A fixed-focus lens

Abstract

An embodiment of the present invention discloses a fixed-focus lens. The lens includes a first lens with a negative optical power, a second lens with a positive or negative optical power, a third lens with a positive or negative optical power, a fourth lens with a positive 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 aperture stop is located between the second lens and the third lens or between the third lens and the fourth lens; the fourth lens is a spherical lens, and the first lens, the second lens, the third lens, the fifth lens, the sixth lens, and the seventh lens are all aspherical lenses. The technical solution of the present invention can meet the requirements of a large target surface and an ultra-large aperture for the lens, support a maximum target surface of 1 / 1.7 inches at a relatively low cost, the aperture number satisfies 0.8 ≤ F ≤ 1.2, the field of view angle is greater than 110°, and the imaging requirements are met when used in an environment of -40°C to 80°C.

Description

Technical Field

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

[0002] With the development of society, the application scope and scenarios of security monitoring video technology are gradually expanding, and the requirements for security monitoring in terms of high definition, intelligence, networking, etc. are increasing day by day.

[0003] With the increasing development of security monitoring systems, the requirements for security lenses are getting higher and higher, mainly reflected in higher image quality, larger aperture diameter, larger field of view and larger target surface. Currently, existing ultra-large aperture lenses often have low image quality, and the target surface is generally 1 / 2.7 inches. Therefore, in view of the existing phenomenon, it is necessary to develop a large-target-surface ultra-large aperture 4K optical lens. Summary of the Invention

[0004] Embodiments of the present invention provide a fixed-focus lens to meet the requirements of a large target surface and an ultra-large aperture for the lens. The fixed-focus lens supports a maximum target surface of 1 / 1.7 inches at a relatively low cost, the aperture number satisfies 0.8 ≤ F ≤ 1.2, the field of view angle is greater than 110°, and it meets the imaging requirements when used in an environment of -40°C to 80°C.

[0005] Embodiments of the present invention provide a fixed-focus lens, which includes a first lens with negative optical power, a second lens with positive or negative optical power, a third lens with positive or negative optical power, a fourth lens with positive optical power, a fifth lens with positive optical power, a sixth lens with negative optical power, and a seventh lens with positive optical power arranged in sequence from the object side to the image side along the optical axis;

[0006] The fixed-focus lens further includes a diaphragm, and the diaphragm is located between the second lens and the third lens or between the third lens and the fourth lens;

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

[0008] Optionally, the surface of the first lens close to the object side is convex, the surface close to the image side is concave, the surface of the second lens close to the object side is concave, the surface close to the image side is convex, the surface of the third lens close to the object side is convex, the surface close to the image side is concave, the two surfaces of the fourth lens are both convex, the two surfaces of the fifth lens are both convex, the surface of the sixth lens close to the object side is concave, the surface close to the image side is concave or convex, and the surface of the seventh lens close to the object side is convex, the surface close to the image side is convex or concave.

[0009] Optionally, the optical powers of the first lens to the seventh lens satisfy:

[0010]

[0011]

[0012]

[0013]

[0014]

[0015]

[0016]

[0017] Wherein, and respectively represent the optical powers of the first lens to the seventh lens, represents the optical power of the fixed-focus lens.

[0018] Optionally, the refractive indices and dispersion coefficients of the first lens to the seventh lens satisfy:

[0019] 1.50 ≤ n1 ≤ 1.60; 50.0 ≤ v1 ≤ 65.0;

[0020] 1.50 ≤ n2 ≤ 1.75; 20.0 ≤ v2 ≤ 65.0;

[0021] 1.50 ≤ n3 ≤ 1.70; 18.0 ≤ v3 ≤ 25.0;

[0022] 1.49 ≤ n4 ≤ 1.70; 60.0 ≤ v4 ≤ 75.0;

[0023] 1.50 ≤ n5 ≤ 1.60; 50.0 ≤ v5 ≤ 75.0;

[0024] 1.60 ≤ n6 ≤ 1.75; 15.0 ≤ v6 ≤ 25.0;

[0025] 1.50 ≤ n7 ≤ 1.60; 50.0 ≤ v7 ≤ 60.0;

[0026] Wherein, n1, n2, n3, n4, n5, n6 and n7 respectively represent the refractive indices of the first lens to the seventh lens in sequence, and v1, v2, v3, v4, v5, v6 and v7 respectively represent the dispersion coefficients of the first lens to the seventh lens in sequence.

