Fixed-focus image capturing lens

Abstract

A fixed focus image capturing lens comprises a first lens group, an aperture diaphragm and a second lens group which are sequentially arranged from an object side to an image side. The first lens group comprises two plastic aspheric lenses, the second lens group comprises three plastic aspheric lenses, and the lens, closest to the object side, of the first lens group is a glass lens. The fixed-focus image taking lens satisfies 45 lt; lT is the length of the outer surfaces of the two outermost lenses of the fixed-focus image capturing lens on the optical axis of the fixed-focus image capturing lens, and GD is the distance between the first lens group and the second lens group on the optical axis of the fixed-focus image capturing lens. The fixed-focus image taking lens provided by the invention can reduce the manufacturing cost and consider the image quality under the condition that the fixed-focus image taking lens can tolerate relatively high temperature and temperature change of a use environment.

Description

Technical Field

[0001] The present invention relates to an imaging lens, and particularly to a fixed-focus imaging lens that can be used for security monitoring. Background Art

[0002] In recent years, electronic products with imaging functions have been applied in various fields, such as security monitoring, in-vehicle camera systems, and action cameras. In this context, an imaging lens that can balance wide viewing angle, miniaturization, and high imaging quality is required. However, due to limitations such as lens shape and lens material, existing wide-angle lenses are difficult to provide good imaging quality on a sensor with a large target surface while meeting the requirements of both a wide viewing angle and a large aperture. Summary of the Invention

[0003] Other objects and advantages of the present invention can be further understood from the technical features disclosed in the embodiments of the present invention.

[0004] An embodiment of the present invention provides a fixed-focus imaging lens, which includes a first lens group, a second lens group arranged in sequence from the object side to the image side of the fixed-focus imaging lens, and an aperture stop disposed between the first lens group and the second lens group. The number of lenses with refractive power in the fixed-focus imaging lens is 7 to 8. The first lens group includes 2 plastic aspherical lenses, the second lens group includes 3 plastic aspherical lenses, the lens closest to the object side in the first lens group is a glass lens, the diagonal field of view angle of the fixed-focus imaging lens is between 140 and 165 degrees, and the offset of the focal plane of the fixed-focus imaging lens under an 850 nm light beam and under a 550 nm light beam is less than 0.01 mm. The fixed-focus imaging lens satisfies the condition of 45 < LT / GD, where LT is the length of the outer surfaces of the two outermost lenses of the fixed-focus imaging lens on the optical axis of the fixed-focus imaging lens, and GD is the distance between the first lens group and the second lens group on the optical axis of the fixed-focus imaging lens.

[0005] Another embodiment of the present invention provides a fixed-focus imaging lens, which includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, and a seventh lens arranged in sequence from the object side to the image side of the fixed-focus imaging lens, and the aperture stop is disposed between the third lens and the fourth lens. The first lens and the fourth lens are glass lenses, and the second lens, the third lens, the fifth lens, the sixth lens, and the seventh lens are plastic aspherical lenses. The diagonal field of view angle of the fixed-focus imaging lens is between 140 and 165 degrees, and the offset of the focal plane of the fixed-focus imaging lens under an 850 nm light beam and under a 550 nm light beam is less than 0.01 mm. The fixed-focus imaging lens satisfies the condition of 45 < LT / GD, where LT is the length of the outer surfaces of the two outermost lenses of the fixed-focus imaging lens on the optical axis of the lens, and GD is the distance between the two lenses closest to the aperture stop on the optical axis of the fixed-focus imaging lens.

[0006] Through the design of each embodiment of the present invention, good imaging quality can be provided for the wavelength range of visible light and infrared light under the conditions of wide viewing angle and large aperture, and good imaging quality can be provided even when imaging on a sensor with a large target surface (image height can reach 4.4mm). In addition, the fixed-focus imaging lens of the embodiment of the present invention, by appropriately matching glass and plastic lenses with spherical and aspherical surfaces, and using a glass lens as the lens closest to the object side in the lens, can reduce manufacturing costs and take into account image quality while being able to withstand the high temperature and temperature changes of the use environment.

[0007] In order to make the above features and advantages of the present invention more obvious and easy to understand, embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 FIG. 4 is a schematic diagram of a fixed-focus imaging lens according to a first embodiment of the present invention.

