A folded fisheye lens

Abstract

The present application relates to the field of fisheye lens, and more particularly to a fold-back fisheye lens, which comprises a first lens, a second lens, a third lens, a fourth lens, a diaphragm, a fifth lens, a sixth lens, a seventh lens, an eighth lens and a ninth lens in sequence along an optical axis from an object side to an image side; each of the first lens to the ninth lens comprises an object side surface facing the object side and allowing imaging light to pass through and an image side surface facing the image side and allowing imaging light to pass through; the first lens has positive focal power, the second lens has positive focal power, the third lens has negative focal power, the fourth lens and the fifth lens are isosceles right-angle reflecting prisms, and the reflecting surfaces of the fourth lens and the fifth lens are mutually bonded to form a prism group; the sixth lens has positive focal power, the seventh lens has positive focal power, the eighth lens has negative focal power, and the ninth lens has positive focal power; the fold-back fisheye lens has good imaging quality, a large field of view and uniform imaging.

Description

Technical Field

[0001] This patent relates to the field of fisheye lenses, and more specifically, to a reflex fisheye lens. Background Technology

[0002] A reflex lens, also known as a reflective lens or telephoto lens, is a special type of super telephoto lens. In a typical photographic lens, light enters through the first group of lens elements and reaches the film directly. Lenses with focal lengths of 300mm-500mm or even 1000mm become very large and heavy, making them extremely inconvenient to use. A reflex lens utilizes the principle of light reflection, so that light does not reach the film directly after passing through the first group of lens elements, but is reflected before reaching the film. This allows for effective control over the lens length. However, existing reflex lenses generally have poor image quality and a narrow field of view. Summary of the Invention

[0003] In order to overcome the shortcomings of the prior art, the present invention provides a reflex fisheye lens, which can solve the technical problems of poor imaging effect and small field of view of existing reflex lenses.

[0004] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0005] A reflex fisheye lens is characterized in that it comprises, from the object side to the image side, a first lens, a second lens, a third lens, a fourth lens, an aperture stop, a fifth lens, a sixth lens, a seventh lens, an eighth lens, and a ninth lens along an optical axis; each of the first to ninth lenses includes an object side facing the object side and allowing imaging light to pass through, and an image side facing the image side and allowing imaging light to pass through.

[0006] The first lens has positive optical power, with a convex object side and a concave image side;

[0007] The second lens has positive optical power, with a convex object side and a concave image side;

[0008] The third lens has negative optical power, and the object side and the image side are both concave.

[0009] The fourth and fifth lenses are isosceles right-angle reflecting prisms, and the reflecting surfaces of the fourth and fifth lenses are cemented together to form a prism group.

[0010] The sixth lens has positive optical power, and the object side and the image side are both convex.

[0011] The seventh lens has positive optical power, and the object side and the image side are both convex.

[0012] The eighth lens has a negative optical power, with the object side being concave and the image side being concave;

[0013] The ninth lens has a positive optical power, with the object side being convex and the image side being convex.

[0014] Furthermore, the third lens, the sixth lens, and the ninth lens are plastic aspherical lenses.

[0015] Furthermore, the following conditional expressions are satisfied: f1 < |30|, f2 < |20|, f3 < |60|, f4 > |0|, f5 > |0|, f6 < |20|, f7 < |80|, f8 < |20|, f9 < |30|, where f1 to f9 are the focal lengths of the first lens to the ninth lens respectively.

[0016] Furthermore, the following conditional expressions are satisfied: 3 < |f1 / f| < 8, 3 < |f2 / f| < 15, 5 < |f3 / f| < 25, 2 < |f6 / f| < 5, 7 < |f7 / f| < 35, 1.9 < |f8 / f| < 2.5, 4 < |f9 / f| < 8, where f1, f2, f3, f6, f7, f8, and f9 are the focal lengths of the first lens, the second lens, the third lens, the sixth lens, the seventh lens, the eighth lens, and the ninth lens respectively, and f is the focal length of the fisheye lens.

