A wide-angle fixed-focus lens

Abstract

An embodiment of the present invention discloses a wide-angle fixed-focus lens. The lens includes a first lens with a negative optical power, a second lens with a negative optical power, a third lens with a positive optical power, a diaphragm, a fourth lens with a negative optical power, a fifth lens with a positive optical power, a sixth lens with a negative optical power, and a seventh lens with a positive optical power, which are arranged in sequence from the object side to the image side along the optical axis; the surface of the first lens close to the image side is concave; the surface of the second lens close to the object side is convex, and the surface close to the image side is concave; the surface of the third lens close to the image side is convex; the surface of the fifth lens close to the image side is convex; the surface of the sixth lens close to the object side is concave; the surface of the seventh lens close to the image side is convex. The wide-angle fixed-focus lens provided by the present invention has the characteristics of low cost, high performance, small distortion, and wide angle, can be matched with a 1 / 2.8-inch photosensitive chip, its distortion is less than 5%, and it meets the use conditions of -40°C to 80°C.

Description

Technical Field

[0001] The embodiments of the present invention relate to lens technology, and in particular, to a wide-angle fixed-focus lens. Background Art

[0002] With the development of technology, the application scope of lenses is becoming more and more extensive. Accordingly, people's requirements for lens performance are also becoming more diverse.

[0003] Existing lenses generally have the following disadvantages: the field of view angle is not large enough, and multiple lenses are often required to capture the required range, which greatly increases the production cost; at the same time, the distortion of existing security lenses is too large, which increases the difficulty of the next image processing. Therefore, it is very necessary to develop a small-sized low-distortion wide-angle lens. Summary of the Invention

[0004] The embodiments of the present invention provide a wide-angle fixed-focus lens, which has the characteristics of low cost, high performance, small distortion, and wide angle. It can be maximally matched with a 1 / 2.8-inch photosensitive chip, and its distortion is less than 5%, and it can meet the use conditions of -40°C to 80°C.

[0005] The embodiments of the present invention provide a wide-angle fixed-focus lens, including a first lens with negative optical power, a second lens with negative optical power, a third lens with positive optical power, a diaphragm, a fourth lens with negative optical power, a fifth lens with positive optical power, a sixth lens with negative optical power, and a seventh lens with positive optical power, which are arranged in sequence from the object side to the image side along the optical axis;

[0006] Wherein, the surface of the first lens close to the image side is concave; the surface of the second lens close to the object side is convex, and the surface close to the image side is concave; the surface of the third lens close to the image side is convex; the surface of the fifth lens close to the image side is convex; the surface of the sixth lens close to the object side is concave; the surface of the seventh lens close to the image side is convex.

[0007] Optionally, the third lens is a glass spherical lens, and the first lens, the second lens, the fourth lens, the fifth lens, the sixth lens, and the seventh lens are all plastic aspherical lenses.

[0008] Optionally, the first lens and the second lens satisfy:

[0009] 1.2 < f1 / f12 < 2.0;

[0010] 3.5 < f2 / f12 < 5.0;

[0011] Where f1 represents the focal length of the first lens, f2 represents the focal length of the second lens, and f12 represents the combined focal length of the first lens and the second lens.

[0012] Optionally, the first lens to the third lens satisfy:

[0013] 0.3 < f3 / f13 < 0.75;

[0014] -0.65 < f12 / f13 < -0.1;

[0015] wherein, f3 represents the focal length of the third lens, f12 represents the combined focal length of the first lens and the second lens, and f13 represents the combined focal length of the first lens, the second lens and the third lens.

[0016] Optionally, the fifth lens to the seventh lens satisfy:

[0017] 0.7 < f5 / f57 < 1.3;

[0018] -1.8 < f6 / f57 < -0.9;

[0019] 0.8 < f7 / f57 < 1.4;

[0020] wherein, f5 represents the focal length of the fifth lens, f6 represents the focal length of the sixth lens, f7 represents the focal length of the seventh lens, and f57 represents the combined focal length of the fifth lens, the sixth lens and the seventh lens.

