A fixed focus lens

Abstract

An embodiment of the present invention discloses a fixed-focus lens. The fixed-focus lens includes a first lens with a negative optical power, a second lens with a negative optical power, a third lens with a positive or negative optical power, a diaphragm, 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; wherein, both the first lens and the third lens are spherical lenses, and the second lens, the fourth lens, the fifth lens, the sixth lens, and the seventh lens are all aspherical lenses. The technical solution of the embodiment of the present invention can realize a 4K wide-angle optical lens with a large target surface and an ultra-large aperture. The lens supports a maximum target surface of 1 / 1.8 inch at a relatively low cost, the aperture number satisfies 0.8 < F < 1.2, the field of view angle is greater than 120°, and the imaging requirements are met when used in an environment of -30°C to 80°C.

Description

Technical Field

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

[0002] With the rapid development of technology, people have a higher level of understanding of security, and surveillance lenses have emerged accordingly. In recent years, surveillance lenses have become a major force in the security industry, driving the continuous progress and rapid development of the security industry.

[0003] With the increasing development of security surveillance systems, the requirements for security lenses are getting higher and higher, mainly reflected in higher image quality, larger field of view, larger aperture, and larger target surface. Currently, existing ultra-large aperture lenses often have a relatively small field of view, generally less than 120°, and the target surface is generally 1 / 2.7 inches. However, in the field of security surveillance, a larger field of view means a wider surveillance range, and a larger target surface means better detail representation. Therefore, in view of the current situation of relatively small field of view and small target surface, it is necessary to develop a large-target-surface ultra-large aperture 4K wide-angle optical lens. Summary of the Invention

[0004] The embodiments of the present invention provide a fixed-focus lens to achieve a large-target-surface, ultra-large aperture 4K wide-angle optical lens. This lens supports a maximum target surface of 1 / 1.8 inches at a relatively low cost, the aperture number satisfies 0.8 < F < 1.2, the field of view is greater than 120°, and it meets the imaging requirements when used in an environment of -30°C to 80°C.

[0005] The embodiments of the present invention provide a fixed-focus lens, which includes a first lens with negative optical power, a second lens with negative optical power, a third lens with positive or negative optical power, a diaphragm, 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;

[0006] Among them, the first lens and the third lens are both spherical lenses, and the second lens, the fourth lens, the fifth lens, the sixth lens, and the seventh lens are all aspherical lenses.

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

[0008] Optionally, the fourth lens is a glass aspherical lens or a plastic aspherical lens.

[0009] Optionally, the first lens satisfies:

[0010] 1.5 < |f1 / f| < 4.0;

[0011] Wherein f1 represents the focal length of the first lens, and f represents the focal length of the fixed-focus lens.

[0012] Optionally, the second lens satisfies:

[0013] 2.0<|f2 / f|<5.0;

[0014] 1.0<|ET2 / CT2|<2.0;

[0015] Wherein f2 represents the focal length of the second lens, f represents the focal length of the fixed-focus lens, ET2 represents the thickness of the edge of the second lens along the axial direction or the thickness at the thickest position along the axial direction, and CT2 represents the center thickness of the second lens.

[0016] Optionally, the third lens satisfies:

[0017] |f3 / f|>5.0;

[0018] Wherein f3 represents the focal length of the third lens, and f represents the focal length of the fixed-focus lens.

[0019] Optionally, the fourth lens satisfies:

[0020] 1.5<|f4 / f|<4.0;

[0021] Wherein f4 represents the focal length of the fourth lens, and f represents the focal length of the fixed-focus lens.

[0022] Optionally, the fifth lens to the seventh lens satisfy:

[0023] 1.5<|f5 / f|<4.0;

[0024] 1.1<|f6 / f|<3.0;

[0025] 1.5<|f7 / f|<4.0;

[0026] 40 <vd5<70;

[0027] 20 <vd6<40;

[0028] 40 <vd7<70;

[0029] Wherein f5, f6 and f7 represent the focal lengths of the fifth lens, the sixth lens and the seventh lens respectively, f represents the focal length of the fixed-focus lens, and vd5, vd6 and vd7 represent the Abbe numbers of the fifth lens, the sixth lens and the seventh lens respectively.