[0027] Optionally, the focal length f of the fixed-focus lens and the entrance pupil diameter d satisfy:

[0028] 0.8 ≤ f / d ≤ 1.2.

[0029] Optionally, the focal length f of the fixed-focus lens and the image plane diameter IC satisfy:

[0030] 0.29 ≤ f / IC ≤ 0.9.

[0031] Optionally, the image plane diameter IC of the fixed-focus lens satisfies:

[0032] 8.5 mm ≤ IC ≤ 9.6 mm.

[0033] Optionally, the back focal length BFL of the fixed-focus lens and the total lens length TTL satisfy:

[0034] BFL / TTL ≥ 0.1.

[0035] Optionally, the diameter D1 of the first lens and the total lens length TTL satisfy:

[0036] D1 / TTL < 0.5.

[0037] Optionally, the f-number F of the fixed-focus lens satisfies:

[0038] 0.8 ≤ F ≤ 1.2.

[0039] The 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 positive or negative optical power, a third lens with a positive or negative optical power, a fourth lens with a positive 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; it also includes a diaphragm located between the second lens and the third lens or between the third lens and the fourth lens; the fourth lens is a spherical lens, and the first lens, the second lens, the third lens, the fifth lens, the sixth lens, and the seventh lens are all aspherical lenses. By setting the first lens with a negative optical power, it is beneficial to the collection of light rays of the optical system, and can effectively increase the monitoring field of view; by setting the fourth lens with a positive optical power, it undertakes a 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 comprehensively setting the optical power and the shape matching relationship of each lens, various aberrations such as spherical aberration, chromatic aberration, field curvature, astigmatism, and distortion of the system can be effectively corrected, so as to meet the requirements of a large target surface and an ultra-large aperture of the lens. The fixed-focus lens supports a maximum target surface of 1 / 1.7 inch at a relatively low cost, the f-number satisfies 0.8 ≤ F ≤ 1.2, the field of view angle is greater than 110°, and it meets the imaging requirements when used in the environment of -40°C to 80°C. Description of the Drawings

[0040] Figure 1Schematic diagram of the structure of a fixed-focus lens provided by an embodiment of the present invention;

[0041] Figure 2 Schematic diagram of the spherical aberration curve of a fixed-focus lens provided by an embodiment of the present invention;

[0042] Figure 3 Schematic diagram of the light fan of a fixed-focus lens provided by an embodiment of the present invention;

[0043] Figure 4 Schematic diagram of the field distortion of a fixed-focus lens provided by an embodiment of the present invention;

[0044] Figure 5 Schematic diagram of the structure of another fixed-focus lens provided by an embodiment of the present invention;

[0045] Figure 6 Schematic diagram of the spherical aberration curve of a fixed-focus lens provided by an embodiment of the present invention;

[0046] Figure 7 Schematic diagram of the light fan of a fixed-focus lens provided by an embodiment of the present invention;

[0047] Figure 8 Schematic diagram of the field distortion of a fixed-focus lens provided by an embodiment of the present invention;

[0048] Figure 9 Schematic diagram of the structure of yet another fixed-focus lens provided by an embodiment of the present invention;

[0049] Figure 10 Schematic diagram of the spherical aberration curve of a fixed-focus lens provided by an embodiment of the present invention;

[0050] Figure 11 Schematic diagram of the light fan of a fixed-focus lens provided by an embodiment of the present invention;

[0051] Figure 12 Schematic diagram of the field distortion of a fixed-focus lens provided by an embodiment of the present invention. Detailed implementation manners

[0052] 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 parts related to the present invention rather than all structures are shown in the drawings.