[0021] Optionally, the focal length of the wide-angle fixed-focus lens satisfies:

[0022] 3.1 < f13 / f < 7.5;

[0023] -13 < f4 / f < -7.5;

[0024] 1.2 < f57 / f < 1.8;

[0025] where f13 represents the combined focal length of the first lens, the second lens and the third lens, f4 represents the focal length of the fourth lens, f57 represents the combined focal length of the fifth lens, the sixth lens and the seventh lens, and f represents the focal length of the wide-angle fixed-focus lens.

[0026] Optionally, the refractive index of the third lens satisfies:

[0027] ND3 > 1.6.

[0028] Optionally, the fifth lens to the seventh lens satisfy:

[0029] 20 < VD5 - VD6 < 45;

[0030] 20 < VD7 - VD6 < 45;

[0031] Wherein, VD5 represents the Abbe number of the fifth lens, VD6 represents the Abbe number of the sixth lens, and VD7 represents the Abbe number of the seventh lens.

[0032] Optionally, the back focal length BFL and the total length TTL of the optical system of the wide-angle fixed-focus lens satisfy:

[0033] 0.15 < BFL / TTL < 0.35.

[0034] Optionally, the total length of the wide-angle fixed-focus lens is less than 15 mm.

[0035] The wide-angle fixed-focus lens provided by the embodiment of the present invention includes a first lens with a negative optical power, a second lens with a negative optical power, a third lens with a positive optical power, a diaphragm, a fourth lens with a negative optical power, a fifth lens with a positive optical power, a sixth lens with a negative optical power, and a seventh lens with a positive optical power arranged in sequence along the optical axis from the object side to the image side; wherein, the surface of the first lens close to the image side is concave; the surface of the second lens close to the object side is convex, and the surface close to the image side is concave; the surface of the third lens close to the image side is convex; the surface of the fifth lens close to the image side is convex; the surface of the sixth lens close to the object side is concave; the surface of the seventh lens close to the image side is convex. By providing the first lens with a negative optical power and the surface close to the image side being concave, it is more conducive to the collection of light rays in the optical system and can effectively increase the monitoring field of view; by providing the second lens with a negative optical power, the surface close to the object side being convex, and the surface close to the image side being concave, while effectively expanding the field of view of the optical system, off-axis aberrations such as system field curvature and astigmatism can be corrected; by providing the third lens with a positive optical power and the surface close to the image side being convex, the system distortion is reduced, which is beneficial to the optimization of the optical system distortion. At the same time, the third lens undertakes a relatively large optical power of the system and changes the propagation direction of the light beam, which is more conducive to the light beam imaging on the image plane; by providing the fourth lens with a negative optical power and being located near the diaphragm, it is beneficial to the correction of on-axis aberrations such as system spherical aberration and position chromatic aberration; by providing the fifth lens with a positive optical power and the surface close to the image side being convex, it is beneficial to the correction of system distortion; by respectively selecting the sixth lens and the seventh lens with negative and positive optical powers, it is beneficial to the correction of system coma, astigmatism, and chromatic aberration, thereby realizing a wide-angle fixed-focus lens with low cost, high performance, and small distortion. The maximum can match a 1 / 2.8-inch photosensitive chip, and its distortion is less than 5%, and it can meet the use conditions of -40°C to 80°C. Description of the Drawings

[0036] Figure 1 It is a schematic structural diagram of a wide-angle fixed-focus lens provided by the embodiment of the present invention;

[0037] Figure 2Schematic diagram of the spherical aberration curve of a wide-angle fixed-focus lens provided by an embodiment of the present invention;

[0038] Figure 3 Schematic diagram of the distortion curve of a wide-angle fixed-focus lens provided by an embodiment of the present invention;

[0039] Figure 4 Schematic diagram of the structure of another wide-angle fixed-focus lens provided by an embodiment of the present invention;

