Ultra-wide-angle lens

Abstract

The present invention is applicable to the field of lens technology and provides an ultra-wide-angle lens. The ultra-wide-angle lens sequentially includes a first lens, a second lens, a fixed diaphragm, and a third lens along the optical axis from the object side to the imaging surface. The first lens has a negative refractive index and is a lens with concave surfaces on both sides; the second lens has a positive refractive index and is a lens with convex surfaces on both sides; the third lens has a positive refractive index and is a meniscus lens with the concave surface facing the object side. At least one surface of the first lens, the second lens, and the third lens is an aspherical surface, and the optical centers are located on the same straight line. The ultra-wide-angle lens satisfies the conditional formula: 2.5 < TL / 2Y < 3.0, where TL is the overall optical length of the ultra-wide-angle lens; 2Y is the imaging height of the maximum usable field angle of the entire ultra-wide-angle lens on the imaging surface. The ultra-wide-angle lens provided by the present invention ensures miniaturization and light weight under the condition of a large field angle, and at the same time has good optical performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of lenses, and particularly relates to an ultra-wide-angle lens. Background Art

[0002] At present, the examinee can take a capsule endoscope with an internal image acquisition and wireless communication device orally, so that the capsule endoscope can acquire images in the digestive tract. The doctor uses an external instrument to receive the images taken by the capsule endoscope to understand the digestive tract condition of the examinee, and thus make a diagnosis of the disease. The capsule endoscope examination has the advantages of convenient examination, non-invasive, wire-free, painless, no cross-infection, and does not affect the normal work of the patient. It expands the field of vision of digestive tract examination, overcomes the defects of poor tolerance, inapplicability to the elderly, weak and critically ill patients of traditional insertion endoscopy, and can be used as the preferred method for the diagnosis of digestive tract diseases, especially small intestine diseases.

[0003] Of course, it can be easily known from the above that the image quality of the capsule endoscope taking pictures of the stomach and intestines directly affects the effect of the capsule endoscope examination. However, in the actual use of the capsule endoscope, such as moving forward with the peristalsis of the human digestive tract in the intestine, the shooting angle and orientation of the captured images cannot be controlled. This requires ensuring the image resolution while expanding the shooting field of view as much as possible.

[0004] An ultra-wide-angle lens is usually used to expand the shooting field of view to take pictures of large scenes within a limited distance range. The problems faced in designing an ultra-wide-angle lens are complex structure, large volume, difficult to eliminate off-axis aberrations, poor image quality at the edge of the image plane, low relative illumination, which is not conducive to image observation and doctor diagnosis. To overcome the above aberrations, lens designers usually use a lot of lenses in the lens to compensate. Generally speaking, the design becomes difficult whether the lens is too long or too short, and the manufacturing process requirements are relatively high, resulting in a higher lens cost while improving the imaging quality. Summary of the Invention

[0005] An embodiment of the present invention provides an ultra-wide-angle lens, aiming to provide an ultra-wide-angle lens with miniaturization, large field of view, and good optical performance at the same time.

[0006] An embodiment of the present invention proposes an ultra-wide-angle lens, which sequentially includes a first lens, a second lens, a fixed aperture, and a third lens along the optical axis from the object side to the imaging plane. Among them,

[0007] The first lens has a negative refractive index near the optical axis. The first lens is a lens with both concave surfaces, and at least one surface of the first lens is an aspherical surface;

[0008] The second lens has a positive refractive index near the optical axis. The second lens is a lens with both convex surfaces, and at least one surface of the second lens is an aspherical surface;

[0009] The third lens has a positive refractive index near the optical axis. The third lens is a meniscus lens with a concave surface facing the object side, and at least one surface of the third lens is aspherical.

[0010] The optical centers of the first lens, the second lens, and the third lens are located on the same straight line.

[0011] The ultra-wide-angle lens satisfies the conditional formula: 2.5 < TL / 2Y < 3.0, where TL is the total optical length of the ultra-wide-angle lens; 2Y is the imaging height of the maximum usable field angle of the entire ultra-wide-angle lens on the imaging surface.

