low development cost, large image surface, compact structure, no blind spot in imaging, day and night confocality, and high clarity.

Description

Technical Field

[0001] The present invention relates to the field of optical imaging technology, and in particular to a fisheye lens and imaging equipment. Background Art

[0002] Fisheye lenses typically have a field of view of 140° or greater. Due to their exceptionally wide field of view, particularly those exceeding 180°, and their seamless imaging, fisheye lenses are commonly used in video doorbells, security surveillance, panoramic cameras, sports DVs, and in-vehicle systems. The lens is a core component in video doorbells, and the market places numerous demands on these lenses—large field of view, large image area, large aperture, high definition, day / night confocality, compact design, waterproofing, and excellent weather resistance. To meet these requirements, existing lenses typically utilize a glass-plastic hybrid structure.

[0003] For example, the lens disclosed in patent application CN110058386A, published on July 26, 2019, and titled "An Ultra-Short TTL Day-Night Confocal Optical Lens," utilizes a structure consisting of two glass spherical lenses and three plastic aspherical lenses, with one plastic aspherical lens in front of the aperture and four lenses behind the aperture. While the number of lenses is relatively small, the outermost plastic lens is not scratch-resistant.

[0004] Another example is the lens disclosed in patent application CN211786309U, published on October 27, 2020, and titled "A Fisheye Lens." It uses a structure consisting of one glass spherical lens and five plastic aspherical lenses, with two lenses positioned before the aperture and four behind it. The first lens is made of glass. The high number of plastic lenses leads to high development costs.

[0005] For example, the lens disclosed in the patent document named "Fisheye Lens" with application publication number CN110646919A and application publication date January 3, 2020, adopts a structure of 4 glass spherical lenses and 2 plastic aspherical lenses, with 3 lenses before and after the aperture, and the first lens is made of glass. However, the maximum image height is not large enough and it is difficult to reach 1 / 2.7 inches.

[0006] Therefore, the current compact fisheye lenses have problems such as being scratch-resistant, having high development costs, and having insufficient image height, and need further improvement. Summary of the Invention

[0007] To address the problems of the compact fisheye lens mentioned in the background art, such as poor scratch resistance, high development cost, and insufficient image height, the present invention provides a fisheye lens comprising, in order from the object side to the image side along the optical axis, a first lens, a second lens, an aperture, a third lens, a fourth lens, a fifth lens, a sixth lens, and a filter.

[0008] The first lens is a glass lens with negative optical power, the object side of the first lens is convex, and the image side is concave;

[0009] The second lens has negative optical power, and the object side of the second lens is concave and the image side is convex;

[0010] The third lens has positive refractive power, and the object side of the third lens is convex, and the image side of the third lens is convex;

[0011] The fourth lens has positive refractive power, and the object side of the fourth lens is convex, and the image side of the fourth lens is convex;

[0012] The fifth lens has negative optical power, and the object side and image side of the fifth lens are concave.

[0013] The sixth lens has positive refractive power, and the object side and image side of the sixth lens are convex;

[0014] The fourth lens and the fifth lens are cemented together to form a cemented lens, and the cemented lens has negative optical power.

[0015] Furthermore, the third lens, the fourth lens and the fifth lens are glass lenses, and the second lens and the sixth lens are plastic lenses.

[0016] Furthermore, the first lens, the third lens, the fourth lens and the fifth lens are spherical lenses, and the second lens and the sixth lens are aspherical lenses.

[0017] Furthermore, the fourth lens is a symmetrical biconvex lens, and the fifth lens is a symmetrical biconcave lens.

[0018] Furthermore, the absolute value range of the ratio of the focal length f1' of the first lens to the focal length f' of the fisheye lens is 1.2 < |f1' / f'| < 2.0; the absolute value range of the ratio of the focal length f2' of the second lens to the focal length f' of the fisheye lens is 15 < |f2' / f'| < 40; the absolute value range of the ratio of the focal length f3' of the third lens to the focal length f' of the fisheye lens is 1.2 < |f3' / f'| < 2.0; the combined focal length f of the fourth lens and the fifth lens is 45 The absolute value range of the ratio of ' to the focal length f' of the fisheye lens is 2.0<|f 45 ' / f'|<3.5; the absolute value range of the ratio of the focal length f6' of the sixth lens to the focal length f' of the fisheye lens is 1.5<|f6' / f'|<3.0.