[0030] Optionally, the object side of the first lens is convex, and the image side of the first lens is concave; the object side of the second lens is concave, and the image side of the first lens is concave or convex; the object side of the third lens is convex, and the image side of the third lens is concave; the object side of the fourth lens is convex, and the image side of the fourth lens is convex; the object side of the fifth lens is convex, and the image side of the fifth lens is convex; the object side of the sixth lens is concave, and the image side of the sixth lens is concave; the object side of the seventh lens is convex, and the image side of the seventh lens is convex.

[0031] Optionally, the fixed-focus lens satisfies:

[0032] 5.0 < TTL / f < 10.0;

[0033] where TTL represents the overall optical length of the fixed-focus lens, and f represents the focal length of the fixed-focus lens.

[0034] 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 negative optical power, a third lens with a positive or negative optical power, a diaphragm, 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; wherein, both the first lens and the third lens are spherical lenses, and the second lens, the fourth lens, the fifth lens, the sixth lens, and the seventh lens are all aspherical lenses. By setting the first lens and the second lens with negative optical powers, it plays a role in collecting light for a large-field optical system, and the second lens can correct the axial aberration while collecting light; by setting the third lens with a positive or negative optical power, it is used to correct the off-axis aberration; by setting the fourth lens with a positive optical power, it is beneficial to correct spherical aberration and coma, and helps to control the volume of the lens to meet the need for a large aperture; the combination of the fifth lens to the seventh lens is beneficial to the correction of system chromatic aberration; through the combination of spherical lenses and aspherical lenses, a large-aperture fixed-focus lens suitable for monitoring requirements under complex conditions is realized, and a large aperture with an aperture number of 0.8 < F < 1.2 can be achieved, supporting a 1 / 1.8-inch target surface, with a field-of-view angle range greater than 120°, and meeting the imaging requirements when used in an environment of -30°C to 80°C. Description of the Drawings

[0035] Figure 1 is a schematic structural diagram of a fixed-focus lens provided by the embodiment of the present invention;

[0036] Figure 2 is a schematic diagram of the axial aberration curve of a fixed-focus lens provided by the embodiment of the present invention;

[0037] Figure 3is a schematic diagram of a field curvature curve of a fixed-focus lens provided by an embodiment of the present invention;

[0038] Figure 4 is a schematic diagram of a distortion curve of a fixed-focus lens provided by an embodiment of the present invention;

[0039] Figure 5 is a schematic structural diagram of another fixed-focus lens provided by an embodiment of the present invention;

[0040] Figure 6 is a schematic diagram of an axial aberration curve of another fixed-focus lens provided by an embodiment of the present invention;

[0041] Figure 7 is a schematic diagram of a field curvature curve of another fixed-focus lens provided by an embodiment of the present invention;

[0042] Figure 8 is a schematic diagram of a distortion curve of another fixed-focus lens provided by an embodiment of the present invention;

[0043] Fig. 9 is a structural schematic diagram of another fixed-focus lens provided by an embodiment of the present invention;

[0044] Fig.10 is a schematic diagram of an axial aberration curve of another fixed-focus lens provided by an embodiment of the present invention;

[0045] Fig.11 is a schematic diagram of a field curvature curve of another fixed-focus lens provided by an embodiment of the present invention;

[0046] Fig.12 It is a schematic diagram of a distortion curve of another fixed-focus lens provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0047] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0048] 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 directional words such as "upper", "lower", "left", "right" and the like described in the embodiments of the present invention are described at the angles shown in the accompanying drawings and should not be understood as limitations on the embodiments of the present invention. In addition, in the context, it is also necessary to understand 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 indirectly formed "on" or "under" another element through an intermediate element. The terms "first", "second" and the like 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 the specific circumstances.

