Fisheye lens with 238-degree view field range

Abstract

The invention discloses a fisheye lens with a view field range of 238 degrees, and belongs to the technical field of optical imaging. The fisheye lens provided by the invention is arranged from the object side to the image side along the optical axis direction; the lens sequentially comprises a first lens with negative focal power, a second lens with negative focal power, a third lens with negative focal power, a fourth lens with positive focal power, a fifth lens with negative focal power, a sixth lens with positive focal power, a seventh lens with positive focal power, an eighth lens with positive focal power, a ninth lens with negative focal power and a tenth lens. The fourth lens and the fifth lens form a doublet lens, and the sixth lens and the seventh lens form a doublet lens. The image space optical surface of the lens III is an aspheric surface, and the object space optical surface is a spherical surface; the image space optical surface of the lens 8 is an aspheric surface, and the object space optical surface is a spherical surface; the object-side optical surface of the lens 9 is aspheric, and the image-side optical surface of the lens 9 is spherical. The fisheye lens provided by the invention has the advantages of ultra-large view field range, high resolution, good image plane uniformity, compact structure, easy processing and the like.

Description

Technical Field

[0001] The present invention relates to the field of optical imaging technology, and more specifically, to a fisheye lens with a 238° field of view, which is suitable for scene monitoring, robot navigation, satellite positioning, military detection and other fields. Background Art

[0002] Fisheye lenses, with their exceptionally large field of view, are widely used in fields such as scene surveillance, robotic navigation, satellite positioning, micro-intelligent systems, and engineering surveying. With increasing demand, they play a crucial role in optical systems with an exceptionally large field of view. Because they can capture real-time information across the entire airspace and across the entire temporal domain, meeting the information acquisition requirements of modern warfare, a capability unmatched by other optoelectronic detection methods, fisheye lenses have also found significant application in the defense and military sectors.

[0003] A fisheye lens primarily consists of a front and rear optical system. The front optical system is typically composed of several negative meniscus lenses, which compress the field of view; the rear optical system consists of conventional optics to balance aberrations. However, current fisheye lenses on the market suffer from low resolution and a small aperture. This results in insufficient clarity and sharpness in images captured at wide angles of view and in low light conditions, failing to meet resolution requirements.

[0004] With technological advancements, fisheye lenses are developing towards high imaging quality, a large working field of view, a large clear aperture, miniaturization, lightweight, and a simple structure. This makes the design of fisheye lens optical systems more complex. Fisheye lenses with a large field of view often require the use of more than 10 different optical lenses in combination. Optical lenses have a variety of optical surfaces (such as spherical and aspherical surfaces) and a wide range of parameter options. How to choose the appropriate lens type and parameters to meet imaging performance has become a difficult problem in the design of fisheye lenses with a large field of view. Existing aberration theories are mainly applicable to small field of view situations. The aberration analysis and optimization effects of fisheye lenses with a large field of view are limited. New theories and methods are urgently needed to improve the design level. Summary of the Invention

[0005] 1. Technical problem to be solved by the invention

[0006] The purpose of the present invention is to provide a fisheye lens with a 238° field of view to solve the problems of limited field of view and insufficient aberration correction in existing fisheye lenses. The technical solution of the present invention is adopted by using lens 1, lens 2 and lens 3 with negative optical focal length to effectively compress the object side field of view angle, ensure that the lens can cover an ultra-large working field of view and achieve high-quality imaging; at the same time, three optical aspheric surfaces and two doublet lenses are used to significantly correct system aberrations and improve imaging clarity and uniformity; in addition, through innovative calculation methods, the focal length and aberration of each optical surface are accurately analyzed and optimized, so that the fisheye lens has the advantages of ultra-large field of view, high resolution, excellent image surface uniformity, compact structure and easy processing, meeting the requirements of ultra-large field of view and high-precision imaging.