[0012] The ultra-wide-angle lens provided by the present invention, through the design of using three plastic aspherical lenses, can reduce the number of lenses, effectively reduce the total length, weight, and manufacturing cost of the lens, and can achieve miniaturization. Furthermore, the ultra-wide-angle lens has a long service life and high stability; the ultra-wide-angle lens provided by the present invention can reach a large field angle of 140°, has good correction of field curvature and distortion, and has good resolution ability at the same time; by setting the fixed aperture between the second lens and the third lens, off-axis aberration can be well corrected; the aspherical surfaces provided on each lens enable a powerful aberration correction function, improving the imaging clarity and sharpness; enabling the ultra-wide-angle lens to be more miniaturized, lightweight, and have a large field of view, while obtaining good optical performance, ensuring excellent imaging quality at a large field angle. Description of the Drawings

[0013] Figure 1 It is a schematic cross-sectional structure diagram of the ultra-wide-angle lens in the first embodiment of the present invention;

[0014] Figure 2 It is a transfer function curve diagram of the ultra-wide-angle lens in the first embodiment of the present invention at a working distance of 5 mm;

[0015] Figure 3 It is a transfer function curve diagram of the ultra-wide-angle lens in the first embodiment of the present invention at a working distance of 10 mm;

[0016] Figure 4 It is a transfer function curve diagram of the ultra-wide-angle lens in the first embodiment of the present invention at a working distance of 40 mm;

[0017] Figure 5 It is a field curvature and distortion curve diagram of the ultra-wide-angle lens in the first embodiment of the present invention at a working distance of 5 mm;

[0018] Figure 6 It is a field curvature and distortion curve diagram of the ultra-wide-angle lens in the first embodiment of the present invention at a working distance of 10 mm;

[0019] Figure 7 It is the field curvature and distortion curve diagram of the ultra-wide-angle lens in the first embodiment of the present invention at a working distance of 40 mm;

[0020] Figure 8 It is the relative illumination curve diagram of the ultra-wide-angle lens in the first embodiment of the present invention;

[0021] Figure 9 It is the transfer function curve diagram of the ultra-wide-angle lens in the second embodiment of the present invention at a working distance of 5 mm;

[0022] Figure 10 It is the transfer function curve diagram of the ultra-wide-angle lens in the second embodiment of the present invention at a working distance of 10 mm;

[0023] Figure 11 It is the transfer function curve diagram of the ultra-wide-angle lens in the second embodiment of the present invention at a working distance of 40 mm;

[0024] Figure 12 It is the field curvature and distortion curve diagram of the ultra-wide-angle lens in the second embodiment of the present invention at a working distance of 5 mm;

[0025] Figure 13 It is the field curvature and distortion curve diagram of the ultra-wide-angle lens in the second embodiment of the present invention at a working distance of 10 mm;

[0026] Figure 14 It is the field curvature and distortion curve diagram of the ultra-wide-angle lens in the second embodiment of the present invention at a working distance of 40 mm;

[0027] Figure 15 It is the relative illumination curve diagram of the ultra-wide-angle lens in the second embodiment of the present invention. Detailed implementation manners

[0028] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0029] The ultra-wide-angle lens provided by the present invention sequentially includes a first lens, a second lens, a fixed diaphragm, and a third lens along the optical axis from the object side to the imaging surface. The first lens has a negative refractive index and is a lens with concave surfaces on both sides; the second lens has a positive refractive index and is a lens with convex surfaces on both sides; the third lens has a positive refractive index and is a meniscus lens with the concave surface facing the object side. At least one surface of the first lens, the second lens, and the third lens is an aspherical surface, and the optical centers are located on the same straight line. The ultra-wide-angle lens satisfies the conditional formula: 2.5 < TL / 2Y < 3.0, where TL is the total optical length of the ultra-wide-angle lens; 2Y is the imaging height of the maximum usable field angle of the entire ultra-wide-angle lens on the imaging surface. By adopting a design with three lenses, the number of lenses can be reduced, effectively reducing the total length, weight, and manufacturing cost of the lens, enabling miniaturization, and further making the ultra-wide-angle lens have a long service life and high stability, while good optical performance can be obtained.

[0030] As Figure 1 shown is a schematic cross-sectional structure diagram of the ultra-wide-angle lens provided by an embodiment of the present invention.

