Prime lens

Abstract

The prime lens comprises a first lens, a second lens, a diaphragm, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens and an eighth lens which are sequentially arranged from an object plane to an image plane along an optical axis, the first lens is a biconcave plastic aspheric lens with negative focal power in the direction from the object plane to the image plane along the optical axis; the second lens is a concave-convex plastic aspheric lens with negative focal power; the third lens is a convex-concave plastic aspheric lens with positive focal power; the fourth lens is a glass spherical lens with positive focal power, and the second surface of the fourth lens is convex; the fifth lens is a biconvex plastic aspheric lens with positive focal power; the sixth lens is a biconcave plastic aspheric lens with negative focal power; the seventh lens is a biconvex plastic aspheric lens with positive focal power; and the eighth lens is a center convex-center concave type plastic aspheric lens with negative focal power. Clear imaging under a 1 / 1.8 ''target surface can be realized, and the advantages of large aperture and high image quality are realized.

Description

Technical Field

[0001] The embodiments of the present utility model relate to the technical field of optical devices, and particularly to a fixed-focus lens. Background Art

[0002] With the increasing popularity of security monitoring facilities, the market has higher and higher requirements for security monitoring lenses used. As a mainstream product in the security industry, fixed-focus lenses are very popular in the market demand. Moreover, 1 / 1.8″ chips are more and more widely used, and the requirements for the volume, aperture and usage environment of the lenses matched with them are also becoming more and more strict.

[0003] Currently, the mainstream optical lenses in the market that are matched with 1 / 1.8″ have a small aperture and are too large in volume, which is not conducive to the use and promotion of products. Summary of the Utility Model

[0004] The present utility model provides a fixed-focus lens, which can achieve clear imaging under a 1 / 1.8″ target surface, has the advantages of a large aperture and high image quality, and is suitable for the security use requirements in more cases.

[0005] The embodiments of the present application provide a fixed-focus lens, which includes a first lens, a second lens, a diaphragm, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens and an eighth lens arranged in sequence along the optical axis from the object surface to the image surface;

[0006] Along the direction of the optical axis from the object surface to the image surface, the first lens is a negative-power biconcave plastic aspherical lens; the second lens is a negative-power concave-convex plastic aspherical lens; the third lens is a positive-power convex-concave plastic aspherical lens; the fourth lens is a positive-power glass spherical lens with a convex second surface; the fifth lens is a positive-power biconvex plastic aspherical lens; the sixth lens is a negative-power biconcave plastic aspherical lens; the seventh lens is a positive-power biconvex plastic aspherical lens; the eighth lens is a negative-power center-convex center-concave plastic aspherical lens.

[0007] Optionally, the focal length of the first lens is f1, the focal length of the second lens is f2, and the focal length of the fixed-focus lens is f, satisfying the following relationship:

[0008] -6.19 < (f1 + f2) / f < -5.27.

[0009] Optionally, the maximum aperture of the first lens is Φ, and it is the largest aperture among all the lenses of the entire fixed-focus lens; the optical total length of the fixed-focus lens is TTL, satisfying the following relationship:

[0010] 0.49 < Φ / TTL < 0.52.

[0011] Optionally, the focal length of the third lens is f3, the focal length of the fourth lens is f4, and the focal length of the fixed-focus lens is f, satisfying the following relationship:

[0012] 5.95 < (f3 + f4) / f < 6.85.

[0013] Optionally, the focal length of the fourth lens is f4, and the focal length of the fixed-focus lens is f, satisfying the following relationship:

[0014] 1.90 ≤ f4 / f ≤ 3.16.

[0015] Optionally, the refractive index of the fourth lens is nd4, and the Abbe number is vd4, satisfying the following requirements:

[0016] 1.43 ≤ nd4 ≤ 1.80; 37.00 ≤ vd4 ≤ 94.50.

[0017] Optionally, the focal length of the fifth lens is f5, the focal length of the sixth lens is f6, the focal length of the seventh lens is f7, and the focal length of the fixed-focus lens is f, satisfying the following relationship:

[0018] 1.59 < (f5 + f6 + f7) / f < 2.12.

[0019] Optionally, the focal length of the third lens is f3, the focal length of the eighth lens is f8, and the focal length of the fixed-focus lens is f, satisfying the following relational expression:

[0020] 3.53 < f3 / f < 4.95; -6.22 < f8 / f < -2.92.

[0021] Optionally, along the optical axis from the object plane to the image plane, the maximum sagittal height of the second surface of the eighth lens is SAG; the maximum aperture of the eighth lens is Φ, satisfying the following relationship:

[0022] 0.13 < SAG / Φ < 0.17.

[0023] Optionally, it further includes a flat glass, and the flat glass is located in the optical path between the eighth lens and the image plane.