[0040] Figure 5 Schematic diagram of the spherical aberration curve of a wide-angle fixed-focus lens provided by an embodiment of the present invention;

[0041] Figure 6 Schematic diagram of the distortion curve of a wide-angle fixed-focus lens provided by an embodiment of the present invention;

[0042] Figure 7 Schematic diagram of the structure of yet another wide-angle fixed-focus lens provided by an embodiment of the present invention;

[0043] Figure 8 Schematic diagram of the spherical aberration curve of a wide-angle fixed-focus lens provided by an embodiment of the present invention;

[0044] Figure 9 Schematic diagram of the distortion curve of a wide-angle fixed-focus lens provided by an embodiment of the present invention. Detailed implementation manners

[0045] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It can be understood that the specific embodiments described herein are only used to explain the present invention, rather than limiting the present invention. Additionally, it should be noted that for the sake of description, only the parts related to the present invention are shown in the accompanying drawings, rather than all the structures.

[0046] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. It should be noted that the orientation terms such as "upper", "lower", "left", and "right" described in the embodiments of the present invention are described from the angles shown in the accompanying drawings, and should not be construed as limiting the embodiments of the present invention. In addition, in the context, it should also be understood that when it is mentioned that an element is formed "on" or "under" another element, it can not only be directly formed "on" or "under" another element, but also be indirectly formed "on" or "under" another element through an intermediate element. The terms "first", "second", etc. are only used for descriptive purposes, and do not indicate any order, quantity, or importance, but are only used to distinguish different components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0047] Figure 1The figure is a schematic structural diagram of a wide-angle fixed-focus lens provided by an embodiment of the present invention. Refer to Figure 1 , the wide-angle fixed-focus lens provided by the embodiment of the present invention includes a first lens 10 with a negative optical power, a second lens 20 with a negative optical power, a third lens 30 with a positive optical power, a diaphragm 80, a fourth lens 40 with a negative optical power, a fifth lens 50 with a positive optical power, a sixth lens 60 with a negative optical power, and a seventh lens 70 with a positive optical power, which are arranged in sequence from the object side to the image side along the optical axis; wherein, the surface of the first lens 10 close to the image side is concave; the surface of the second lens 20 close to the object side is convex, and the surface close to the image side is concave; the surface of the third lens 30 close to the image side is convex; the surface of the fifth lens 50 close to the image side is convex; the surface of the sixth lens 60 close to the object side is concave; the surface of the seventh lens 70 close to the image side is convex.

[0048] Among them, it can be understood that the optical power is equal to the difference between the convergence of the image-side light beam and the convergence of the object-side light beam, and it characterizes the ability of the optical system to deflect light rays. The greater the absolute value of the optical power, the stronger the bending ability of the light rays, and the smaller the absolute value of the optical power, the weaker the bending ability of the light rays. When the optical power is positive, the refraction of the light rays is convergent; when the optical power is negative, the refraction of the light rays is divergent. The optical power can be used to characterize a certain refracting surface of a lens (i.e., a surface of the lens), can be used to characterize a certain lens, or can be used to characterize a system formed by multiple lenses together (i.e., a lens group). In this embodiment, each lens can be fixed in a lens barrel ( Figure 1 not shown in the figure). By reasonably distributing the optical power of the lenses, the lens can have the characteristics of small distortion and wide angle. Optionally, the back focal length BFL and the total length TTL of the optical system of the wide-angle fixed-focus lens provided by this embodiment satisfy: 0.15 < BFL / TTL < 0.35, which is beneficial to the compression of the total length of the lens. In this embodiment, the total length of the lens is less than 15 mm, the size is small, it supports a 1 / 2.8-inch image plane, and the diagonal field of view can reach 120°.