[0007] 2. Technical solution

[0008] In order to achieve the above object, the technical solution provided by the present invention is:

[0009] The present invention provides a fisheye lens with a 238° field of view, which comprises, from the object side to the image side along the optical axis, a first lens with negative optical power, a second lens with negative optical power, a third lens with negative optical power, a fourth lens with positive optical power, a fifth lens with negative optical power, a sixth lens with positive optical power, a seventh lens with positive optical power, an eighth lens with positive optical power, a ninth lens with negative optical power, and a tenth lens; wherein,

[0010] The lens four and the lens five form a doublet lens, and the lens six and the lens seven form a doublet lens;

[0011] The first lens, the second lens and the third lens are all negative meniscus lenses, and their object-side and image-side optical surfaces are convex toward the object side;

[0012] The object-side optical surface of the lens 4 is convex toward the object, and the image-side optical surface is convex toward the image; the object-side optical surface of the lens 5 is concave toward the object, and the image-side optical surface is concave toward the image; the object-side optical surface of the lens 6 is convex toward the object, and the image-side optical surface is concave toward the image; the object-side optical surface of the lens 7 is convex toward the object, and the image-side optical surface is convex toward the image; the object-side optical surface of the lens 8 is convex toward the object, and the image-side optical surface is convex toward the image; the object-side optical surface of the lens 9 is concave toward the object, and the image-side optical surface is convex toward the image; the lens 10 is a parallel plate;

[0013] The image side optical surface of the lens 3 is aspherical, and the object side optical surface is spherical; the image side optical surface of the lens 8 is aspherical, and the object side optical surface is spherical; the object side optical surface of the lens 9 is aspherical, and the image side optical surface is spherical;

[0014] The first lens, the second lens, and the third lens constitute the front optical group of the fisheye lens, and the fourth lens, the fifth lens, the sixth lens, the seventh lens, the eighth lens, the ninth lens, and the tenth lens constitute the rear optical group of the fisheye lens. The calculation of the front optical group and the rear optical group is as follows:

[0015] Apply the calculation expressions (1) to (8) of field curvature, axial chromatic aberration and vertical chromatic aberration to calculate the field curvature X′ in the meridian direction of the optical front group when the initial object side field angle is ω0 = 60°. m , sagittal field curvature X′ s , axial chromatic aberration L′ FC , vertical axis chromatic aberration Y′ FC ,

[0016] -X′ m(g) =(r′ c(g) -r′ m(g) )cosω g ,-X′ s(g) =(r′ c(g) -r′ s(g) )cosω g (1)

[0017] Among them, r′ c(g) It represents the distance from the g-th optical surface to the Gaussian image surface along the principal ray, and the calculation expression is:

[0018]

[0019] In expressions (1) and (2), ω g represents the output field angle of the g-th optical surface; r′ m(g) and r′ s(g) They represent the image focal length in the meridional and sagittal directions after the main ray passes through the optical system composed of g optical surfaces, respectively, and the wavefront aberration coefficient w 200 =0 and w 020 = 0, the image-side focal length and object-side focal length of each optical surface in the tangential and sagittal directions are calculated in turn. The calculation expressions are:

[0020]

[0021] Among them, c 0,2 and c 2,0 is the surface coefficient of the optical surface,

[0022]

[0023] In expression (3), r m(i) , r s(i)are the object-side focal lengths of the i-th optical surface in the tangential and sagittal directions, respectively. The conversion relationship from the image-side focal length of the i-th optical surface to the object-side focal length of the (i+1)-th optical surface is:

[0024]

[0025] in, represents the optical spacing between optical surfaces along the direction of the principal ray,

[0026]

[0027] The deviation of the Gaussian image distance between F light and C light is the axial chromatic aberration L' FC , the wavelength of F light is 486.13nm, the wavelength of C light is 656.27nm,

[0028] L′ FC(g) =r′ F(g) -r′ C(g) (7)

[0029] After the chief rays of light F and light C pass through the optical system composed of g optical surfaces, the image heights on the image plane are y′ F(g) and y′ C(g) The deviation between them is defined as the vertical axis chromatic aberration Y′ FC ,

[0030] Y′ FC(g) =y′ F(g) -y′ C(g) (8)

[0031] Apply expressions (1) to (8) to calculate the object-side focal length and image-side focal length of each optical surface in the tangential and sagittal directions of the optical system; all the chief ray parameters α, β, ω in the above expressions can be obtained by chief ray tracing, where α i and β i are the incident angle and refraction angle of the principal ray, n i is the refractive index of the optical medium, Γ i and ρ i represents the curvature radius of the i-th optical surface in the meridian and sagittal directions;

