CN114460716B - Fisheye lens comprising two aspherical lenses - Google Patents
Fisheye lens comprising two aspherical lenses Download PDFInfo
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- CN114460716B CN114460716B CN202210026993.4A CN202210026993A CN114460716B CN 114460716 B CN114460716 B CN 114460716B CN 202210026993 A CN202210026993 A CN 202210026993A CN 114460716 B CN114460716 B CN 114460716B
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B13/00—Optical objectives specially designed for the purposes specified below
- G02B13/001—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras
- G02B13/0015—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras characterised by the lens design
- G02B13/002—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras characterised by the lens design having at least one aspherical surface
- G02B13/0045—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras characterised by the lens design having at least one aspherical surface having five or more lenses
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B13/00—Optical objectives specially designed for the purposes specified below
- G02B13/001—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras
- G02B13/0055—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras employing a special optical element
- G02B13/006—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras employing a special optical element at least one element being a compound optical element, e.g. cemented elements
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B13/00—Optical objectives specially designed for the purposes specified below
- G02B13/06—Panoramic objectives; So-called "sky lenses" including panoramic objectives having reflecting surfaces
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B13/00—Optical objectives specially designed for the purposes specified below
- G02B13/18—Optical objectives specially designed for the purposes specified below with lenses having one or more non-spherical faces, e.g. for reducing geometrical aberration
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Abstract
The invention discloses a fish-eye lens comprising two aspheric lenses, wherein an optical system consists of 12 lenses in total, the system is provided with a front light group, an aperture diaphragm and a rear light group in sequence from an object side to an image side along an optical axis, and the front light group consists of a front three lenses of which the convex surfaces face the object side, a first biconcave lens, a lens of which the convex surfaces face the object side, a first biconvex lens, a second biconvex lens and a biconvex lens of which the first convex surfaces face the image side; the aperture diaphragm is a thin metal disc with a central opening, so that the size of the clear aperture is limited; the rear light group comprises a double-cemented lens formed by a third biconvex lens and a lens with the second convex surface facing the image space, and a double-cemented lens formed by a second biconcave lens and a fourth biconvex lens. The optical system can realize a maximum working field angle of 220 degrees, the receiving aperture can reach F/2.8, and the focal length is 3.878mm; and the system has good illumination uniformity of an image plane, excellent imaging performance, simple and compact structure and easy processing.
Description
Technical Field
The invention relates to an optical system, in particular to a large relative aperture fisheye lens comprising two aspheric lenses, which is applied to the technical field of imaging of an ultra-large field optical system.
Background
The fish-eye lens is an optical system with a large field angle and a large aperture, and the full field angle of the optical system can reach more than 180 degrees. The fisheye lens can obtain all optical information in hemispherical space and even hyper hemispherical space field of view without rotation, so that the fisheye lens has wide application in fields such as safety monitoring, unmanned driving, panoramic photography, military national defense and the like.
However, since in its working environment, a light beam emitted from an object point enters an optical system at a large incident angle, after the grazing incidence light beam is imaged by the optical system, the focusing position and the wavefront parameters in the meridian and sagittal planes may be completely inconsistent, the shape of the wavefront will deviate from the sphere seriously, the imaging characteristics of the plane-symmetric optical system are possessed, and the seidel theory is no longer suitable for aberration analysis of such systems. Therefore, the design of the fisheye lens is very difficult due to the special and complicated structure, and the imaging performance is not easy to control, which is a technical problem to be solved.
Disclosure of Invention
In order to solve the problems in the prior art, the invention aims to overcome the defects in the prior art, and provides a fisheye lens comprising two aspheric lenses, which is based on the developed oversized view field aberration theory and design method, and is optimally designed by combining with the imaging quality evaluation function research of an oversized view field optical system, so that the fisheye lens has the advantages that in the imaging process, the overall aberration change of the system is more severe due to the change of the optical surface along with the aspheric coefficients, and the influence of the aspheric surfaces on the imaging quality of the system is obvious and is far greater than the contribution of other optical surfaces. Therefore, the invention develops a novel fisheye lens system, optimizes the surface of an optical element sensitive to the aspheric coefficients as an aspheric surface, and the obtained optical system has the advantages of good image plane uniformity, good imaging quality, reliable performance, compact structure and easy processing.
