Wide-angle lens for motion camera

Abstract

The invention discloses a wide-angle lens for a motion camera, which sequentially comprises a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens and an eighth lens from an object side to an image side along an optical axis, and is characterized in that the first lens has negative focal power, the object side surface of the first lens is a convex surface, and the image side surface of the first lens is a concave surface; the second lens has negative focal power, the object side surface of the second lens is a convex surface, and the image side surface of the second lens is a concave surface; the third lens has positive focal power, the object side surface of the third lens is a convex surface, and the image side surface of the third lens is a concave surface; the fourth lens has positive focal power, the object side surface of the fourth lens is a convex surface, and the image side surface of the fourth lens is a convex surface; the fifth lens has positive focal power, the object side surface of the fifth lens is a convex surface, and the image side surface of the fifth lens is a convex surface; the sixth lens has negative focal power, the object side surface of the sixth lens is a concave surface, and the image side surface of the sixth lens is a concave surface; the seventh lens has positive focal power, the object side surface of the seventh lens is a convex surface, and the image side surface of the seventh lens is a convex surface; the eighth lens has negative focal power, the object side face of the eighth lens is a concave face, and the image side face of the eighth lens is a concave face. The wide-angle lens is used for solving at least one problem that a motion camera is too long in total length, too heavy in weight, high in cost, too small in aperture, too small in target surface, too small in field angle, large in field edge resolution, too fast in illumination reduction and the like.

Description

Technical Field

[0001] This invention relates to the field of optical lenses, and more particularly to a wide-angle lens for action cameras. Background Technology

[0002] With the development of outdoor sports, users' requirements for the overall performance of action cameras are constantly increasing. The optical lenses used in existing action cameras on the market still have many shortcomings, and always include one or more of the following defects: too long overall length, too heavy and too expensive (all-glass structure or including molded glass structure), too small aperture (FNO too large), too small target surface, too small field of view, resolution or illumination drop too quickly at the edge of a large field of view, etc., which are not conducive to panoramic stitching with a large field of view and a large target surface. Summary of the Invention

[0003] To address the shortcomings of at least one of the prior art, the present invention provides a wide-angle lens for action cameras.

[0004] The technical problem to be solved by the present invention is achieved through the following technical solution:

[0005] A wide-angle lens for an action camera, comprising, in sequence along the optical axis from the object side to the image side, a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, and an eighth lens.

[0006] The first lens has negative optical power, and its object side is convex and its image side is concave.

[0007] The second lens has negative optical power, and its object side is convex and its image side is concave.

[0008] The third lens has positive optical power, and its object side is convex and its image side is concave.

[0009] The fourth lens has positive optical power, and its object side and image side are both convex.

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

[0011] The sixth lens has negative optical power, and its object side and image side are both concave.

[0012] The seventh lens has positive optical power, and its object side and image side are both convex.

[0013] The eighth lens has negative optical power, and its object side and image side are both concave.

[0014] In the wide-angle lens of this invention, the object-side surface of the first lens is convex, which facilitates the collection of off-axis incident light rays with a large field of view, while simultaneously reducing the lens aperture, making the product more compact and lightweight. The image-side surface of the first lens is concave, ensuring that the first lens has negative optical power, reducing the tilt angle between the large field-of-view incident light rays and the optical axis, alleviating the pressure on subsequent off-axis light rays to continue propagating forward, and also increasing the beam aperture, preparing for subsequent light rays to enter the aperture stop with a larger aperture. The second lens also uses negative optical power, further bending off-axis light rays, especially those with a large field of view, towards the optical axis, which is more conducive to the correction and balance of advanced aberrations, and also further increases the beam aperture, ensuring that the subsequent beam, after propagation through the positive optical power lens, can still enter the aperture stop with a sufficiently large aperture, thereby facilitating... To ensure the large aperture requirement, the third lens has positive optical power and is located at a crucial position in the conversion between positive and negative optical power lenses. Its object side is designed as a convex surface, which plays a significant role in correcting and balancing astigmatism. The fifth lens has positive optical power, the sixth lens has negative optical power, the seventh lens has positive optical power, and the eighth lens has negative optical power. The fifth, sixth, seventh, and eighth lenses are arranged in pairs with alternating positive and negative optical powers. Since the focal shift directions of the positive and negative optical power lenses are opposite as they change with temperature, they can cancel each other out to reduce temperature sensitivity. This allows for a smoother transition of overall light while improving image height and adjusting CRA, which is more conducive to balancing and correcting aberrations caused by temperature changes, thus achieving a heat-free lens.