[0032] Then, the aberration theory of plane symmetric optical system is applied to analyze the aberration of fisheye lens, and the calculation expression is:

[0033]

[0034]

[0035] W sph =w 400 x 4 +w220 x 2 y 2 +w 040 y 4 (13)

[0036] W coma =w 300 x 3 +w 120 xy 2 (14)

[0037] in W sph and W coma They are the meridional field curvature wave aberration, sagittal field curvature wave aberration, axial chromatic aberration wave aberration, vertical chromatic aberration wave aberration, spherical aberration wave aberration and coma wave aberration, respectively, where n′ g is the image-side refractive index of the g-th optical surface, x g and y g is the diameter coordinate of the gth optical hole, x g-0 is the aperture coordinate of the gth optical surface at 0° field of view, w 400 、w 220 and w 040 is the spherical aberration coefficient, w 300 and w 120 is the coma aberration coefficient.

[0038] Furthermore, the fisheye lens has a working field of view of up to 238°, a total focal length of 10mm, an F / # value of 2.8, a total length of 171.88mm, a detectable wavelength range of 400nm to 700nm, and a dominant wavelength of 586.7nm.

[0039] Furthermore, a small air gap is provided between the eighth lens and the ninth lens for correcting field curvature.

[0040] Furthermore, the object-side and image-side optical surfaces of lens 1, lens 2, lens 4, lens 5, lens 6 and lens 7 are all spherical surfaces.

[0041] Furthermore, the surface shape coefficient of the image-side optical surface of the lens three is -1.607; the surface shape coefficient of the image-side optical surface of the lens eight is -0.239; and the surface shape coefficient of the object-side optical surface of the lens nine is 0.021.

[0042] Furthermore, the material of the lens 1 (L1) and the lens 2 (L2) is N-LAK8, with a refractive index n=1.713;

[0043] The lens three (L3), lens seven (L7) and lens ten (L 10 ) is made of K3, with a refractive index of n=1.51823;

[0044] The material of the lens four (L4) is F1, and the refractive index n=1.62588;

[0045] The material of the lens five (L5) is N-LAF32, with a refractive index n=1.79457;

[0046] The material of the lens six (L6) is LF5, with a refractive index n=1.58144;

[0047] The material of the lens eight (L8) is PK50, with a refractive index n=1.52054;

[0048] The material of the lens nine (L9) is SF56A, and the refractive index n=1.7847.

[0049] 3. Beneficial effects

[0050] Compared with the existing known technologies, the technical solution provided by the present invention has the following significant effects:

[0051] (1) The present invention provides a fisheye lens with a 238° field of view, which includes 10 lenses. Lens 1, lens 2, and lens 3 constitute the optical front group of the fisheye lens, which effectively compresses the object side field of view angle, ensures that the lens can cover an ultra-large working field of view and achieve high-quality imaging, and lens 4, lens 5, lens 6, lens 7, lens 8, lens 9, and lens 10 constitute the optical rear group of the fisheye lens. Three optical aspheric surfaces and two doublets are used to correct field curvature, chromatic aberration, and distortion, significantly correcting system aberrations and improving imaging clarity and uniformity. In addition, an innovative calculation method is used to accurately analyze and optimize the focal length and aberration of each optical surface, so that the fisheye lens has the advantages of ultra-large field of view, high resolution, excellent image surface uniformity, compact structure, and easy processing, meeting the requirements of ultra-large field of view and high-precision imaging.

[0052] (2) The present invention provides a fisheye lens with a 238° field of view, which has a working field of view of up to 238°, a total focal length of 10 mm, an F / # value of 2.8, a total length of 171.88 mm, a detectable wavelength range of 400 nm to 700 nm, and a dominant wavelength of 586.7 nm, achieving a large field of view, high resolution, a compact structure, and low aberration performance;

[0053] (3) A fisheye lens with a 238° field of view of the present invention has a small air gap between lens eight and lens nine, which has a very significant effect on correcting field curvature, making the field curvature of the fisheye lens very small and the distortion meeting the use requirements;

[0054] (4) The present invention relates to a fisheye lens with a 238° field of view, wherein the surface coefficient of the image-side optical surface of lens 3 is -1.607, the surface coefficient of the image-side optical surface of lens 8 is -0.239, and the surface coefficient of the object-side optical surface of lens 9 is 0.021. The use of optical surfaces with the above surface coefficients has a significant effect on correcting aberrations in a large working field of view, significantly improving imaging resolution.