In order to achieve the aim of the invention, the invention adopts the following technical scheme:
the fisheye lens comprises 12 lenses, a front light group, an aperture diaphragm and a rear light group are sequentially arranged from an object side to an image side along an optical axis, wherein the front light group consists of a front three lenses of which the convex surfaces face the object side, a first biconcave lens, a lens of which the convex surfaces face the object side, a first biconvex lens, a second biconvex lens and a biconvex lens of which the first convex surfaces face the image side; the second biconvex lens and the first biconvex lens are formed by lenses with the convex surfaces facing the image space; the first biconvex lens is a fourth lens, the lenses with the convex surfaces facing the object side are fifth lenses, the first biconvex lens is a sixth lens, the second biconvex lens is a seventh lens, and the lenses with the first convex surfaces facing the image side are eighth lenses;
the aperture diaphragm is a thin metal disc with a central opening, and limits the size of the clear aperture;
the rear light group comprises a double-cemented lens formed by a third biconvex lens and a lens with the convex surface of the second block facing the image space, and a double-cemented lens formed by a second biconcave lens and a fourth biconvex lens; the third biconvex lens is a ninth lens, the lenses with the convex surfaces facing the image space of the second biconvex lens are tenth lenses, the second biconcave lens is an eleventh lens, and the fourth biconvex lens is a twelfth lens;
the optical surfaces of all lenses of the rear light group are spherical surfaces; the rear optical surface and the convex surface of the first biconcave lens in the front light group face the front optical surface of the lens in the object space, the front optical surface and the convex surface of the first biconcave lens face the rear optical surface of the lens in the object space, and the optical surfaces of the other lenses in the front light group are spherical surfaces.
Preferably, when the rear optical surface of the first biconcave lens and the front optical surface of the lens with the convex surface facing the object side adopt a conic surface of quadratic rotation, the aspheric surface type coefficients of the rear optical surface of the first biconcave lens and the front optical surface of the lens with the convex surface facing the object side should satisfy the following equation:
x′ 2 +y′ 2 ＝a 1 z′+a 2 z′ 2
in the equation, a 1 ＝2R 0 ，R 0 Aspherical surface profile representing optical surface of lensRadius of curvature at the apex, a 2 Is a coefficient for determining the type of the secondary conic surface, namely, an aspheric coefficient, when a 2 >0 is hyperboloid, when a 2 Parabolic when=0, when-1<a 2 <0 is a long ellipsoid, a 2 Spherical surface when= -1, a 2 <-1 is a flat ellipsoid. The rear optical surface of the fourth lens adopts an aspheric structure, the front optical surface adopts a spherical structure, the front optical surface of the fifth lens adopts an aspheric structure, the rear optical surface adopts a spherical structure, and the front optical surface and the rear optical surface of the other lenses adopt spherical structures.
According to the aberration theory of the planar symmetrical optical system of Lu, the wave aberration distribution of each optical surface of the fish-eye lens system is calculated, and one or more optical surfaces which are sensitive to the change of the aspherical coefficients, namely the optical surface with larger influence of the aspherical coefficients on the total aberration of the system, are found by combining the evaluation function capable of quantifying the imaging performance of the optical system, so that the invention selects two optical surfaces with larger influence of the aspherical coefficients in the fish-eye lens on the aberration of the system as the aspherical surfaces.
Further preferably, the aspherical surface profile of the rear optical surface of the first biconcave lens as the fourth lens is a 2 -1.646, the aspherical surface profile coefficient of the front optical surface of the lens, which is the fifth lens, with the convex surfaces both facing the object, being a 2 = -1.092, the surface form coefficients of the rest of the optical surfaces in the optical system are all a 2 = -1. The aspherical coefficients in the invention are all close to spherical surfaces, are easy to process, detect, install and debug, and play a critical role in improving the imaging performance of the optical system.
Preferably, the full field angle of the fisheye lens optical system is 220 degrees, the total focal length is 3.878mm, the D/f' value is 1/2.8, and the rear working distance, namely the distance from the last optical surface of the optical system to the image surface, is 22.645mm. The axial length of the optical system, the distance from the first reflecting surface of the catadioptric optical system to the image surface, is 175.825mm.
Preferably, the air space between the front light group and the back light group is 8.67mm, the air space between the front light group and the aperture stop STO is 6.488mm, and the air space between the aperture stop STO and the back light group is 2.182mm.