[0049] In the technical solution of this embodiment, by providing a first lens with a negative focal power and having a concave surface on the image side, it is more conducive to the collection of light rays in the optical system, and can effectively increase the monitoring field of view range; by providing a second lens with a negative focal power, having a convex surface on the object side and a concave surface on the image side, it can correct off-axis aberrations such as field curvature and astigmatism in the optical system while effectively expanding the field of view of the optical system; by providing a third lens with a positive focal power and having a convex surface on the image side, it reduces the system distortion, is conducive to the optimization of the optical system distortion, and at the same time the third lens undertakes a relatively large focal power of the system, changing the propagation direction of the light beam, which is more conducive to the light beam imaging on the image plane; by providing a fourth lens with a negative focal power and located near the aperture stop, it is conducive to the correction of on-axis aberrations such as spherical aberration and longitudinal chromatic aberration of the system; by providing a fifth lens with a positive focal power and having a convex surface on the image side, it is conducive to the correction of the system distortion; by respectively selecting a sixth lens and a seventh lens with negative and positive focal powers, it is conducive to the correction of coma, astigmatism and chromatic aberration of the system, thereby realizing a wide-angle fixed-focus lens with low cost, high performance and small distortion, which can be maximally matched with a 1 / 2.8-inch photosensitive chip, with a distortion less than 5%, and can meet the use conditions of -40°C to 80°C.

[0050] Based on the above technical solution, continuing to refer to Figure 1 , optionally, the third lens 30 is a glass spherical lens, and the first lens 10, the second lens 20, the fourth lens 40, the fifth lens 50, the sixth lens 60 and the seventh lens 70 are all plastic aspherical lenses. Using a glass spherical lens is beneficial to improving the imaging effect of the lens in high and low temperature environments and ensuring the imaging consistency of the image quality under different conditions. Using plastic aspherical lenses is beneficial to optimizing high-order aberrations while reducing the cost of the lens, thereby improving the image quality of the peripheral field of view.

[0051] Optionally, the first lens 10 and the second lens 20 satisfy:

[0052] 1.2 < f1 / f12 < 2.0;

[0053] 3.5 < f2 / f12 < 5.0;

[0054] Where f1 represents the focal length of the first lens 10, f2 represents the focal length of the second lens 20, and f12 represents the combined focal length of the first lens 10 and the second lens 20. In this embodiment, the focal lengths of the first lens 10 and the second lens 20 are both negative, and both play the role of light collection.

[0055] Optionally, the first lens 10 to the third lens 30 satisfy:

[0056] 0.3 < f3 / f13 < 0.75;

[0057] -0.65 < f12 / f13 < -0.1;

[0058] Wherein, f3 represents the focal length of the third lens 30, f12 represents the combined focal length of the first lens 10 and the second lens 20, and f13 represents the combined focal length of the first lens 10, the second lens 20, and the third lens 30.

[0059] Optionally, the fifth lens 50 to the seventh lens 70 satisfy:

[0060] 0.7 < f5 / f57 < 1.3;

[0061] -1.8 < f6 / f57 < -0.9;

[0062] 0.8 < f7 / f57 < 1.4;

[0063] Wherein, f5 represents the focal length of the fifth lens 50, f6 represents the focal length of the sixth lens 60, f7 represents the focal length of the seventh lens 70, and f57 represents the combined focal length of the fifth lens 50, the sixth lens 60, and the seventh lens 70.

[0064] Optionally, the focal length of the wide-angle fixed-focus lens satisfies:

[0065] 3.1 < f13 / f < 7.5;

[0066] -13 < f4 / f < -7.5;

[0067] 1.2 < f57 / f < 1.8;

[0068] Where f13 represents the combined focal length of the first lens 10, the second lens 20, and the third lens 30, f4 represents the focal length of the fourth lens 40, f57 represents the combined focal length of the fifth lens 50, the sixth lens 60, and the seventh lens 70, and f represents the focal length of the wide-angle fixed-focus lens. The optical system of this embodiment is symmetric about the fourth lens 40, forming a quasi-Gaussian structure, which is beneficial to the correction of lateral aberration.

[0069] Optionally, the refractive index of the third lens 30 satisfies: ND3 > 1.6, which is beneficial to the optimization of the large-field optical system and is more beneficial to reducing the incident angle of light and lowering the sensitivity of the lens.