[0055] (5) The fisheye lens with a 238° field of view of the present invention has only 10 lenses and is combined with specific material selection, which not only improves imaging uniformity and resolution but also reduces the manufacturing cost of the fisheye lens. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 This is a schematic structural diagram of a fisheye lens with a 238° field of view according to the present invention;

[0057] Figure 2 is an MTF curve diagram of the fisheye lens of the present invention;

[0058] Figure 3 is a spot diagram of the fisheye lens of the present invention;

[0059] Figure 4 is a graph showing the field curvature and distortion of the fisheye lens of the present invention;

[0060] Figure 5 is a relative illumination curve diagram of the fisheye lens of the present invention;

[0061] Figure 6 This is a light path diagram of a fisheye lens with a 238° field of view according to the present invention.

[0062] Explanation of the numbers in the schematic diagram:

[0063] L1, lens one; L2, lens two; L3, lens three; L4, lens four; L5, lens five; L6, lens six; L7, lens seven; L8, lens eight; L9, lens nine; L 10 , lens ten. DETAILED DESCRIPTION

[0064] In order to further understand the content of the present invention, the present invention is described in detail with reference to the accompanying drawings and embodiments.

[0065] [Example]

[0066] like Figure 1 As shown, a fisheye lens with a 238° field of view of this embodiment includes the following components in order from the object side to the image side along the optical axis:

[0067] A lens with negative optical power: L1;

[0068] a second lens L2 having negative optical power;

[0069] Lens three L3 with negative optical power;

[0070] Lens four L4 having positive optical power;

[0071] Lens five L5 with negative optical power;

[0072] Lens six L6 having positive optical power;

[0073] Lens seven L7 having positive optical power;

[0074] Lens eight L8 having positive optical power;

[0075] Lens nine L9 with negative optical power;

[0076] Lens 10L 10 ;

[0077] Among them, lens four L4 and lens five L5 form a double cemented lens, and lens six L6 and lens seven L7 form a double cemented lens; lens one L1, lens two L2 and lens three L3 are all negative meniscus lenses, and their object-side and image-side optical surfaces are convex toward the object side; the object-side optical surface of lens four L4 is convex toward the object side, and the image-side optical surface is convex toward the image side; the object-side optical surface of lens five L5 is concave toward the object side, and the image-side optical surface is concave toward the image side; the object-side optical surface of lens six L6 is convex toward the object side, and the image-side optical surface is concave toward the image side; the object-side optical surface of lens seven L7 is convex toward the object side, and the image-side optical surface is convex toward the image side; the object-side optical surface of lens eight L8 is convex toward the object side, and the image-side optical surface is convex toward the image side; the object-side optical surface of lens nine L9 is concave toward the object side, and the image-side optical surface is convex toward the image side; 10 The first lens is L1, the second lens is L2, and the third lens is L3. It is a parallel plate; the image side optical surface of lens three L3 is aspherical, and the object side optical surface is spherical; the image side optical surface of lens eight L8 is aspherical, and the object side optical surface is spherical; the object side optical surface of lens nine L9 is aspherical, and the image side optical surface is spherical. Lens one L1, lens two L2, and lens three L3 form the optical front group of the fisheye lens, which mainly plays the role of compressing the working field of view, ensuring that the lens can cover a large working field of view and achieve high-quality imaging; lens four L4, lens five L5, lens six L6, lens seven L7, lens eight L8, lens nine L9, and lens ten L 10 The rear optical group of a fisheye lens is primarily responsible for imaging and balancing optical system aberrations. Three optical aspheric surfaces and two doublets correct for field curvature, chromatic aberration, and distortion, significantly correcting system aberrations and improving image clarity and uniformity. The initial structure of the rear optical group is designed based on the aberration balance between the front and rear optical groups. The calculations for the front and rear optical groups are as follows:

[0078] Apply the calculation expressions (1) to (8) of field curvature, axial chromatic aberration and vertical chromatic aberration to calculate the field curvature X′ in the meridian direction of the optical front group when the initial object side field angle is ω0 = 60°. m , sagittal field curvature X′ s , axial chromatic aberration L′ FC , vertical axis chromatic aberration Y′ FC ,

[0079] -X′ m(g) =(r′ c(g) -r′ m(g) )cosω g ,-X′ s(g) =(r′ c(g) -r′ s(g) )cosω g (1)

[0080] Among them, r′ c(g) It represents the distance from the g-th optical surface to the Gaussian image surface along the principal ray, and the calculation expression is:

[0081]

[0082] In expressions (1) and (2), ω g represents the output field angle of the g-th optical surface; r′ m(g) and r′ s(g) They represent the image focal length in the meridional and sagittal directions after the main ray passes through the optical system composed of g optical surfaces, respectively, and the wavefront aberration coefficient w 200 =0 and w 020 = 0, the image-side focal length and object-side focal length of each optical surface in the tangential and sagittal directions are calculated in turn. The calculation expressions are:

[0083]

[0084] Among them, c 0,2 and c 2,0 is the surface coefficient of the optical surface,

[0085]

[0086] In expression (3), r m(i) , r s(i) are the object-side focal lengths of the i-th optical surface in the meridional and sagittal directions, respectively. The conversion relationship from the image-side focal length of the i-th optical surface to the object-side focal length of the i+1-th optical surface is:

[0087]

[0088] in, represents the optical spacing between optical surfaces along the direction of the principal ray,

[0089]

[0090] The deviation of the Gaussian image distance between F light (wavelength 486.13nm) and C light (wavelength 656.27nm) is the axial chromatic aberration L' FC ,

[0091] L′ FC(g) =r′ F(g) -r′ C(g) (7)

[0092] After the chief rays of light F and light C pass through the optical system composed of g optical surfaces, the image heights on the image plane are y′ F(g) and y′ C(g) The deviation between them is defined as the vertical axis chromatic aberration Y′ FC ,

[0093] Y′ FC(g) =y′ F(g) -y′ C(g) (8)

[0094] Apply expressions (1) to (8) to calculate the object focal length and image focal length in the tangential and sagittal directions, as well as the axial chromatic aberration and vertical chromatic aberration of each optical surface in the optical system; all the chief ray parameters α, β, ω in the above expressions can be calculated by chief ray tracing, where α i and β i are the incident angle and refraction angle of the principal ray, n i is the refractive index of the optical medium, Γ i and ρ i represents the curvature radius of the i-th optical surface in the meridian and sagittal directions;

[0095] Then, the aberration theory of plane symmetric optical system is applied to analyze the aberration of fisheye lens, and the calculation expression is:

[0096]

[0097]

[0098] W sph =w 400 x 4 +w 220 x 2 y 2 +w 040 y 4 (13)

[0099] W coma =w 300 x 3 +w120 xy 2 (14)

[0100] in W sph and W coma They are the meridional field curvature wave aberration, sagittal field curvature wave aberration, axial chromatic aberration wave aberration, vertical chromatic aberration wave aberration, spherical aberration wave aberration and coma wave aberration, respectively, where n′ g is the image-side refractive index of the g-th optical surface, x g and y g is the diameter coordinate of the gth optical hole, x g-0 is the aperture coordinate of the gth optical surface at 0° field of view, w 400 、w 220 and w 040 is the spherical aberration coefficient, w 300 and w 120 is the coma aberration coefficient.

[0101] The above-mentioned innovative calculation method is used to accurately analyze and optimize the focal length and aberration of each optical surface, so that the fisheye lens has the advantages of ultra-large field of view, high resolution, excellent image surface uniformity, compact structure and easy processing, meeting the requirements of ultra-large field of view and high-precision imaging.

[0102] In this embodiment, the fisheye lens has a working field of view of up to 238°, a total focal length of 10 mm, an F / # value of 2.8, a total length of 171.88 mm, a detectable wavelength range of 400 nm to 700 nm, and a main wavelength of 586.7 nm, achieving a large field of view, high resolution, compact structure, and low aberration performance.