Preferably, the air space between the three lenses with the convex surfaces facing the object is 36.714mm and 12.269mm, the air space between the lens with the convex surfaces facing the object and the first biconcave lens is 14.253mm, the air space between the first biconcave lens and the lens with the convex surfaces facing the object is 0.469mm, the air space between the lens with the convex surfaces facing the object and the first biconvex lens is 25.311mm, the air space between the first biconvex lens and the biconvex lens composed of the second biconvex lens and the lens with the first convex surface facing the image is 0.074mm, and the air space between the biconvex lens composed of the third biconvex lens and the second convex surface facing the image and the biconvex lens composed of the second biconvex lens and the fourth biconvex lens is 0.08mm.
Preferably, the material of the three lenses with convex surfaces facing the object side and the fourth biconvex lens is N-BK7, the material of the first biconvex lens is SK51, the material of the lens with convex surfaces facing the object side is SF10, the material of the first biconvex lens is SF12, the material of the second biconvex lens is D263TECO, the material of the lens with the first convex surface facing the image side is LAFN28, the material of the third biconvex lens is K3, the material of the lens with the second convex surface facing the image side is P-LASF47, and the material of the second biconvex lens is SF1.
Further preferably, the materials of the first lens, the second lens, the third lens and the twelfth lens of the lens group are all N-BK7, the refractive index is 1.5168, and the Abbe number is 64.167; the fourth lens material is SK51, the refractive index is 1.6209, and the Abbe number is 60.311; the fifth lens material is SF10, the refractive index is 1.7283, and the Abbe number is 28.41; the sixth lens material is SF12, the refractive index is 1.6483, and the Abbe number is 33.841; the seventh lens material is D263TECO, the refractive index is 1.5233, and the Abbe number is 54.517; the eighth lens material is LAFN28, the refractive index is 1.7731, and the Abbe number is 49.568; the ninth lens material is K3, the refractive index is 1.5182, and the Abbe number is 58.977; the tenth lens material is P-LASF47, the refractive index is 1.8061, and the Abbe number is 40.9; the eleventh lens material was SF1, the refractive index was 1.7174, and the abbe number was 29.513.
Compared with the prior art, the invention has the following obvious prominent substantive features and obvious advantages:
1. the optical system has the advantages of large aperture, wide rear working distance, long axial length of the optical system and strong adjustability, and the aperture F/# of the optical system reaches 2.8, so that the optical system has more practical value;
2. the fisheye lens optical system designed by the invention adopts two aspheric surfaces, effectively improves the imaging performance of an oversized view field by more than 180 degrees, has the aspheric coefficients close to the spherical surfaces, is easy to process and manufacture, and reduces the cost.
Drawings
Fig. 1 is a schematic diagram of a structure of an optical system including two aspherical fisheye lenses according to a preferred embodiment of the invention.
Fig. 2 is a schematic diagram of optical parameter labeling of an optical system including two aspheric fisheye lenses according to a preferred embodiment of the present invention.
Fig. 3 is a graph of MTF curves for an optical system including two aspherical fisheye lenses in accordance with a preferred embodiment of the invention.
Fig. 4 is a dot column diagram of an optical system including two aspherical fisheye lenses according to a preferred embodiment of the invention.
Fig. 5 is a graph of field curvature and distortion curve of an optical system comprising two aspherical fisheye lenses in accordance with a preferred embodiment of the invention.
Fig. 6 is an optical path diagram of an optical system including two aspherical fisheye lenses according to a preferred embodiment of the invention.
Detailed Description
The foregoing aspects are further described in conjunction with specific embodiments, and the following detailed description of preferred embodiments of the present invention is provided:
embodiment one:
in this embodiment, a fisheye lens including two aspheric lenses includes 12 lenses, and a front light group, an aperture stop, and a rear light group are sequentially disposed from an object side to an image side along an optical axis, where the front light group is composed of front three lenses (1, 2, 3) each having a convex surface facing the object side, a first biconcave lens 4, a lens 5 each having a convex surface facing the object side, a first biconvex lens 6, a second biconvex lens 7, and a lens 8 each having a convex surface facing the image side; the second biconvex lens 7 and the lens 8 with the first convex surface facing the image space form a biconvex lens;
the aperture diaphragm is a thin metal disc with a central opening, and limits the size of the clear aperture;
the rear light group comprises a double-cemented lens formed by a third biconvex lens 9 and a lens 10 with the convex surface of the second block facing the image space, and a double-cemented lens formed by a second biconcave lens 11 and a fourth biconvex lens 12;
the optical surfaces of the rear light group lenses are spherical surfaces; the rear optical surface and the convex surface of the front light group first biconcave lens 4 face the front optical surface of the lens 5 in the object space, the front optical surface and the convex surface of the front light group first biconcave lens 4 face the rear optical surface of the lens 5 in the object space, and the optical surfaces of the other lenses in the front light group are spherical surfaces.