[0015] Furthermore, the third lens has the lowest optical power among all lenses with positive optical power.

[0016] In the wide-angle lens of this invention, the third lens has the smallest optical power among all the positive optical power lenses. Its thickness gradually decreases from the center to the periphery, and its cross-section is crescent-shaped. This ensures that after light passes through two negative optical power lenses, it can smoothly transition and enter the positive optical power lens to begin propagation, preventing excessive bending of the light. The fourth and fifth lenses behind it both have a large positive optical power. Their core function is to undertake the main task of light convergence and compress the total optical length. Together with the third lens, they form a "transition-main force" synergistic combination. First, the weak convergence effect of the third lens guides the light to deflect along the optical axis without excessively compressing the beam aperture. Then, the strong convergence effect of the fourth and fifth lenses achieves efficient focusing of the light, avoiding premature compression of the beam aperture and thus preventing the achievement of a large aperture.

[0017] Furthermore, the first and fourth lenses are glass spherical lenses, while the second, third, fifth, sixth, seventh, and eighth lenses are plastic aspherical lenses.

[0018] In the wide-angle lens of this invention, the lens adopts a glass-plastic hybrid structure of 2 glass elements and 6 plastic elements. Compared with an all-glass lens (or one containing more expensive molded glass), it is lower in cost, lighter in weight, and easier to carry; compared with an all-plastic lens, it has better reliability and more stable performance during operation. Considering the actual use of action cameras, the first lens uses a glass lens with high material hardness to ensure the safety of the product during outdoor work; while the fourth lens, which bears a large optical power, uses a glass lens with high heat resistance and a low coefficient of thermal expansion to increase the stability of the wide-angle lens at high and low temperatures. The second, third, fifth, sixth, seventh, and eighth lenses are plastic aspherical lenses, which have greater freedom in terms of radius, thickness, conic coefficient, and aspherical coefficient, which is more conducive to aberration correction and balance, improves lens resolution, and also better realizes the miniaturization design of the lens.

[0019] Furthermore, the image-side surface of the fifth lens extends into the object-side surface of the sixth lens, and the image-side surface of the seventh lens extends into the object-side surface of the eighth lens.

[0020] In the wide-angle lens of the present invention, the image-side surface of the fifth lens is convex, and the object-side surface of the sixth lens is concave, so that the image-side surface of the fifth lens can extend into the object-side surface of the sixth lens, thereby shortening the distance between the fifth and sixth lenses and reducing chromatic aberration and higher-order aberrations; similarly, the image-side surface of the seventh lens is convex, and the object-side surface of the eighth lens is concave, so that the image-side surface of the seventh lens can extend into the object-side surface of the eighth lens, thereby shortening the distance between the seventh and eighth lenses and reducing chromatic aberration and higher-order aberrations.

[0021] The smaller the distance between the fifth and sixth lenses, and between the seventh and eighth lenses, the better. Preferably, when the distance on the central optical axis approaches the assembly limit of 0.03 mm, the fifth and sixth lenses are equivalent to a set of cemented lenses, and the seventh and eighth lenses are equivalent to another set of cemented lenses. These two sets of cemented lenses play a significant role in correcting and balancing chromatic aberration during light propagation, similar to the effect of cemented doublet lenses.

[0022] Furthermore, the image-side surface of the eighth lens includes a central region and a peripheral region, wherein the central circular region is concave and the peripheral region is convex.

[0023] In the wide-angle lens of the present invention, the image-side cross-section of the eighth lens is generally M-shaped. Through the gradual change of curvature of the aspherical partition, it can effectively correct astigmatism, field curvature, coma, and chromatic aberration while adjusting CRA.

[0024] Furthermore, the focal lengths of each lens satisfy the following condition:

[0025] -1.22 < (f1 + f2) / f < -0.95;

[0026] 5.62 < (f3 / f) < 9.66;

[0027] 1.95 < (f4 / f) < 2.3;

[0028] 1.45 < (f5 + f6 + f7) / f < 1.8;

[0029] -2.7 < (f8 / f) < -1.42;

[0030] Wherein, the total focal length of the wide-angle lens is f, the focal length of the first lens is f1, the focal length of the second lens is f2, the focal length of the third lens is f3, the focal length of the fourth lens is f4, the focal length of the fifth lens is f5, the focal length of the sixth lens is f6, the focal length of the seventh lens is f7, and the focal length of the eighth lens is f8.