[0049] Figure 1 FIG. 1 is a schematic diagram of the structure of a fixed-focus lens provided by an embodiment of the present invention. Figure 1 The fixed-focus lens provided by the embodiment of the present invention comprises a first lens 10 with negative optical power, a second lens 20 with negative optical power, a third lens 30 with positive or negative optical power, an aperture 80, a fourth lens 40 with positive optical power, a fifth lens 50 with positive optical power, a sixth lens 60 with negative optical power, and a seventh lens 70 with positive optical power, which are arranged in sequence from the object side to the image side along the optical axis; wherein the first lens 10 and the third lens 30 are spherical lenses, and the second lens 20, the fourth lens 40, the fifth lens 50, the sixth lens 60, and the seventh lens 70 are aspherical lenses.

[0050] Among them, it can be understood that the optical focal length 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. The larger the absolute value of the optical focal length, the stronger the ability to bend light, and the smaller the absolute value of the optical focal length, the weaker the ability to bend light. When the optical focal length is a positive number, the refraction of light is convergent; when the optical focal length is a negative number, the refraction of light is divergent. The optical focal length can be used to characterize a certain refractive surface of a lens (i.e., a surface of a lens), can be used to characterize a certain lens, and can also be used to characterize a system formed by multiple lenses (i.e., a lens group). In this embodiment, each lens can be fixed to a lens barrel ( Figure 1Inside (not shown in the figure), by reasonably distributing the optical power and shape of the lenses, for example, setting the first lens 10 and the second lens 20 with negative optical power is beneficial for light reception, increasing the field of view angle. The third lens 30 with positive or negative optical power corrects off-axis aberrations. The diaphragm 80 can adjust the field of view size, block off-axis light rays, avoid the influence of off-axis light rays on the imaging quality, improve the image quality, and enable the lens to have a large light throughput. Optionally, the optical total length TTL of the fixed-focus lens provided in this embodiment satisfies 5.0 < TTL / f < 10.0, where f represents the focal length of the fixed-focus lens, the aperture F can reach 0.8 to 1.2, supports an image plane of 1 / 1.8 inches, and the field of view angle FOV range is greater than 120°.

[0051] In the technical solution of this embodiment, by setting the first lens and the second lens with negative optical power, it plays a role in collecting light for a large-field optical system, and the second lens can correct on-axis aberrations while collecting light; by setting the third lens with positive or negative optical power, it is used to correct off-axis aberrations; by setting the fourth lens with positive optical power, it is beneficial for correcting spherical aberration and coma, and helps to control the lens volume to meet the requirements of a large aperture; the combination of the fifth lens to the seventh lens is beneficial for correcting system chromatic aberration; through the combination of spherical lenses and aspherical lenses, a large-aperture fixed-focus lens suitable for monitoring requirements under complex conditions is realized, and a large aperture with an aperture number of 0.8 < F < 1.2 can be achieved, supports a 1 / 1.8-inch target surface, the field of view angle range is greater than 120°, and imaging requirements are met when used in an environment of -30°C to 80°C.

[0052] On the basis of the above technical solution, optionally, both the first lens 10 and the third lens 30 are glass spherical lenses, and the second lens 20, the fifth lens 50, the sixth lens 60, and the seventh lens 70 are all plastic aspherical lenses. Optionally, the fourth lens 40 is a glass aspherical lens or a plastic aspherical lens.

[0053] By setting the first lens 10 as a glass spherical lens, the glass spherical lens is easy to process and has good physical and chemical properties, and has stronger adaptability to the environment; the third lens 30 is a glass lens, which can be designed as a positive or negative optical power according to requirements and is used to correct off-axis aberrations; the fourth lens 40 is designed as a glass aspherical lens or a plastic aspherical lens, and this position is more beneficial for correcting spherical aberration and coma; the remaining lenses are all plastic aspherical lenses, which can ensure good aberration correction ability under the condition of low cost.

[0054] Optionally, the first lens 10 satisfies:

[0055] 1.5 < |f1 / f| < 4.0;

[0056] where f1 represents the focal length of the first lens 10, and f represents the focal length of the fixed-focus lens.

[0057] Optionally, the second lens 20 satisfies:

[0058] 2.0<|f2 / f|<5.0;

[0059] 1.0<|ET2 / CT2|<2.0;

[0060] Wherein f2 represents the focal length of the second lens 20 , f represents the focal length of the fixed-focus lens, ET2 represents the thickness of the edge of the second lens 20 along the axial direction or the thickness at the thickest position along the axial direction, and CT2 represents the center thickness of the second lens 20 .