[0024] The fixed-focus lens provided by the embodiment of the present application adopts 7 plastic aspherical lenses and 1 glass spherical lens, namely the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the seventh lens, and the eighth lens arranged in sequence along the optical axis from the object plane to the image plane. By reasonably setting the number of lenses in the fixed-focus lens and the combination relationship of the optical powers of each lens, clear imaging can be achieved under a 1 / 1.8″ target surface, and it has the advantages of a large aperture and high image quality, and is suitable for the security use requirements in more cases. Description of the Drawings

[0025] Figure 1 Schematic diagram of the structure of a fixed-focus lens provided in the first embodiment of the present application;

[0026] Figure 2 Axial aberration curve diagram of a fixed-focus lens provided in the first embodiment of the present application;

[0027] Figure 3 Ray fan diagram of a fixed-focus lens provided in the first embodiment of the present application;

[0028] Figure 4 Lateral chromatic aberration diagram of a fixed-focus lens provided in the first embodiment of the present application;

[0029] Figure 5 Schematic diagram of the structure of a fixed-focus lens provided in the second embodiment of the present application;

[0030] Figure 6 Axial aberration curve diagram of a fixed-focus lens provided in the second embodiment of the present application;

[0031] Figure 7 Ray fan diagram of a fixed-focus lens provided in the second embodiment of the present application;

[0032] Figure 8 Lateral chromatic aberration diagram of a fixed-focus lens provided in the second embodiment of the present application;

[0033] Figure 9 Schematic diagram of the structure of a fixed-focus lens provided in the third embodiment of the present application;

[0034] Figure 10 Axial aberration curve diagram of a fixed-focus lens provided in the third embodiment of the present application;

[0035] Figure 11 Ray fan diagram of a fixed-focus lens provided in the third embodiment of the present application;

[0036] Figure 12 Lateral chromatic aberration diagram of a fixed-focus lens provided in the third embodiment of the present application. Detailed implementation manners

[0037] The present application 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 application, rather than limiting the present application. Additionally, it should be noted that for the convenience of description, only parts related to the present application rather than all structures are shown in the drawings.

[0038] Figure 1 Schematic diagram of the structure of a fixed-focus lens provided in the first embodiment of the present application. As Figure 1As shown in the figure, the fixed-focus lens 100 provided by the embodiment of the present application includes a first lens 11, a second lens 12, a third lens 13, a fourth lens 14, a fifth lens 15, a sixth lens 16, a seventh lens 17, and an eighth lens 18 arranged in sequence along the optical axis from the object plane to the image plane; along the direction of the optical axis from the object plane to the image plane, the first lens 11 is a negative-power biconcave plastic aspherical lens; the second lens 12 is a negative-power concave-convex plastic aspherical lens; the third lens 13 is a positive-power convex-concave plastic aspherical lens; the fourth lens 14 is a glass spherical lens with a convex second surface and positive power; the fifth lens 15 is a positive-power biconvex plastic aspherical lens; the sixth lens 16 is a negative-power biconcave plastic aspherical lens; the seventh lens 17 is a positive-power biconvex plastic aspherical lens; the eighth lens 18 is a negative-power center-convex center-concave plastic aspherical lens.

[0039] Among them, the optical power is equal to the difference between the converging degree of the image plane light beam and the converging degree of the image plane light beam, which characterizes the ability of the optical system to deflect light rays. The larger the absolute value of the optical power, the stronger the bending ability of the light rays, and the smaller the absolute value of the optical power, the weaker the bending ability of the light rays. When the optical power is positive, the refraction of the light rays is convergent; when the optical power is negative, the refraction of the light rays is divergent. The optical power can be used to characterize a certain refracting surface of a lens (i.e., a surface of the lens), can be used to characterize a certain lens, or can be used to characterize a system formed by multiple lenses together (i.e., a lens group).

[0040] Exemplarily, referring to Figure 1 As shown in the figure, along the direction of the optical axis from the object plane M1 to the image plane M2, the first lens 11 has negative power, the second lens 12 has negative power, the third lens 13 has positive power, the fourth lens 14 has positive power, the fifth lens 15 has positive power, the sixth lens 16 has negative power, the seventh lens 17 has positive power, and the eighth lens 18 has negative power.

[0041] Referring to Figure 1As shown in the figure, the surface of the lens on the side closer to the object plane M1 is the object side surface, and the surface of the lens on the side closer to the image plane M2 is the image side surface. The object side surface of the first lens 11 is concave, the image side surface of the first lens 120 is concave, and the surface type is double concave; the object side surface of the second lens 12 is concave, the image side surface of the second lens 120 is convex, and the surface type is concave-convex; the object side surface of the third lens 13 is convex, the image side surface of the third lens 13 is concave, and the surface type is convex-concave; the object side surface of the fourth lens 14 is flat, the image side surface of the fourth lens 14 is convex, and the surface type is plano-convex; the object side surface of the fifth lens 15 is convex, the image side surface of the fifth lens 15 is convex, and the surface type is double convex; the object side surface of the sixth lens 16 is concave, the image side surface of the sixth lens 16 is concave, and the surface type is double concave; the object side surface of the seventh lens 17 is convex, the image side surface of the seventh lens 17 is convex, and the surface type is double convex; the object side surface of the eighth lens 18 is convex at the center, the image side surface of the eighth lens 18 is concave at the center, and the surface type is convex at the center-concave at the center. Through the surface type matching of the above lenses, not only can the optical power be reasonably distributed, but also the space can be effectively saved, and the use scenarios of the lens can be expanded.