[0031] Furthermore, the refractive index and Abbe number of each lens satisfy the following conditions:

[0032] 1.72<Nd1<1.96, 32<Vd1<50;

[0033] 1.53<Nd2<1.57, 37<Vd2<56;

[0034] 1.53<Nd3<1.67, 20<Vd3<56;

[0035] 1.69<Nd4<1.82, 46<Vd4<56;

[0036] 1.53<Nd5<1.57, 37<Vd5<56;

[0037] 1.63<Nd6<1.67, 20<Vd6<24;

[0038] 1.53<Nd7<1.57, 37<Vd7<56;

[0039] 1.53<Nd8<1.67, 20<Vd8<56;

[0040] Wherein, Nd1, Nd2, Nd3, Nd4, Nd5, Nd6, Nd7, and Nd8 are the refractive indices of the first lens to the eighth lens in sequence, and Vd1, Vd2, Vd3, Vd4, Vd5, Vd6, Vd7, and Vd8 are the Abbe numbers of the first lens to the eighth lens in sequence.

[0041] Furthermore, the wide-angle lens and the first lens satisfy the following conditions:

[0042] 0.55 < EPD / f < 0.58.

[0043] 6.32 < TTL / f < 6.68;

[0044] 0.92 < LD / TTL < 0.99;

[0045] 0.4 < IC / TTL < 0.43;

[0046] The wide-angle lens has an entrance pupil diameter of EPD, an optical length of TTL, and a total focal length of f. The first lens has an object diameter of LD and an image diameter of IC.

[0047] In the wide-angle lens of the present invention, the large aperture (small FNO), short total length and small volume of the wide-angle lens can be achieved by coordinating the entrance pupil diameter, total optical length and total focal length f of the wide-angle lens; the large target area of ​​the wide-angle lens can be achieved by coordinating the total optical length of the wide-angle lens with the object plane diameter and image plane diameter of the first lens.

[0048] Furthermore, the aspherical surface profiles of each lens satisfy the following formula:

[0049]

[0050] Where Z is the axial sagitta in the direction of the optical axis of the aspherical surface; r is the distance from a point on the aspherical surface to the optical axis; c represents the reciprocal of the radius of curvature of the fitted sphere; k is the coefficient of the fitted cone; and A, B, C, D, E, F, and G are the coefficients of the 4th, 6th, 8th, 10th, 12th, 14th, and 16th order terms of the aspherical polynomial, respectively.

[0051] Furthermore, the wide-angle lens also includes an aperture stop and a filter, the aperture stop being disposed between the fourth lens and the fifth lens, and the filter being disposed between the eighth lens and the imaging plane.

[0052] In the wide-angle lens of the present invention, the aperture stop is positioned between the fourth lens and the fifth lens, which have positive optical power. At this time, the beam aperture is guaranteed, the light transition tends to be smooth, and the higher aberrations are effectively suppressed, ensuring the light flux and illuminance of the edge field of view. This provides a basis for further expanding the target surface and correcting CRA. Here, CRA refers to the angle between the principal rays of each field of view incident on the image plane. Adjusting CRA is to adapt to the imaging plane size used by the system and ensure imaging quality and illuminance.

[0053] The present invention has the following beneficial effects: the wide-angle lens of the present invention is designed for action cameras, which can simultaneously meet the optical and structural requirements of action cameras such as ultra-wide angle, large aperture, short overall length, large target area, high definition and uniform resolution, uniform illumination, low cost, and light weight. Attached Figure Description

[0054] Figure 1 This is a schematic diagram of the structure of the wide-angle lens described in Embodiment 1 of the present invention.

[0055] Figure 2 The optical fan diagram of the wide-angle lens described in Embodiment 1 of the present invention.

[0056] Figure 3 The polarization illuminance curve of the wide-angle lens described in Embodiment 1 of the present invention.

[0057] Figure 4 The spatial frequency-MTF curve of the wide-angle lens described in Embodiment 1 of the present invention.

[0058] Figure 5 The field of view-MTF curve of the wide-angle lens described in Embodiment 1 of the present invention.

[0059] Figure 6 This is a schematic diagram of the structure of the wide-angle lens described in Embodiment 2 of the present invention.

[0060] Figure 7 This is the optical fan diagram of the wide-angle lens described in Embodiment 2 of the present invention.

[0061] Figure 8 The polarization illuminance curve of the wide-angle lens described in Embodiment 2 of the present invention.

[0062] Figure 9 The spatial frequency-MTF curve of the wide-angle lens in Embodiment 2 of the present invention.

[0063] Figure 10 The field of view-MTF curve of the wide-angle lens described in Embodiment 2 of the present invention.