[0017] Furthermore, the following conditional expressions are satisfied: 1.80 < nd1 < 2.00, 1.7 < nd2 < 1.9, 1.5 < nd3 < 1.7, 1.55 < nd6 < 1.7, 1.5 < nd7 < 1.8, 1.7 < nd8 < 1.93, 1.5 < nd9 < 1.7, where nd1, nd2, nd3, nd6, nd7, nd8, and nd9 are the refractive indices of the first lens, the second lens, the third lens, the sixth lens, the seventh lens, the eighth lens, and the ninth lens respectively.

[0018] Furthermore, the following conditional expressions are satisfied: 20 < vd1 < 50, 45 < vd2 < 60, 19 < vd3 < 60, 50 < vd6 < 60, 55 < vd7 < 80, 20 < vd8 < 50, 50 < vd9 < 60, where vd1, vd2, vd3, vd6, vd7, vd8, and vd9 are the Abbe numbers of the first lens, the second lens, the third lens, the sixth lens, the seventh lens, the eighth lens, and the ninth lens respectively.

[0019] Furthermore, the following conditional expression is satisfied: vd1 + vd2 + vd3 < 135, where vd1, vd2, and vd3 are the Abbe numbers of the first lens, the second lens, and the third lens respectively.

[0020] Furthermore, the following condition must be met: 5.0 ≤ TTL / AAG, where TTL is the total length of the fisheye lens and AAG is the sum of the three air gaps on the optical axis between the first and fourth lenses.

[0021] Furthermore, the following condition is met: ALT < 14.55, ALT = CT1 + CT2 + CT3 + CT4, where CT1, CT2, CT3, and CT4 are the center thicknesses of the first lens, the second lens, the third lens, and the fourth lens, respectively.

[0022] Furthermore, the following condition must be met: TTL / F < 18.5, where TTL is the total length of the fisheye lens and F is the aperture size of the fisheye lens.

[0023] The beneficial effects of this invention are:

[0024] This design combines four glass spherical lenses and three plastic aspherical lenses, which can effectively improve image quality. When the spatial frequency reaches 112 lp / mm, the MTF of the reflex fisheye lens is greater than 0.30 across the entire field of view, resulting in good image quality. The HFOV of the reflex fisheye lens reaches 178°, providing a large field of view. At the same time, the RI is greater than 45%, resulting in uniform imaging and no vignetting at the edges. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0026] Figure 1 Optical path diagram of the folding fisheye lens described in Embodiment 1 of the present invention;

[0027] Figure 2 MTF curve of the reflex fisheye lens described in Embodiment 1 of the present invention;

[0028] Figure 3 The defocus curve of the reflex fisheye lens described in Embodiment 1 of the present invention;

[0029] Figure 4 The relative illumination diagram of the folding fisheye lens described in Embodiment 1 of the present invention;

[0030] Figure 5 Longitudinal chromatic aberration diagram of the folding fisheye lens described in Embodiment 1 of the present invention;

[0031] Figure 6Field curvature and distortion curves of the reflex fisheye lens described in Embodiment 1 of the present invention;

[0032] Figure 7 Optical path diagram of the folding fisheye lens described in Embodiment 2 of the present invention;

[0033] Figure 8 MTF curve of the reflex fisheye lens described in Embodiment 2 of the present invention;

[0034] Figure 9 The defocus curve of the reflex fisheye lens described in Embodiment 2 of the present invention;

[0035] Figure 10 Relative illumination diagram of the folding fisheye lens described in Embodiment 2 of the present invention;

[0036] Figure 11 Longitudinal chromatic aberration diagram of the folding fisheye lens described in Embodiment 2 of the present invention;

[0037] Figure 12 Field curvature and distortion curves of the reflex fisheye lens described in Embodiment 2 of the present invention;

[0038] Figure 13 Optical path diagram of the folding fisheye lens described in Embodiment 3 of the present invention;

[0039] Figure 14 MTF curve of the reflex fisheye lens described in Embodiment 3 of the present invention;

[0040] Figure 15 The defocus curve of the reflex fisheye lens described in Embodiment 3 of the present invention;

[0041] Figure 16 The relative illumination diagram of the folding fisheye lens described in Embodiment 3 of the present invention;

[0042] Figure 17 Longitudinal chromatic aberration diagram of the folding fisheye lens described in Embodiment 3 of the present invention;

[0043] Figure 18 Field curvature and distortion curves of the reflex fisheye lens described in Embodiment 3 of the present invention.