[0042] Among them, the double concave surface type of the first lens 11 and the concave-convex surface type of the second lens 12 form a lens with negative optical power, which can ensure that the light has a larger aperture before entering the aperture STO, thereby increasing the aperture of the lens; by setting the aperture STO in the optical path between the second lens 12 and the third lens 13, the propagation angle of light can be restricted, the propagation direction of the light beam can be adjusted, and the incident angle of light can be adjusted, which is beneficial to improving the imaging quality of the lens; at the same time, the convex-concave surface type of the third lens 13 and the convex surface type of the second surface of the fourth lens 14 form two lens groups with positive optical power. The two cooperate with each other to ensure that the light passes through the aperture STO smoothly, can avoid stray light such as reflection at the position of the aperture STO, and can adjust the aberration of the lens to a certain extent, ensuring the aberration balance and the stability of high and low temperature performance of the lens.

[0043] In addition, the double convex surface type of the fifth lens 15, the double concave surface type of the sixth lens 16, and the double convex surface type of the seventh lens 17 can form a three-lens group with positive optical power. The lens group composed of the three can better correct the chromatic aberration of the light passing through the aperture STO, make the light pass through smoothly, and ensure clear imaging of the lens under the 1 / 1.8″ target surface.

[0044] Among them, considering that the cost of the plastic lens is much lower than that of the glass lens, the first lens 11, the second lens 12, the third lens 13, the fifth lens 15, the sixth lens 16, the seventh lens 17, and the eighth lens 18 are all plastic aspherical lenses. This setting not only meets the high pixel requirements of the lens but also reduces costs. Further, considering that the glass material has more stable performance than the plastic material in high and low temperature environments, the fourth lens 14 is set as a glass aspherical lens. At the same time, placing the fourth lens 14 near the aperture ST0 can effectively correct the off-axis image quality and axial chromatic aberration while ensuring no focus shift in high and low temperatures.

[0045] Furthermore, in cooperation with the center-convex and center-concave aspherical lens of the eighth lens 18, it is possible to minimize the remaining high-order aberrations of the lens, expand the lens target surface (size), and improve the image quality to meet the usage requirements in more situations.

[0046] In addition, these two types of materials, glass and plastic, can compensate for each other, and can well balance the expansion and contraction amounts at the front and rear ends of the lens under temperature changes, which is beneficial to improving the overall high and low temperature performance of the lens. Using a combination of glass lenses and plastic lenses in the lens can better balance the resolution of the lens in high and low temperature states. At the same time, using a reasonable combination of glass lenses also has a good correction effect on the aberrations of the lens. Using the above materials can ensure that the lens has good resolution in the range of -40 to 80 °C, meeting the application requirements in various security environments.

[0047] It should be noted that the materials of the above plastic aspherical lenses can be various plastics known to those skilled in the art, and the materials of the glass spherical lenses can be various types of glass known to those skilled in the art. The embodiments of the present application do not elaborate or limit this.

[0048] Refer to Figure 1 As shown, each lens of the fixed-focus lens provided by the embodiment of the present application can be fixed in a lens barrel for sealing or vacuum packaging. The user fixes each lens to ensure the stability and clarity of each lens surface and the imaging quality. The embodiments of the present application do not show them one by one.

[0049] The fixed-focus lens provided by the embodiment of the present application uses 7 plastic aspherical lenses and 1 glass spherical lens, and can achieve clear imaging under a 1 / 1.8″ target surface, with the advantages of a large aperture and high image quality, and is suitable for the security use requirements in most situations.

[0050] Optionally, the fixed-focus lens 100 may further include a flat glass CG, which is arranged in the optical path between the eighth lens 18 and the image plane M2. The flat glass CG can protect the photosensitive chip in the imaging sensor. Among them, the imaging chip is used to convert the optical signal collected by the fixed-focus lens into an electrical signal, thereby ensuring the imaging effect of the fixed-focus lens.

[0051] Furthermore, by reasonably setting one or more of the parameters such as the curvature radius, central thickness, focal length, refractive index, and Abbe number of the lens, a low-cost fixed-focus lens design with a small volume and a large aperture can be achieved.

[0052] Optionally, continue to refer to Figure 1 As shown, the focal length of the first lens 11 is f1, the focal length of the second lens 12 is f2, and the focal length of the fixed-focus lens 100 is f, satisfying the following relationship: -6.19 < (f1 + f2) / f < -5.27.

[0053] Specifically, both the first lens 11 and the second lens 12 are plastic aspherical lenses with a negative optical power. The combination of the negative optical powers of the two lenses can diverge light, expand the beam aperture before the light enters the aperture STO, increase the light input amount of the optical fiber into the aperture STO, and adapt to clear imaging of the fixed-focus lens in the dark or dim light environment, thereby expanding the applicable environment of the lens for security protection.

[0054] Optionally, continue to refer to Figure 1 As shown, the maximum aperture of the first lens 11 is Φ, and it is the largest aperture among all the lenses of the fixed-focus lens 100; the overall optical length of the fixed-focus lens 100 is TTL, satisfying the following relationship: 0.49 < Φ / TTL < 0.52.

[0055] Specifically, by reasonably controlling the ratio relationship between the maximum aperture Φ of the first lens 11 and the overall optical length TTL of the fixed-focus lens 100, the volume of the fixed-focus lens can be effectively compressed to achieve miniaturization of the lens. At the same time, the field of view angle and light input amount of the lens can be increased to meet the usage requirements under more stringent conditions of security protection.

[0056] Optionally, continue to refer to Figure 1 As shown, the focal length of the fourth lens 14 is f4, and the focal length of the fixed-focus lens 100 is f, satisfying the following relationship: 1.90 ≤ f4 / f ≤ 3.16.