[0064] Figure 11 This is a schematic diagram of the structure of the wide-angle lens described in Embodiment 3 of the present invention.

[0065] Figure 12 The aperture fan diagram of the wide-angle lens described in Embodiment 3 of the present invention.

[0066] Figure 13 The polarization illuminance curve of the wide-angle lens described in Embodiment 3 of the present invention.

[0067] Figure 14The spatial frequency-MTF curve of the wide-angle lens described in Embodiment 3 of the present invention.

[0068] Figure 15 The field of view-MTF curve of the wide-angle lens described in Embodiment 3 of the present invention. Detailed Implementation

[0069] The present invention will now be described in detail with reference to the accompanying drawings and embodiments, examples of which are shown in the drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0070] In the description of this invention, it should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0071] Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first," "second," or "third" may explicitly or implicitly include one or more of that feature. In the description of this invention, "multiple" means two or more, unless otherwise explicitly specified.

[0072] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," "fixing," and "setting," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0073] Example 1

[0074] like Figure 1As shown, the wide-angle lens of this embodiment includes, in sequence along the optical axis from the object side to the image side, a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, an aperture ST, a fifth lens L5, a sixth lens L6, a seventh lens L7, an eighth lens L8, and a filter G.

[0075] The wide-angle lens in this embodiment satisfies the following parameters:

[0076] Total focal length f: 2.10mm, aperture value FNO: 1.7, field of view FOV: 205°, total optical length TTL: 13.9mm, image size: Φ5.9mm, EPD = 1.235.

[0077] The relevant parameters of each lens L1 to L8, the aperture ST, and the filter G of the wide-angle lens described in this embodiment are shown in Table 1-1:

[0078] Table 1-1 (Unit: mm, except for refractive index Nd and Abbe number Vd, K is the quadratic surface coefficient)

[0079]

[0080]

[0081] It should be noted that the thickness in Table 1-1 refers to the distance between the corresponding surface of each lens, aperture, or filter and the next surface along the light-gathering direction. Using thickness to refer to the distance between a certain surface and the next surface is a common practice in the art. The thickness between the image side of the fourth lens L4 and the aperture ST is a negative number, indicating that the image side of the fourth lens L4 passes through the light-passing hole inside the aperture ST.

[0082] The surface shape parameters of the aspherical surfaces of each lens in the wide-angle lens described in this embodiment are shown in Table 1-2:

[0083] Table 1-2 (A, B, C, D, E, F, and G represent the coefficients of the 4th, 6th, 8th, 10th, 12th, 14th, and 16th order terms of the aspheric polynomial, respectively)

[0084] Face number A B C D E F G S3 <![CDATA[ - 6.207956E-03]]> <![CDATA[ - 3.372141E-03]]> 3.435317E-04 <![CDATA[ - 3.234475E-05]]> 3.592472E-06 2.893731E-07 <![CDATA[ - 6.956976E-08]]> S4 <![CDATA[ - 1.045237E-02]]> <![CDATA[ - 9.473898E-03]]> 3.127755E-03 <![CDATA[ - 7.219408E-04]]> 5.286039E-05 3.208270E-05 <![CDATA[ - 5.709772E-06]]> S5 <![CDATA[ - 3.303122E-02]]> <![CDATA[ - 6.402289E-03]]> 3.933057E-03 <![CDATA[ - 4.215691E-04]]> 3.151893E-05 <![CDATA[ - 2.472068E-05]]> 4.404390E-06 S6 <![CDATA[ - 2.470333E-02]]> <![CDATA[ - 4.682481E-03]]> 7.025319E-03 <![CDATA[ - 1.032728E-03]]> <![CDATA[ - 4.296511E-04]]> 1.675483E-04 <![CDATA[ - 1.339045E-05]]> S9 <![CDATA[ - 3.407100E-03]]> 2.762131E-03 <![CDATA[ - 1.814186E-03]]> 6.155861E-04 <![CDATA[ - 5.839274E-05]]> 1.787315E-05 <![CDATA[ - 3.050696E-06]]> S10 <![CDATA[ - 2.829924E-02]]> 1.688897E-02 <![CDATA[ - 4.683644E-03]]> 3.555153E-04 5.622702E-04 <![CDATA[ - 4.255376E-05]]> <![CDATA[ - 1.603798E-05]]> S11 <![CDATA[ - 6.861208E-03]]> 3.313881E-03 <![CDATA[ - 3.422020E-03]]> 5.825515E-04 1.460550E-04 2.132558E-04 <![CDATA[ - 7.472878E-05]]> S12 <![CDATA[ 3 . 824377E-03]]> 4.089114E-03 <![CDATA[ - 2.313383E-03]]> 3.499985E-04 <![CDATA[ - 2.355170E-05]]> 5.613055E-05 <![CDATA[ - 1.542709E-05]]> S13 <![CDATA[ - 2.702346E-02]]> 8.931880E-03 <![CDATA[ - 2.546357E-03]]> 2.026398E-04 4.913557E-05 1.049691E-05 <![CDATA[ - 4.150555E-06]]> S14 <![CDATA[ - 4.050653E-03]]> <![CDATA[ - 1.949441E-03]]> <![CDATA[ - 2.260619E-04]]> 1.416797E-04 <![CDATA[ - 2.210487E-05]]> <![CDATA[ - 4.785030E-06]]> 1.298394E-06 S15 <![CDATA[ - 4.634350E-02]]> 1.141587E-02 <![CDATA[ - 1.560027E-03]]> 1.174845E-04 <![CDATA[ - 2.177635E-05]]> 2.537643E-06 <![CDATA[ - 1.886753E-07]]> S16 <![CDATA[ - 2.958380E-02]]> 7.030209E-03 <![CDATA[ - 1.033898E-03]]> 6.522160E-05 7.959833E-06 <![CDATA[ - 2.269679E-06]]> 1.366510E-07