[0044] Explanation of main component symbols

[0045] 1. First lens; 2. Second lens; 3. Third lens; 4. Fourth lens; 5. Fifth lens; 6. Sixth lens; 7. Seventh lens; 8. Eighth lens; 9. Ninth lens; 10. Aperture stop; 11. Protective plate; 12. Imaging plane. Detailed Implementation

[0046] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to represent selected embodiments of the invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0047] Please refer to Figure 1-18 The present invention provides a reflex fisheye lens, which includes, in sequence along an optical axis from the object side to the image side, a first lens, a second lens, a third lens, a fourth lens, an aperture stop, a fifth lens, a sixth lens, a seventh lens, an eighth lens, and a ninth lens; each of the first to ninth lenses includes an object side facing the object side and allowing imaging light to pass through, and an image side facing the image side and allowing imaging light to pass through.

[0048] The first lens has positive optical power, with a convex object side and a concave image side;

[0049] The second lens has positive optical power, with a convex object side and a concave image side.

[0050] The third lens has negative optical power, and both the object side and the image side are concave.

[0051] The fourth and fifth lenses are isosceles right-angle reflecting prisms, and the reflecting surfaces of the fourth and fifth lenses are cemented together to form a prism group.

[0052] The sixth lens has positive optical power, and both the object-side and image-side surfaces are convex.

[0053] The seventh lens has positive optical power, and both the object-side and image-side surfaces are convex.

[0054] The eighth lens has negative optical power, and both the object-side and image-side surfaces are concave.

[0055] The ninth lens has positive optical power, and both the object-side and image-side surfaces are convex.

[0056] The first lens, the second lens, and the third lens are the front group lenses, and the sixth lens, the seventh lens, the eighth lens, and the ninth lens are the rear group lenses. The third lens, the sixth lens, and the ninth lens are plastic aspherical lenses, and the first lens, the second lens, the seventh lens, and the eighth lens are glass spherical lenses. The design that combines four glass spherical lenses and three plastic aspherical lenses can better improve the imaging quality and also enhance the relative illumination well. At the same time, the first lens uses a glass material with high hardness and wear resistance, which can well meet the use in outdoor environments with high temperature, high humidity, friction, etc., and has good imaging quality under the conditions of -40°C to 105°C.

[0057] Preferably, the following conditional expressions are satisfied: f1 < |30|, f2 < |20|, f3 < |60|, f4 > |0|, f5 > |0|, f6 < |20|, f7 < |80|, f8 < |20|, f9 < |30|, where f1, f2, f3, f, f5, f6, f7, f8, and f9 are the focal lengths of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the seventh lens, the eighth lens, and the ninth lens, respectively.

[0058] Preferably, the following conditional expressions are satisfied: 3 < |f1 / f| < 8, 3 < |f2 / f| < 15, 5 < |f3 / f| < 25, 2 < |f6 / f| < 5, 7 < |f7 / f| < 35, 1.9 < |f8 / f| < 2.5, 4 < |f9 / f| < 8, where f1, f2, f3, f6, f7, f8, and f9 are the focal lengths of the first lens, the second lens, the third lens, the sixth lens, the seventh lens, the eighth lens, and the ninth lens, respectively, and f is the focal length of the fisheye lens. Controlling the ratio between the focal length of the lens and the focal length of the lens helps to correct aberrations and improve the imaging quality.

[0059] Preferably, the following conditional expressions are satisfied: 1.80 < nd1 < 2.00, 1.7 < nd2 < 1.9, 1.5 < nd3 < 1.7, 1.55 < nd6 < 1.7, 1.5 < nd7 < 1.8, 1.7 < nd8 < 1.93, 1.5 < nd9 < 1.7, where nd1, nd2, nd3, nd6, nd7, nd8, and nd9 are the refractive indices of the first lens, the second lens, the third lens, the sixth lens, the seventh lens, the eighth lens, and the ninth lens, respectively. Among them, the first lens and the second lens use high-refractive-index glass, which can make the light of the large wide angle deflect gently through the system, the lens bending will not be剧烈, and it can also correct the large wide angle aberrations such as coma and astigmatism.