[0070] Optionally, the fifth lens 50 to the seventh lens 70 satisfy:

[0071] 20 < VD5 - VD6 < 45;

[0072] 20 < VD7 - VD6 < 45;

[0073] Among them, VD5 represents the Abbe number of the fifth lens 50, VD6 represents the Abbe number of the sixth lens 60, and VD7 represents the Abbe number of the seventh lens 70, which is beneficial to the correction of chromatic aberration of the system.

[0074] The wide-angle fixed-focus lens provided in this embodiment adopts a glass spherical lens and a hybrid glass-plastic structure of six plastic aspherical lenses. Through reasonable matching of materials, focal lengths, refractive indices, and Abbe numbers, the glass spherical lens is easy to process, and the plastic aspherical lens has good aberration correction ability, effectively controlling the cost while ensuring the performance of the optical system. The lens has the characteristics of low cost, high performance, small distortion, and wide angle, and can be maximally matched with a 1 / 2.8-inch photosensitive chip, with distortion less than 5% and a diagonal field of view angle that can reach 120°, meeting the imaging requirements in a variety of application scenarios.

[0075] Optionally, the surface shape of the aspherical lens satisfies the formula:

[0076]

[0077] Among them, z represents the axial sagittal height of the aspherical surface in the Z direction; y represents the height of the aspherical surface; c represents the curvature of the fitted spherical surface, numerically the reciprocal of the radius of curvature, k represents the conic coefficient, and A, B, C, D, E, F, and G respectively represent the high-order aspherical coefficients.

[0078] Exemplarily, Table 1 shows Figure 1 the specific parameter design values of the corresponding wide-angle fixed-focus lens:

[0079] Table 1 Specific parameters of the wide-angle fixed-focus lens

[0080]

[0081]

[0082] The focal length f of the wide-angle fixed-focus lens in this embodiment is 2.13 mm, and the aperture value F is 2.19.

[0083] Table 2 shows a set of design values of the wide-angle fixed-focus lens provided in Table 1:

[0084] Table 2 A set of design values of the wide-angle fixed-focus lens

[0085]

[0086]

[0087] The surface numbers in Table 2 are numbered according to the surface order of each lens. Among them, "S1" represents the front surface of the first lens 10 (the surface closer to the object side), "S2" represents the rear surface of the first lens 10 (the surface closer to the image side), and so on. "STO" represents the aperture of the lens. The radius of curvature represents the degree of curvature of the lens surface. A positive value represents that the surface is curved towards the image side, and a negative value represents that the surface is curved towards the object side. Among them, "PL" represents that the surface is a plane and the radius of curvature is infinite; the thickness represents the central axial distance from the current surface to the next surface, the refractive index represents the ability of the material between the current surface and the next surface to deflect light, and the space represents that the current position is air and the refractive index is 1; the k value represents the numerical value of the best-fit conic coefficient of the aspheric surface.

[0088] Among them, Table 3 shows the aspheric surface type parameters in this embodiment:

[0089] A design value of the aspheric coefficient in the wide-angle fixed-focus lens in Table 3

[0090]

[0091]

[0092] Among them, -2.6058E-03 means that the coefficient A of the surface with the surface number being surface S1 is -2.6058×10 -3 .

[0093] Figure 2 is a schematic diagram of the spherical aberration curve of a wide-angle fixed-focus lens provided by an embodiment of the present invention. Figure 3 is a schematic diagram of the distortion curve of a wide-angle fixed-focus lens provided by an embodiment of the present invention. Among them, from Figure 2 and Figure 3 it can be seen that the wide-angle fixed-focus lens provided in this embodiment has good imaging ability and its distortion is less than 5%.

[0094] Figure 4 is a schematic diagram of the structure of another wide-angle fixed-focus lens provided by an embodiment of the present invention. Similar to the above embodiment, Table 4 is Figure 4 the specific parameter design values of the corresponding wide-angle fixed-focus lens:

[0095] Table 4 Specific parameters of the wide-angle fixed-focus lens

[0096]

[0097]

[0098] The focal length f of the wide-angle fixed-focus lens in this embodiment is 2.14 mm, and the aperture F is 2.12.