[0019] Furthermore, the refractive index nd1 of the material of the first lens is in the range of 1.70≤nd1≤1.80, and the Abbe number Vd1 is in the range of 45≤Vd1≤55; the refractive index nd2 of the material of the second lens is in the range of 1.53≤nd2≤1.70, and the Abbe number Vd2 is in the range of 20≤Vd2≤30; the refractive index nd3 of the material of the third lens is in the range of 1.85≤nd3≤1.95, and the Abbe number Vd3 is in the range of 25≤Vd3≤ 45; the refractive index nd4 of the material of the fourth lens is in the range of 1.43≤nd4≤1.55, and the Abbe number Vd4 is in the range of 65≤Vd4≤95; the refractive index nd5 of the material of the fifth lens is in the range of 1.80≤nd5≤1.95, and the Abbe number Vd5 is in the range of 17≤Vd5≤30; the refractive index nd6 of the material of the sixth lens is in the range of 1.53≤nd6≤1.70, and the Abbe number Vd6 is in the range of 40≤Vd6≤60.

[0020] Furthermore, a difference between a refractive index nd5 of the fifth lens and a refractive index nd4 of the fourth lens satisfies nd5-nd4>0.3, and a difference between an Abbe number Vd5 of the fifth lens and an Abbe number Vd4 of the fourth lens satisfies Vd4-Vd5>40.

[0021] Furthermore, the aperture is located on a side close to the third lens.

[0022] Furthermore, the optical filter includes but is not limited to a day and night confocal filter or a dual filter switch.

[0023] The present invention also provides an imaging device using the above-mentioned fisheye lens. The imaging device further includes an imaging element, which is used to convert the optical signal collected by the fisheye lens into an electrical signal.

[0024] Compared with the prior art, the fisheye lens provided by the present invention includes a first lens, a second lens, an aperture, a third lens, a fourth lens, a fifth lens, a sixth lens and a filter in sequence from the object side to the image side along the optical axis. The first lens, the third lens, the fourth lens and the fifth lens are spherical lenses, and the second lens and the sixth lens are aspherical lenses. This solves the problems of scratch resistance, high development cost and insufficient image height, and embodies the advantages of scratch resistance, low development cost, large image surface, compact structure, no blind spots in imaging, day and night confocality, and high clarity. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0026] Figure 1 Schematic diagram of the optical path of the lens of the present invention;

[0027] Figure 2 Schematic diagram of the structure of the lens of the present invention;

[0028] Figure 3 This is a spot diagram of the lens of the present invention under visible light;

[0029] Figure 4 This is the MTF curve of the lens of the present invention under visible light;

[0030] Figure 5 This is the MTF curve of the lens of the present invention under near-infrared light of 850nm;

[0031] Figure 6 This is a diagram of field curvature and distortion of the lens of the present invention under visible light;

[0032] Figure 7 This is a relative illumination curve diagram of the lens of the present invention under visible light;

[0033] Figure 8 This is a through-focus MTF curve diagram of the lens of the present invention under visible light;

[0034] Figure 9 This is the defocus MTF curve of the lens of the present invention under near-infrared light of 850nm;

[0035] Figure 10 This is a graph showing the magnification chromatic aberration curve of the lens of the present invention under visible light.

[0036] Reference numerals:

[0037] 10. First lens 20, second lens 30, third lens

[0038] 40, fourth lens 50, fifth lens 60, sixth lens

[0039] 70, aperture 80, filter DETAILED DESCRIPTION

[0040] To make the purpose, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0041] In the description of the present invention, it should be noted that the terms "upper," "lower," "front," "back," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limiting the present invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0042] Specific embodiments are given below:

[0043] refer to Figure 1 、 Figure 2 A fisheye lens comprises, along the optical axis direction from the object side to the image side, a first lens 10, a second lens 20, an aperture 70, a third lens 30, a fourth lens 40, a fifth lens 50, a sixth lens 60 and a filter 80; the first lens 10 is a glass lens with negative optical power, the object side of the first lens 10 is convex, and the image side is concave; the second lens 20 has negative optical power, the object side of the second lens 20 is concave, and the image side is convex; the third lens 30 has positive optical power, The object side of the third lens 30 is convex, and the image side is convex; the fourth lens 40 has positive optical power, and the object side of the fourth lens 40 is convex, and the image side is convex; the fifth lens 50 has negative optical power, and the object side of the fifth lens 50 is concave, and the image side is concave; the sixth lens 60 has positive optical power, and the object side of the sixth lens 60 is convex, and the image side is convex; the fourth lens 40 and the fifth lens 50 are bonded to each other to form a cemented lens, and the cemented lens has negative optical power.

