Fisheye imaging lens and camera equipment

Abstract

The utility model discloses a fisheye imaging lens and camera shooting equipment. Wherein the lenses are sequentially a first lens, a second lens, a third lens, a fourth lens, a fifth lens and a sixth lens from an object side to an image side; wherein the first lens has negative diopter, the object side surface is a convex surface, and the image side surface is a concave surface; the second lens has negative diopter, the object side surface is a concave surface, and the image side surface is a concave surface; the third lens has positive diopter, the object side surface is a convex surface, and the image side surface is a convex surface; the fourth lens has negative diopter, the object side surface is a concave surface, and the image side surface is a concave surface; the fifth lens has positive diopter, the object side surface is a convex surface, and the image side surface is a convex surface; the sixth lens has positive diopter, the object side surface is a convex surface, and the image side surface is a convex surface. The lens adopts a scheme of six glass spherical surfaces, the material cost is low, the definition of an image is ensured by reasonably distributing light angles, and the overall image quality is uniform. According to the scheme, the front three lenses form a lens front group, so that a large field angle is realized, and the resolution is improved and optimized.

Description

Technical Field

[0001] The utility model relates to the technical field of fish-eye imaging lenses, and in particular to a fish-eye imaging lens and a camera device. Background Art

[0002] A fish-eye lens is a lens with a focal length of 16 mm or shorter and a viewing angle close to or equal to 180°. It is an extreme wide-angle lens, and "fish-eye lens" is its common name. To achieve the maximum photographic viewing angle, the front lens of this photographic lens has a short diameter and protrudes forward in a parabolic shape, which is quite similar to the eye of a fish, hence the name "fish-eye lens". The existing fish-eye imaging lenses have at least one of the following disadvantages:

[0003] 1. Generally, the resolution of fish-eye lenses is not high, especially in the edge area, the resolving power is poor and the uniformity is poor;

[0004] 2. Generally, fish-eye lenses have large chromatic aberration, especially in the edge area, the chromatic aberration is large and the color restoration degree is poor;

[0005] 3. Generally, the operating temperature range of fish-eye lenses is relatively narrow, and it is easy to lose focus at high and low temperatures;

[0006] 4. Generally, the image plane of fish-eye lenses is small. Summary of the Utility Model

[0007] In view of this, the purpose of the present utility model is to provide a fish-eye imaging lens and a camera device with high optical performance. This lens can solve at least one of the technical disadvantages mentioned in the background art.

[0008] According to one aspect of the present utility model, a fish-eye imaging lens is provided, which sequentially includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and a sixth lens from the object side to the image side; wherein,

[0009] The first lens has a negative refractive power, the object side is a convex surface, and the image side is a concave surface;

[0010] The second lens has a negative refractive power, the object side is a concave surface, and the image side is a concave surface;

[0011] The third lens has a positive refractive power, the object side is a convex surface, and the image side is a convex surface;

[0012] The fourth lens has a negative refractive power, the object side is a concave surface, and the image side is a concave surface;

[0013] The fifth lens has a positive refractive power, the object side is a convex surface, and the image side is a convex surface;

[0014] The sixth lens has a positive refractive power, the object side is a convex surface, and the image side is a convex surface;

[0015] Among them, the lens satisfies the following relational expression:

[0016] -10.00 < f 1 <-6.00; -8.00 < f 2 <-3.00; 3.00 < f 3 <8.00

[0017] In the formula, f 1 is the focal length of the first lens, f 2 is the focal length of the second lens, f 3 is the focal length of the third lens.

[0018] In the above technical solution, the lens adopts a 6-piece glass spherical surface solution, with low material cost, and ensures the clarity of the image by reasonably distributing the light angle, and the overall image quality is uniform. In this case, the first three lenses form the front group of the lens, achieving a large field of view angle and improving the optimized resolution.

[0019] In some embodiments, the lens satisfies the following relational expression:

[0020] D 1 / R 1 ≤1.20; D 2 / R 2 ≤1.50

[0021] In the formula, D 1 is the outer diameter value of the convex surface of the first lens, R 1 is the radius value of the convex surface of the first lens, D 2 is the outer diameter value of the convex surface of the second lens, R 2 is the radius value of the convex surface of the second lens.