[0085] The key optical characteristics of the wide-angle lens described in this embodiment are shown in Table 1-3:

[0086] Table 1-3

[0087] Basic parameters numerical values Basic parameters numerical values (f1+f2) / f -1.11 Vd1 49.6 f3 / f 7.99 Vd2 55.71 f4 / f 2.17 Vd3 20.38 (f5+f6+f7) / f 1.7 Vd4 52.32 f8 / f -2.14 Vd5 55.71 Nd1 1.773 Vd6 20.38 Nd2 1.535 Vd7 55.71 Nd3 1.66 Vd8 23.5 Nd4 1.755 TTL / f 6.64 Nd5 1.535 LD / TTL 0.95 Nd6 1.66 IC / TTL 0.42 Nd7 1.535 EPD / f 0.588 Nd8 1.64

[0088] Please see Figure 2-5 These are the light field diagram, polarization illuminance curve, and MTF curve of the wide-angle lens in this embodiment, respectively.

[0089] Fan diagram ( Figure 2 The wavelengths of this wide-angle lens can closely match the horizontal axis at various field of view angles, and the curves are smooth without the wave-like trend of a sine curve, indicating that the system aberrations, including higher aberrations, have been well corrected. At the same time, the wavelength curves are well-coordinated and do not have obvious dispersion, indicating that chromatic aberration has also been well corrected.

[0090] Polarized illuminance curve ( Figure 3 The polarization illuminance curve at the edge of the wide field of view of this wide-angle lens decreases relatively gently, and the attenuation is relatively uniform throughout the entire field of view and remains at a high level (above 40%), which is beneficial for panoramic stitching of large field of view and large target surface.

[0091] MTF curve ( Figure 4 and Figure 5 ): The MTF value of this wide-angle lens varies with spatial frequency ( Figure 4 ) and field of view ( Figure 5 The increase and decrease of MTF are relatively gradual; the MTF value of the full field of view is greater than 0.6 at 125 lp / mm, the curve is concentrated and close to the diffraction limit; the imaging quality is uniform and has high resolution; it is conducive to panoramic stitching of large field of view and large target surface.

[0092] Example 2

[0093] like Figure 6 As shown, the wide-angle lens of this embodiment includes, in sequence along the optical axis from the object side to the image side, a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, an aperture ST, a fifth lens L5, a sixth lens L6, a seventh lens L7, an eighth lens L8, and a filter G.

[0094] The wide-angle lens in this embodiment satisfies the following parameters:

[0095] Total focal length f: 2.16mm, aperture value FNO: 1.7, field of view FOV: 205°, total optical length TTL: 14.2mm, image size: Φ5.9mm, EPD = 1.271.

[0096] The relevant parameters of each lens L1-L8, aperture ST, and filter G of the wide-angle lens described in this embodiment are shown in Table 2-1:

[0097] Table 2-1 (Unit: mm, except for refractive index Nd and Abbe number Vd, K is the quadratic surface coefficient)

[0098]

[0099]

[0100] It should be noted that the thickness in Table 2-1 refers to the distance between the corresponding surface of each lens, aperture, or filter and the next surface along the light-gathering direction. Using thickness to refer to the distance between a certain surface and the next surface is a common practice in the art. The thickness between the image side of the fourth lens L4 and the aperture ST is a negative number, indicating that the image side of the fourth lens L4 passes through the light-passing hole inside the aperture ST.