[0103] In addition, if Figure 1As shown, in this embodiment, a small air gap is provided between lens eight L8 and lens nine L9, which has a significant effect on correcting field curvature, making the field curvature of the fisheye lens very small and the distortion also meeting the use requirements. Furthermore, the object-side and image-side optical surfaces of lens one L1, lens two L2, lens four L4, lens five L5, lens six L6, and lens seven L7 are all spherical, and the surface coefficient of the standard spherical surface is -1. Through the calculation and analysis of the above expressions (9) to (14), it is found that the use of aspheric surfaces on the image-side optical surface of lens three L3, the image-side optical surface of lens eight L8, and the object-side optical surface of lens nine L9 has a more significant effect on correcting large working field aberrations. The aberrations are calculated using expressions (9) to (14), and the aspheric surface shape coefficients are optimized. The surface shape coefficient of the image-side optical surface of lens three L3 is -1.607, the surface shape coefficient of the image-side optical surface of lens eight L8 is -0.239, and the surface shape coefficient of the object-side optical surface of lens nine L9 is 0.021. Optical surfaces with the above-mentioned surface shape coefficients are significantly effective in correcting aberrations in a large working field, significantly improving imaging resolution. The optical system of the above-mentioned fisheye lens uses three optical aspheric surfaces, two doublets, and a set of small spacers with similar curvature radii to correct aberrations in a large working field. These surfaces play a very important role in correcting aberrations in the fisheye lens.

[0104] In this embodiment, the material of the lens 1 L1 and the lens 2 L2 is N-LAK8, with a refractive index n=1.713; the lens 3 L3, the lens 7 L7 and the lens 10 L 10 The material of lens L4 is K3, with a refractive index of n=1.51823; lens L4 is F1, with a refractive index of n=1.62588; lens L5 is N-LAF32, with a refractive index of n=1.79457; lens L6 is LF5, with a refractive index of n=1.58144; lens L8 is PK50, with a refractive index of n=1.52054; and lens L9 is SF56A, with a refractive index of n=1.7847. This fisheye lens consists of only 10 lenses, and the combination of these materials not only improves imaging uniformity and resolution, but also reduces manufacturing costs.

[0105] Figure 2 、 Figure 3 、 Figure 4 and Figure 5 The following are the structural diagram, modulation transfer function (MTF) curve, image plane point diagram, field curvature, F-theta distortion diagram and image plane illumination curve of the 238° field of view fisheye lens of the present invention. Figure 2 and Figure 3 It can be seen that the imaging quality of the fisheye lens is very high. Within the full working field of view, the MTF values in the meridian and sagittal directions can reach above 0.7 when there are 10 lines, and the MTF value in the meridian direction can reach above 0.4 when there are 30 lines. Figure 4 It can be concluded that the field curvature of the fisheye lens is very small, ≤0.1mm, and the distortion also meets the use requirements. Figure 5 The relative illumination curve shows that the relative illumination of the present invention is very good, and the relative illumination uniformity is greater than 90%.

[0106] The optical structure parameters of the fisheye lens with a 238° field of view of this embodiment are shown in Table 1.

[0107] Table 1 Optical structural parameters of 240° fisheye lens

[0108]

[0109]

[0110] In Table 1, along the optical axis from the object plane to the image plane, 1 and 2 correspond to the object-side and image-side optical surfaces of lens one L1, respectively; 3 and 4 correspond to the object-side and image-side optical surfaces of lens two L2, respectively; 5 and 6 correspond to the object-side and image-side optical surfaces of lens three L3, respectively; 7 and 8 correspond to the object-side and image-side optical surfaces of lens four L4, respectively; 8 and 9 correspond to the object-side and image-side optical surfaces of lens five L5, respectively; 10 is the aperture stop position; 11 and 12 correspond to the object-side and image-side optical surfaces of lens six L6, respectively; 12 and 13 correspond to the object-side and image-side optical surfaces of lens seven L7, respectively; 14 and 15 correspond to the object-side and image-side optical surfaces of lens eight L8, respectively; 16 and 17 correspond to the object-side and image-side optical surfaces of lens nine L9, respectively; 18 and 19 correspond to the object-side and image-side optical surfaces of lens ten L1, respectively. 10 The object-side and image-side optical surfaces of the lens. Among them, the fourth lens L4 and the fifth lens L5 form a double cemented lens, so 8 is both the image-side optical surface of the fourth lens L4 and the object-side optical surface of the fifth lens L5; the sixth lens L6 and the seventh lens L7 form a double cemented lens, so 12 is both the image-side optical surface of the sixth lens L6 and the object-side optical surface of the seventh lens L7; the tenth lens L 10 It is a parallel plate, and the object and image optical surfaces are both flat.