[0053] The terms used in the embodiments of the present invention are for the purpose of describing specific embodiments only 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 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.

[0054] Figure 1 FIG. is a schematic structural diagram of a fixed-focus lens provided by an embodiment of the present invention. Refer to Figure 1 , the 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 positive or negative optical power, a third lens 30 with a positive or negative optical power, a fourth lens 40 with a positive 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; the fixed-focus lens further includes a diaphragm ( Figure 1 not shown), and the diaphragm is located between the second lens 20 and the third lens 30 or between the third lens 30 and the fourth lens 40; the fourth lens 40 is a spherical lens, and the first lens 10, the second lens 20, the third lens 30, the fifth lens 50, the sixth lens 60, and the seventh lens 70 are all aspherical lenses.

[0055] 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; 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 applicable to characterize a certain refracting surface of a lens (i.e., a surface of the lens), can be applicable to characterize a certain lens, and can also be applicable 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 a large target surface and a large aperture, the aperture value F satisfies 0.8 ≤ F ≤ 1.2, supports an image surface of 1 / 1.7 inches, and the field of view angle is greater than 110°.

[0056] The technical solution of this embodiment is beneficial to the collection of light rays in the optical system by setting the first lens with negative focal power, which can effectively increase the monitoring field of view. By setting the fourth lens with positive focal power, it undertakes a large focal 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 comprehensively setting the focal power and the matching relationship of the shapes of each lens, various aberrations such as spherical aberration, chromatic aberration, field curvature, astigmatism and distortion of the system can be effectively corrected, so as to meet the requirements of a large target surface and an ultra-large aperture for the lens. This fixed-focus lens supports a maximum target surface of 1 / 1.7 inches at a relatively low cost, the aperture number satisfies 0.8 ≤ F ≤ 1.2, the field of view angle is greater than 110°, and it meets the imaging requirements when used in the environment of -40°C to 80°C.

[0057] Based on the above technical solution, continuing to refer to Figure 1 , optionally, the surface of the first lens 10 close to the object side is convex, and the surface close to the image side is concave; the surface of the second lens 20 close to the object side is concave, and the surface close to the image side is convex; the surface of the third lens 30 close to the object side is convex, and the surface close to the image side is concave; the two surfaces of the fourth lens 40 are both convex; the two surfaces of the fifth lens 50 are both convex; the surface of the sixth lens 60 close to the object side is concave, and the surface close to the image side is concave or convex; the surface of the seventh lens 70 close to the object side is convex, and the surface close to the image side is convex or concave. That is, the first lens 10 is a convex-concave lens, the second lens 20 is a concave-convex lens, the third lens 30 is a convex-concave lens, the fourth lens 40 is a biconvex lens, the fifth lens 50 is a biconvex lens, the sixth lens 60 is a biconcave or concave-convex lens, and the seventh lens 70 is a biconvex or convex-concave lens.

[0058] Optionally, the focal powers of the first lens 10 to the seventh lens 70 satisfy:

[0059]

[0060]

[0061]

[0062]

[0063]

[0064]

[0065]

[0066] Among them, and respectively represent the focal powers of the first lens 10 to the seventh lens 70. Represents the optical power of the fixed-focus lens. By setting the optical powers of the respective lenses to satisfy the above relationship, it is possible to ensure that the fixed-focus lens achieves a clear imaging effect.

[0067] Optionally, the refractive indices and dispersion coefficients of the first lens 10 to the seventh lens 70 satisfy:

[0068] 1.50 ≤ n1 ≤ 1.60; 50.0 ≤ v1 ≤ 65.0;

[0069] 1.50 ≤ n2 ≤ 1.75; 20.0 ≤ v2 ≤ 65.0;

[0070] 1.50 ≤ n3 ≤ 1.70; 18.0 ≤ v3 ≤ 25.0;

[0071] 1.49 ≤ n4 ≤ 1.70; 60.0 ≤ v4 ≤ 75.0;

[0072] 1.50 ≤ n5 ≤ 1.60; 50.0 ≤ v5 ≤ 75.0;

[0073] 1.60 ≤ n6 ≤ 1.75; 15.0 ≤ v6 ≤ 25.0;

[0074] 1.50 ≤ n7 ≤ 1.60; 50.0 ≤ v7 ≤ 60.0;

[0075] Wherein, n1, n2, n3, n4, n5, n6, and n7 respectively represent the refractive indices of the first lens 10 to the seventh lens 70 in sequence, and v1, v2, v3, v4, v5, v6, and v7 respectively represent the dispersion coefficients of the first lens 10 to the seventh lens 70 in sequence.