[0031] Please refer to Figure 1 For the ultra-wide-angle lens provided by the present invention, along the optical axis from the object side to the imaging surface 17, it sequentially includes a first lens 11, a second lens 12, a fixed diaphragm 13, and a third lens 14, where

[0032] the first lens 11 has a negative refractive index near the optical axis, the first lens 11 is a lens with concave surfaces on both sides, and at least one surface of the first lens 11 is an aspherical surface;

[0033] the second lens 12 has a positive refractive index near the optical axis, the second lens 12 is a lens with convex surfaces on both sides, and at least one surface of the second lens 12 is an aspherical surface;

[0034] the third lens 14 has a positive refractive index near the optical axis, the third lens 14 is a meniscus lens with the concave surface facing the object side, and at least one surface of the third lens 14 is an aspherical surface;

[0035] the optical centers of the first lens 11, the second lens 12, and the third lens 14 are located on the same straight line;

[0036] the ultra-wide-angle lens satisfies the conditional formula: 2.5 < TL / 2Y < 3.0, where TL is the total optical length of the ultra-wide-angle lens, that is, the distance from the object-side surface of the first lens 11 to the imaging surface 17 on the optical axis; 2Y is the imaging height of the maximum usable field angle of the entire ultra-wide-angle lens on the imaging surface 17.

[0037] Specifically, the object side of the first lens 11 is concave, the image side of the first lens 11 is concave, and it has a negative optical power. The object side of the second lens 12 is convex, the image side of the second lens 12 is convex, and it has a positive optical power. The object side of the third lens 14 is concave, the image side of the first lens 11 is convex, and it has a positive optical power

[0038] Among them, the fixed diaphragm 13 is located between the second lens 12 and the third lens 14 and is close to the object-side surface of the third lens 14. The fixed diaphragm 13 adopts a central aperture design, which can correct off-axis aberrations and reduce the sensitivity to eccentricity. When there are assembly errors, the aberrations are less serious

[0039] Among them, the ultra-wide-angle lens satisfies the above conditional formula, so that when the imaging height of the maximum field of view angle on the imaging surface 17 remains fixed, by setting the upper limit value of TL / 2Y to 3.0, the optical total length of the ultra-wide-angle lens can be effectively reduced, making the overall size of the lens thinner, achieving the functions of being compact, short, and ultra-wide-angle while maintaining the optical performance

[0040] Among them, the ultra-wide-angle lens satisfies the conditional formula:

[0041] f1 < 0, -1.5 < f1 / f < -1.2;

[0042] f2 > 0, 2.7 < f2 / f < 3.0;

[0043] f3 > 0, 1.8 < f3 / f < 2.2;

[0044] Among them, f is the focal length of the entire ultra-wide-angle lens; f1 is the focal length of the first lens 11; f2 is the focal length of the second lens 12; f3 is the focal length of the third lens 14; through reasonable optical power distribution, a 140° ultra-wide-angle design can be achieved, realizing more miniaturization and lightweight, and at the same time good optical performance can be obtained

[0045] Among them, the first lens 11, the second lens 12, and the third lens 14 are all plastic aspherical lenses. Using aspherical surfaces on both sides of each lens can not only correct spherical aberration and chromatic aberration but also help shorten the total length of the lens optical system. Each lens is made of optical plastic material, which can achieve the aspherical shape with high precision while realizing lightweight and low cost

[0046] Among them, the ultra-wide-angle lens satisfies the conditional formula: Vd1 > Vd2, Vd3 > Vd2. Herein, Vd1, Vd2, and Vd3 respectively represent the Abbe numbers of the first lens 11, the second lens 12, and the third lens 14. By manufacturing the first lens 11 and the third lens 14 with materials having a relatively large Abbe number and the second lens 12 with a material having a relatively small Abbe number, good correction of magnification chromatic aberration can be achieved.

[0047] Among them, the aspherical surface shapes of the first lens 11, the second lens 12, and the third lens 14 all satisfy the following equation: where Y is the height of the light ray, R is the radius of curvature of the aspherical surface near the optical axis, A2 is the conic quadratic surface coefficient, A4, A6, A8, A 10 、A 12 are high-order aspherical coefficients, X is the length perpendicular from the point on the aspherical surface at a distance Y from the optical axis to the tangent plane of the aspherical surface vertex, and the tangent plane is a plane perpendicular to the optical axis, that is, X represents the distance of the aspherical surface from the aspherical surface vertex in the optical axis direction. When A2 is less than -1, the surface curve is a hyperboloid; when it is equal to -1, it is a paraboloid; when it is between -1 and 0, it is an ellipsoid; when it is equal to 0, it is a sphere; when it is greater than 0, it is a prolate spheroid. Through the above parameters, the surface shape dimensions of the front and rear surfaces of each lens can be accurately set. The aspherical shape satisfies the even-order aspherical equation. By using different aspherical coefficients, the role of the aspherical surface in the system is maximized, and a more perfect resolving power is obtained. Preferably, through the above surface equation, the surface shape dimensions of the front and rear aspherical surfaces of the first lens 11, the second lens 12, and the third lens 14 can be accurately set, and by utilizing the powerful aberration correction function of the aspherical surface, the imaging clarity and sharpness of the ultra-wide-angle lens are thus greatly improved.