[0061] Optionally, the third lens 30 satisfies:

[0062] |f3 / f|>5.0;

[0063] Wherein f3 represents the focal length of the third lens 30, and f represents the focal length of the fixed-focus lens.

[0064] Optionally, the fourth lens 40 satisfies:

[0065] 1.5<|f4 / f|<4.0;

[0066] Wherein f4 represents the focal length of the fourth lens 40, and f represents the focal length of the fixed-focus lens.

[0067] Optionally, the fifth lens 50 to the seventh lens 70 satisfy:

[0068] 1.5<|f5 / f|<4.0;

[0069] 1.1<|f6 / f|<3.0;

[0070] 1.5<|f7 / f|<4.0;

[0071] 40 <vd5<70;

[0072] 20 <vd6<40;

[0073] 40 <vd7<70;

[0074] Wherein f5, f6 and f7 represent the focal lengths of the fifth lens 50, the sixth lens 60 and the seventh lens 70 respectively, f represents the focal length of the fixed-focus lens, and vd5, vd6 and vd7 represent the Abbe numbers of the fifth lens 50, the sixth lens 60 and the seventh lens 70 respectively.

[0075] Among them, the second lens 20 is designed to meet 1.0<|ET2 / CT2|<2.0, which can ensure that the second lens 20 has good processability; the focal length range of the fourth lens 40 is designed to help control the volume of the lens and ensure the need for a large aperture; the matching of the Abbe number range of the fifth lens 50, the sixth lens 60, and the seventh lens 70 is beneficial to correcting the chromatic aberration of the lens; by comprehensively setting the optical parameters of the first lens 10 to the seventh lens 70, the aperture F can reach 0.8 to 1.2 under the condition of -30°C to 80°C, supporting a 1 / 1.8-inch image plane, and the field of view FOV range greater than 120° can be met.

[0076] Optionally, the object side surface of the first lens 10 is convex, and the image side surface of the first lens 10 is concave; the object side surface of the second lens 20 is concave, and the image side surface of the first lens 20 is concave or convex; the object side surface of the third lens 30 is convex, and the image side surface of the third lens 30 is concave; the object side surface of the fourth lens 40 is convex, and the image side surface of the fourth lens 40 is convex; the object side surface of the fifth lens 50 is convex, and the image side surface of the fifth lens 50 is convex; the object side surface of the sixth lens 60 is concave, and the image side surface of the sixth lens 60 is concave; the object side surface of the seventh lens 70 is convex, and the image side surface of the seventh lens 70 is convex.

[0077] It can be understood that, in specific implementation, the specific lens shape can be selected according to the design of the optical focal length. The above is only a specific example and is not a limitation to the embodiments of the present invention.

[0078] Optionally, the surface shape of the aspheric lens satisfies the formula:

[0079]

[0080] Among them, z represents the axial sagitta of the aspheric surface along the optical axis, r represents the distance from the point where the sagitta is calculated to the center, R represents the radius of curvature of the surface center, k represents the cone coefficient, and A, B, C, D, E, and F represent high-order aspheric coefficients.

[0081] For example, Table 1 is Figure 1 The parameter design values ​​of a specific embodiment of the fixed-focus lens are shown, and the focal length of the lens is f=4.28 mm, and the aperture number is F=1.0.

[0082] Table 1 A design value of the lens in the fixed focus lens

[0083]

[0084]

[0085] The surface numbers in Table 1 are numbered according to the order of the surfaces of each lens, where "S1" represents the front surface of the first lens 10 (the surface close to the object side), "S2" represents the rear surface of the first lens 10 (the surface close to the image side), and so on, "S16" and "S17" respectively represent the front and rear surfaces of the protective glass in front of the photosensitive chip; "STO" represents the aperture of the fixed-focus lens; the radius of curvature represents the degree of curvature of the lens surface, a positive value represents that the surface is bent toward the image side, and a negative value represents that the surface is bent toward the object side, where "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, and the refractive index represents the ability of the material between the current surface and the next surface to deflect light; the Abbe number represents the dispersion characteristics of the material between the current surface and the next surface to the light; the k value represents the numerical value of the best fitting cone coefficient of the aspheric surface.