The embodiment comprises two aspherical fisheye lens optical systems, can complete the imaging of an object with an oversized view field, and has the advantages of good adjustability, high imaging quality, low cost and convenient processing.
Embodiment two:
this embodiment is substantially the same as the first embodiment, and is characterized in that:
in the present embodiment, the air space between the front light group and the rear light group of the fisheye lens optical system including the two aspherical surfaces is 8.67mm, the air space between the front light group and the aperture stop STO is 6.488mm, and the air space between the aperture stop STO and the rear light group is 2.182mm.
In the present embodiment, the air space between the three lenses (1, 2, 3) each having a convex surface facing the object side is 36.714mm and 12.269mm, the air space between the lens 3 each having a convex surface facing the object side and the first biconcave lens 4 is 14.253mm, the air space between the first biconcave lens 4 and the lens 5 each having a convex surface facing the object side is 0.469mm, the air space between the lens 5 each having a convex surface facing the object side and the first biconvex lens 6 is 25.311mm, the air space between the first biconvex lens 6 and the biconvex lens composed of the second biconvex lens 7 and the lens 8 each having a convex surface facing the image side is 0.074mm, and the air space between the biconvex lens composed of the third biconvex lens 9 and the lens 10 each having a convex surface facing the image side and the biconvex lens composed of the second biconvex lens 11 and the fourth biconvex lens 12 is 0.08mm.
In this embodiment, when the rear optical surface of the first biconcave lens 4 and the front optical surface of the lens 5 with the convex surface facing the object side adopt a conic surface of quadratic rotation, the aspheric surface profile coefficients of the rear optical surface of the first biconcave lens 4 and the front optical surface of the lens 5 with the convex surface facing the object side should satisfy the following equation:
x′ 2 +y′ 2 ＝a 1 z′+a 2 z′ 2
in the equation, a 1 ＝2R 0 ，R 0 A represents the radius of curvature, a, at the apex of an aspherical surface curve of the optical surface of the lens 2 Is a coefficient for determining the type of the secondary conic surface, namely, an aspheric coefficient, when a 2 >0 is hyperboloid, when a 2 Parabolic when=0, when-1<a 2 <0 is a long ellipsoid, a 2 Spherical surface when= -1, a 2 <-1 is a flat ellipsoid.
In the present embodiment, the three lenses (1, 2, 3) each having a convex surface facing the object side and the fourth biconvex lens 12 are made of N-BK7, the first biconcave lens 4 is made of SK51, the lens 5 each having a convex surface facing the object side is made of SF10, the first biconvex lens 6 is made of SF12, the second biconvex lens 7 is made of D263TECO, the lens 8 each having a first convex surface facing the image side is made of lan 28, the third biconvex lens 9 is made of K3, the lens 10 each having a second convex surface facing the image side is made of P-LASF47, and the second biconcave lens 11 is made of SF1.
In this example, the full field angle of the fisheye lens optical system is 220 °, the total focal length is 3.878mm, and the f number is 2.8. The rear working distance, the distance from the last optical surface of the optical system to the image surface, is 22.645mm, and the axial length of the optical system, the distance from the first reflecting surface of the catadioptric optical system to the image surface, is 175.825mm.
The working field angle of the optical system comprising the two aspheric fisheye lens is in the range of 0-110 degrees, and the imaging of an object with an oversized field of view can be completed; the optical system of the embodiment has large aperture, wide rear working distance, long axial length of the optical system and strong adjustability; in the working view field range, the optical system of the embodiment has good image plane uniformity and high imaging quality, and meanwhile, the optical system has a simple structure, low cost and convenient processing and has more practical value.
Embodiment III:
this embodiment is substantially the same as the above embodiment, and is characterized in that:
in this embodiment, the fisheye lens including two aspheric lenses includes 12 lenses, and is provided with a front light group, an aperture stop, and a rear light group in order from an object space to an image space along an optical axis, and is characterized in that: the front light group consists of front three lenses (1, 2 and 3) with convex surfaces facing the object, a first biconcave lens 4, a lens 5 with convex surfaces facing the object, a first biconvex lens 6, a second biconvex lens 7 and a biconvex lens 8 with the first convex surfaces facing the image; the second biconvex lens 7 and the lens 8 with the first convex surface facing the image space form a biconvex lens;
the aperture diaphragm is a thin metal disc with a central opening, and limits the size of the clear aperture;
the rear light group comprises a double-cemented lens formed by a third biconvex lens 9 and a lens 10 with the convex surface of the second block facing the image space, and a double-cemented lens formed by a second biconcave lens 11 and a fourth biconvex lens 12; the rear optical surface of the first biconcave lens 4 and the front optical surface of the lens 5 with the convex surface facing the object side are both conic surfaces, and the front optical surface of the first biconcave lens 4 and the rear optical surface of the lens 5 with the convex surface facing the object side are both spherical surfaces; the optical surfaces of the rest lenses of the rear light group are spherical surfaces.