[0060] Preferably, the following conditional expressions are satisfied: 20 < vd1 < 50, 45 < vd2 < 60, 19 < vd3 < 60, 50 < vd6 < 60, 55 < vd7 < 80, 20 < vd8 < 50, 50 < vd9 < 60, and vd1 + vd2 + vd3 < 135; where vd1, vd2, vd3, vd6, vd7, vd8, and vd9 are the Abbe numbers of the first lens, the second lens, the third lens, the sixth lens, the seventh lens, the eighth lens, and the ninth lens, respectively. Among them, the fourth lens and the sixth lens use high Abbe number materials to correct longitudinal chromatic aberration.

[0061] Preferably, the following conditional expression is satisfied: 5.0 ≤ TTL / AAG, where TTL is the overall length of the fisheye lens, and AAG is the sum of three air gaps on the optical axis between the first lens and the fourth lens. Controlling the air gaps between the front group of lenses and the air gap between the front group of lenses and the fourth lens can effectively shorten the volume of the lens, making its installation and use more convenient.

[0062] Preferably, the following conditional expression is satisfied: ALT < 14.55, ALT = CT1 + CT2 + CT3 + CT4, where CT1, CT2, CT3, and CT4 are the central thicknesses of the first lens, the second lens, the third lens, and the fourth lens, respectively.

[0063] Preferably, the following conditional expression is satisfied: TTL / F < 18.5, where TTL is the overall length of the fisheye lens, and F is the size of the clear aperture of the fisheye lens.

[0064] Hereinafter, the folding fisheye lens according to the present invention will be described in detail with specific embodiments.

[0065] Embodiment 1

[0066] Please refer to the attached Figure 1-6 , the present invention provides a folding fisheye lens, which sequentially includes a first lens, a second lens, a third lens, a fourth lens, an aperture stop, a fifth lens, a sixth lens, a seventh lens, an eighth lens, and a ninth lens along an optical axis from the object side to the image side; each of the first lens to the ninth lens includes an object side surface facing the object side and allowing imaging light to pass through, and an image side surface facing the image side and allowing imaging light to pass through;

[0067] The first lens has a positive optical power, the object side surface is convex, and the image side surface is concave;

[0068] The second lens has a positive optical power, the object side surface is convex, and the image side surface is concave;

[0069] The third lens has a negative optical power, the object side surface is concave, and the image side surface is concave;

[0070] The fourth and fifth lenses are isosceles right-angle reflecting prisms, and the reflecting surfaces of the fourth and fifth lenses are cemented together to form a prism group.

[0071] The sixth lens has positive optical power, and both the object-side and image-side surfaces are convex.

[0072] The seventh lens has positive optical power, and both the object-side and image-side surfaces are convex.

[0073] The eighth lens has negative optical power, and both the object-side and image-side surfaces are concave.

[0074] The ninth lens has positive optical power, and both the object-side and image-side surfaces are convex.

[0075] Detailed optical data for this specific embodiment are shown in Table 1.

[0076] Table 1 Detailed optical data for Example 1

[0077]

[0078]

[0079] In this embodiment, the third lens 3, the sixth lens 6, and the ninth lens 9 are all plastic aspherical lenses. For detailed parameters of the aspherical surfaces of the third lens 3, the sixth lens 6, and the ninth lens 9, please refer to Table 2 below.

[0080] Table 2: Aspheric Coefficients

[0081]

[0082] The reflex fisheye lens described in this embodiment has a TTL of 27.74mm, an F-number of 1.9, and an HFOV of 178°.

[0083] In this specific embodiment, please refer to the attached diagram for the optical path diagram of the folding fisheye lens. Figure 1 Please refer to the attached diagram for the MTF curves of the reflex fisheye lens disclosed in this embodiment at different focal lengths in the visible light band of 435nm-660nm. Figure 2 As can be seen from the figure, the reflex fisheye lens described in this embodiment has an MTF greater than 0.48 across the entire field of view when the spatial frequency reaches 112 lp / mm, indicating good image quality. Please refer to the attached figure for the defocus curve of the reflex fisheye lens in the visible light 435nm-660nm band. Figure 3 Different curves represent defocus curves in the meridional and sagittal directions under different fields of view, as indicated by the attached curves. Figure 3 As can be seen, the peaks of almost all the curves are near the zero-offset vertical axis. At this point, the defocusing characteristics of the reflex fisheye lens are excellent, allowing for a wider effective depth of focus range. Please refer to [link / reference]. Figure 4 As can be seen, the reflex fisheye lens disclosed in this embodiment exhibits an RI > 58% at maximum field of view, indicating high relative illumination, high image uniformity, and excellent imaging performance. The longitudinal chromatic aberration curve of the reflex fisheye lens disclosed in this embodiment in the visible light 435nm-660nm band is shown in the attached figure. Figure 5 , by appendix Figure 5 It can be seen that the maximum longitudinal chromatic aberration of the reflex fisheye lens operating in the visible light band is 0.02mm, indicating that the longitudinal chromatic aberration of this optical lens is well corrected. Please refer to the appendix for the field curvature distortion curves of the reflex fisheye lens disclosed in this embodiment in the visible light 435nm-660nm band. Figure 6 , by appendix Figure 6 It can be seen that the optical distortion of the reflex fisheye lens is less than 6%, resulting in good image quality and reducing the difficulty of post-correction.