[0101] The surface shape parameters of the aspherical surfaces of each lens in the wide-angle lens described in this embodiment are shown in Table 2-2:

[0102] Table 2-2 (A, B, C, D, E, F, and G represent the coefficients of the 4th, 6th, 8th, 10th, 12th, 14th, and 16th order terms of the aspheric polynomial, respectively)

[0103]

[0104]

[0105] The key optical characteristics of the wide-angle lens described in this embodiment are shown in Table 2-3:

[0106] Table 2-3

[0107]

[0108]

[0109] Please see Figure 7-10 These are the light field diagram, polarization illuminance curve, and MTF curve of the wide-angle lens in this embodiment, respectively.

[0110] Fan diagram ( Figure 7 The wavelengths of this wide-angle lens can closely match the horizontal axis at various field of view angles, and the curves are smooth without the wave-like trend of a sine curve, indicating that the system aberrations, including higher aberrations, have been well corrected. At the same time, the wavelength curves are well-coordinated and do not have obvious dispersion, indicating that chromatic aberration has also been well corrected.

[0111] Polarized illuminance curve ( Figure 8 The polarization illuminance curve at the edge of the wide field of view of this wide-angle lens decreases relatively gently, and the attenuation is relatively uniform throughout the entire field of view and remains at a high level (above 40%), which is beneficial for panoramic stitching of large field of view and large target surface.

[0112] MTF curve ( Figure 9 and 10 ): The MTF value of this wide-angle lens varies with spatial frequency ( Figure 9 ) and field of view ( Figure 10The increase and decrease of MTF are relatively gradual; the MTF value of the full field of view is greater than 0.6 at 125 lp / mm, the curve is concentrated and close to the diffraction limit; the imaging quality is uniform and has high resolution; it is conducive to panoramic stitching of large field of view and large target surface.

[0113] Example 3

[0114] like Figure 11 As shown, the wide-angle lens of this embodiment includes, in sequence along the optical axis from the object side to the image side, a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, an aperture ST, a fifth lens L5, a sixth lens L6, a seventh lens L7, an eighth lens L8, and a filter G.

[0115] The wide-angle lens in this embodiment satisfies the following parameters:

[0116] Total focal length f: 2.20mm, aperture value FNO: 1.7, field of view FOV: 205°, total optical length TTL: 14.2mm, image size: Φ5.9mm, EPD = 1.294.

[0117] The relevant parameters of each lens L1 to L8, the aperture ST, and the filter G of the wide-angle lens described in this embodiment are shown in Table 3-1:

[0118] Table 3-1 (Unit: mm, except for refractive index Nd and Abbe number Vd, K is the quadratic surface coefficient)

[0119] Face number Surface name Surface type radius of curvature thickness Nd / Vd K value S1 The object side of the first lens L1 Standard surface 18.041 2.130 1.773 / 49.6 / S2 Image side of the first lens L1 Standard surface 3.470 1.898 / / S3 The object side of the second lens L2 aspherical 4.998 0.749 1.535 / 55.71 2.191 S4 Image side of the second lens L2 aspherical 1.776 0.447 / -0.490 S5 The object side of the third lens L3 aspherical 2.532 0.889 1.66 / 20.38 0.036 S6 The image side of the third lens L3 aspherical 3.112 0.492 / -0.637 S7 The object side of the fourth lens L4 Standard surface 9.923 1.813 1.755 / 52.32 / S8 The image side of the fourth lens L4 Standard surface -4.904 -0.008 / / ST Aperture Standard surface Infinity 0.041 / / S9 Fifth lens L5 object side aspherical 2.899 1.507 1.535 / 55.71 -0.358 S10 The image side of the fifth lens L5 aspherical -4.658 0.049 / 5.110 S11 The object side of the sixth lens L6 aspherical -8.258 0.515 1.66 / 20.38 10.637 S12 The image side of the sixth lens L6 aspherical 4.309 0.206 / 1.990 S13 The object side of the seventh lens L7 aspherical 3.354 1.512 1.535 / 55.71 -1.604 S14 The image side of the seventh lens L7 aspherical -6.443 0.122 / -32.658 S15 The object side of the eighth lens L8 aspherical -61.565 0.619 1.535 / 55.71 / S16 The image side of the eighth lens L8 aspherical 3.316 0.824 / -8.287 G1 Filter G object side Standard surface Infinity 0.21 1.517 / 64.2 / G2 Filter G image side view Standard surface Infinity 0.2 / / IMA Imaging surface Standard surface Infinity / / /

[0120] It should be noted that the thickness in Table 3-1 refers to the distance between the corresponding surface of each lens, aperture, or filter and the next surface along the light-gathering direction. Using thickness to refer to the distance between a certain surface and the next surface is a common practice in the art. The thickness between the image side of the fourth lens L4 and the aperture ST is a negative number, indicating that the image side of the fourth lens L4 passes through the light-passing hole inside the aperture ST.