[0022] In the above technical solution, the purpose of the above relationship is to assist in the cold processing of optical lenses

[0023] In some embodiments, the first lens is a meniscus negative lens.

[0024] In the above technical solution, the above setting can ensure a large field of view, large angle, and large aperture ratio of the optical system, which is beneficial to compressing the outer diameter of the optical element and realizing the miniaturization of the lens by reducing the front aperture of the lens.

[0025] In some embodiments, the lens satisfies the following relational expression:

[0026] ∣R 3 ∣>30

[0027] In the formula, R 3 is the radius value of the side of the second lens facing the object.

[0028] In the above technical solution, the larger the absolute value of R3, the smaller the energy of the ghost image generated between the protective sheet and this surface.

[0029] In some embodiments, the lens satisfies the following relationship:

[0030] nd 1 > 1.70; vd 1 < 50

[0031] nd 2 < 1.55; vd 2 > 70

[0032] In the formula, nd 1 is the refractive index of the first front lens, vd 1 is the Abbe number of the first lens, nd 2 is the refractive index of the second front lens, vd 2 is the Abbe number of the second lens.

[0033] In the above technical solution, the first lens is made of a material with a small Abbe number, and the second lens is made of a material with a large Abbe number. Using the two in combination is beneficial to improving the resolution of the optical system.

[0034] In some embodiments, the second lens, the fifth lens, and the sixth lens respectively satisfy the following relationships:

[0035] dn 2 / dT 2 > -2 * 10E-6; dn 5 / dT 5 < -9 * 10E-6; dn 6 / dT 6 < -9 * 10E-6

[0036] In the formula, dn 2 / dT 2 is the refractive index temperature coefficient of the second lens in the temperature range of -40°C to 80°C, and dn 5 / 6 / dT 5 / 6 is the refractive index temperature coefficient of the fifth lens and the sixth lens in the temperature range of -40°C to 80°C.

[0037] In the above technical solution, the second lens is a negative focal length lens. The larger the refractive index temperature coefficient, the more beneficial it is to balance the temperature drift. The fifth and sixth lenses are positive focal length lenses. The smaller the refractive index temperature coefficient, the more beneficial it is to balance the temperature drift. Through the cooperation of the three lenses, passive athermalization of the lens at extreme temperatures is achieved.

[0038] In some embodiments, the lens satisfies the following relationship:

[0039] nd 3>1.95; Vd 3 <25

[0040] Wherein, nd 3 is the refractive index of the third lens, and Vd 3 is the Abbe number of the third lens.

[0041] In the above technical solution, selecting a high refractive index material is beneficial to improving the resolution of the optical system.

[0042] In some embodiments, the fourth lens and the fifth lens form a cemented lens group and satisfy the following relational expression:

[0043] Vd 5 -Vd 4 >50

[0044] Wherein, Vd 4 is the Abbe number of the fourth lens, and Vd 5 is the Abbe number of the fifth lens.

[0045] In the above technical solution, by combining high and low dispersions, off-axis chromatic aberration is corrected and the lens resolution is improved.

[0046] In some embodiments, the lens satisfies the following relational expression:

[0047] BFL / IMH>0.70

[0048] Wherein, BFL is the back focal length of the lens, and IMH is the size of the lens target surface.

[0049] In the above technical solution, the above settings are beneficial to reducing the chief ray angle, shortening the lens length, and facilitating lens assembly.

[0050] According to another aspect of the present invention, there is provided an imaging device, including the above fisheye imaging lens; and

[0051] an image sensor configured to receive the image formed by the fisheye imaging lens.

[0052] In the above technical solution, the advantages of the imaging device rely on the fisheye imaging lens and will not be elaborated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] 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. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0054] Figure 1 It is a schematic structural diagram of Example 1 of a fisheye imaging lens of the present utility model;

[0055] Figure 2 It is an MTF curve graph of Example 1 of a fisheye imaging lens of the present utility model;

[0056] Figure 3 It is a field curvature and distortion curve graph of Example 1 of a fisheye imaging lens of the present utility model;

[0057] Figure 4 It is a lateral chromatic aberration graph of Example 1 of a fisheye imaging lens of the present utility model;

[0058] Figure 5 It is an axial chromatic aberration graph of Example 1 of a fisheye imaging lens of the present utility model;

[0059] Figure 6 It is a relative illumination graph curve of Example 1 of a fisheye imaging lens of the present utility model;