In the present embodiment, the rear optical surface profile coefficient a of the first biconcave lens 4 2 A front optical surface form factor a of the lens 5 with convex surfaces facing the object side of-1.646 2 Is-1.092, i.e. the two aspheric surfaces are flat ellipsoidsSurface profile coefficient a of each lens of front group remaining lenses and rear group optical system 2 Are all-1.
In the present embodiment, the working field angle of the fisheye lens optical system ranges from 0 ° to 110 °, the total focal length is 22.68mm, f/# = 2.8, and the system axial length is 175.825mm.
In the present embodiment, an aperture stop STO is provided between the front group optical system and the rear group optical system, that is, the aperture stop STO is provided between the lens 8 and the third lenticular lens 9, both of which have the first convex surfaces facing the image side, and the aperture stop STO has a diameter of 4.679mm.
In the present embodiment, the materials of the lenses (1, 2, 3) with convex surfaces facing the object side and the fourth biconvex lens 12 are N-BK7, the refractive index is 1.5168, and the abbe number is 64.167; the material of the first biconcave lens 4 is SK51, the refractive index is 1.6209, and the Abbe number is 60.311; the lens 5 with convex surfaces facing the object is made of SF10, the refractive index is 1.7283, and the Abbe number is 28.41; the material of the first biconvex lens 6 is SF12, the refractive index is 1.6483, and the Abbe number is 33.841; the material of the second biconvex lens 7 is D263TECO, the refractive index is 1.5233, and the Abbe number is 54.517; the material of the lens 8 with the first convex surfaces facing the image side is LAFN28, the refractive index is 1.7731, and the Abbe number is 49.568; the material of the third biconvex lens 9 is K3, the refractive index is 1.5182, and the abbe number is 58.977; the material of the lens 10 with the second convex surfaces facing the image side is P-LASF47, the refractive index is 1.8061, and the Abbe number is 40.9; the material of the lens 11 with the second convex surfaces facing the object side is SF1, the refractive index is 1.7174, and the abbe number is 29.513.
Fig. 1 is a schematic diagram of a fisheye lens optical system in this embodiment, which includes two aspherical surfaces, from an object plane to an image plane, a principal ray sequentially passes through an incident surface 1' and an exit surface 2' of a first lens block 1, each of which has a convex surface facing the object side, an incident surface 3' and an exit surface 4' of a second lens block 2, each of which has a convex surface facing the object side, an incident surface 5' and an exit surface 6' of a third lens block 3, each of which has a convex surface facing the object side, an incident surface 7' and an exit surface 8' of a first biconcave lens 4, each of which has a convex surface facing the incident surface 9' and an exit surface 10' of a lens 5, each of which has a convex surface facing the object side, an incident surface 11' and an exit surface 12' of a first biconvex lens 6, each of which has a convex surface 7' and a convex surface facing the incident surface 13', a cemented surface 14' and an exit surface 15' of a cemented lens of a biconvex lens composed of a lens 8, each of which has a convex surface 9 and a convex surface facing the lens 10 facing the image side, each of which has a cemented surface 17' and a cemented surface 18', and each of which has a cemented surface 11' composed of a biconvex lens composed of a second biconvex lens 11 and each of the fourth biconvex lens.