[0057] Specifically, when the ratio of the focal length f4 of the fourth lens 14 to the focal length f of the fixed-focus lens 100 satisfies this range setting, a reasonable combination of the optical powers of the fourth lens 14 and other lenses can be achieved, enabling light to pass through the lens more smoothly, largely correcting the influence of the high-order aberrations of the lens on the imaging quality, and improving the imaging clarity.

[0058] Optionally, continue to refer to Figure 1 As shown, the refractive index of the fourth lens 14 is nd4, and the Abbe number is vd4, satisfying the following requirements: 1.43 ≤ nd4 ≤ 1.80; 37.00 ≤ vd4 ≤ 94.50.

[0059] Among them, the refractive index is the ratio of the speed of light in a vacuum to the speed of light in the medium, mainly used to describe the refractive ability of the material, and the refractive indices of different materials are different. The Abbe number is an index used to represent the dispersion ability of a transparent medium. The more severe the medium dispersion, the smaller the Abbe number; conversely, the milder the medium dispersion, the larger the Abbe number.

[0060] Specifically, the fourth lens 14 uses a glass spherical lens. The glass lens has a wide range of refractive index and Abbe number matching options. By reasonably matching the refractive index nd4 and Abbe number vd4 of the fourth lens 14, the chromatic aberration of the lens can be corrected to a large extent, which is more conducive to forming an approximate gluing effect with other lenses for achromatism. For example, the third lens 13 and the fourth lens 14 can be arranged in contact.

[0061] Optionally, continue to refer to Figure 1 As shown, the focal length of the third lens 13 is f3, the focal length of the fourth lens 14 is f4, and the focal length of the fixed-focus lens 100 is f, satisfying the following relationship: 5.95 < (f3 + f4) / f < 6.85.

[0062] Specifically, the third lens 13 uses a plastic aspherical lens, and the fourth lens 14 uses a glass spherical lens. Using the above glass lens combination can ensure good resolution under the above temperature conditions and expand the usage range of the lens. When light passes through the aperture STO and enters the third lens 13 and the fourth lens 14, setting the sum of the focal length f3 of the third lens 13 and the focal length f4 of the fourth lens 14 within the above range has a large focal length sum, which is conducive to converging light to the fifth lens 15, and can avoid excessive pressure on the rear lenses during the correction of chromatic aberration, spherical aberration, and incident angle, reducing the difficulty of lens processing; in addition, using a plastic aspherical lens for the third lens 13 is also conducive to correcting the above spherical aberration.

[0063] Optionally, continue to refer to Figure 1 As shown, the focal length of the fifth lens 15 is f5, the focal length of the sixth lens 16 is f6, the focal length of the seventh lens 17 is f7, and the focal length of the fixed-focus lens 100 is f, satisfying the following relationship:

[0064] 1.59 < (f5 + f6 + f7) / f < 2.12.

[0065] Specifically, it is set that the fifth lens 15, the sixth lens 16, and the seventh lens 17 all use plastic aspherical lenses. After the third lens 13 and the fourth lens 14 eliminate certain aberrations for the light rays, the aspherical lens L5 can eliminate the high-order aberrations and residual spherical aberrations that the front-end lenses have not eliminated. When paired with the sixth lens 16 and the seventh lens 17, which are also aspherical lenses, it can eliminate the remaining high-order aberrations to the greatest extent. In addition, such a combination of optical powers enables the light rays to pass smoothly through the rear end of the lens. At the same time, the reasonable combination of the optical powers of the fifth lens 15, the sixth lens 16, and the seventh lens 17 can also keep the chief ray angle within a suitable range, and can also adjust the height of the intersection of the chief ray of the maximum field of view and the image plane at the end of the optical system to adapt to various chips, saving the lens cost on the other hand.

[0066] Optionally, continue to refer to Figure 1 As shown, the focal length of the third lens 13 is f3, the focal length of the eighth lens 18 is f8, and the focal length of the fixed-focus lens 100 is f, satisfying the following relational expressions:

[0067] 3.53 < f3 / f < 4.95; -6.22 < f8 / f < -2.92.

[0068] Specifically, both the third lens 13 and the eighth lens 18 use plastic aspherical lenses. The third lens 13 uses a positive optical power to better converge the light rays at the front end of the lens and reduce the pressure at the rear end. The eighth lens 18 uses a negative optical power to enable the light rays to hit the chip target surface smoothly after correcting various aberrations. Using lenses with such a combination of optical powers can enable the light rays to pass smoothly through the entire lens and avoid large and difficult-to-correct aberrations.

[0069] Optionally, continue to refer to Figure 1 As shown, along the direction of the optical axis from the object plane to the image plane, the maximum sagittal height of the second surface of the eighth lens 18 is SAG; the maximum aperture of the eighth lens 18 is Φ, satisfying the following relationship:

[0070] 0.13 < SAG / Φ < 0.17.

[0071] Specifically, the eighth lens 18 uses a plastic aspherical lens. After the light rays pass through the fifth lens 15, the sixth lens 16, and the seventh lens 17 to eliminate certain aberrations, the aspherical lens L8 can further eliminate the high-order aberrations and residual spherical aberrations that the front end has not eliminated. In addition, setting the ratio of the maximum sagittal height SAG to the maximum aperture Φ of the eighth lens 18 to satisfy the range of 0.13 to 0.17 can adjust the height of the intersection of the chief ray of the maximum field of view and the image plane at the end of the optical system to adapt to various chips, increasing the application range and saving the lens cost.