[0111] Figure 6 yes Figure 1 The optical path diagram of the fisheye lens with a 238° field of view is shown.

[0112] In summary, the fisheye lens with a 238° field of view of the present invention is a compact fisheye lens with an ultra-large field of view, which can make the image surface uniformity of the lens better and the imaging quality higher. It has a simple and compact structure and is easier to process and install.

[0113] The above is a schematic description of the present invention and its embodiments, which is not restrictive. The drawings show only one embodiment of the present invention, and the actual structure is not limited thereto. Therefore, if a person skilled in the art is inspired by this and, without departing from the purpose of the present invention, designs structures and embodiments similar to this technical solution without creatively designing them, they shall fall within the scope of protection of the present invention.

Claims

1. A fisheye lens with a 238° field of view, characterized by: Along the optical axis, from the object side to the image side, it includes lens 1 (L1) with negative focal power, lens 2 (L2) with negative focal power, lens 3 (L3) with negative focal power, lens 4 (L4) with positive focal power, lens 5 (L5) with negative focal power, lens 6 (L6) with positive focal power, lens 7 (L7) with positive focal power, lens 8 (L8) with positive focal power, lens 9 (L9) with negative focal power and lens 10 (L10) with positive focal power. 10 );in, The lens four (L4) and the lens five (L5) form a doublet lens, and the lens six (L6) and the lens seven (L7) form a doublet lens; The lens 1 (L1), lens 2 (L2) and lens 3 (L3) are all negative meniscus lenses, and their object-side and image-side optical surfaces are convex toward the object side; The object side optical surface of the lens four (L4) is convex toward the object side, and the image side optical surface is convex toward the image side; the object side optical surface of the lens five (L5) is concave toward the object side, and the image side optical surface is concave toward the image side; the object side optical surface of the lens six (L6) is convex toward the object side, and the image side optical surface is concave toward the image side; the object side optical surface of the lens seven (L7) is convex toward the object side, and the image side optical surface is convex toward the image side; the object side optical surface of the lens eight (L8) is convex toward the object side, and the image side optical surface is convex toward the image side; the object side optical surface of the lens nine (L9) is concave toward the object side, and the image side optical surface is convex toward the image side; the lens ten (L 10 ) are parallel plates; The image-side optical surface of the lens three (L3) is an aspherical surface, and the object-side optical surface is a spherical surface; the image-side optical surface of the lens eight (L8) is an aspherical surface, and the object-side optical surface is a spherical surface; the object-side optical surface of the lens nine (L9) is an aspherical surface, and the image-side optical surface is a spherical surface; The lens 1 (L1), lens 2 (L2) and lens 3 (L3) form the optical front group of the fisheye lens, and the lens 4 (L4), lens 5 (L5), lens 6 (L6), lens 7 (L7), lens 8 (L8), lens 9 (L9) and lens 10 (L1) form the optical front group of the fisheye lens. 10 ) constitutes the optical rear group of the fisheye lens; the calculations of the optical front group and the optical rear group are as follows: Apply the calculation expressions (1) to (8) of field curvature, axial chromatic aberration and vertical chromatic aberration to calculate the field curvature X′ in the meridian direction of the optical front group when the initial object side field angle is ω0 = 60°. m , sagittal field curvature X′ s , axial chromatic aberration L′ FC , vertical axis chromatic aberration Y′ FC , -X′ m(g) =(r′ c(g) -r′ m(g) )cosω g ,-X′ s(g) =(r′ c(g) -r′ s(g) )cosω g (1) Among them, r′ c(g) It represents the distance from the g-th optical surface to the Gaussian image surface along the principal ray, and the calculation expression is: In expressions (1) and (2), ω g represents the output field angle of the g-th optical surface; r′ m(g) and r′ s(g) They represent the image focal length in the meridional and sagittal directions after the main ray passes through the optical system composed of g optical surfaces, respectively, and the wavefront aberration coefficient w 200 =0 and w 020 = 0, the image-side focal length and object-side focal length of each optical surface in the tangential and sagittal directions are calculated in turn. The calculation expressions are: Among them, c 0,2 and c 2,0 is the surface coefficient of the optical surface, In expression (3), r m(i) , r s(i) are the object-side focal lengths of the i-th optical surface in the tangential and sagittal directions, respectively. The conversion relationship from the image-side focal length of the i-th optical surface to the object-side focal length of the (i+1)-th optical surface is: in, represents the optical spacing between optical surfaces along the direction of the principal ray, The deviation of the Gaussian image distance between F light and C light is the axial chromatic aberration L' FC , the wavelength of F light is 486.13nm, the wavelength of C light is 656.27nm, L′ FC ( g) ＝r′ F(g) -r′ C(g) (7) After the chief rays of light F and light C pass through the optical system composed of g optical surfaces, the image heights on the image plane are y′ F(g) and y′ C(g) The deviation between them is defined as the vertical axis chromatic aberration Y′ FC , AND' FC(g) =y′ F(g) -and' C(g) (8) Apply expressions (1) to (8) to calculate the object focal length and image focal length in the tangential and sagittal directions, as well as the axial chromatic aberration and vertical chromatic aberration of each optical surface in the optical system; all the chief ray parameters α, β, ω in the above expressions can be calculated by chief ray tracing, where α i and β i are the incident angle and refraction angle of the principal ray, n i is the refractive index of the optical medium, Γ i and ρ i represents the curvature radius of the i-th optical surface in the meridian and sagittal directions; Then, the aberration theory of plane symmetric optical system is applied to analyze the aberration of fisheye lens, and the calculation expression is: W sph =w 400 x 4 +w 220 x 2 y 2 +w 040 y 4 (13) W coma =w 300 x 3 +w 120 xy 2 (14) in, W sph and W coma They are the meridional field curvature wave aberration, sagittal field curvature wave aberration, axial chromatic aberration wave aberration, vertical chromatic aberration wave aberration, spherical aberration wave aberration and coma wave aberration, respectively, where n′ g is the image-side refractive index of the g-th optical surface, x g and y g is the diameter coordinate of the gth optical hole, x g-0 is the aperture coordinate of the gth optical surface at 0° field of view, w 400 、w 220 and w 040 is the spherical aberration coefficient, w 300 and w 120 is the coma aberration coefficient.