Fig. 2 is a schematic illustration of optical parameter labeling of an optical system of a fisheye lens with two aspheric surfaces in the present embodiment. r is (r) 1 、r 2 Radius of curvature, r, of the entrance face 1 'and exit face 2' of the first lens 1 3 、r 4 Radius of curvature r for the entrance face 3 'and exit face 4' of the second lens 2 5 、r 6 Radius of curvature, r, of the entrance face 5 'and exit face 6' of the third lens 3 7 Is the radius of curvature, r, of the entrance face 7' of the first biconcave lens 4 8 Is the radius of curvature, r, at the apex of the exit face 8' of the first biconcave lens 4 9 Radius of curvature, r, at the apex of the incident face 9' of the lens 5, with convex faces both facing the object 10 Radius of curvature, r, of the exit face 10' of the lens 5, which is convex towards the object 11 、r 12 Radius of curvature r for the entrance face 11 'and exit face 12' of the first lenticular lens 6 13 、r 14 、r 15 The radii of curvature, r, of the entrance face 13', the cemented face 14' and the exit face 15' of a doublet lens consisting of a lens 8 with both the second doublet lens 7 and the first convex face facing the image side 16 、r 17 、r 18 The radii of curvature, r, of the entrance face 16', the cemented face 17' and the exit face 18' of the doublet lens consisting of the lens 10 with both the third lenticular lens 9 and the second convex face facing the image side 19 、r 20 、r 21 The radii of curvature of the entrance face 19', the cemented face 20', and the exit face 21' of the cemented lens that is the combination of the second biconcave lens 11 and the fourth biconvex lens 12; d, d 1 、d 3 、d 5 、d 7 、d 9 、d 11 、d 13 、d 14 、d 17 、d 18 、d 20 、d 21 The lens thicknesses d of the lens 10 having the convex surfaces of the first lens 1 to the second lens facing the image space 2 Is the air spacing, d, between the first lens 1 and the second lens 2 4 Is the air spacing, d, between the second lens 2 and the third lens 3 6 D is the air space between the third lens 3 and the first biconcave lens 4 8 Is the air spacing, d, between the first biconcave lens 4 and the lens 5 with its convex surface facing the object 10 An air space d between the lens 5 and the first biconvex lens 6, which are convex surfaces facing the object 12 An air space d between the first biconvex lens 6 and the biconvex lens 7 and the biconvex lens formed by the first lens 8 with the convex surface facing the image side 15 An air space d between the aperture stop and the doublet lens composed of the lens 8 with both the second biconvex lens 7 and the first convex surface facing the image side 16 D is the air spacing between the aperture stop and the doublet lens consisting of the third biconvex lens 9 and the lens 10 with the second convex surface facing the image side 19 An air space d between the cemented doublet consisting of the lens 10 with both the third biconvex lens 9 and the second convex surface facing the image space and the cemented doublet consisting of the second biconcave lens 11 and the fourth biconvex lens 12 22 An air space between the image plane and the cemented lens composed of the second biconcave lens 11 and the fourth biconvex lens 12.
Fig. 3 is an MTF curve of the FFT method of the fisheye lens optical system including two aspherical surfaces in the present embodiment, wherein the horizontal axis represents the working field angle in degrees (°); the vertical axis represents MTF values ranging from 0 to 1; the imaging quality of the optical system is evaluated in accordance with the MTF value of the optical system. Wherein, the higher and flatter the curve value is, the better the imaging quality of the representing optical system is. Solid lines with solid figures (circles and triangles) and solid lines with open figures (circles and triangles) are shown as chief rays with spatial frequencies of 30lp/mm and 10lp/mm, respectively; the solid lines with circles (including solid and hollow patterns) and the solid lines with triangles (including solid and hollow patterns) in the figure are respectively shown as meridian direction and arc losing direction, and it can be seen from the figure that the MTF curve of the fisheye lens optical system is kept very stable in the range of 0 ° to 110 ° in the working field angle, which means that the imaging quality of the optical system is very good in the working range of the field angle.
Fig. 4 is a ray trace point chart of the fisheye lens optical system including two aspheric surfaces in the present embodiment, in which ray trace point charts with working field angles of 0 °, 30 °, 60 °, 90 ° and 110 ° are respectively shown. The figure contains a point plot of three different wavelengths of light as the operating light, respectively, C (red light, wavelength 656.27 nm), D (yellow light, wavelength 587.56 nm) and F (blue light, wavelength 486.13 nm). As can be seen from fig. 4, the spot radius of the optical system is smaller at different angles of view and working light, which means that the corresponding geometrical aberration of the optical system is smaller in the range of the working angle of view.