[0060] Figure 7 It is a schematic structural diagram of Example 2 of a fisheye imaging lens of the present utility model;

[0061] Figure 8 It is an MTF curve graph of Example 2 of a fisheye imaging lens of the present utility model;

[0062] Figure 9 It is a field curvature and distortion curve graph of Example 2 of a fisheye imaging lens of the present utility model;

[0063] Figure 10 It is a lateral chromatic aberration graph of Example 2 of a fisheye imaging lens of the present utility model;

[0064] Figure 11 It is an axial chromatic aberration graph of Example 2 of a fisheye imaging lens of the present utility model;

[0065] Figure 12 It is a relative illumination graph curve of Example 2 of a fisheye imaging lens of the present utility model;

[0066] Figure 13 It is a schematic structural diagram of Example 3 of a fisheye imaging lens of the present utility model;

[0067] Figure 14 It is an MTF curve graph of Example 3 of a fisheye imaging lens of the present utility model;

[0068] Figure 15 It is a field curvature and distortion curve graph of Example 3 of a fisheye imaging lens of the present utility model;

[0069] Figure 16It is the lateral chromatic aberration diagram of Example 3 of a fish-eye imaging lens of the present utility model;

[0070] Figure 17 It is the longitudinal chromatic aberration diagram of Example 3 of a fish-eye imaging lens of the present utility model;

[0071] Figure 18 It is the relative illumination diagram curve of Example 3 of a fish-eye imaging lens of the present utility model;

[0072] Figure 19 It is the structural schematic diagram of Example 4 of a camera device of the present utility model. Detailed implementation manners

[0073] The following will further describe the present utility model in detail in conjunction with the drawings and embodiments. It should be specifically pointed out that the following embodiments are only used to illustrate the present utility model, but do not limit the scope of the present utility model. Similarly, the following embodiments are only partial embodiments of the present utility model rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present utility model.

[0074] The purpose of the present utility model is to propose a fish-eye imaging lens and a camera device with high optical performance. The embodiments according to the present utility model will now be described in detail with reference to the drawings.

[0075] Figure 1 , Figure 7 , Figure 13 are respectively the sectional views of the fish-eye imaging lenses (optical systems) according to Examples 1 to 3. The fish-eye imaging lenses according to the respective examples are used for camera devices including, such as digital video cameras, digital still cameras, broadcast cameras, film cameras, surveillance cameras, etc., and camera devices with interchangeable lenses. In each sectional view, the left side is the object side OBJ and the right side is the image side IMA. In each sectional view, i (natural number) represents the order of the lens surface numbers counted from the object side, and Ln (natural number) represents the nth lens. ST represents the aperture (aperture stop). IMA represents the image plane, and when the fish-eye imaging lenses 1 to 3 according to the respective examples are used in the imaging optical systems of digital video cameras or digital still cameras, a solid-state imaging element (photoelectric conversion element) such as a CCD sensor or a CMOS sensor is arranged on the imaging plane IMA. When the fish-eye imaging lenses 1 to 3 according to the respective examples are used in the imaging optical systems of film cameras, the photosensitive surface of the film is arranged on the image plane IMA. Hereinafter, the characteristic structures and conditions of the fish-eye imaging lenses will be described according to the respective examples. The fish-eye imaging lenses according to the respective examples include, in order from the object side to the image side:

[0076] The first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, the sixth lens L6, the seventh lens L7, the eighth lens L8, the ninth lens L9, the G1 filter, the G2 protective sheet, and the aperture ST; among them, the first lens L1 has a negative refractive power, the object side is convex, and the image side is concave; the second lens L2 has a negative refractive power, the object side is concave, and the image side is concave; the third lens L3 has a positive refractive power, the object side is convex, and the image side is convex; the fourth lens L4 has a negative refractive power, the object side is concave, and the image side is concave; the fifth lens L5 has a positive refractive power, the object side is convex, and the image side is convex; the sixth lens L6 has a positive refractive power, the object side is convex, and the image side is convex; this structure has a compact and lightweight fish-eye imaging lens with high optical performance. The fish-eye imaging lens according to each example can satisfy at least one of the following setting conditions 1) to 9):