[0048] Among them, the ultra-wide-angle lens further includes a filter 15, and the filter 15 is disposed at the rear side of the third lens 14. The filter 15 is an infrared filter. Through the design of the filter 15, the transmission of light in non-working bands is suppressed, and the chromatic aberration and stray light of the optical system can be effectively reduced, thereby improving the imaging effect.

[0049] Among them, the focal length F of the aspherical lens satisfies the following formula:

[0050]

[0051] In this formula, r1 represents the radius of curvature of the first surface of the aspherical lens; r2 represents the radius of curvature of the second surface of the aspherical lens; d represents the optical surface spacing of the aspherical lens, and n represents the refractive index of the aspherical lens. Through the above parameters, the focal lengths of each lens can be accurately set and calculated.

[0052] Furthermore, in all embodiments of the present invention, f represents the focal length of the entire ultra-wide-angle lens, r represents the radius of curvature of the vertex of the optical surface, d represents the optical surface spacing (the distance between the vertices of two adjacent optical surfaces), N d represents the refractive index of each lens, and V d represents the Abbe number of the material of each lens. TL represents the total optical length of the entire ultra-wide-angle lens, that is, the distance from the object side surface of the first lens 11 to the imaging surface 17 on the optical axis in the entire ultra-wide-angle lens.

[0053] In the following different embodiments, the relevant parameters of each lens in the ultra-wide-angle lens can be referred to the parameter table of each embodiment.

[0054] Example 1

[0055] Please refer to Figure 1 , which is the ultra-wide-angle lens provided by the first embodiment of the present invention. Among them, in this embodiment, the lens focal length f of the ultra-wide-angle lens is 0.46 mm, F / NO = 3.0, 2ω = 140°, and the depth of field is 5 - 40 mm. The first lens 11 and the third lens 14 adopt the F52R material with a relatively large Abbe coefficient, and the second lens 12 adopts the EP5000 material with a relatively small Abbe coefficient. This embodiment satisfies the above conditional formula, where TL / 2Y = 2.77, f1 < 0, f1 / f = -1.33, f2 > 0, f2 / f = 2.85, f3 > 0, f3 / f = 2.02. The relevant parameters of each lens in the ultra-wide-angle lens in this embodiment are shown in Table 1.

[0056] Table 1

[0057]

[0058]

[0059] The aspheric coefficients of the first lens 11, the second lens 12, and the third lens 14 in this embodiment are shown in Table 2.

[0060] Table 2

[0061] Surface number S1 S2 S3 S4 S5 S6 A2 5.1778 -1.6637 -4.3338 -47.8895 62.4310 -1.2045 A4 0 0.0748 0.0685 0.0502 -1.1052 -0.1641 A6 0 0.0099 0.0619 0.2389 -0.9890 -1.4150 A8 0 0.0046 0.0549 -0.4535 -160.1033 -1.2118 A10 0 -0.0199 -0.0801 -1.6755 56.7531 11.5776 A12 0 -0.0801 -0.1438 2.9102 0.0036 -43.7078

[0062] Among them, refer to Figures 2 to 8 , which respectively shows the optical characteristic curves of the ultra-wide-angle lens in this embodiment, where Figures 2 to 4The figure shows the transfer function curves of an ultra-wide-angle lens at working distances of 5mm, 10mm, and 40mm respectively. Here, the working distance is the distance between the object being photographed and the lens. The MTF (Modulation Transfer Function) is used to represent the attenuation degree of the contrast after the imaging of various sinusoidal intensity distribution functions with different frequencies through an optical system. In the transfer function curve, the vertical coordinate (Modulation of the OTF) is the modulation degree of the optical transfer function, which represents the attenuation degree of the contrast. The horizontal coordinate (Spaital Frequency in cycles per mm) is the spatial frequency, with the unit lp / mm. Here, T represents the meridional plane, and S represents the sagittal plane. The straight line (DIFF.LIMIT) at the top of the transfer function curve is the ideal MTF transfer function curve when the incident light only produces diffraction and no aberration, that is, under the diffraction limit. In the transfer function curve, the MTF transfer function curves at field angles of 0°, 25°, 35°, 50°, and 70° are also shown respectively. This transfer function curve represents the comprehensive resolution level of the optical system in this embodiment, reflecting the good resolution and image resolution ability of the lens.