[0044] In a specific implementation, the lens is composed of a first lens 10, a second lens 20, an aperture 70, a third lens 30, a fourth lens 40, a fifth lens 50, a sixth lens 60, and a filter 80, which are arranged in sequence. The fourth lens 40 and the fifth lens 50 are bonded together to form a cemented lens, and the aperture 70 is located between the second lens 20 and the third lens 30. Light enters from the object side and passes through the first lens 10, the second lens 20, the aperture 70, the third lens 30, the fourth lens 40, the fifth lens 50, the sixth lens 60, and the filter 80 in sequence to reach the image sensor.

[0045] Compared with the prior art, the present invention provides a fisheye lens, which includes a first lens, a second lens, an aperture, a third lens, a fourth lens, a fifth lens, a sixth lens and a filter in sequence from the object side to the image side along the optical axis, thereby solving the problems of scratch resistance, high development cost and insufficient image height, and embodies the advantages of scratch resistance, low development cost, large image surface, compact structure, no blind spots in imaging, day and night confocality, and high clarity.

[0046] As an embodiment of the present invention, a fisheye lens is provided, wherein the first lens 10 is a meniscus glass spherical lens with negative optical power, the object side is convex, and the image side is concave; the second lens 20 is a plastic aspherical lens with negative optical power, the object side is concave, and the image side is convex; the third lens 30 is a biconvex glass spherical lens with positive optical power; the fourth lens 40 is a symmetrical biconvex glass spherical lens with positive optical power; the fifth lens 50 is a symmetrical biconcave glass spherical lens with negative optical power; the sixth lens 60 is a plastic aspherical lens with positive optical power, both the object and image side sides are convex; the fourth lens 40 and the fifth lens 50 are cemented together, and their optical power is negative.

[0047] Specifically, the surfaces of the second lens 20 and the sixth lens 60 are both aspherical, and the aspherical surface shape satisfies the following equation:

[0048]

[0049] Among them, z represents the vector height along the optical axis, r represents the distance from a point on the optical surface to the optical axis, c represents the curvature of the surface, c = 1 / R (R represents the radius of curvature), k represents the quadratic surface constant of the surface, α1, α2, α3, α4, α5, α6, α7, and α8 are the 2nd, 4th, 6th, 8th, 10th, 12th, 14th, and 16th order aspheric coefficients respectively.

[0050] The fisheye lens is mainly composed of 4 glass spherical lenses and 2 plastic aspherical lenses. The number of lenses is reasonable, and the first lens is made of glass with high hardness. The fisheye lens has many advantages such as scratch resistance, low development cost, large image surface, compact structure, no blind spot imaging, day and night confocality, and high clarity. It is suitable for video doorbells, security monitoring and other fields.

[0051] It should be understood that the material selection of each lens includes but is not limited to the above forms, which will not be described in detail here.

[0052] Specifically, f' is defined as the focal length of the entire fisheye lens, f1' is the focal length of the first lens 10, f2' is the focal length of the second lens 20, f3' is the focal length of the third lens 30, and f 45 f6′ represents the combined focal length of the fourth lens 40 and the fifth lens 50, i.e., the focal length of the cemented lens, and f7′ represents the focal length of the sixth lens 60. The focal length ranges of the lenses are:

[0053] The absolute value range of the ratio of the focal length f1' of the first lens 10 to the focal length f' of the fisheye lens is 1.2 < |f1' / f'| < 2.0; the absolute value range of the ratio of the focal length f2' of the second lens 20 to the focal length f' of the fisheye lens is 15 < |f2' / f'| < 40; the absolute value range of the ratio of the focal length f3' of the third lens 30 to the focal length f' of the fisheye lens is 1.2 < |f3' / f'| < 2.0; the combined focal length f of the fourth lens 40 and the fifth lens 50 is 45 The absolute value range of the ratio of ' to the focal length f' of the fisheye lens is 2.0<|f 45 ' / f'|<3.5; the absolute value range of the ratio of the focal length f6' of the sixth lens 60 to the focal length f' of the fisheye lens is 1.5<|f6' / f'|<3.0.