Fig. 5 shows a field curvature and an F-Theta distortion curve of an optical system of a fisheye lens including two aspheric surfaces in the present embodiment, wherein the field curvature and the distortion are one of important indicators for measuring the quality of the lens of the optical system. The horizontal axis of the field curvature curve represents the field curvature in mm, the vertical axis represents the field angle in degrees (°); the horizontal axis of the F-Theta distortion curve is expressed as the deviation of the distortion between the design lens and the model used in percent (%), and the vertical axis is expressed as the half field angle in degrees (°). The Zemax software only displays the maximum 89 ° field angle. As can be seen from FIG. 5, the fisheye lens optical system comprising two aspheric surfaces designed by the invention has small curvature in the working field angle range, and meanwhile, the axial chromatic aberration is also small, and the distortion meets the lens imaging requirement. The working field angle of the fisheye lens optical system comprising the two aspheric surfaces is wide, and the imaging of the object with the ultra-large field of view can be completed.
The optical parameters of the fisheye lens optical system including two aspherical surfaces in this embodiment are shown in table 1.
Table 1 optical parameters of fisheye lens optical system comprising two aspherical surfaces in examples
| Optical surface | Radius of curvature | Optical spacing | Surface coefficient | Refractive index | Material |
| Object plane | ∞ | ∞ | - | - | - |
| 1 | 101.849 | 5.710 | -1 | 1.51680 | N-BK7 |
| 2 | 42.464 | 36.714 | -1 | ||
| 3 | 62.090 | 3.317 | -1 | 1.51680 | N-BK7 |
| 4 | 26.524 | 16.269 | -1 | ||
| 5 | 183.382 | 2.984 | -1 | 1.51680 | N-BK7 |
| 6 | 14.557 | 14.253 | -1 | ||
| 7 | -44.463 | 7.647 | -1 | 1.62090 | SK51 |
| 8 | 22.639 | 0.469 | -1.646 | ||
| 9 | 22.000 | 10.487 | -1.092 | 1.72825 | SF10 |
| 10 | 82.475 | 25.311 | -1 | ||
| 11 | 179.113 | 2.189 | -1 | 1.64831 | SF12 |
| 12 | -152.798 | 0.074 | -1 | ||
| 13 | 42.159 | 4.467 | -1 | 1.52330 | D263TECO |
| 14 | -25.056 | 2.421 | -1 | 1.77314 | LAFN28 |
| 15 | -63.236 | 6.488 | -1 | ||
| STO | ∞ | 2.182 | - | ||
| 16 | 31.733 | 7.478 | -1 | 1.51820 | K3 |
| 17 | -8.615 | 0.602 | -1 | 1.80610 | P-LASF47 |
| 18 | -28.284 | 0.080 | -1 | ||
| 19 | -147.334 | 0.720 | -1 | 1.71736 | SF1 |
| 20 | 28.339 | 3.283 | -1 | 1.51680 | N-BK7 |
| 21 | -14.176 | 22.680 | - | - | - |
| Image plane | ∞ | ∞ | - | - | - |
In summary, the present invention discloses a panoramic imaging optical system including an aspheric catadioptric system. The system is provided with a front light group, an aperture diaphragm and a rear light group along an optical axis from an object side to an image side in sequence, wherein the front light group consists of three convex surfaces, namely a negative lens with the convex surfaces facing the object side, a biconcave lens and a lens with the convex surfaces facing the object side, the rear light group mainly comprises a biconvex lens, a biconvex lens with the convex surfaces facing the lens of the image side, and a biconvex lens with the convex surfaces facing the lens of the object side, wherein the rear optical surface of the lens and the front optical surface of the lens are aspheric surfaces, and the rest optical surfaces are spherical surfaces. The aperture diaphragm is a thin metal disc with a central opening, and aims to limit the size of a clear aperture. The embodiment adopts 12 independent lenses, can realize a maximum working field angle of 220 degrees, has a receiving aperture of F/2.8 and has a focal length of 22.68mm; the system has the characteristics of good uniformity of illumination of the image plane, excellent imaging performance, simple and compact structure and easy processing.
The embodiments of the present invention have been described above with reference to the accompanying drawings, but the present invention is not limited to the embodiments described above, and various changes, modifications, substitutions, combinations or simplifications made under the spirit and principles of the technical solution of the present invention can be made according to the purpose of the present invention, and all the changes, modifications, substitutions, combinations or simplifications should be equivalent to the substitution, so long as the purpose of the present invention is met, and all the changes are within the scope of the present invention without departing from the technical principles and the inventive concept of the present invention.