[0084] Example 2

[0085] Please refer to the appendix. Figure 7-12 The present invention provides a reflex fisheye lens, which includes, in sequence along an optical axis from the object side to the image side, a first lens, a second lens, a third lens, a fourth lens, an aperture stop, a fifth lens, a sixth lens, a seventh lens, an eighth lens, and a ninth lens; each of the first to ninth lenses includes an object side facing the object side and allowing imaging light to pass through, and an image side facing the image side and allowing imaging light to pass through.

[0086] The first lens has positive optical power, with a convex object side and a concave image side;

[0087] The second lens has positive optical power, with a convex object side and a concave image side.

[0088] The third lens has negative optical power, and both the object side and the image side are concave.

[0089] The fourth and fifth lenses are isosceles right-angle reflecting prisms, and the reflecting surfaces of the fourth and fifth lenses are cemented together to form a prism group.

[0090] The sixth lens has positive optical power, and both the object-side and image-side surfaces are convex.

[0091] The seventh lens has positive optical power, and both the object-side and image-side surfaces are convex.

[0092] The eighth lens has negative optical power, and both the object-side and image-side surfaces are concave.

[0093] The ninth lens has positive optical power, and both the object-side and image-side surfaces are convex.

[0094] Detailed optical data for this specific embodiment are shown in Table 3.

[0095] Table 3 Detailed optical data for Example 2

[0096]

[0097] In this embodiment, the third lens 3, the sixth lens 6, and the ninth lens 9 are all plastic aspherical lenses. For detailed parameters of the aspherical surfaces of the third lens 3, the sixth lens 6, and the ninth lens 9, please refer to Table 4 below.

[0098] Table 4: Aspheric Coefficients

[0099]

[0100] The reflex fisheye lens described in this embodiment has a TTL of 32.22mm, an F-number of 1.9, and an HFOV of 178°.

[0101] In this specific embodiment, please refer to the attached diagram for the optical path diagram of the folding fisheye lens. Figure 7 Please refer to the attached diagram for the MTF curves of the reflex fisheye lens disclosed in this embodiment at different focal lengths in the visible light band of 435nm-660nm. Figure 8 As can be seen from the figure, the reflex fisheye lens described in this embodiment has an MTF greater than 0.46 across the entire field of view when the spatial frequency reaches 112 lp / mm, exhibiting good image quality. Please refer to the attached figure for the defocus curve of the reflex fisheye lens in the visible light 435nm-660nm band. Figure 9 Different curves represent defocus curves in the meridional and sagittal directions under different fields of view, as indicated by the attached curves. Figure 9 As can be seen, the peaks of almost all the curves are near the zero-offset vertical axis. At this point, the defocusing characteristics of the reflex fisheye lens are excellent, allowing for a wider effective depth of focus range. Please refer to [link / reference]. Figure 10 As can be seen, the reflex fisheye lens disclosed in this embodiment exhibits an RI > 46% at maximum field of view, indicating high relative illumination, high image uniformity, and excellent imaging performance. The longitudinal chromatic aberration curve of the reflex fisheye lens disclosed in this embodiment in the visible light 435nm-660nm band is shown in the attached figure. Figure 11 , by appendix Figure 11 It can be seen that the maximum longitudinal chromatic aberration of the reflex fisheye lens operating in the visible light band is 0.02mm, indicating that the longitudinal chromatic aberration of this optical lens is well corrected. Please refer to the appendix for the field curvature distortion curves of the reflex fisheye lens disclosed in this embodiment in the visible light 435nm-660nm band. Figure 12 , by appendix Figure 12 It can be seen that the optical distortion of the reflex fisheye lens is less than 5%, resulting in good image quality and reducing the difficulty of post-correction.