[0063] Figures 5 to 7 The figure shows the field curvature and distortion curves of an ultra-wide-angle lens at working distances of 5mm, 10mm, and 40mm respectively. Here, the left curve is the field curvature curve (FIELD CURVATURE). In the field curvature curve, the vertical coordinate is the normalized field of view; the horizontal coordinate is the distance from the image plane to the paraxial image plane, with the unit mm. Here, T is the meridional plane; S is the sagittal plane. The right curve is the distortion curve (DISTORTION). In the distortion curve, the vertical coordinate is the normalized field of view; the horizontal coordinate is the distortion value, where the distortion value is expressed as a percentage. This field curvature and distortion curve represents the field curvature and distortion values of the optical system in this embodiment at different field angles, where the unit of field curvature is mm and the unit of distortion is %.

[0064] Figure 8 The figure shows the relative illumination curve of the ultra-wide-angle lens, which represents the ratio of the illumination at different field angles to the illumination at the field center of the optical system in this embodiment. Here, the vertical coordinate is the relative illumination, and the horizontal coordinate is the field angle.

[0065] From the above optical performance curves, it can be seen that the ultra-wide-angle lens proposed in this embodiment has good imaging quality, and at the same time, the field curvature and distortion are well corrected.

[0066] Example 2

[0067] The cross-sectional structural schematic diagram of the ultra-wide-angle lens provided in the second embodiment of the present invention is generally the same as that of the first embodiment. The difference lies in that the relevant parameters of each lens of the ultra-wide-angle lens in this embodiment are different from those of each lens in the first embodiment. Among them, in this embodiment, the focal length f of the ultra-wide-angle lens is 0.45 mm, F / NO = 3.5, and 2ω = 140°. The first lens 11 and the third lens 14 are made of F52R material with a relatively large Abbe number, and the second lens 12 is made of EP5000 material with a relatively small Abbe number. This embodiment satisfies the above conditional formula, where TL / 2Y = 2.65, f1 < 0, f1 / f = -1.35, f2 > 0, f2 / f = 2.73, f3 > 0, f3 / f = 2.1. The relevant parameters of each lens in the ultra-wide-angle lens in this embodiment are shown in Table 3:

[0068] Table 3

[0069]

[0070]

[0071] The aspheric coefficients of the first lens 11, the second lens 12, and the third lens 14 in this embodiment are shown in Table 4.

[0072] Table 4

[0073] Surface number S1 S2 S3 S4 S5 S6 A2 19.5417 -2.8988 -15.5775 -11.0708 88.5345 -5.1374 A4 -0.0036 0.0213 0.0015 -5.0633 -0.2329 -0.0018 A6 -0.018 0.0056 0.0256 5.2610 1.2056 -0.6324 A8 -0.0006 -0.0192 0.0741 -0.3403 180.8515 0.4863 A10 0.0001 -0.1045 0.0349 -1.5194 1812.12 6.8241 A12 0.0002 -0.1521 -0.2731 5.5243 -0.0008 -82.9705

[0074] Among them, referring to Figures 9 to 15 , which respectively show the optical characteristic curves of the ultra-wide-angle lens in this embodiment. Among them Figures 9 to 11 is the transfer function curve graph of the ultra-wide-angle lens at working distances of 5 mm, 10 mm, and 40 mm respectively, Figures 12 to 14 is the field curvature and distortion curve graph of the ultra-wide-angle lens at working distances of 5 mm, 10 mm, and 40 mm respectively, Figure 15 is the relative illumination curve graph of the ultra-wide-angle lens. It can be seen from the above-listed optical characteristic curves that the ultra-wide-angle lens provided in this embodiment has good imaging quality, and at the same time, the field curvature and distortion are well corrected.