[0072] As a feasible implementation manner, Table 1 shows the optical physical parameters of the first lens 11 to the eighth lens 18 in the fixed-focus lens 100 provided in the first embodiment of the present application. Table 2 shows the aspheric coefficient values of the aspheric lenses in the fixed-focus lens 100 provided in the first embodiment of the present application.

[0073] Table 1 Design values of the optical physical parameters of the fixed-focus lens

[0074]

[0075] Among them, the surface numbers in Table 1 are numbered according to the surface order of each lens. For example, the surfaces with surface numbers S1 and S2 are the object side and the image side of the first lens 11 respectively, and the surfaces with surface numbers S3 and S4 are the object side and the image side of the second lens 12 respectively, and so on; "STO" represents the aperture stop of the fixed-focus lens; the radius of curvature R represents the degree of curvature of the corresponding lens surface. A positive value represents that the surface bends towards the image side, and a negative value represents that the surface bends towards the object side. Among them, "INF" means that the surface is a plane and the radius of curvature is infinite. The thickness T represents the central axial distance from the current surface to the next surface. The units of the radius of curvature and the thickness are both millimeters (mm); the refractive index Nd 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.

[0076] Table 2 Aspheric coefficients of the fixed-focus lens

[0077] Surface Serial Number k a4 a6 a8 S1 299.37 1.383934067E-03 -1.266482704E-04 9.549258420E-06 S2 -1.33 2.809793100E-03 -2.640719281E-05 -2.545178047E-05 S3 -7.42 -3.181977931E-04 6.690489432E-04 -6.198716184E-05 S4 2.25 1.008695999E-02 1.557694524E-04 -1.106866123E-04 S6 -13.09 -5.096942153E-04 1.353270146E-04 -1.391019927E-05 S7 -57.49 -3.670101120E-03 2.979606028E-04 -1.335719302E-05 S10 -6.43 2.086255992E-03 -2.924957570E-04 1.441786318E-07 S11 -5.43 -1.145264169E-03 -9.497423629E-05 3.533012679E-07 S12 -8.02 3.176322174E-03 -1.560709980E-05 -1.798805067E-05 S13 -187.05 7.407357002E-04 7.980440993E-04 -1.007783362E-04 S14 -38.61 1.794624482E-04 2.140360078E-04 -1.629269229E-05 S15 -4.57 -5.275001420E-04 -2.007707319E-05 -8.347435081E-08 S16 -5.40 -4.745782110E-03 1.871249553E-05 2.862868931E-06 S17 -4.35 -4.884044201E-03 1.243172781E-04 -1.389932333E-06 Surface Serial Number a10 a12 a14 a16 S1 -4.064858918E-07 8.009868156E-09 -9.919074716E-12 -1.237964621E-12 S2 6.955532257E-06 -4.364002336E-07 -5.473472810E-09 9.391372777E-10 S3 1.711910943E-06 3.585487232E-07 -3.138297035E-08 6.596831318E-10 S4 2.567388948E-05 -2.555210279E-06 1.119590093E-07 -5.381050819E-10 S6 6.522501510E-07 -2.903503346E-09 -7.854255314E-10 1.889994611E-11 S7 2.843027845E-07 -9.892614459E-10 -8.402689428E-11 1.850963114E-12 S10 2.138980467E-06 -1.340307129E-07 2.692003581E-09 -3.114493777E-12 S11 7.138148860E-07 -4.298459323E-08 8.581115933E-10 -5.881179334E-13 S12 4.141412978E-07 3.659847102E-08 -1.363188051E-09 1.211730502E-12 S13 5.075892015E-06 -9.803437153E-08 6.062526090E-10 -1.180703243E-11 S14 3.870603705E-07 5.385078734E-09 3.513389042E-11 -6.746665058E-12 S15 3.283571488E-07 -2.696330645E-08 6.418317613E-10 -1.785250871E-12 S16 -4.277652166E-07 6.775574825E-09 4.706014392E-10 -7.240035457E-12 S17 -1.990107070E-07 1.630779044E-08 -4.211236774E-10 3.559688835E-12

[0078] Among them, -4.064858918E-07 in Table 2 means that the coefficient a10 of the surface with surface number S1 is -4.064858918×10 -7 , and so on.

[0079] In the first embodiment of the present application, the aspheric lenses of the fixed-focus lens 100 satisfy the following formula:

[0080]

[0081] Among them, Z is the axial distance from the vertex of the surface to the surface at the position perpendicular to the optical axis with a height of r along the optical axis direction; c represents the curvature at the vertex of the aspheric surface; a4, a6, a8, a10, a12, a14, a16 are the fourth-order, sixth-order, eighth-order, tenth-order, twelfth-order, fourteenth-order, and sixteenth-order high-order aspheric coefficients of the corresponding aspheric surface, a i r i Combined into the high-order terms of the corresponding aspheric surface; k is the conic coefficient; among them, the units of Z, r, and c are all mm.