[0076] Optionally, the focal length f of the fixed-focus lens and the entrance pupil diameter d satisfy:

[0077] 0.8 ≤ f / d ≤ 1.2. When f and d satisfy the above relationship, the fixed-focus lens has the characteristic of a super large aperture, and still has an excellent imaging effect in a low illuminance environment, and can meet the imaging requirements of bright and dark environments.

[0078] Optionally, the focal length f of the fixed-focus lens and the image plane diameter IC satisfy:

[0079] 0.29 ≤ f / IC ≤ 0.9. When f and IC satisfy the above relationship, the fixed-focus lens has a wide-angle performance, can ensure the shooting range of the fixed-focus lens, and enables the system to have a large field of view.

[0080] Optionally, the image plane diameter IC of the fixed-focus lens satisfies:

[0081] 8.5mm ≤ IC ≤ 9.6mm. When the IC satisfies the above relationship, the fixed-focus lens has a larger target surface, which can ensure better imaging quality of the fixed-focus lens and a clearer picture.

[0082] Optionally, the back focal length BFL of the fixed-focus lens and the total lens length TTL satisfy:

[0083] BFL / TTL ≥ 0.1. When BFL and TTL satisfy the above relationship, it can ensure sufficient installation space for the imaging sensor and the flat filter.

[0084] Optionally, the diameter D1 of the first lens and the total lens length TTL satisfy:

[0085] D1 / TTL < 0.5. When D1 and TTL satisfy the above relationship, it can avoid too large an aperture of the lens and meet the installation space requirements of the final product.

[0086] The fixed-focus lens provided in this embodiment adopts a hybrid structure design of one spherical lens and six aspherical lenses. Through reasonable combinations of optical power, refractive index, and dispersion coefficient, the aspherical lens has good aberration correction ability, effectively controlling the cost while ensuring the performance of the optical system. This lens has the characteristics of low cost, high performance, large aperture, and large field of view angle. It can match a 1 / 1.7-inch photosensitive chip at most, with a field of view angle greater than 110°, meeting the imaging requirements in various application scenarios.

[0087] Optionally, the surface shape of the aspherical lens satisfies the formula:

[0088]

[0089] where 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, and F respectively represent the high-order aspherical coefficients.

[0090] Exemplarily, Table 1 shows Figure 1 the specific parameters of the corresponding fixed-focus lens:

[0091] Table 1 Specific Parameters of the Fixed-Focus Lens

[0092]

[0093]

[0094] The focal length f of the fixed-focus lens in this embodiment is 5.1mm, the aperture value F is 0.95, the image plane diameter is 9.2mm, and the diagonal field of view angle is 120°.

[0095] Table 2 shows a set of design values of the fixed-focus lens provided in Table 1:

[0096] Table 2 Design values of a fixed-focus lens

[0097]

[0098]

[0099] The surface numbers in Table 2 are numbered according to the surface order of each lens. Among them, "1" represents the front surface of the first lens 10 (the surface closer to the object side), "2" represents the rear surface of the first lens 10 (the surface closer to the image side), and so on. The radius of curvature represents the degree of curvature of the lens surface. A positive value indicates that the surface bends towards the image plane side, and a negative value indicates that the surface bends towards the object plane side. Among them, "infinity" 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, and 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. "16" and "17" represent the two surfaces of the filter, and "18" represents the image plane.

[0100] Among them, Table 3 shows the aspherical surface type parameters of this embodiment:

[0101] Table 3 Design values of aspherical coefficients in a fixed-focus lens

[0102]

[0103]

[0104] Among them, -1.397276E-03 means that the coefficient A of the surface number 1 is -1.397276×10 -3 .