[0075] Combining the above embodiments, the convex surface curvature radius of the second lens 12 close to the object side is smaller than the convex surface curvature radius of the imaging surface 17, and the concave surface curvature radius of the third lens 14 close to the object side is larger than the convex surface curvature radius close to the imaging surface 17. The smaller the data range of the field curvature curve and the distortion curve, the better the lens performance. It can be obtained from the drawings in each embodiment that the field curvature and distortion in each embodiment can be well corrected, and at the same time, it has good resolution ability.

[0076] In summary, the ultra-wide-angle lens of the present invention can reduce the number of lenses by adopting a design of three plastic aspherical lenses, effectively reducing the total length, weight and manufacturing cost of the lens, enabling miniaturization, and further making the ultra-wide-angle lens have a long service life and high stability; the ultra-wide-angle lens provided by the present invention can achieve a large field of view angle of 140°, well corrects field curvature and distortion while having good resolution ability; by setting the fixed diaphragm between the second lens and the third lens, off-axis aberration can be well corrected; the aspherical surfaces provided on each lens enable a powerful aberration correction function, improving imaging clarity and sharpness; enabling the ultra-wide-angle lens to be more miniaturized, lightweight, and have a large field of view, while obtaining good optical performance.

[0077] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An ultra-wide-angle lens, characterized in that, It sequentially includes a first lens, a second lens, a fixed diaphragm, and a third lens along the optical axis from the object side to the imaging surface, where the first lens has a negative optical power near the optical axis, the first lens is a lens with both concave surfaces, and at least one surface of the first lens is an aspherical surface; the second lens has a positive optical power near the optical axis, the second lens is a lens with both convex surfaces, and at least one surface of the second lens is an aspherical surface; the third lens has a positive optical power near the optical axis, the third lens is a meniscus lens with the concave surface facing the object side, and at least one surface of the third lens is an aspherical surface; the optical centers of the first lens, the second lens, and the third lens are located on the same straight line; the ultra-wide-angle lens satisfies the conditional formula: 2.5 < TL / 2Y < 3.0, where TL is the overall optical length of the ultra-wide-angle lens; 2Y is the imaging height of the maximum usable field of view of the entire ultra-wide-angle lens on the imaging surface; the number of lenses with optical power in the ultra-wide-angle lens is 3.

2. The ultra-wide-angle lens according to claim 1, wherein The ultra-wide-angle lens satisfies the conditional formula: f1 < 0, -1.5 < f1 / f < -1.2; f2 > 0, 2.7 < f2 / f < 3.0; f3 > 0, 1.8 < f3 / f < 2.2; where f is the focal length of the entire ultra-wide-angle lens; f1 is the focal length of the first lens; f2 is the focal length of the second lens; f3 is the focal length of the third lens.

3. The ultra-wide-angle lens according to claim 1, wherein, The first lens, the second lens, and the third lens are all made of plastic aspherical lenses, and the ultra-wide-angle lens satisfies the conditional formula: Vd1 > Vd2, Vd3 > Vd2, where Vd1, Vd2, and Vd3 respectively represent the Abbe numbers of the first lens, the second lens, and the third lens.

4. The ultra-wide-angle lens according to claim 2, wherein, The convex surface curvature radius of the second lens near the object side is smaller than the convex surface curvature radius near the imaging surface, and the concave surface curvature radius of the third lens near the object side is larger than the convex surface curvature radius near the imaging surface.

5. The ultra-wide-angle lens according to claim 3, characterized in that, The aspherical surface shapes of the first lens, the second lens, and the third lens satisfy the following formula: where Y is the height of the light ray, R is the radius of curvature of the aspherical surface near the optical axis, A2 is the conic coefficient, A4, A6, A8, A 10 , A 12 are higher-order aspherical coefficients, X is the length perpendicular from the point on the aspherical surface at a distance Y from the optical axis to the tangent plane of the aspherical surface vertex, and the tangent plane is a plane perpendicular to the optical axis.

6. The ultra-wide-angle lens according to claim 1, wherein, The ultra-wide-angle lens further includes a filter, and the filter is disposed behind the third lens.

7. The ultra-wide-angle lens according to claim 6, characterized in that, The filter is an infrared filter.

8. The ultra-wide-angle lens according to claim 1, wherein The fixed diaphragm is a central aperture.

Images