[0077] 1) -10.00 < f 1 < -6.00; -8.00 < f 2 < -3.00; 3.00 < f 3 < 8.00

[0078] 2) D 1 / R 1 ≤1.20; D 2 / R 2 ≤1.50

[0079] 3) ∣R 3 ∣ > 30

[0080] 4) nd 1 > 1.70; nd 2 < 1.55; vd 2 > 70

[0081] 5) dn 2 / dT 2 > -2 * 10E - 6; dn 5 / dT 5 < -9 * 10E - 6; dn 6 / dT 6 < -9 * 10E - 6

[0082] 6) nd 3 >1.95;

[0083] 7) Vd 5 -Vd 4 >50

[0084] 8) BFL / IMH > 0.70

[0085] 9) The first lens L1 is a meniscus negative lens.

[0086] In the above conditional formula, f 1 is the focal length of the first lens, f 2 is the focal length of the second lens, f 3 is the focal length of the third lens; D 1 is the outer diameter value of the convex surface of the first lens, R 1 is the radius value of the convex surface of the first lens, D 2 is the outer diameter value of the convex surface of the second lens, R 2 is the radius value of the convex surface of the second lens; R 3 is the radius value of the side of the second lens facing the object; nd 1 is the refractive index of the first front lens, vd 1 is the Abbe number of the first lens, nd 2 is the refractive index of the second front lens, vd 2 is the Abbe number of the second lens; dn 2 / dT 2 is the refractive index temperature coefficient of the second lens in the temperature range of -40°C to 80°C, dn 5 / 6 / dT 5 / 6 is the refractive index temperature coefficient of the fifth lens and the sixth lens in the temperature range of -40°C to 80°C; nd 3 is the refractive index of the third lens, Vd 3 is the Abbe number of the third lens; Vd 4 is the Abbe number of the fourth lens, Vd 5 is the Abbe number of the fifth lens; BFL is the optical back focal length of the lens, and IMH is the target surface size of the lens.

[0087] Conditional formula 1) defines the focal lengths of the first three lenses in the lens. By appropriately setting the conditions, a large field of view of the lens can be achieved, and the resolution can be improved. If the focal length values of the three lenses are lower than the lower limit value, it will be more difficult to control the radius of the lens D / R, and at the same time, it is not conducive to sharing the optical power of the lens, resulting in a larger light deflection angle, low resolution and assembly resolution. On the other hand, if the focal length values of the three lenses are higher than the upper limit value, in order to ensure a large field of view in the front group, the length of the front group of lenses and the total length of the lens will increase, which is not conducive to the compactness and miniaturization of the lens.

[0088] Conditional formula 2) defines the ratio condition of the outer diameter of the lens to the radius of the corresponding surface. The smaller the ratio, the more beneficial it is to the cold processing of the optical lens. If the two ratios are higher than the upper limit value, the cold processing cost of the lens will increase exponentially, or it is not conducive to compressing the mass production cost, resulting in additional waste of the lens cost.

[0089] Conditional formula 3) defines the absolute value of the radius value of the side of the second lens L2 facing the object. The larger the absolute value, the smaller the energy of the ghost image generated by the protective sheet G2 on this surface.

[0090] Conditional formula 4) defines the refractive index and Abbe number of the first lens and the second lens. The first lens uses a material with a small Abbe number, and the second lens uses a material with a large Abbe number. Using the two in combination is beneficial to improving the resolution of the optical system. If the refractive index value of the first lens is lower than the lower limit value, it is not conducive to the improvement of the field of view angle and the lens length. On the other hand, if the refractive index value of the second lens is higher than the upper limit value, it is not conducive to sharing the optical power of the lens, resulting in greater light deflection and focus, and the resolution is not high after the lens is assembled. If the Abbe number value of the second lens is higher than the upper limit value, it is not conducive to correcting the chromatic aberration of the lens and is not conducive to the improvement of the resolution.

[0091] Conditional formula 5) defines the refractive index temperature coefficient of the second lens and the fifth and sixth lenses in the temperature range of -40°C to 80°C. The second lens is a negative focal length lens, and the larger the refractive index temperature coefficient, the more beneficial it is to the balance of temperature drift. The fifth and sixth lenses are positive focal length lenses, and the smaller the refractive index temperature coefficient, the more beneficial it is to the balance of temperature drift. Through the cooperation of the three lenses, the lens realizes passive athermalization at extreme temperatures. If the refractive index temperature coefficient value of the second lens is lower than the lower limit value, the cost will increase exponentially, which is not conducive to cost compression, large-scale production, and market occupation. On the other hand, if the refractive index temperature coefficient of the fifth and sixth lenses is higher than the upper limit value, it is not conducive to realizing the passive athermalization of the lens.