[0009] Figure 2A and Figure 2B for Figure 1 The visible light fan diagram of the fixed-focus imaging lens, Figure 3A and Figure 3B for Figure 1 Infrared light fan diagram of a fixed-focus imaging lens.

[0010] Figure 4 FIG. 4 is a schematic diagram of a fixed-focus imaging lens according to a second embodiment of the present invention.

[0011] Figure 5A and Figure 5B for Figure 4 The visible light fan diagram of the fixed-focus imaging lens, Fig. 6A and Figure 6B for Figure 4 Infrared light fan diagram of a fixed-focus imaging lens.

[0012] Figure 7 FIG. 4 is a schematic diagram of a fixed-focus imaging lens according to a third embodiment of the present invention.

[0013] Fig. 8A and Figure 8B for Figure 7 The visible light fan diagram of the fixed-focus imaging lens, Fig. 9A and Fig. 9B for Figure 7 Infrared light fan diagram of a fixed-focus imaging lens.

[0014] Description of Figure Numbers:

[0015] 10a, 10b, 10c: Fixed-focus imaging lenses

[0016] 12: Optical axis

[0017] 14: Aperture diaphragm

[0018] 16: Cover

[0019] 18: Imaging surface

[0020] L1 to L8: Lens

[0021] S1 to S19: Surface

[0022] G1, G2: Lens group

[0023] OS: Physical side

[0024] IS: Image side DETAILED DESCRIPTION

[0025] The terms "first" and "second" used in the following embodiments are intended to identify the aforementioned and other technical contents, features and functions of the same or similar invention, which will be clearly presented in the detailed description of the embodiments in conjunction with the accompanying drawings. The directional terms mentioned in the following embodiments, such as up, down, left, right, front or back, etc., are only reference directions of the accompanying drawings. Therefore, the directional terms used are used to illustrate and are not used to limit the present invention. In order to show the characteristics of this embodiment, only the structures related to this embodiment are shown, and the remaining structures are omitted.

[0026] The lens referred to in the present invention refers to a component that is partially or completely made of a transparent material and has refractive power, usually including glass or plastic.

[0027] When a lens is used in an imaging system, the magnification side (object side) of the lens refers to the side on the optical path closer to the object being photographed, while the image reduction side (image side) refers to the side on the optical path closer to the image sensor.

[0028] The object-side surface (or image-side surface) of a lens has a convex portion (or concave portion) located in a certain area, which means that the area is more "convex outwardly" (or "concave inwardly") in a direction parallel to the optical axis than the outer area adjacent to the area in the radial direction.

[0029] Figure 1 Schematic diagram of a fixed-focus imaging lens according to the first embodiment of the present invention. Figure 1, in this embodiment, the fixed-focus imaging lens 10a includes a first lens group G1, a second lens group G2, and an aperture stop 14 disposed between the first lens group G1 and the second lens group G2. The refractive power of the first lens group G1 is negative and includes lenses L1, L2, and L3 arranged in sequence from the object side OS to the image side IS of the fixed-focus imaging lens 10a. The refractive power of the second lens group G2 is positive and includes lenses L4, L5, L6, and L7 arranged in sequence from the object side OS to the image side IS of the fixed-focus imaging lens 10a. Furthermore, a cover plate 16 and an image sensor (not shown in the figure) can be provided on the image side IS. The cover plate 16 can be made of any suitable light-transmitting material, such as glass material, and the cover plate 16 can be used to adjust the overall length of the fixed-focus imaging lens and can also provide a protection effect for the fixed-focus imaging lens. The imaging surface of the lens 10a on the image sensor is marked as 18. Light from the side of the object to be photographed can enter the fixed-focus imaging lens 10a and sequentially pass through the lenses L1, L2, L3, aperture stop 14, lenses L4, L5, L6, L7, and cover plate 16 to form an image on the imaging surface 18.

[0030] In the specific embodiments of the present invention, the object side OS is disposed on the left side of each figure, and the image side IS is disposed on the right side of each figure, which will not be repeated hereinafter. In this embodiment, the aperture stop 14 is disposed between the lens L3 and the lens L4, and the refractive powers of the lenses L1-L7 are negative, negative, positive, positive, positive, negative, and positive, respectively. In this embodiment, the lenses L1 and L4 are glass spherical lenses, and the lenses L2, L3, L5, L6, and L7 are plastic aspherical lenses, but the present invention is not limited thereto. The lenses L5 and L6 are joined together to form a combined lens, for example, a doublet lens is formed by gluing, but the present invention is not limited thereto. Forming a glued lens by gluing the lenses L5 and L6 can improve the chromatic aberration problem of the fixed-focus imaging lens 10a and can tolerate higher manufacturing tolerances, thereby improving the yield rate.