[0082] The fixed-focus lens 100 of the first embodiment has achieved the following technical indicators:

[0083] The focal length f of the fixed-focus lens 100 is 4.9097 mm, and the f-number F / # is 1.08178.

[0084] Furthermore, multiple performance tests were conducted on the fixed-focus lens 100 provided in the first embodiment, and the test results are as follows:

[0085] Figure 2 It is a schematic diagram of an axial aberration curve provided in the first embodiment of the present application. As Figure 2 shown, the vertical direction is the normalized aperture, 0 indicates on the optical axis, and the vertex in the vertical direction represents the maximum pupil radius; the horizontal direction represents the offset relative to the ideal focus, in millimeters (mm). Different linear curves in the figure represent different wavelengths of the system imaging. It can be Figure 2 seen that the axial aberrations of different wavelengths from 0 to 1.0 normalized aperture are all controlled within the range of (-0.02 mm, +0.02 mm), indicating that the spherical aberration of the fixed-focus lens 100 provided in the first embodiment of the present application is well controlled and can meet the requirements of wide-spectrum applications.

[0086] Figure 3 It is a schematic diagram of a ray fan diagram provided in the first embodiment of the present application. The ray fan diagram is one of the commonly used evaluation methods by current optical designers. As Figure 3 shown, in a single figure, the abscissa is the normalized beam aperture, and the ordinate is the lateral aberration. Ideally, each curve should completely coincide with the horizontal axis, and at this time, all rays in the field of view focus on the same point on the image plane; the ordinate in a single image can also represent the maximum dispersion range of the beam on the ideal image plane. The ray fan diagram can not only reflect the monochromatic aberration of different wavelengths but also represent the magnitude of the lateral chromatic aberration. It can be Figure 3 seen that this optical system is well approximated to the horizontal axis at each wavelength in each field of view, indicating that the lateral aberration of each wavelength is well corrected. In addition, the curves of each color do not show obvious dispersion, indicating that this optical system also has good correction for chromatic aberration, thus ensuring the imaging requirement of the fixed-focus lens 100 provided in the first embodiment to form clear images in the full wavelength range.

[0087] Figure 4 It is an axial chromatic aberration diagram of a fixed-focus lens provided in the embodiment of the present application. As Figure 4 shown, the vertical direction represents the normalization of the aperture, 0 indicates on the optical axis, and the vertex in the vertical direction represents the maximum pupil radius; the principal wavelength is 546.074 nm, and the horizontal direction represents the offset relative to the principal wavelength, in micrometers (um). It can be Figure 4It can be seen that the lateral chromatic aberrations of different wavelengths are all controlled within a reasonable range, indicating that the lateral chromatic aberration of the fixed-focus lens 100 provided in the first embodiment of the present application is well controlled and can meet the wide-spectrum application requirements of the full wavelength band.

[0088] In summary, the fixed-focus lens provided in the first embodiment of the present application adopts a glass-plastic hybrid method, which can take into account the design requirements of small size, large aperture, and low cost, and realizes large aperture, high image quality, and clear imaging under a 1 / 1.8″ target surface, and is suitable for security use requirements in most cases.

[0089] Embodiment 2

[0090] Figure 5 FIG. is a schematic structural diagram of a fixed-focus lens provided in the second embodiment of the present application. As Figure 5 shown, the fixed-focus lens 200 provided in the second embodiment of the present application includes a first lens 21, a second lens 22, a stop STO, a third lens 23, a fourth lens 24, a fifth lens 25, a sixth lens 26, a seventh lens 27, and an eighth lens 28 arranged in sequence along the optical axis from the object plane to the image plane; in the direction of the optical axis from the object plane to the image plane, the first lens 21 is a negative-power biconcave plastic aspherical lens; the second lens 22 is a negative-power concave-convex plastic aspherical lens; the third lens 23 is a positive-power convex-concave plastic aspherical lens; the fourth lens 24 is a glass spherical lens with a convex second surface and positive power; the fifth lens 25 is a positive-power biconvex plastic aspherical lens; the sixth lens 26 is a negative-power biconcave plastic aspherical lens; the seventh lens 27 is a positive-power biconvex plastic aspherical lens; the eighth lens 28 is a negative-power center-convex center-concave plastic aspherical lens.

[0091] As a feasible implementation manner, Table 3 shows the optical physical parameters of the first lens 21 to the eighth lens 28 in the fixed-focus lens 200 provided in the second embodiment of the present application. Table 4 shows the aspherical coefficient values of the aspherical lenses in the fixed-focus lens 200 provided in the second embodiment of the present application.

[0092] Table 3 Design values of optical physical parameters of the fixed-focus lens

[0093]

[0094] Among them, the surface numbers in Table 3 are numbered according to the surface order of each lens. For example, the surfaces with surface numbers S1 and S2 are the object side and image side of the first lens 21 respectively, the surfaces with surface numbers S3 and S4 are the object side and image side of the second lens 22 respectively, and so on; "STO" represents the aperture of the fixed-focus lens; the radius of curvature R represents the degree of curvature of the corresponding lens surface. A positive value represents that the surface bends towards the image side, and a negative value represents that the surface bends towards the object side. Among them, "INF" indicates that the surface is a plane and the radius of curvature is infinite. The thickness T represents the central axial distance from the current surface to the next surface. The units of the radius of curvature and thickness are both millimeters (mm); the refractive index Nd 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.