[0092] Conditional formula 6) defines the refractive index and Abbe number of the third lens. Selecting a high refractive index material is beneficial to improving the resolution of the optical system. If the refractive index value of the third lens is lower than the lower limit, it is not conducive to improving the resolution of the optical system.

[0093] Conditional formula 7) defines the lower limit of the difference between the fourth lens and the fifth lens. By combining high and low dispersions, off-axis chromatic aberration is corrected, and the lens resolution is improved. If it is lower than the lower limit value, it will be difficult to correct chromatic aberration, resulting in poor color restoration of the lens.

[0094] Conditional formula 8) defines the ratio of the optical back focal length of the lens to the target surface of the lens, which is beneficial to reducing the principal ray angle, shortening the lens length, and facilitating lens assembly. If it is lower than the lower limit value, it is not conducive to the miniaturization of the lens.

[0095] Conditional formula 9) defines that the first lens L1 is a meniscus negative lens, which can ensure a large field of view, large angle, and large aperture ratio of the optical system, is beneficial to compressing the outer diameter of the optical element, and realizes the miniaturization of the lens by reducing the front aperture of the lens.

[0096] Now, a detailed description of the zoom lens according to each example will be given.

[0097] For the optical structure of Example 1, please refer to Figure 1, the specific parameters of Example 1 are shown in Table 1 below. In this Example 1, the lens focal length f = 2.9 mm, the aperture FNO = 2.8, the field of view FOV = 180°, the target surface size IMH = 8.4 mm, the total optical length is 23 mm, and the optical back focal length is 6 mm.

[0098] Table 1 Parameter Table of Example 1

[0099] Surface number Type Radius of curvature Thickness Material Refractive index Abbe number Lens focal length 1 First lens 20.50 3.00 Glass 1.72 47.80 -8.76 2 4.60 3.73 3 Second lens -38.50 1.90 Glass 1.49 70.44 -4.53 4 2.50 0.34 5 Third lens 5.20 1.60 Glass 2.00 19.31 4.10 6 -20.50 0.10 7 Diaphragm Infinity 0.09 8 Fourth lens -11.50 1.75 Glass 1.92 18.90 -3.75 9 Fifth lens 5.45 2.10 Glass 1.57 71.30 3.93 10 -3.25 0.10 11 Sixth lens 12.80 2.20 Glass 1.57 71.30 9.64 12 -9.30 0.50 13 Filter Infinity 0.30 Glass 1.52 64.20 14 Infinity 4.38 15 Protective glass Infinity 0.50 Glass 1.52 64.20 16 Infinity 0.40 17 Imaging surface Infinity -

[0100] Please refer to Figure 2 , the MTF curve graph of Example 1. This graph shows the diffraction modulation transfer function (MTF) data for all fields of view. The larger the area enclosed by the MTF curve and the coordinate axes, the more information the optical system transmits, the better the imaging quality of the optical system, the clearer the image. It can be seen from the graph that at 200 lp / mm on the abscissa, the ordinate values of all curves are > 0.35.

[0101] Please refer to Figure 3 : The field curvature and distortion curve graph of Example 1. In the distortion graph, the field of view is the ordinate and the distortion value is the abscissa. It can be seen from the graph that the F-Theta distortion is < 8% across the entire field of view.

[0102] Please refer to Figure 4 : The lateral chromatic aberration graph of Example 1. The horizontal axis represents the chromatic aberration values at different wavelengths, and the vertical axis represents the field of view size; it can be seen from the graph that from a wavelength of 435 nm to 650 nm, the chromatic aberration value of the 435 nm wavelength (blue line) deviating from the main wavelength of 555 nm (red line) is less than 4.5 um, enabling the system to have an achromatic effect and high color reducibility.

[0103] Please refer to Figure 5 : The longitudinal chromatic aberration graph of Example 1, also known as position chromatic aberration and spherical chromatic aberration. The horizontal axis represents the deviation from the image value, and the vertical axis represents the normalization of the maximum entrance pupil radius. It can be seen from the graph that from a wavelength of 435 nm to 650 nm, the chromatic aberration curves at different wavelengths intersect, and the common focus deviates relatively little from the d-line red of the principal ray, indicating that the optical system has excellent image quality and good apochromatism.