[0054] Specifically, the refractive index nd1 of the material of the first lens 10 is in the range of 1.70≤nd1≤1.80, and the Abbe number Vd1 is in the range of 45≤Vd1≤55; the refractive index nd2 of the material of the second lens 20 is in the range of 1.53≤nd2≤1.70, and the Abbe number Vd2 is in the range of 20≤Vd2≤30; the refractive index nd3 of the material of the third lens 30 is in the range of 1.85≤nd3≤1.95, and the Abbe number Vd3 is in the range of 25≤Vd3≤4 5; the refractive index nd4 of the material of the fourth lens element 40 is in the range of 1.43≤nd4≤1.55, and the Abbe number Vd4 is in the range of 65≤Vd4≤95; the refractive index nd5 of the material of the fifth lens element 50 is in the range of 1.80≤nd5≤1.95, and the Abbe number Vd5 is in the range of 17≤Vd5≤30; the refractive index nd6 of the material of the sixth lens element 60 is in the range of 1.53≤nd6≤1.70, and the Abbe number Vd6 is in the range of 40≤Vd6≤60.

[0055] Preferably, the difference between the refractive index nd5 of the material of the fifth lens element 50 and the refractive index nd4 of the material of the fourth lens element 40 satisfies nd5-nd4>0.3, and the difference between the Abbe number Vd5 of the fifth lens element 50 and the Abbe number Vd4 of the fourth lens element 40 satisfies Vd4-Vd5>40. The cemented lens is used to better achromatize and achieve day and night confocality.

[0056] Preferably, the aperture 70 is located between the second lens 20 and the third lens 30 , and the aperture 70 is located on a side close to the third lens 30 .

[0057] Preferably, a filter 80 is provided between the sixth lens 60 and the image sensor to filter out infrared rays so that the lens imaging is not disturbed; preferably, the filter 80 includes but is not limited to a day and night confocal filter or a dual filter switch.

[0058] Table 1 is a detailed parameter table of a specific embodiment of the fisheye lens of the present invention, which includes the curvature radius value, center thickness, material properties and effective aperture of each lens.

[0059] Table 1:

[0060]

[0061]

[0062] In Table 1, in the surface number column, 1 and 2 correspond to the two surfaces of the first lens 10; 3 and 4 correspond to the two surfaces of the second lens 20; 5 / Stop corresponds to the aperture stop 70; 6 and 7 correspond to the two surfaces of the third lens 30; 8 and 9 correspond to the two surfaces of the fourth lens 40; 10 and 11 correspond to the two surfaces of the fifth lens 50; 12 and 13 correspond to the two surfaces of the sixth lens 60; 14 and 15 correspond to the two surfaces of the filter 80; 16 and 17 correspond to the two surfaces of the image sensor surface protection glass; IMA is the image plane.

[0063] Table 2 shows the aspheric surface values of the second lens element 20 and the sixth lens element 60 in a specific embodiment of the fisheye lens of the present invention.

[0064] Table 2:

[0065]

[0066]

[0067] In Table 2, 5.6635E-3 represents the value 5.6635×10-3, and the rest are similar.

[0068] In this embodiment, the overall focal length of the optical imaging lens is EFL = 2.41 mm, the aperture value is FNO = 2.1, the diagonal field of view angle DFOV = 172°, the total optical length TTL of the lens is 13.59 mm, and when used with the 1 / 2.7-inch OminiVision OV2710 image sensor, the image plane chief ray incidence angle CRA ≤ 21.73°.

[0069] refer to Figure 2 , a structural diagram of the fisheye lens of the present invention, defining the bottom of the lens barrel as the end close to the image side, and the top of the lens barrel as the end close to the object side; a first gasket, a second gasket and a third gasket are provided in sequence from the image side to the object side.

[0070] The lens consists of six lenses. The filter 80 is glued to the bottom groove of the lens barrel, and the image side bearing surface of the sixth lens 60 is against the bottom of the lens barrel; the fourth lens 40 and the fifth lens 50 are glued into a cemented lens, and a first gasket is provided between the cemented lens and the sixth lens.