[0086] Table 2 shows the aspheric surface parameters in this embodiment:

[0087] Table 2 A design value of aspheric coefficient in fixed focus lens

[0088]

[0089]

[0090] Among them, 1.44E-003 means that the coefficient A of the surface number S3 is 1.44×10 -3 .

[0091] Figure 2 FIG. 1 is a schematic diagram of an axial aberration curve of a fixed-focus lens provided by an embodiment of the present invention. Figure 3 FIG. 1 is a schematic diagram of a field curvature curve of a fixed-focus lens provided by an embodiment of the present invention. Figure 4 FIG. 1 is a schematic diagram of a distortion curve of a fixed-focus lens provided by an embodiment of the present invention, wherein Figures 2 to 4 It can be seen that the fixed-focus lens provided in this embodiment has good imaging capability.

[0092] Figure 5 The structure diagram of another fixed-focus lens provided by an embodiment of the present invention is shown in Table 3. The focal length of the lens is f=4.30 mm and the aperture number is F=1.0. Figure 5 Parameter design values ​​of a specific embodiment of the fixed focus lens shown:

[0093] Table 3 A design value of the lens in the fixed focus lens

[0094]

[0095]

[0096] The surface numbers in Table 3 are numbered according to the order of the surfaces of each lens, where "S1" represents the front surface of the first lens 10 (the surface close to the object side), "S2" represents the rear surface of the first lens 10 (the surface close to the image side), and so on, "S16" and "S17" respectively represent the front and rear surfaces of the protective glass in front of the photosensitive chip; "STO" represents the aperture of the fixed-focus lens; the radius of curvature represents the degree of curvature of the lens surface, a positive value represents that the surface is bent toward the image side, and a negative value represents that the surface is bent toward the object side, where "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, and the refractive index represents the ability of the material between the current surface and the next surface to deflect light; the Abbe number represents the dispersion characteristics of the material between the current surface and the next surface to the light; the k value represents the numerical value of the best fitting cone coefficient of the aspheric surface.

[0097] Table 4 shows the aspheric surface parameters in this embodiment:

[0098] Table 4 A design value of aspheric coefficient in fixed focus lens

[0099]

[0100]

[0101] Among them, 1.25E-003 means that the coefficient A of the surface number S3 is 1.25×10 -3 .

[0102] Figure 6 FIG. 1 is a schematic diagram of an axial aberration curve of another fixed-focus lens provided by an embodiment of the present invention. Figure 7 FIG. 1 is a schematic diagram of a field curvature curve of another fixed-focus lens provided by an embodiment of the present invention. Figure 8 FIG. 1 is a schematic diagram of a distortion curve of another fixed-focus lens provided by an embodiment of the present invention, wherein Figures 6 to 8 It can be seen that the fixed-focus lens provided in this embodiment has good imaging capability.

[0103] Fig. 9 The structure diagram of another fixed-focus lens provided by an embodiment of the present invention is shown in Table 5. The focal length of the lens is f=4.27 mm and the aperture number is F=1.0. Fig. 9 Parameter design values ​​of a specific embodiment of the fixed focus lens shown:

[0104] Table 5 A design value of the lens in the fixed focus lens

[0105]

[0106]

[0107] The surface numbers in Table 5 are numbered according to the order of the surfaces of each lens, where "S1" represents the front surface of the first lens 10 (the surface close to the object side), "S2" represents the back surface of the first lens 10 (the surface close to the image side), and so on, "S16" and "S17" respectively represent the front and back surfaces of the protective glass in front of the photosensitive chip; "STO" represents the aperture of the fixed-focus lens; the radius of curvature represents the degree of curvature of the lens surface, a positive value represents that the surface is bent toward the image side, and a negative value represents that the surface is bent toward the object side, where "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, and the refractive index represents the ability of the material between the current surface and the next surface to deflect light; the Abbe number represents the dispersion characteristics of the material between the current surface and the next surface to the light; the k value represents the numerical value of the best fitting cone coefficient of the aspheric surface.