[0104] Please refer to Figure 6 : The relative illumination graph curve of Example 1. The horizontal axis represents different fields of view, and the vertical axis represents the relative illumination level; it can be seen from the graph that the curve is relatively flat, and the RI is greater than 60% in the edge field of view, indicating that the system has high relative illumination, high brightness from the center to the edge, and is uniform.

[0105] For the optical structure of Example 2, please refer to Figure 7, the specific parameters of Example 2 are shown in Table 2 below. In this Example 2, the lens focal length f = 2.95 mm, the aperture FNO = 2.8, the field of view FOV = 180°, the target surface size IMH = 8.4 mm, the total optical length is 23 mm, and the optical back focal length is 6.7 mm.

[0106] Table 2 Parameter Table of Example 2

[0107] Surface number Type Radius of curvature Thickness Material Refractive index Abbe number Lens focal length 1 First lens 16.44 2.40 Glass 1.88 39.20 -8.10 2 4.66 2.10 3 Second lens 25.32 1.00 Glass 1.62 63.40 -5.53 4 2.97 1.70 5 Third lens 7.56 3.00 Glass 1.95 17.90 6.62 6 -31.13 0.37 7 Diaphragm Infinity 0.73 8 Fourth lens Infinity 1.00 Glass 1.95 18.00 -5.23 9 Fifth lens 5.00 2.00 Glass 1.57 71.30 4.73 10 -5.00 0.10 11 Sixth lens 11.10 1.90 Glass 1.74 52.70 8.43 12 -13.37 0.50 13 Filter Infinity 0.30 Glass 1.52 64.20 14 Infinity 5.00 15 Protective glass Infinity 0.50 Glass 1.52 64.20 16 Infinity 0.40 17 Imaging surface Infinity 0.00

[0108] Please refer to Figure 8 , the MTF curve graph of Example 2. This graph shows the diffraction modulation transfer function (MTF) data for all fields of view. The larger the area enclosed by the MTF curve and the coordinate axes, the more information the optical system transmits, the better the imaging quality of the optical system, and the clearer the image. It can be seen from the graph that at 200 lp / mm on the abscissa, the ordinate values of all curves are > 0.2.

[0109] Please refer to Figure 9 : The field curvature and distortion curve graph of Example 2. In the distortion graph, the field of view is the ordinate and the distortion value is the abscissa. It can be seen from the graph that the F-Theta distortion is < 9% across the entire field of view.

[0110] Please refer to Figure 10 : The lateral chromatic aberration graph of Example 2. The horizontal axis represents the chromatic aberration values of different wavelengths, and the vertical axis represents the field of view size; it can be seen from the graph that from a wavelength of 435 nm to 650 nm, the chromatic aberration value of the 435 nm wavelength (blue line) deviating from the main wavelength of 555 nm (red line) is less than 8 um, enabling the system to have an achromatic effect, and the color reducibility is slightly worse than that of Example 1.

[0111] Please refer to Figure 11 : The longitudinal chromatic aberration graph of Example 2 is also called axial chromatic aberration and spherical chromatic aberration. The horizontal axis represents the deviation from the image value, and the vertical axis represents the normalization of the maximum entrance pupil radius. It can be seen from the graph that from a wavelength of 435 nm to 650 nm, the chromatic aberration curves of different wavelengths intersect, and the common focus deviates relatively little from the main ray d-line red, indicating that the optical system has excellent image quality and good apochromatism.

[0112] Please refer to Figure 12 : The relative illumination graph curve of Example 2. The horizontal axis represents different fields of view, and the vertical axis represents the relative illumination magnitude; it can be seen from the graph that the curve is relatively flat, and the RI is greater than 50% in the edge field of view, indicating that the relative illumination of the system is slightly worse than that of Example 1.

[0113] For the optical structure of Example 3, please refer to Figure 13, the specific parameters of Example 3 are shown in Table 3 below. In this Example 3, the lens focal length f = 2.95 mm, the aperture FNO = 2.8, the field of view FOV = 180°, the target surface size IMH = 8.5 mm, the total optical length is 23 mm, and the optical back focal length is 5.75 mm.