[0071] A second gasket is provided between the cemented lens and the third lens 30. The second gasket is provided with a stepped hole. The stepped hole includes a large hole and a small hole. The large hole is located at the end close to the object side, and the small hole is located at the end close to the image side. The third lens 30 is embedded in the large hole of the second gasket. At the same time, the second gasket separates the third lens 30 from the cemented lens.

[0072] A third gasket is provided between the second lens 20 and the third lens 30; the object side bearing surface of the second lens 20 abuts against the image side bearing surface of the first lens 10; a screw thread is provided on the head of the lens barrel for cooperating with the locking cover to lock the lens.

[0073] Figure 3 This is a point diagram under visible light, where the wavelengths are 450nm, 487nm, 546nm, 587nm, and 656nm, and the weight ratio is 10:23:29:27:10. Figure 3 It can be seen that the diffuse spots in each field of view are relatively concentrated, with a root mean square radius of less than 3.5 μm, and are relatively evenly distributed. At the same time, it can be seen that when the embodiment of the present invention is used with a 1 / 2.7-inch image sensor, the HFOV is ≥ 140°.

[0074] Figure 4 is the MTF curve under visible light, and Figure 5 The MTF curve at 850nm. The MTF curve represents the comprehensive resolution level of an optical system. Figure 4 、 Figure 5 It can be seen that the MTF values at the center field of view of 200lp / mm are all ≥0.3, the MTF values at the edge field of view of 125lp / mm are all ≥0.3, and the MTF values at 160lp / mm are all ≥0.2. Therefore, after adjusting the focus during the day, it is still clear at night, meeting the day and night confocal function.

[0075] Figure 6 The field curvature / distortion curve under visible light. The distortion curve shows the distortion value under different field angles, and the unit is %. Figure 6 It can be seen that the absolute value of F-Theta distortion is ≤9%, which basically satisfies the equidistant projection object-image relationship.

[0076] Figure 7 is the relative illumination curve under visible light. Figure 7 It can be seen that the curve descends smoothly, the relative illumination value at the maximum field of view is greater than 0.42, and the imaging image is relatively bright.

[0077] Figure 8 This is the defocus MTF curve under visible light. Figure 9 This is the defocus MTF curve at 850nm, the spatial frequency is 100lp / mm, and the defocus range (abscissa) is -0.05mm to +0.05mm. Figure 8 、 Figure 9 It can be seen that compared with visible light during the day, the maximum defocus at near-infrared 850nm is less than 10μm.

[0078] Figure 10 This is a magnification chromatic aberration curve under visible light. The degree of magnification chromatic aberration correction can be known by combining this graph with the size of pixel particles. Figure 10 It can be seen that the chromatic aberration of magnification is well corrected.

[0079] In summary, the fisheye lens has the following advantages:

[0080] The first lens 10 is made of glass, which is relatively hard and scratch-resistant. The lens structure consists of four glass lenses plus two plastic aspherical lenses, with low development costs. The maximum imaging circle can reach φ6.6mm, which can support a 1 / 2.7-inch image sensor. The total optical length of the lens is less than 13.6mm TTL, and the outer diameter can be less than 14.0mm, with a compact structure. The lens has high clarity and a full-field resolution of: MTF value ≥ 0.2@160lp / mm, and is confocal day and night, with a defocus amount ≤ 10μm in near-infrared 850nm fill light mode.

[0081] The present invention also provides an imaging device using the above-mentioned fisheye lens. The imaging device also includes an imaging element, which is used to convert the light signal collected by the fisheye lens into an electrical signal. The imaging device can be, but is not limited to, one of a video doorbell, security monitoring, panoramic camera, sports DV, and vehicle-mounted.

[0082] Although terms such as first lens, second lens, aperture, third lens, fourth lens, fifth lens, sixth lens, cemented lens, and filter are frequently used herein, the use of other terms is not excluded. These terms are used solely to more conveniently describe and explain the essence of the present invention. Any interpretation of these terms as additional limitations would be contrary to the spirit of the present invention.

[0083] Finally, it should be noted that the above embodiments are intended only to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art will appreciate that the technical solutions described in the above embodiments may be modified or some or all of the technical features thereof may be replaced with equivalents; such modifications or replacements do not deviate from the essence of the corresponding technical solutions within the scope of the present invention.