[0099] Table 5 shows a set of design values for the wide-angle fixed-focus lens provided in Table 4:

[0100] Table 5 A set of design values for the wide-angle fixed-focus lens

[0101]

[0102]

[0103] The surface numbers in Table 5 are numbered according to the surface order of each lens. Among them, "S1" represents the front surface of the first lens 10 (the surface closer to the object side), "S2" represents the rear surface of the first lens 10 (the surface closer to the image side), and so on. "STO" represents the aperture stop of the lens. The radius of curvature represents the degree of curvature of the lens surface. A positive value indicates that the surface bends towards the image side, and a negative value indicates that the surface bends towards the object side. Among them, "PL" represents that the surface is a plane and the radius of curvature is infinite; the thickness represents the central axial distance from the current surface to the next surface, the refractive index represents the ability of the material between the current surface and the next surface to deflect light, a space represents that the current position is air and the refractive index is 1; the k value represents the numerical value of the best-fit conic coefficient of the aspherical surface.

[0104] Among them, Table 6 shows the aspherical surface type parameters in this embodiment:

[0105] Table 6 A set of design values for the aspherical coefficients in the wide-angle fixed-focus lens

[0106]

[0107]

[0108] Among them, 1.5125E-03 means that the coefficient A of the surface with the surface number S1 is 1.5125×10 -3 .

[0109] Figure 5 is a schematic diagram of the spherical aberration curve of a wide-angle fixed-focus lens provided by an embodiment of the present invention. Figure 6 is a schematic diagram of the distortion curve of a wide-angle fixed-focus lens provided by an embodiment of the present invention. Among them, from Figure 5 and Figure 6 , it can be seen that the wide-angle fixed-focus lens provided in this embodiment has good imaging ability, and its distortion is less than 5%.

[0110] Figure 7 is a schematic diagram of the structure of another wide-angle fixed-focus lens provided by an embodiment of the present invention. Similar to the above embodiment, Table 7 is Figure 7 the specific parameter design values of the corresponding wide-angle fixed-focus lens:

[0111] Table 7 The specific parameters of the wide-angle fixed-focus lens

[0112]

[0113]

[0114] The focal length f of the wide-angle fixed-focus lens in this embodiment is 1.94 mm, and the aperture F is 2.18.

[0115] Table 8 shows a set of design values for the wide-angle fixed-focus lens provided in Table 7:

[0116] Table 8 A set of design values for the wide-angle fixed-focus lens

[0117]

[0118]

[0119] The surface numbers in Table 8 are numbered according to the surface order of each lens. Among them, "S1" represents the front surface of the first lens 10 (the surface closer to the object side), "S2" represents the rear surface of the first lens 10 (the surface closer to the image side), and so on. "STO" represents the aperture stop of the lens. The radius of curvature represents the degree of curvature of the lens surface. A positive value indicates that the surface bends towards the image side, and a negative value indicates that the surface bends towards the object side. Among them, "PL" represents that the surface is a plane and the radius of curvature is infinite; the thickness represents the central axial distance from the current surface to the next surface, the refractive index represents the ability of the material between the current surface and the next surface to deflect light, a space represents that the current position is air and the refractive index is 1; the k value represents the numerical value of the best-fit conic coefficient of the aspherical surface.

[0120] Among them, Table 9 shows the aspherical surface type parameters in this embodiment:

[0121] Table 9 A set of design values for the aspherical coefficients of the wide-angle fixed-focus lens

[0122]

[0123]

[0124] Among them, 1.5500E-03 means that the coefficient A of the surface numbered S1 is 1.5500×10 -3 .