[0114] Table 3 Parameter Table of Example 3

[0115] Surface number Type Radius of curvature Thickness Material Refractive index Abbe number Lens focal length 1 First lens 11.445 1.000 Glass 2.00 25.50 -7.19 2 4.251 2.950 3 Second lens -32.232 0.800 Glass 1.50 81.60 -6.86 4 3.846 2.320 5 Third lens 5.885 1.650 Glass 1.92 20.90 6.32 6 Infinity 1.050 7 Diaphragm Infinity 1.130 8 Fourth lens -50.054 2.350 Glass 1.69 54.50 3.33 9 Fifth lens -2.253 1.200 Glass 1.95 17.90 -5.31 10 -5.103 0.900 11 Sixth lens 9.469 1.900 Glass 1.62 63.40 13.73 12 -77.652 0.500 13 Filter Infinity 0.300 Glass 1.52 64.20 14 Infinity 4.050 15 Protective glass Infinity 0.500 Glass 1.52 64.20 16 Infinity 0.400 17 Imaging surface Infinity 0.000

[0116] Please refer to Figure 14 , the MTF curve graph of Example 3. This graph represents the diffraction modulation transfer function (MTF) data of all fields of view. The larger the area enclosed by the MTF curve and the coordinate axes, the more information the optical system transmits, the better the imaging quality of the optical system, and the clearer the image. It can be seen from the graph that at 200 lp / mm on the abscissa, the ordinate values of all curves are > 0.2.

[0117] Please refer to Figure 15 : The field curvature and distortion curve graph of Example 3. In the distortion graph, the field of view is the ordinate and the distortion value is the abscissa. It can be seen from the graph that the F-Theta distortion is < 9% across the entire field of view.

[0118] Please refer to Figure 16 : The lateral chromatic aberration graph of Example 3. The horizontal axis represents the chromatic aberration values of different wavelengths, and the vertical axis represents the field of view size; it can be seen from the graph that from a wavelength of 435 nm to 650 nm, the chromatic aberration value of the 435 nm wavelength (blue line) deviating from the main wavelength of 555 nm (red line) is less than 8 um, enabling the system to have an achromatic effect, and the color reproducibility is slightly worse than that of Example 1.

[0119] Please refer to Figure 17 : The longitudinal chromatic aberration graph of Example 3, also known as position chromatic aberration and spherical chromatic aberration. The horizontal axis represents the deviation from the image value, and the vertical axis represents the normalization of the maximum entrance pupil radius. It can be seen from the graph that from a wavelength of 435 nm to 650 nm, the chromatic aberration curves of different wavelengths intersect, and the common focus deviates relatively large from the main ray d-line red, indicating that the optical system has excellent image quality and good apochromatic performance.

[0120] Please refer to Figure 18 : The relative illumination graph curve of Example 3. The horizontal axis represents different fields of view, and the vertical axis represents the relative illumination size; it can be seen from the graph that the curve is relatively flat, and the RI is greater than 50% in the edge field of view, indicating that the relative illumination of the system is slightly worse than that of Example 1.

[0121] Based on Examples 1 to 3, the present case has the following specific advantages:

[0122] 1. The fish-eye lens of this structure has a field of view angle of 180°, supports a 1 / 2-inch target surface, and the full-field resolution can reach 200 lp / mm > 0.3. Moreover, the uniformity from the center to the edge is high, ensuring the clarity of the image and the overall image quality is uniform;

[0123] 2. The fish-eye lens of this structure is designed at wavelengths from 435 nm to 650 nm to control off-axis chromatic aberration, with high color reducibility and no obvious blue-violet edge;

[0124] 3. The fish-eye lens of this structure adopts a 6-piece glass spherical surface solution, with low material costs. The assembly method is the surface bearing method, and the lens production yield is high, making it easy for mass production and market occupation;

[0125] 4. The fish-eye lens of this structure adopts an athermal design and can maintain stable high-definition image quality;

[0126] Example 4

[0127] Now referring to Figure 19 , a description of the imaging device A according to Example 4 of the present invention will be given. Figure 19 is a schematic diagram of an imaging device (digital still camera) that uses any one of the fish-eye imaging lenses according to Examples 1 to 3 in an imaging optical system.