Claims

1. A fisheye lens, characterized by: The optical system includes, from the object side to the image side, a first lens (10), a second lens (20), an aperture (70), a third lens (30), a fourth lens (40), a fifth lens (50), a sixth lens (60), and a filter (80); The first lens (10) is a glass lens with negative optical power, the object side of the first lens (10) is a convex surface, and the image side is a concave surface; The second lens (20) has a negative optical power, and the object side of the second lens (20) is a concave surface, and the image side is a convex surface; The third lens (30) has positive optical power, and the object side of the third lens (30) is a convex surface, and the image side is a convex surface; The fourth lens (40) has positive optical power, and the object side of the fourth lens (40) is a convex surface, and the image side is a convex surface; The fifth lens (50) has a negative optical power, and the object side of the fifth lens (50) is a concave surface, and the image side is a concave surface; The sixth lens (60) has positive optical power, and the object side of the sixth lens (60) is a convex surface, and the image side is a convex surface; The fourth lens (40) and the fifth lens (50) are bonded to each other to form a cemented lens, and the cemented lens has negative optical power; Wherein, the combined focal length of the fourth lens (40) and the fifth lens (50) is f 45 'With the focal length of the fisheye lens f The absolute value range of the ratio is .

2. The fisheye lens according to claim 1, wherein: The third lens (30), the fourth lens (40) and the fifth lens (50) are glass lenses, and the second lens (20) and the sixth lens (60) are plastic lenses.

3. The fisheye lens according to claim 1, wherein: The first lens (10), the third lens (30), the fourth lens (40) and the fifth lens (50) are spherical lenses, and the second lens (20) and the sixth lens (60) are aspherical lenses.

4. The fisheye lens according to claim 1, wherein: The fourth lens (40) is a symmetrical biconvex lens, and the fifth lens (50) is a symmetrical biconcave lens.

5. The fisheye lens according to claim 1, wherein: Focal length of the first lens 10 f 1' with the focal length of the fisheye lens f The absolute value range of the ratio is ;The focal length of the second lens 20 f 2' with the focal length of the fisheye lens f The absolute value range of the ratio is ;The focal length of the third lens 30 f 3' with the focal length of the fisheye lens f The absolute value range of the ratio is The focal length of the sixth lens 60 f 6' with the focal length of the fisheye lens f The absolute value range of the ratio is .

6. The fisheye lens according to claim 1, characterized in that: The refractive index of the material of the first lens (10) nd 1 range is 1.70 ≤nd 1 ≤ 1.80, Abbe number Vd 1 range is 45 ≤Vd 1 ≤ 55; refractive index of the material of the second lens (20) nd 2 range is 1.53 ≤nd 2 ≤ 1.70, Abbe number Vd 2 range is 20 ≤Vd 2 ≤ 30; the refractive index nd3 of the material of the third lens (30) is in the range of 1.85 ≤nd 3 ≤ 1.95, Abbe number Vd 3 range is 25 ≤Vd 3 ≤ 45; the refractive index of the material of the fourth lens (40) nd 4 range is 1.43 ≤nd 4 ≤ 1.55, Abbe number Vd 4 range is 65 ≤Vd 4 ≤ 95; the refractive index of the material of the fifth lens (50) nd 5 range is 1.80 ≤nd 5 ≤ 1.95, Abbe number Vd 5 range is 17 ≤Vd 5 ≤ 30; the refractive index of the material of the sixth lens (60) nd 6 range is 1.53 ≤nd 6 ≤ 1.70, Abbe number Vd 6 range is 40 ≤Vd 6 ≤ 60.

7. The fisheye lens according to claim 6, characterized in that: The refractive index of the material of the fifth lens (50) nd 5 and the refractive index of the material of the fourth lens (40) nd The difference of 4 satisfies nd 5- nd 4 ＞ 0.3, the Abbe number of the fifth lens (50) Vd 5 and the Abbe number of the fourth lens (40) Vd The difference of 4 satisfies Vd 4- Vd 5 ＞ 40.

8. The fisheye lens according to claim 1, wherein: The aperture (70) is located on a side close to the third lens (30).

9. The fisheye lens according to claim 1, wherein: The optical filter (80) comprises a day / night confocal filter or a dual filter switch.

10. An imaging device, characterized in that: The fisheye lens according to any one of claims 1 to 9 further comprises an imaging element, wherein the imaging element is used to convert the optical signal collected by the fisheye lens into an electrical signal.

Images