[0125] Figure 8 is a schematic diagram of the spherical aberration curve of a wide-angle fixed-focus lens provided by an embodiment of the present invention. Figure 9 is a schematic diagram of the distortion curve of a wide-angle fixed-focus lens provided by an embodiment of the present invention. Among them, from Figure 8 and Figure 9 it can be seen that the wide-angle fixed-focus lens provided in this embodiment has good imaging ability, and its distortion is less than 5%.

[0126] Note that the above is only a preferred embodiment of the present invention and the technical principles applied. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein. Various obvious changes, re-adjustments, and substitutions can be made by those skilled in the art without departing from the protection scope of the present invention. Therefore, although the present invention has been described in more detail through the above embodiments, the present invention is not limited to the above embodiments. Without departing from the concept of the present invention, it may also include more other equivalent embodiments, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A wide-angle fixed-focus lens, characterized in that, It includes a first lens with negative optical power, a second lens with negative optical power, a third lens with positive optical power, a diaphragm, a fourth lens with negative optical power, a fifth lens with positive optical power, a sixth lens with negative optical power, and a seventh lens with positive optical power, which are arranged in sequence from the object side to the image side along the optical axis; Among them, the surface of the first lens on the image side is concave; the surface of the second lens on the object side is convex, and the surface on the image side is concave; the surface of the third lens on the image side is convex; the surface of the fifth lens on the image side is convex; the surface of the sixth lens on the object side is concave; the surface of the seventh lens on the image side is convex; The third lens is a glass spherical lens, and the first lens, the second lens, the fourth lens, the fifth lens, the sixth lens, and the seventh lens are all plastic aspherical lenses; The focal length of the wide-angle fixed-focus lens satisfies: 3.1 < f13 / f < 7.5; -13 < f4 / f < -7.5; 1.2 < f57 / f < 1.8; Where f13 represents the combined focal length of the first lens, the second lens, and the third lens, f4 represents the focal length of the fourth lens, f57 represents the combined focal length of the fifth lens, the sixth lens, and the seventh lens, and f represents the focal length of the wide-angle fixed-focus lens; The back focal length BFL and the total length TTL of the optical system of the wide-angle fixed-focus lens satisfy: 0.15 < BFL / TTL < 0.

35.

2. The wide-angle fixed-focus lens according to claim 1, wherein The first lens and the second lens satisfy: 1.2 < f1 / f12 < 2.0; 3.5 < f2 / f12 < 5.0; Where f1 represents the focal length of the first lens, f2 represents the focal length of the second lens, and f12 represents the combined focal length of the first lens and the second lens.

3. The wide-angle fixed-focus lens according to claim 1, wherein, The first lens to the third lens satisfy: 0.3 < f3 / f13 < 0.75; -0.65 < f12 / f13 < -0.1; Among them, f3 represents the focal length of the third lens, f12 represents the combined focal length of the first lens and the second lens, and f13 represents the combined focal length of the first lens, the second lens, and the third lens.

4. The wide-angle fixed-focus lens according to claim 1, wherein The fifth lens to the seventh lens satisfy: 0.7 < f5 / f57 < 1.3; -1.8 < f6 / f57 < -0.9; 0.8 < f7 / f57 < 1.4; Among them, f5 represents the focal length of the fifth lens, f6 represents the focal length of the sixth lens, f7 represents the focal length of the seventh lens, and f57 represents the combined focal length of the fifth lens, the sixth lens, and the seventh lens.

5. The wide-angle fixed-focus lens according to claim 1, wherein The refractive index of the third lens satisfies: ND3 > 1.

6.

6. The wide-angle fixed-focus lens according to claim 1, characterized in that, The fifth lens to the seventh lens satisfy: 20 < VD5 - VD6 < 45; 20 < VD7 - VD6 < 45; Among them, VD5 represents the Abbe number of the fifth lens, VD6 represents the Abbe number of the sixth lens, and VD7 represents the Abbe number of the seventh lens.

7. The wide-angle fixed-focus lens according to any one of claims 1 to 6, characterized in that, The total length of the wide-angle fixed-focus lens is less than 15 mm.

Images