[0102] Example 3

[0103] Please refer to the appendix. Figure 13-18 The present invention provides a reflex fisheye lens, which includes, in sequence along an optical axis from the object side to the image side, a first lens, a second lens, a third lens, a fourth lens, an aperture stop, a fifth lens, a sixth lens, a seventh lens, an eighth lens, and a ninth lens; each of the first to ninth lenses includes an object side facing the object side and allowing imaging light to pass through, and an image side facing the image side and allowing imaging light to pass through.

[0104] The first lens has positive optical power, with a convex object side and a concave image side;

[0105] The second lens has positive optical power, with a convex object side and a concave image side.

[0106] The third lens has negative optical power, and both the object side and the image side are concave.

[0107] The fourth and fifth lenses are isosceles right-angle reflecting prisms, and the reflecting surfaces of the fourth and fifth lenses are cemented together to form a prism group.

[0108] The sixth lens has positive optical power, and both the object-side and image-side surfaces are convex.

[0109] The seventh lens has positive optical power, and both the object-side and image-side surfaces are convex.

[0110] The eighth lens has negative optical power, and both the object-side and image-side surfaces are concave.

[0111] The ninth lens has positive optical power, and both the object-side and image-side surfaces are convex.

[0112] Detailed optical data for this specific embodiment are shown in Table 5.

[0113] Table 5 Detailed optical data for Example 3

[0114]

[0115] In this embodiment, the third lens 3, the sixth lens 6, and the ninth lens 9 are all plastic aspherical lenses. For detailed parameters of the aspherical surfaces of the third lens 3, the sixth lens 6, and the ninth lens 9, please refer to Table 6 below.

[0116] Table 6: Aspheric Coefficients

[0117]

[0118]

[0119] The reflex fisheye lens described in this embodiment has a TTL of 35.11mm, an F-number of 1.9, and an HFOV of 178°.

[0120] In this specific embodiment, please refer to the attached diagram for the optical path diagram of the folding fisheye lens. Figure 13 Please refer to the attached diagram for the MTF curves of the reflex fisheye lens disclosed in this embodiment at different focal lengths in the visible light band of 435nm-660nm. Figure 14 As can be seen from the figure, the reflex fisheye lens described in this embodiment has an MTF greater than 0.30 across the entire field of view when the spatial frequency reaches 112 lp / mm, exhibiting good image quality. Please refer to the attached figure for the defocus curve of the reflex fisheye lens in the visible light 435nm-660nm band. Figure 15 Different curves represent defocus curves in the meridional and sagittal directions under different fields of view, as indicated by the attached curves. Figure 15 As can be seen, the peaks of almost all the curves are near the zero-offset vertical axis. At this point, the defocusing characteristics of the reflex fisheye lens are excellent, allowing for a wider effective depth of focus range. Please refer to [link / reference]. Figure 16 As can be seen, the reflex fisheye lens disclosed in this embodiment exhibits an RI > 45% at maximum field of view, indicating high relative illumination, high image uniformity, and excellent imaging performance. The longitudinal chromatic aberration curve of the reflex fisheye lens disclosed in this embodiment in the visible light 435nm-660nm band is shown in the attached figure. Figure 17 , by appendix Figure 17 It can be seen that the maximum longitudinal chromatic aberration of the reflex fisheye lens operating in the visible light band is 0.04mm, indicating that the longitudinal chromatic aberration of this optical lens is well corrected. Please refer to the appendix for the field curvature distortion curves of the reflex fisheye lens disclosed in this embodiment in the visible light 435nm-660nm band. Figure 18 , by appendix Figure 18 It can be seen that the optical distortion of the reflex fisheye lens is less than 6%, resulting in good image quality and reducing the difficulty of post-correction.