[0105] Figure 2 Figure Figure 3 Figure Figure 4 Figure Figures 2 to 4 It can be seen that the fixed-focus lens provided in this embodiment has good imaging ability.

[0106] Figure 5 Figure Figure 5 shows the structural schematic diagram of another fixed-focus lens provided in the embodiment of the present invention. Similar to the above embodiment, Table 4 shows

[0107] the specific parameters of the corresponding fixed-focus lens:

[0108]

[0109]

[0110] For the fixed-focus lens of this embodiment, the focal length f = 4.8 mm, the aperture value F = 1.0, the image plane diameter is 9.2 mm, and the diagonal field of view angle is 118°.

[0111] Table 5 shows a set of design values for the fixed-focus lens provided in Table 4:

[0112] Table 5 A set of design values for the fixed-focus lens

[0113]

[0114]

[0115] In Table 5, the surface numbers are numbered according to the surface order of each lens. Here, "1" represents the front surface of the first lens 10 (the surface closer to the object side), "2" represents the rear surface of the first lens 10 (the surface closer to the image side), and so on. The radius of curvature represents the degree of curvature of the lens surface. A positive value indicates that the surface bends towards the image plane side, and a negative value indicates that the surface bends towards the object plane side. Here, "infinity" represents that the surface is a plane with an infinite radius of curvature; 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 with a refractive index of 1, "16" and "17" represent the two surfaces of the filter, and "18" represents the image plane.

[0116] Among them, Table 6 shows the aspherical surface type parameters of this embodiment:

[0117] Table 6 A set of design values for the aspherical coefficients of the fixed-focus lens

[0118]

[0119]

[0120] Among them, -3.208228E-03 means that the coefficient A of the surface with surface number 1 is -3.208228×10 -3 .

[0121] Figure 6 is a schematic diagram of the spherical aberration curve of a fixed-focus lens provided by an embodiment of the present invention, Figure 7 is a schematic diagram of the light fan of a fixed-focus lens provided by an embodiment of the present invention, Figure 8 is a schematic diagram of the field distortion of a fixed-focus lens provided by an embodiment of the present invention. It can be seen from Figures 6 to 8 that the fixed-focus lens provided by this embodiment has good imaging ability.

[0122] Figure 9 Schematic diagram of the structure of another fixed-focus lens provided by an embodiment of the present invention. Similar to the above embodiment, Table 7 shows Figure 9 the specific parameters of the corresponding fixed-focus lens:

[0123] Table 7 Specific parameters of the fixed-focus lens

[0124]

[0125] For the fixed-focus lens of this embodiment, the focal length f = 4.8 mm, the aperture value F = 0.96, the image plane diameter is 9.2 mm, and the diagonal field of view angle is 118°.

[0126] Table 8 shows a set of design values for the fixed-focus lens provided in Table 7:

[0127] Table 8 A set of design values for the fixed-focus lens

[0128]

[0129]

[0130] In Table 8, the surface numbers are numbered according to the surface order of each lens. Among them, "1" represents the front surface of the first lens 10 (the surface closer to the object side), "2" represents the rear surface of the first lens 10 (the surface closer to the image side), and so on. The radius of curvature represents the degree of curvature of the lens surface. A positive value indicates that the surface bends towards the image plane side, and a negative value indicates that the surface bends towards the object plane side. Among them, "infinity" 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, "16" and "17" represent the two surfaces of the filter, and "18" represents the image plane.

[0131] Among them, Table 9 shows the aspherical surface type parameters of this embodiment:

[0132] Table 9 A set of design values for the aspherical coefficients of the fixed-focus lens

[0133]

[0134]

[0135] Among them, -4.599183E-03 means that the coefficient A of the surface numbered 1 is -4.599183×10 -3 .