[0095] Aspherical coefficients of the fixed-focus lens in Table 4

[0096] Surface Serial Number k a4 a6 a8 S1 320.69 1.479868834E-03 -1.352834679E-04 9.594063875E-06 S2 -1.12 2.794382855E-03 -5.200212140E-05 -3.083579573E-05 S3 -7.37 -1.152956684E-03 5.783457520E-04 -6.873252096E-05 S4 2.26 1.007032655E-02 1.064652869E-04 -1.126133028E-04 S6 -16.96 -5.577760393E-04 1.354923068E-04 -1.421578936E-05 S7 -47.31 -3.633045995E-03 2.999644966E-04 -1.334716065E-05 S10 -7.42 2.069755169E-03 -2.967634284E-04 -5.389600737E-08 S11 -286.04 -1.148482290E-03 -9.707191131E-05 2.260597162E-07 S12 -7.99 3.162188736E-03 -1.663732229E-05 -1.794454307E-05 S13 -179.83 7.527068681E-04 7.975756613E-04 -1.008373482E-04 S14 -38.87 1.759461401E-04 2.140842532E-04 -1.627976091E-05 S15 -4.83 -4.061199889E-04 -1.726079973E-05 -2.178993474E-07 S16 -5.53 -4.361169823E-03 3.906316961E-05 2.588110881E-06 S17 -5.09 -4.396860005E-03 1.154930491E-04 -1.853404328E-06 Surface Serial Number a10 a12 a14 a16 S1 -4.184916896E-07 7.653361128E-09 -9.461358289E-12 -1.074171065E-12 S2 7.309476582E-06 -4.315821778E-07 -5.038342383E-09 1.533295145E-09 S3 2.077137511E-06 3.651823077E-07 -3.398394980E-08 1.023648829E-09 S4 2.559324502E-05 -2.553486332E-06 1.136412448E-07 -6.830689342E-10 S6 6.688395465E-07 -2.256145917E-09 -7.710084714E-10 1.160564817E-11 S7 2.950109319E-07 -5.493904568E-10 -1.008275371E-10 -1.225541157E-12 S10 2.142826746E-06 -1.337354335E-07 2.708491772E-09 -2.623718285E-12 S11 7.177517811E-07 -4.298979446E-08 8.475491718E-10 -1.524620917E-12 S12 4.069473878E-07 3.625134556E-08 -1.380084069E-09 6.744311778E-14 S13 5.078090037E-06 -9.807146087E-08 6.120397973E-10 -1.185142131E-11 S14 3.863330877E-07 5.357870312E-09 3.343382837E-11 -6.325349231E-12 S15 3.379322292E-07 -2.689976534E-08 6.232912167E-10 -1.155503679E-12 S16 -3.947119108E-07 8.856058546E-09 5.439925720E-10 -1.512895026E-11 S17 -1.883119014E-07 1.590047802E-08 -4.660594690E-10 4.017664789E-12

[0097] Among them, -4.184916896E-07 in Table 4 indicates that the coefficient a10 of the surface with surface number S1 is -4.184916896×10 -7 , and so on.

[0098] In the second embodiment of the present application, the aspherical lens of the fixed-focus lens 200 satisfies the following formula:

[0099]

[0100] Among them, Z is the axial distance from the vertex of the surface at the position perpendicular to the optical axis with a height of r along the optical axis direction to the vertex of this surface; c represents the curvature at the vertex of the aspherical surface; a4, a6, a8, a10, a12, a14, a16 are the fourth-order, sixth-order, eighth-order, tenth-order, twelfth-order, fourteenth-order, and sixteenth-order high-order aspherical coefficients of the corresponding aspherical surface. a i r i Combined to form the high-order terms of the corresponding aspherical surface; k is the conic coefficient; among them, the units of Z, r, and c are all mm.

[0101] The fixed-focus lens 200 in the second embodiment has reached the following technical indicators:

[0102] The focal length f of the fixed-focus lens 200 is 4.9098 mm, and the f-number F / # is 1.08020.

[0103] Furthermore, a number of performance tests were carried out on the fixed-focus lens 200 provided in the second embodiment, and the test results are as follows:

[0104] Figure 6 This is the axial aberration curve diagram of a fixed-focus lens provided in the second embodiment of the present application. As Figure 6As shown, the vertical direction is the normalized aperture, 0 indicates on the optical axis, and the vertical vertex indicates the maximum pupil radius; the horizontal direction represents the offset relative to the ideal focus, in millimeters (mm). Different linear curves in the figure represent different wavelengths of the system imaging, from Figure 6 It can be seen that the axial aberration of the normalized aperture of different wavelengths from 0 to 1.0 is controlled within the range of (-0.02 mm, +0.02 mm), indicating that the spherical aberration of the fixed-focus lens 200 provided in the second embodiment of the present application is well controlled and can meet the requirements of wide-spectrum applications.