[0031] In a specific embodiment of the present invention, the first lens group G1 may include three lenses with refractive power. Two of the three lenses may be aspherical lenses, and the lens closest to the object side OS in the first lens group G1 is a glass lens. The second lens group G2 may include four lenses with refractive power, and at least three of the four lenses may be aspherical lenses. In a specific embodiment of the present invention, the number of lenses, the shape of the lenses, and the optical characteristics can all be designed differently according to actual needs and are not limited.

[0032] In a specific embodiment of the present invention, the fixed-focus imaging lens may meet the condition of 45 < LT / GD, where LT is the outer surface of the two outermost lenses of the fixed-focus imaging lens (for example Figure 1The length of the surfaces S1 and S14 on the lens optical axis 12. GD is the distance between the first lens group G1 and the second lens group G2 on the lens optical axis 12, that is, the distance between the two lenses closest to the aperture stop 14 (for example Figure 1 The distance between the lenses L3 and L4) on the lens optical axis 12. In a specific embodiment of the present invention, the fixed-focus imaging lens can satisfy the condition of 0.2 < IMH / LT < 0.3, where IMH is the maximum image height of the fixed-focus imaging lens. The maximum image height refers to 1 / 2 of the diameter of the largest imaging circle on the imaging surface 18 (image circle diameter). Satisfying this condition can achieve a balance between miniaturization and optical performance. In a specific embodiment of the present invention, the fixed-focus imaging lens can satisfy the condition of 0.15 < EFL / LT < 0.25, where EFL is the effective focal length of the fixed-focus imaging lens, thereby providing a better design range for the image sensor corresponding to the total lens length. In this embodiment, for the fixed-focus imaging lens 10a, LT = 19.82 mm, GD = 0.2 mm, IMH = 4.4 mm, EFL = 4.03 mm, LT / GD = 99.1, IMH / LT = 0.222, and EFL / LT = 0.203.

[0033] In a specific embodiment of the present invention, the back focal length (BFL) of the fixed-focus imaging lens is between 4 and 8 mm, and the back focal length BFL is the distance measured along the optical axis 12 from the optical surface closest to the image side IS (for example Figure 1 The surface S14 of the lens L7) to the imaging surface 18. In this embodiment, the back focal length BFL of the fixed-focus imaging lens 10a is 6.18 mm. Furthermore, in a specific embodiment of the present invention, the entrance pupil diameter of the fixed-focus imaging lens can be greater than 2 mm, and the total track length (TTL) of the fixed-focus imaging lens is between 24 and 28 mm, where the total lens length TTL is the distance measured along the optical axis 12 between the optical surface closest to the object side OS (for example Figure 1 The surface S1 of the lens L1) and the imaging surface 18.

[0034] The diagonal field of view (DFOV) refers to the light-gathering angle of the optical surface closest to the object side OS, that is, the field of view measured diagonally (diagonal field of view). In a specific embodiment of the present invention, the diagonal field of view DFOV can be between 140 degrees and 165 degrees. In this embodiment, the diagonal field of view DFOV of the fixed-focus imaging lens 10a is 160 degrees.

[0035] The aperture stop 14 achieves a similar effect by using a mechanism to block peripheral light and retain the light transmission in the middle, and the aforementioned mechanism is adjustable. The so-called adjustable refers to the adjustment of the position, shape or transparency of the mechanism. In some embodiments, the aperture stop 14 may not be an independent optical element, but the inner diameter of the lens barrel may be used as the aperture stop 14.

[0036] Alternatively, the aperture stop 14 may also be coated with an opaque light-absorbing material on the lens surface, and the central portion of the lens is left transparent to achieve the effect of limiting the light path. In this embodiment, the aperture value (F-number) of the fixed-focus imaging lens 10a is 1.9.