[0136] Figure 10 Schematic diagram of the spherical aberration curve of a fixed-focus lens provided by an embodiment of the present invention, Figure 11Schematic diagram of the light fan of a fixed-focus lens provided by an embodiment of the present invention Figure 12 Schematic diagram of the field distortion of a fixed-focus lens provided by an embodiment of the present invention, where it can be seen from Figures 10 to 12 that the fixed-focus lens provided by this embodiment has good imaging ability.

[0137] 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 here, and 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, more other equivalent embodiments can be included, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A fixed-focus lens, characterized in that, It includes a first lens with negative optical power, a second lens with positive or negative optical power, a third lens with positive or negative optical power, a fourth lens with positive 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; The fixed-focus lens further includes a diaphragm, and the diaphragm is located between the second lens and the third lens or between the third lens and the fourth lens; The fourth lens is a spherical lens, and the first lens, the second lens, the third lens, the fifth lens, the sixth lens, and the seventh lens are all aspherical lenses; The surface of the first lens on the object-side is convex, and the surface on the image-side is concave. The surface of the second lens on the object-side is concave, and the surface on the image-side is convex. The surface of the third lens on the object-side is convex, and the surface on the image-side is concave. Both surfaces of the fourth lens are convex. Both surfaces of the fifth lens are convex. The surface of the sixth lens on the object-side is concave, and the surface on the image-side is concave or convex. The surface of the seventh lens on the object-side is convex, and the surface on the image-side is convex or concave; The optical power of the third lens satisfies: -0.30≤φ3 / φ≤0.25; where φ3 represents the optical power of the third lens, and φ represents the optical power of the fixed-focus lens.

2. The fixed-focus lens according to claim 1, wherein The optical powers of the first lens, the second lens, the fourth lens to the seventh lens satisfy: -0.65≤φ1 / φ≤-0.30; -0.55≤φ2 / φ≤0.35; 0.35≤φ4 / φ≤0.55; 0.35≤φ5 / φ≤0.65; -0.75≤φ6 / φ≤-0.55; 0.35≤φ7 / φ≤0.65; where φ1, φ2, φ4, φ5, φ6, and φ7 respectively represent the optical powers of the first lens, the second lens, the fourth lens to the seventh lens.

3. The fixed-focus lens according to claim 1, characterized in that, The refractive indices and dispersion coefficients of the first lens to the seventh lens satisfy: 1.50≤n1≤1.60; 50.0≤v1≤65.0; 1.50≤n2≤1.75; 20.0≤v2≤65.0; 1.50≤n3≤1.70; 18.0≤v3≤25.0; 1.49≤n4≤1.70; 60.0≤v4≤75.0; 1.50≤n5≤1.60; 50.0≤v5≤75.0; 1.60≤n6≤1.75; 15.0≤v6≤25.0; 1.50≤n7≤1.60; 50.0≤v7≤60.0; where n1, n2, n3, n4, n5, n6, and n7 respectively represent the refractive indices of the first lens to the seventh lens in sequence, and v1, v2, v3, v4, v5, v6, and v7 respectively represent the dispersion coefficients of the first lens to the seventh lens in sequence.

4. The fixed-focus lens according to claim 1, wherein, The focal length f of the fixed-focus lens and the entrance pupil diameter d satisfy: 0.8≤f / d≤1.

2.

5. The fixed-focus lens according to claim 1, wherein, The focal length f of the fixed-focus lens and the image plane diameter IC satisfy: 0.29 ≤ f / IC ≤ 0.9。 6. The fixed-focus lens according to claim 1, wherein The image plane diameter IC of the fixed-focus lens satisfies: 8.5 mm ≤ IC ≤ 9.6 mm。 7. The fixed-focus lens according to claim 1, characterized in that, The back focal length BFL of the fixed-focus lens and the total lens length TTL satisfy: BFL / TTL ≥ 0.1。 8. The fixed-focus lens according to claim 1, characterized in that, The diameter D1 of the first lens and the total lens length TTL satisfy: D1 / TTL < 0.5。 9. The fixed-focus lens according to any one of claims 1 to 8, characterized in that, The f-number F of the fixed-focus lens satisfies: 0.8≤F≤1.2。

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