[0128] In Figure 19 , reference numeral A2 represents the imaging device main body, and reference numeral A1 represents an imaging optical system (interchangeable lens) including any one of the fish-eye imaging lenses according to Examples 1 to 3. Reference numeral A3 represents an image sensor (photoelectric conversion element) such as a CCD sensor or a CMOS sensor. The image sensor is built into the camera main body A2 and receives light (the optical image formed by the imaging optical system 11) from the imaging optical system A1 and performs photoelectric conversion.

[0129] By using the fish-eye imaging lens according to any one of Examples 1 to 3 in an imaging device such as a digital still camera, an imaging device with a small lens can be obtained.

[0130] Each example can provide an imaging device with high optical performance.

[0131] Although the present invention has been described with reference to typical embodiments, it should be understood that the present invention is not limited to the disclosed typical embodiments. The scope of the following claims will be given the broadest interpretation to cover all such modifications and equivalent structures and functions.

Claims

1. A fisheye imaging lens, characterized in that: From the object side to the image side, the first lens, the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens are arranged in order; wherein, The first lens has negative refractive power, a convex object side surface and a concave image side surface; The second lens has negative refractive power, a concave object-side surface and a concave image-side surface; The third lens has positive refractive power, and its object side surface is convex and its image side surface is convex; The fourth lens has negative refractive power, and its object side surface is concave and its image side surface is concave; The fifth lens has positive refractive power, and its object side surface is convex and its image side surface is convex; The sixth lens has positive refractive power, and its object-side surface is convex, and its image-side surface is convex; Wherein, the lens satisfies the following relationship: -10.00 <f1<-6.00;-8.00<f2<-3.00;3.00<f3<8.00 Where f1 is the focal length of the first lens, f2 is the focal length of the second lens, and f3 is the focal length of the third lens.

2. The fisheye imaging lens according to claim 1, characterized in that: The lens satisfies the following relationship: D1 / R1≤1.20; D2 / R2≤1.50 Wherein, D1 is the outer diameter of the convex surface of the first lens, R1 is the radius of the convex surface of the first lens, D2 is the outer diameter of the convex surface of the second lens, and R2 is the radius of the convex surface of the second lens.

3. The fisheye imaging lens according to claim 1, characterized in that: The first lens is a meniscus negative lens.

4. The fisheye imaging lens according to claim 1, characterized in that: The lens satisfies the following relationship: ∣R3∣>30 Wherein, R3 is the radius of the second lens facing the object side.

5. The fisheye imaging lens according to claim 1, characterized in that: The lens satisfies the following relationship: nd1>1.70;vd1<50 nd2<1.55;vd2>70 Wherein, nd1 is the refractive index of the first lens, vd1 is the Abbe coefficient of the first lens, nd2 is the refractive index of the second lens, and vd2 is the Abbe coefficient of the second lens.

6. The fisheye imaging lens according to claim 1, characterized in that: The second lens, the fifth lens, and the sixth lens respectively satisfy the following relationships: dn2 / dT2>-2*10E-6; dn5 / dT5<-9*10E-6; dn6 / dT6<-9*10E-6 Where, dn2 / dT2 is the refractive index temperature coefficient of the second lens in the temperature range of -40℃~80℃, dn 5 / 6 / dT 5 / 6 is the refractive index temperature coefficient of the fifth lens and the sixth lens in the temperature range of -40°C to 80°C.

7. The fisheye imaging lens according to claim 1, characterized in that: The lens satisfies the following relationship: nd3>1.95;Vd3<25 Wherein, nd3 is the refractive index of the third lens, and Vd3 is the Abbe coefficient of the third lens.

8. The fisheye imaging lens according to claim 1, characterized in that: The fourth lens and the fifth lens are a cemented lens group and satisfy the following relationship: Vd5-Vd4>50 Wherein, Vd4 is the Abbe coefficient of the fourth lens, and Vd5 is the Abbe coefficient of the fifth lens.

9. The fisheye imaging lens according to claim 1, characterized in that: The lens satisfies the following relationship: BFL / IMH>0.70 Where BFL is the optical back focus of the lens, and IMH is the target surface size of the lens.

10. A camera device, characterized in that: A fisheye imaging lens according to any one of claims 1 to 9; and An image sensor is configured to receive the image formed by the fisheye imaging lens.

Images