Claims (6)
1. The utility model provides a fisheye lens that contains two aspheric lenses, includes 12 lenses, follows the optical axis from object space to image space, is equipped with preceding light group, aperture stop, back light group in proper order, its characterized in that: the front light group consists of a double-cemented lens composed of a front three lenses (1, 2 and 3) with convex surfaces facing an object side, a first biconcave lens (4), a lens (5) with a fourth convex surface facing the object side, a first biconvex lens (6), a second biconvex lens (7) and a lens (8) with the first convex surface facing an image side; the second biconvex lens (7) and the first biconvex lens (8) are formed by lenses (8) with the convex surfaces facing the image space;
the aperture diaphragm is a thin metal disc with a central opening, and limits the size of the clear aperture;
the rear light group comprises a double-cemented lens formed by a third biconvex lens (9) and a lens (10) with the convex surface of the second block facing the image space, and a double-cemented lens formed by a second biconcave lens (11) and a fourth biconvex lens (12);
the optical surfaces of all lenses of the rear light group are spherical surfaces; the front optical surface of the lens (5) with the rear optical surface of the first biconcave lens (4) and the fourth convex surface facing the object side in the front light group is a secondary conical curved surface, the rear optical surface of the lens (5) with the front optical surface of the first biconcave lens (4) and the fourth convex surface facing the object side is a spherical surface, and the optical surfaces of the other lenses in the front light group are spherical surfaces;
the full field angle of the fisheye lens optical system is 220 degrees, the total focal length is 3.878mm, the F number is 2.8, and the rear working distance is 22.645mm.
2. The fisheye lens comprising two aspheric lenses of claim 1, wherein: when the rear optical surface of the first biconcave lens (4) and the front optical surface of the lens (5) with the fourth convex surface facing the object side adopt a conic surface of quadratic rotation, the aspherical surface coefficients of the rear optical surface of the first biconcave lens (4) and the front optical surface of the lens (5) with the fourth convex surface facing the object side should satisfy the following equation:
x' 2 +y' 2 ＝a 1 z'+a 2 z' 2
in the equation, a 1 ＝2R 0 ，R 0 Aspherical surface type curve top representing optical surface of lensRadius of curvature at point, a 2 Is a coefficient for determining the type of the secondary conic surface, namely, an aspheric coefficient, when a 2 >0 is hyperboloid, when a 2 Parabolic when=0, when-1<a 2 <0 is a long ellipsoid, a 2 Spherical surface when= -1, a 2 <-1 is a flat ellipsoid.
3. The fisheye lens comprising two aspheric lenses according to claim 2, wherein: the aspherical surface profile coefficient of the rear optical surface (8') of the first biconcave lens (4) is a 2 -1.646, the aspherical surface profile coefficient of the front optical surface (9') of the lens (5) with the fourth convex surface facing the object being a 2 = -1.092, the surface form coefficients of the rest of the optical surfaces in the optical system are all a 2 ＝-1。
4. The fisheye lens comprising two aspheric lenses of claim 1, wherein: the air interval between the front light group and the rear light group is 8.67mm, the air interval between the front light group and the aperture stop STO is 6.488mm, and the air interval between the aperture stop STO and the rear light group is 2.182mm.
5. The fisheye lens comprising two aspheric lenses of claim 1, wherein: the air interval between the three lenses (1, 2 and 3) with the convex surfaces facing the object side is 36.714mm and 12.269mm, the air interval between the lens (3) with the convex surfaces facing the object side and the first biconvex lens (4) is 14.253mm, the air interval between the lens (5) with the first biconvex lens (4) and the fourth convex surface facing the object side is 0.469mm, the air interval between the lens (5) with the fourth convex surface facing the object side and the first biconvex lens (6) is 25.311mm, the air interval between the first biconvex lens (6) and the biconvex lens formed by the second biconvex lens (7) and the lens (8) with the first convex surface facing the image side is 0.074mm, and the air interval between the biconvex lens formed by the third biconvex lens (9) and the lens (10) with the second biconvex lens (12) facing the image side and the biconvex lens formed by the third biconvex lens (11) and the fourth biconvex lens (12) is 0.08mm.
6. The fisheye lens comprising two aspheric lenses according to any one of claims 1-5, wherein: the three lenses (1, 2, 3) with convex surfaces facing the object side and the fourth biconvex lens (12) are made of N-BK7, the first biconcave lens (4) is made of SK51, the fourth biconvex lens (5) is made of SF10, the first biconvex lens (6) is made of SF12, the second biconvex lens (7) is made of D263TECO, the first lens (8) with convex surfaces facing the image side is made of LAFN28, the third biconvex lens (9) is made of K3, the second lens (10) with convex surfaces facing the image side is made of P-LASF47, and the second biconvex lens (11) is made of SF1.
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