[0121] The surface shape parameters of the aspherical surfaces of each lens in the wide-angle lens described in this embodiment are shown in Table 3-2:

[0122] Table 3-2 (A, B, C, D, E, F, and G represent the coefficients of the 4th, 6th, 8th, 10th, 12th, 14th, and 16th order terms of the aspheric polynomial, respectively)

[0123] Face number A B C D E F G S3 <![CDATA[ - 7.036337E-03]]> -3.422940E-03 3.399716E-04 -3.161966E-05 3.765291E-06 2.995186E-07 -7.137322E-08 S4 <![CDATA[ - 1.134122E-02]]> -9.535567E-03 3.470231E-03 -6.616794E-04 4.901423E-05 2.829958E-05 -6.700055E-06 S5 <![CDATA[ - 2.928494E-02]]> -5.922587E-03 3.842444E-03 -4.465876E-04 3.550714E-05 -2.404376E-05 3.248205E-06 S6 <![CDATA[ - 2.203308E-02]]> -4.741599E-03 7.011043E-03 -1.060712E-03 -4.511449E-04 1.602328E-04 -1.055171E-05 S9 <![CDATA[ - 3.316469E-03]]> 2.782140E-03 -1.808612E-03 6.184398E-04 -5.901495E-05 1.799266E-05 -2.730184E-06 S10 <![CDATA[ - 2.803149E-02]]> 1.694037E-02 -4.685753E-03 3.550818E-04 5.628651E-04 -4.182341E-05 -1.549451E-05 S11 <![CDATA[ - 6.939468E-03]]> 3.512498E-03 -3.361863E-03 5.911362E-04 1.471949E-04 2.126782E-04 -7.535204E-05 S12 <![CDATA[ 2 . 670661E-03]]> 3.947338E-03 -2.306661E-03 3.598943E-04 -2.142264E-05 5.658961E-05 -1.545639E-05 S13 <![CDATA[ - 2.742909E-02]]> 9.097620E-03 -2.511884E-03 2.021754E-04 4.746506E-05 1.032619E-05 -3.865299E-06 S14 <![CDATA[ - 4.243085E-03]]> -1.514617E-03 -1.692713E-04 1.416459E-04 -2.198163E-05 -4.807773E-06 1.314562E-06 S15 <![CDATA[ - 4.047589E-02]]> 1.121458E-02 -1.578159E-03 1.202483E-04 -2.086026E-05 2.573402E-06 -2.291087E-07 S16 <![CDATA[ - 2.880329E-02]]> 7.163075E-03 -1.028709E-03 6.523477E-05 7.992291E-06 -2.287522E-06 1.335673E-07

[0124] The key optical characteristics of the wide-angle lens described in this embodiment are shown in Table 3-3:

[0125] Table 3-3

[0126]

[0127]

[0128] Please see Figure 12-15 These are the light field diagram, polarization illuminance curve, and MTF curve of the wide-angle lens in this embodiment, respectively.

[0129] Fan diagram ( Figure 12 The wavelengths of this wide-angle lens can closely match the horizontal axis at various field of view angles, and the curves are smooth without the wave-like trend of a sine curve, indicating that the system aberrations, including higher aberrations, have been well corrected. At the same time, the wavelength curves are well-coordinated and do not have obvious dispersion, indicating that chromatic aberration has also been well corrected.

[0130] Polarized illuminance curve ( Figure 13 The polarization illuminance curve at the edge of the wide field of view of this wide-angle lens decreases relatively gently, and the attenuation is relatively uniform throughout the entire field of view and remains at a high level (above 40%), which is beneficial for panoramic stitching of large field of view and large target surface.

[0131] MTF curve ( Figure 14 and 15 ): The MTF value of this wide-angle lens varies with spatial frequency ( Figure 14 ) and vertical field of view ( Figure 15 The increase and decrease of MTF are relatively gradual; the MTF value of the full field of view is greater than 0.6 at 125 lp / mm, the curve is concentrated and close to the diffraction limit; the imaging quality is uniform and has high resolution; it is conducive to panoramic stitching of large field of view and large target surface.