[0108] Table 6 shows the aspheric surface parameters in this embodiment:

[0109] Table 6 A design value of aspheric coefficient in fixed focus lens

[0110]

[0111]

[0112] Among them, 1.49E-003 means that the coefficient A of the surface number S3 is 1.49×10 -3 .

[0113] Fig.10 FIG. 4 is a schematic diagram of an axial aberration curve of another fixed-focus lens provided by an embodiment of the present invention. Fig.11 FIG. 4 is a schematic diagram of a field curvature curve of another fixed-focus lens provided by an embodiment of the present invention. Fig.12 FIG. 1 is a schematic diagram of a distortion curve of another fixed-focus lens provided by an embodiment of the present invention, wherein Figures 10-12 It can be seen that the fixed-focus lens provided in this embodiment has good imaging capability.

[0114] Note that the above are only preferred embodiments of the present invention and the technical principles used. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments and substitutions can be made by those skilled in the art without departing from the scope of protection 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, and may include more other equivalent embodiments without departing from the concept of the present invention, 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: The invention comprises a first lens with negative optical power, a second lens with negative optical power, a third lens with positive optical power or negative optical power, an aperture, 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; Wherein, the first lens and the third lens are both spherical lenses, and the second lens, the fourth lens, the fifth lens, the sixth lens and the seventh lens are all aspherical lenses; The object side surface of the first lens is convex, and the image side surface of the first lens is concave; the object side surface of the second lens is concave, and the image side surface of the second lens is concave or convex; the object side surface of the third lens is convex, and the image side surface of the third lens is concave; the object side surface of the fourth lens is convex, and the image side surface of the fourth lens is convex; the object side surface of the fifth lens is convex, and the image side surface of the fifth lens is convex; the object side surface of the sixth lens is concave, and the image side surface of the sixth lens is concave; the object side surface of the seventh lens is convex, and the image side surface of the seventh lens is convex; The aperture number of the fixed focus lens is F, where 0.8 <F<1.2。 2. The fixed-focus lens according to claim 1, characterized in that: The first lens and the third lens are both glass spherical lenses, and the second lens, the fifth lens, the sixth lens and the seventh lens are all plastic aspherical lenses.

3. The fixed-focus lens according to claim 2, characterized in that: The fourth lens is a glass aspheric lens or a plastic aspheric lens.

4. The fixed-focus lens according to claim 1, characterized in that: The first lens satisfies: 1.5<|f1 / f|<4.0; Wherein f1 represents the focal length of the first lens, and f represents the focal length of the fixed-focus lens.

5. The fixed-focus lens according to claim 1, wherein: The second lens satisfies: 2.0<|f2 / f|<5.0; 1.0<|ET2 / CT2|<2.0; Wherein f2 represents the focal length of the second lens, f represents the focal length of the fixed-focus lens, ET2 represents the thickness of the edge of the second lens along the axial direction or the thickness at the thickest position along the axial direction, and CT2 represents the center thickness of the second lens.

6. The fixed-focus lens according to claim 1, wherein: The third lens satisfies: |f3 / f|>5.0; Wherein f3 represents the focal length of the third lens, and f represents the focal length of the fixed-focus lens.

7. The fixed-focus lens according to claim 1, wherein: The fourth lens satisfies: 1.5<|f4 / f|<4.0; Wherein f4 represents the focal length of the fourth lens, and f represents the focal length of the fixed-focus lens.

8. The fixed-focus lens according to claim 1, wherein: The fifth lens to the seventh lens satisfy: 1.5<|f5 / f|<4.0; 1.1<|f6 / f|<3.0; 1.5<|f7 / f|<4.0; 40 <vd5<70; 20 <vd6<40; 40 <vd7<70; Wherein f5, f6 and f7 represent the focal lengths of the fifth lens, the sixth lens and the seventh lens respectively, f represents the focal length of the fixed-focus lens, and vd5, vd6 and vd7 represent the Abbe numbers of the fifth lens, the sixth lens and the seventh lens respectively.

9. The fixed-focus lens according to claim 1, wherein: The fixed focus lens meets the following requirements: 5.0 <TTL / f<10.0; Wherein, TTL represents the total optical length of the fixed-focus lens, and f represents the focal length of the fixed-focus lens.

Images