[0037] The lens design parameters and appearance of the fixed-focus imaging lens 10a are shown in Table 1. However, the data listed in the table below are not intended to limit the present invention, and any person skilled in the art may make appropriate changes to the parameters or settings after referring to the present invention, but they should still fall within the scope of the present invention.

[0038] Table 1 records the values ​​of the optical parameters of each lens in the optical system. The units of the radius of curvature and the spacing in Table 1 are millimeters (mm). In Table 1, the radius of curvature refers to the reciprocal of the curvature. When the radius of curvature is positive, the center of the lens surface is on the image side of the lens. When the radius of curvature is negative, the center of the lens surface is on the object side of the lens. Spacing (mm) refers to the straight-line distance between two adjacent surfaces on the optical axis 12. For example, the spacing of surface S1 is the distance between surface S1 and surface S2, and the spacing of surface S2 is the distance between surface S2 and surface S3. For the spacing, refractive index and Abbe number corresponding to each lens and each optical element in the column, please refer to the corresponding values ​​of each spacing, refractive index and Abbe number in the same column. For the parameter values ​​such as the radius of curvature and spacing of each surface, please refer to Table 1, which will not be repeated here.

[0039] Table 1

[0040]

[0041]

[0042] An aspheric lens refers to a lens whose front and rear surfaces have at least one surface whose radius of curvature changes with the central axis, and can be used to correct aberrations. In the following design examples of the present invention, the aspheric polynomial can be expressed by the following formula:

[0043]

[0044] In the above formula, Z is the offset (sag) in the direction of the optical axis, c is the reciprocal of the radius of the osculating sphere, that is, the reciprocal of the radius of curvature close to the optical axis, k is the quadratic coefficient (conic), and r is the aspheric height, that is, the height from the center of the lens to the edge of the lens. AG in Table 2 represents the coefficient values ​​of the 4th order term, 6th order term, 8th order term, 10th order term, 12th order term, 14th order term, and 16th order term of the aspheric polynomial, respectively. However, the data listed below are not intended to limit the present invention. Any person skilled in the art may make appropriate changes to the parameters or settings after referring to the present invention, but they should still fall within the scope of the present invention.

[0045] Table 2

[0046]

[0047] Figure 2A , Figure 2B , Figure 3A , Figure 3B FIG. 1 is a diagram of imaging optical simulation data of the fixed-focus imaging lens 10 a of this embodiment. Figure 2A and Figure 2B is the ray fan plot of visible light, Figure 3A and Figure 3B is a fan diagram of infrared light (850nm), wherein the X-axis is the position where the light passes through the entrance pupil, and the Y-axis is the relative value of the position where the principal light is projected onto the imaging surface. From these optical simulation data diagrams, it can be seen that the fixed-focus imaging lens 10a can control the aberration within the standard range when imaging with visible light or infrared light, thereby verifying that the fixed-focus imaging lens 10a of this embodiment can indeed have both good optical imaging quality and day and night confocal characteristics.

[0048] In a specific embodiment of the present invention, the offset between the focal plane of the fixed-focus imaging lens under the 850nm light beam and the focal plane of the fixed-focus imaging lens under the 550nm light beam can be less than 0.01mm, so that a day-night confocal effect can be achieved.

[0049] Figure 4Schematic diagram of a fixed-focus imaging lens according to a second embodiment of the present invention. The fixed-focus imaging lens 10b of this embodiment includes a lens L1, a lens L2, a lens L3, a lens L4, a lens L5, a lens L6, a lens L7, and an aperture stop 14 disposed between the lens L3 and the lens L4, which are arranged in order from the object side OS to the image side IS of the fixed-focus imaging lens 10b and have refractive power. The refractive powers of the lenses L1 to L7 are negative, negative, positive, positive, positive, positive, negative, and positive, respectively. In this embodiment, the lens L1 is a glass spherical lens, the lens L4 is a molded glass aspherical lens, and the lenses L2, L3, L5, L6, and L7 are plastic aspherical lenses, but the present invention is not limited thereto. The lens L5 and the lens L6 are bonded to each other to form a combined lens, for example, a double bonded lens is formed by bonding, but the present invention is not limited thereto. The lens L5 and the lens L6 are glued together to form a glued lens, which can improve the chromatic aberration problem of the fixed-focus imaging lens 10b and tolerate a higher manufacturing tolerance, thereby improving the yield rate.