[0132] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the embodiments of the present invention and not to limit them. Although the embodiments of the present invention have been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the embodiments of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A wide-angle lens for an action camera, characterized in that, Along the optical axis from the object side to the image side, the lenses sequentially include a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, and an eighth lens. The first lens has negative optical power, and its object side is convex and its image side is concave. The second lens has negative optical power, and its object side is convex and its image side is concave. The third lens has positive optical power, and its object side is convex and its image side is concave. The fourth lens has positive optical power, and its object side and image side are both convex. The fifth lens has positive optical power, and its object side and image side are both convex. The sixth lens has negative optical power, and its object side and image side are both concave. The seventh lens has positive optical power, and its object side and image side are both convex. The eighth lens has negative optical power, and its object side and image side are both concave.

2. The wide-angle lens according to claim 1, characterized in that, The third lens has the lowest optical power among all lenses with positive optical power.

3. The wide-angle lens according to claim 1 or 2, characterized in that, The first and fourth lenses are glass spherical lenses, while the second, third, fifth, sixth, seventh, and eighth lenses are plastic aspherical lenses.

4. The wide-angle lens according to claim 1, characterized in that, The image-side surface of the fifth lens extends into the object-side surface of the sixth lens, and the image-side surface of the seventh lens extends into the object-side surface of the eighth lens.

5. The wide-angle lens according to claim 1, characterized in that, The image-side surface of the eighth lens includes a central region and a peripheral region, wherein the central circular region is concave and the peripheral region is convex.

6. The wide-angle lens according to claim 1, characterized in that, The focal lengths of each lens satisfy the following condition: -1.22 < (f1 + f2) / f < -0.95; 5.62 < (f3 / f) < 9.66; 1.95 < (f4 / f) < 2.3; 1.45 < (f5 + f6 + f7) / f < 1.8; -2.7 < (f8 / f) < -1.42; Wherein, the total focal length of the wide-angle lens is f, the focal length of the first lens is f1, the focal length of the second lens is f2, the focal length of the third lens is f3, the focal length of the fourth lens is f4, the focal length of the fifth lens is f5, the focal length of the sixth lens is f6, the focal length of the seventh lens is f7, and the focal length of the eighth lens is f8.

7. The wide-angle lens according to claim 1, characterized in that, The refractive index and Abbe number of each lens satisfy the following conditions: 1.72<Nd1<1.96, 32<Vd1<50; 1.53<Nd2<1.57, 37<Vd2<56; 1.53<Nd3<1.67, 20<Vd3<56; 1.69<Nd4<1.82, 46<Vd4<56; 1.53<Nd5<1.57, 37<Vd5<56; 1.63<Nd6<1.67, 20<Vd6<24; 1.53<Nd7<1.57, 37<Vd7<56; 1.53<Nd8<1.67, 20<Vd8<56; Wherein, Nd1, Nd2, Nd3, Nd4, Nd5, Nd6, Nd7, and Nd8 are the refractive indices of the first lens to the eighth lens in sequence, and Vd1, Vd2, Vd3, Vd4, Vd5, Vd6, Vd7, and Vd8 are the Abbe numbers of the first lens to the eighth lens in sequence.

8. The wide-angle lens according to claim 1, characterized in that, The wide-angle lens and the first lens satisfy the following conditions: 0.55 < EPD / f < 0.

58. 6.32 < TTL / f < 6.68; 0.92 < LD / TTL < 0.99; 0.4 < IC / TTL < 0.43; The wide-angle lens has an entrance pupil diameter of EPD, an optical length of TTL, and a total focal length of f. The first lens has an object diameter of LD and an image diameter of IC.

9. The wide-angle lens according to claim 1, characterized in that, The aspherical surface profiles of each lens satisfy the following formula: Where Z is the axial sagitta in the Z direction of the aspherical surface; r represents the distance from a point on the aspherical surface to the optical axis; c represents the curvature of the fitted sphere, which is numerically the reciprocal of the radius of curvature; k is the coefficient of the fitted cone; A, B, C, D, E, F, and G represent the coefficients of the 4th, 6th, 8th, 10th, 12th, 14th, and 16th order terms of the aspherical polynomial, respectively.

10. The wide-angle lens according to claim 1, characterized in that, The wide-angle lens also includes an aperture stop and a filter. The aperture stop is located between the fourth lens and the fifth lens, and the filter is located between the eighth lens and the imaging plane.

Images