2. The fisheye lens according to claim 1, wherein: The fisheye lens has a working field of view of up to 238°, a total focal length of 10mm, an F / # value of 2.8, a total length of 171.88mm, a detectable wavelength range of 400nm to 700nm, and a dominant wavelength of 586.7nm.

3. The fisheye lens according to claim 1 or 2, wherein: A small air gap is provided between the eighth lens (L8) and the ninth lens (L9) for correcting field curvature.

4. The fisheye lens according to claim 1 or 2, wherein: The object-side and image-side optical surfaces of lens 1 (L1), lens 2 (L2), lens 4 (L4), lens 5 (L5), lens 6 (L6) and lens 7 (L7) are all spherical surfaces.

5. The fisheye lens according to claim 1 or 2, wherein: The surface coefficient of the image-side optical surface of the lens three (L3) is -1.607; the surface coefficient of the image-side optical surface of the lens eight (L8) is -0.239; and the surface coefficient of the object-side optical surface of the lens nine (L9) is 0.

021.

6. The fisheye lens according to claim 1 or 2, characterized in that: The material of the lens 1 (L1) and the lens 2 (L2) is N-LAK8, with a refractive index n=1.713; The lens three (L3), lens seven (L7) and lens ten (L 10 ) is made of K3, with a refractive index of n=1.51823; The material of the lens four (L4) is F1, and the refractive index n=1.62588; The material of the lens five (L5) is N-LAF32, with a refractive index n=1.79457; The material of the lens six (L6) is LF5, with a refractive index n=1.58144; The material of the lens eight (L8) is PK50, with a refractive index n=1.52054; The material of the lens nine (L9) is SF56A, and the refractive index n=1.7847.

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