[0050] In this embodiment, the number of lenses with refractive power in the fixed-focus imaging lens 10b is substantially seven, the diagonal field of view DFOV of the fixed-focus imaging lens 10b is 160 degrees, the back focal length BFL is 6.18 mm, LT is 18.848 mm, GD is 0.2 mm, IMH is 4.4 mm, EFL is 3.99 mm, LT / GD is 94.24, IMH / LT is 0.233, and EFL / LT is 0.212. Furthermore, in this embodiment, the aperture value (F-number) of the fixed-focus imaging lens 10b is 2.0.

[0051] Other detailed optical data of the fixed-focus imaging lens 10 b of the second embodiment are shown in Table 3 below.

[0052] Table 3

[0053]

[0054]

[0055] The quadratic surface coefficients and various aspheric coefficients of each aspheric surface of the fixed-focus imaging lens 10b are shown in Table 4.

[0056] Table 4

[0057]

[0058] Figure 5A , Figure 5B , Fig. 6A , Figure 6B FIG. 1 is a diagram of imaging optical simulation data of the fixed-focus imaging lens 10 b of this embodiment. Figure 5A and Figure 5Bis the ray fan plot of visible light, Fig. 6A and Figure 6B is a fan diagram of infrared light (850nm), wherein the X-axis is the position where the light passes through the entrance pupil, and the Y-axis is the relative value of the position where the principal light is projected onto the imaging surface. From these optical simulation data diagrams, it can be seen that the fixed-focus imaging lens 10b can control the aberration within the standard range when imaging with visible light or infrared light, thereby verifying that the fixed-focus imaging lens 10b of this embodiment can indeed have both good optical imaging quality and day and night confocal characteristics.

[0059] Figure 7 Schematic diagram of a fixed-focus imaging lens according to a third embodiment of the present invention. The fixed-focus imaging lens 10c of this embodiment includes a lens L1, a lens L2, a lens L3, a lens L4, a lens L5, a lens L6, a lens L7, a lens L8, and an aperture stop 14 disposed between the lens L4 and the lens L5, which are arranged in order from the object side OS to the image side IS of the fixed-focus imaging lens 10c and have refractive power. The refractive powers of the lenses L1 to L8 are negative, negative, positive, positive, positive, positive, positive, negative, and positive, respectively. In this embodiment, the lenses L1 and L5 are glass spherical lenses, and the lenses L2, L3, L4, L6, L7, and L8 are plastic aspherical lenses, but the present invention is not limited thereto. The lens L6 and the lens L7 are bonded to each other to form a combined lens, for example, a double bonded lens is formed by bonding, but the present invention is not limited thereto. The lens L6 and the lens L7 are glued together to form a glued lens, which can improve the chromatic aberration problem of the fixed-focus imaging lens 10c and tolerate a higher manufacturing tolerance, thereby improving the yield rate.

[0060] In this embodiment, the number of lenses with refractive power in the fixed-focus imaging lens 10c is substantially eight, the diagonal field of view DFOV of the fixed-focus imaging lens 10c is 160 degrees, the back focal length BFL is 5.8 mm, LT is 20.2 mm, GD is 0.2 mm, IMH is 4.4 mm, EFL is 4.03 mm, LT / GD is 101, IMH / LT is 0.218, and EFL / LT is 0.1995. Furthermore, in this embodiment, the aperture value (F-number) of the fixed-focus imaging lens 10c is 1.9.

[0061] Other detailed optical data of the fixed-focus imaging lens 10 c of the third embodiment are shown in Table 5 below.

[0062] Table 5

[0063]

[0064]

[0065] The quadratic surface coefficients and various aspheric coefficients of the aspheric surfaces of the fixed-focus imaging lens 10c are shown in Table 6.

[0066] Table 6

[0067]

[0068] Fig. 8A , Figure 8B , Fig. 9A , Fig. 9B FIG. 1 is a diagram of imaging optical simulation data of the fixed-focus imaging lens 10 c of this embodiment. Fig. 8A and Figure 8B is the ray fan plot of visible light, Fig. 9A and Fig. 9B is a fan diagram of infrared light (850nm), wherein the X-axis is the position where the light passes through the entrance pupil, and the Y-axis is the relative value of the position where the principal light is projected onto the imaging surface. From these optical simulation data diagrams, it can be seen that the fixed-focus imaging lens 10c can control the aberration within the standard range when imaging with visible light or infrared light, thereby verifying that the fixed-focus imaging lens 10c of this embodiment can indeed have both good optical imaging quality and day and night confocal characteristics.