[0121] Table 7 shows the values ​​of relevant important parameters in three embodiments of the present invention:

[0122] Table 7: Key parameters for each embodiment

[0123]

[0124]

[0125] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0126] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A reflex fisheye lens, characterized in that, From the object side to the image side along an optical axis, it sequentially includes a first lens, a second lens, a third lens, a fourth lens, an aperture stop, a fifth lens, a sixth lens, a seventh lens, an eighth lens, and a ninth lens; each of the first lens to the ninth lens includes an object side facing the object side and allowing imaging light to pass through and an image side facing the image side and allowing imaging light to pass through; The first lens has a negative focal power, the object side is convex, and the image side is concave; The second lens has a negative focal power, the object side is convex, and the image side is concave; The third lens has a positive focal power, the object side is concave, and the image side is convex; The fourth lens and the fifth lens are isosceles right-angle reflecting prisms, and the reflecting surfaces of the fourth lens and the fifth lens are mutually cemented to form a prism group; The sixth lens has a positive focal power, the object side is convex, and the image side is convex; The seventh lens has a positive focal power, the object side is convex, and the image side is convex; The eighth lens has a negative focal power, the object side is concave, and the image side is concave; The ninth lens has a positive focal power, the object side is convex, and the image side is convex; 1.80 < nd1 < 2.00, 1.7 < nd2 < 1.9, 1.5 < nd3 < 1.7, 1.55 < nd6 < 1.7, 1.5 < nd7 < 1.8, 1.7 < nd8 < 1.93, 1.5 < nd9 < 1.7, where nd1, nd2, nd3, nd6, nd7, nd8, and nd9 are the refractive indices of the first lens, the second lens, the third lens, the sixth lens, the seventh lens, the eighth lens, and the ninth lens, respectively.

2. The reflex fisheye lens according to claim 1, characterized in that: The third lens, the sixth lens, and the ninth lens are plastic aspherical lenses.

3. The reflex fisheye lens according to claim 1, characterized in that: Meet the following conditional expressions: |f1| < 30mm, |f2| < 20mm, |f3| < 60mm, |f4| > 0mm, |f5| > 0mm, |f6| < 20mm, |f7| < 80mm, |f8| < 20mm, |f9| < 30mm, where f1 to f9 are the focal lengths of the first lens to the ninth lens, respectively.

4. The reflex fisheye lens according to claim 1, characterized in that: Meet the following conditional expressions: 3 < |f1 / f| < 8, 3 < |f2 / f| < 15, 5 < |f3 / f| < 25, 2 < |f6 / f| < 5, 7 < |f7 / f| < 35, 1.9 < |f8 / f| < 2.5, 4 < |f9 / f| < 8, where f1, f2, f3, f6, f7, f8, and f9 are the focal lengths of the first lens, the second lens, the third lens, the sixth lens, the seventh lens, the eighth lens, and the ninth lens, respectively, and f is the focal length of the fish-eye lens.

5. The reflex fisheye lens according to claim 1, characterized in that: Meet the following conditional expressions: 20 < vd1 < 50, 45 < vd2 < 60, 19 < vd3 < 60, 50 < vd6 < 60, 55 < vd7 < 80, 20 < vd8 < 50, 50 < vd9 < 60, where vd1, vd2, vd3, vd6, vd7, vd8, and vd9 are the Abbe numbers of the first lens, the second lens, the third lens, the sixth lens, the seventh lens, the eighth lens, and the ninth lens, respectively.

6. The reflex fisheye lens according to claim 1, characterized in that: The following condition is met: vd1 + vd2 + vd3 < 135, where vd1, vd2, and vd3 are the Abbe numbers of the first lens, the second lens, and the third lens, respectively.

7. The reflex fisheye lens according to claim 1, characterized in that: The following condition must be met: 5.0 ≤ TTL / AAG, where TTL is the total length of the fisheye lens and AAG is the sum of the three air gaps on the optical axis between the first and fourth lenses.

8. The reflex fisheye lens according to claim 1, characterized in that: The following condition is met: ALT < 14.55 mm, ALT = CT1 + CT2 + CT3 + CT4, where CT1, CT2, CT3, and CT4 are the center thicknesses of the first lens, the second lens, the third lens, and the fourth lens, respectively.

9. The reflex fisheye lens according to claim 1, characterized in that: The following condition must be met: TTL / F < 18.5, where TTL is the total length of the fisheye lens and F is the aperture size of the fisheye lens.

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