[0069] In summary, the fixed-focus imaging lens of the embodiment of the present invention, by complying with the above-mentioned component characteristics and configuration conditions, can provide good imaging quality and day-night confocal effect for the wavelength range of visible light and infrared light under the conditions of wide viewing angle and large aperture, and can provide good imaging quality even when imaging on a sensor with a large target surface (image height can reach 4.4mm). In addition, the fixed-focus imaging lens of the embodiment of the present invention, by appropriately matching glass and plastic lenses with spherical and aspherical surfaces, and using a glass lens as the lens closest to the object side in the lens, can reduce manufacturing costs and take into account image quality while being able to withstand the high temperature and temperature changes of the use environment.

[0070] Although the present invention has been disclosed as above by embodiments, it is not intended to limit the present invention. Any person skilled in the art may make some changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be determined by the definition of the claims.

Claims

1. A fixed-focus imaging lens, characterized in that: Comprising: A first lens group, an aperture stop, and a second lens group arranged in sequence from the object side to the image side of the fixed-focus imaging lens, and the number of lenses with diopter in the fixed-focus imaging lens is 7 to 8; The first lens group includes 2 plastic aspherical lenses, the second lens group includes 3 plastic aspherical lenses, and the lens closest to the object side in the first lens group is a glass lens; The diagonal field of view angle of the fixed-focus imaging lens is between 140 and 165 degrees, and the offset of the focal plane of the fixed-focus imaging lens under the 850nm light beam and the 550nm light beam is less than 0.01mm, and The fixed-focus imaging lens satisfies the condition of 45 < LT / GD, where LT is the length of the outer surfaces of the two outermost lenses of the fixed-focus imaging lens on the optical axis of the fixed-focus imaging lens, and GD is the distance between the first lens group and the second lens group on the optical axis of the fixed-focus imaging lens.

2. A fixed-focus imaging lens, characterized in that: Comprising: A first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, and a seventh lens arranged in sequence from the object side to the image side of the fixed-focus imaging lens; And An aperture stop disposed between the third lens and the fourth lens; The first lens and the fourth lens are glass lenses, the second lens, the third lens, the fifth lens, the sixth lens, and the seventh lens are plastic aspherical lenses, and the diagonal field of view angle of the fixed-focus imaging lens is between 140 and 165 degrees, The offset of the focal plane of the fixed-focus imaging lens under the 850nm light beam and the 550nm light beam is less than 0.01mm, and The fixed-focus imaging lens satisfies the condition of 45 < LT / GD, where LT is the length of the outer surfaces of the two outermost lenses of the fixed-focus imaging lens on the optical axis of the fixed-focus imaging lens, and GD is the distance between the two lenses closest to the aperture stop on the optical axis of the fixed-focus imaging lens.

3. The fixed-focus imaging lens according to claim 2, wherein: The fifth lens and the sixth lens form a doublet lens.

4. The fixed-focus imaging lens according to claim 2, wherein: The diopters of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, and the seventh lens are negative, negative, positive, positive, positive, negative, and positive respectively.

5. The fixed-focus imaging lens according to claim 2, wherein: The fourth lens is a molded glass aspherical lens.

6. The fixed-focus imaging lens according to claim 1 or 2, characterized in that: The fixed-focus imaging lens satisfies the condition of 0.2 < IMH / LT < 0.3, and IMH is the maximum image height of the fixed-focus imaging lens.

7. The fixed-focus imaging lens according to claim 1 or 2, characterized in that: The fixed-focus imaging lens satisfies the condition of 0.15 < EFL / LT < 0.25, and EFL is the effective focal length of the fixed-focus imaging lens.

8. The fixed-focus imaging lens according to claim 1 or 2, wherein: The back focal length of the fixed-focus imaging lens is between 4 and 8mm.

9. The fixed-focus imaging lens according to claim 1 or 2, characterized in that: The entrance pupil diameter of the fixed-focus imaging lens is greater than 2mm.

10. The fixed-focus imaging lens according to claim 1 or 2, characterized in that: The total length of the fixed-focus imaging lens is between 24 and 28mm.

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