[0105] Figure 7 This is the ray fan diagram of a fixed-focus lens provided in the second embodiment of the present application. The ray fan diagram is one of the commonly used evaluation methods by current optical designers. As Figure 7 shown, the abscissa in a single figure is the normalized beam aperture, and the ordinate is the lateral aberration. Ideally, each curve should completely coincide with the horizontal axis. At this time, all rays in this field of view focus on the same point on the image plane; the ordinate in a single image can also represent the maximum dispersion range of the beam on the ideal image plane. The ray fan diagram can not only reflect the monochromatic aberration of different wavelengths, but also represent the magnitude of the lateral chromatic aberration. From Figure 7 it can be seen that this optical system is well approximated to the horizontal axis at each wavelength in each field of view, indicating that the lateral aberration of each wavelength is well corrected. In addition, the curves of each color do not show obvious dispersion, indicating that this optical system also has good correction for chromatic aberration, thus ensuring the imaging requirement of clear imaging in the full wavelength band of the fixed-focus lens 200 provided in the second embodiment.

[0106] Figure 8 This is the lateral chromatic aberration diagram of a fixed-focus lens provided in the second embodiment of the present application. As Figure 8 shown, the vertical direction represents the normalization of the aperture, 0 indicates on the optical axis, and the vertical vertex indicates the maximum pupil radius; the principal wavelength is 546.074 nm, and the horizontal direction represents the offset relative to the principal wavelength, in micrometers (um). From Figure 8 it can be seen that the lateral chromatic aberration of different wavelengths is controlled within a reasonable range, indicating that the lateral chromatic aberration of the fixed-focus lens 200 provided in the second embodiment of the present application is well controlled and can meet the requirements of wide-spectrum applications in the full wavelength band.

[0107] Embodiment 3

[0108] Figure 5 This is the structural schematic diagram of a fixed-focus lens provided in the third embodiment of the present application. As Figure 5As shown in the figure, the fixed-focus lens 200 provided in the third embodiment of the present application includes a first lens 31, a second lens 32, a diaphragm STO, a third lens 33, a fourth lens 34, a fifth lens 35, a sixth lens 36, a seventh lens 37, and an eighth lens 38 arranged in sequence along the optical axis from the object plane to the image plane; along the direction of the optical axis from the object plane to the image plane, the first lens 31 is a negative-power double-concave plastic aspherical lens; the second lens 32 is a negative-power concave-convex plastic aspherical lens; the third lens 33 is a positive-power convex-concave plastic aspherical lens; the fourth lens 34 is a positive-power glass spherical lens with a convex second surface; the fifth lens 35 is a positive-power double-convex plastic aspherical lens; the sixth lens 36 is a negative-power double-concave plastic aspherical lens; the seventh lens 37 is a positive-power double-convex plastic aspherical lens; the eighth lens 38 is a negative-power plastic aspherical lens with a convex center and a concave center.

[0109] As a feasible implementation manner, Table 5 shows the optical physical parameters of the first lens to the eighth lens in the fixed-focus lens provided in the third embodiment of the present application. Table 6 shows the aspherical coefficient values of the aspherical lenses in the fixed-focus lens 300 provided in the third embodiment of the present application.

[0110] Table 5 Design values of the optical physical parameters of the fixed-focus lens

[0111]

[0112] Among them, the surface numbers in Table 5 are numbered according to the surface order of each lens. For example, the surfaces with surface numbers S1 and S2 are the object side surface and the image side surface of the first lens 31 respectively, the surfaces with surface numbers S3 and S4 are the object side surface and the image side surface of the second lens 32 respectively, and so on; "STO" represents the diaphragm of the fixed-focus lens; the radius of curvature R represents the degree of curvature of the corresponding lens surface, a positive value represents that the surface bends towards the image plane side, a negative value represents that the surface bends towards the object plane side, where "INF" means that the surface is a plane and the radius of curvature is infinite, the thickness T represents the central axial distance from the current surface to the next surface, and the units of the radius of curvature and the thickness are both millimeters (mm); the refractive index Nd represents the deflection ability of the material between the current surface and the next surface to light, and a space represents that the current position is air and the refractive index is 1.

[0113] Table 6 Aspherical coefficients of the fixed-focus lens

[0114] Surface Serial Number k a4 a6 a8 S1 360.27 1.381659354E-03 -1.372339850E-04 9.613330175E-06 S2 -1.54 2.644514783E-03 -8.076747465E-05 -3.337598573E-05 S3 -7.70 -1.376337142E-03 5.705387574E-04 -7.172645365E-05 S4 2.29 1.021003097E-02 1.063458385E-04 -1.136914686E-04 S6 -24.21 -8.952646497E-04 1.283936959E-04 -1.402405331E-05 S7 -30.91 -3.567338709E-03 2.999150907E-04 -1.341707833E-05 S10 -7.68 1.985524726E-03 -2.982051472E-04 -2.100318012E-08 S11 500.00 -1.206023189E-03 -9.669413912E-05 3.322872707E-07 S12 -7.35 3.178479071E-03 -1.584326869E-05 -1.779584009E-05 S13 -156.77 7.673095607E-04 7.985192141E-04 -1.007955455E-04 S14 -39.11 1.859000280E-04 2.147568823E-04 -1.627500408E-05 S15 -4.95 -4.063149940E-04 -1.917741917E-05 -2.998158255E-07 S16 -6.37 -4.624598533E-03 3.888016499E-05 2.812737520E-06 S17 -6.40 -4.608231230E-03 1.191307608E-04 -1.765971997E-06 Surface Serial Number a10 a12 a14 a16 S1 -4.049318774E-07 7.979500925E-09 -1.477966680E-11 -9.296830659E-13 S2 6.761065556E-06 -4.454443810E-07 -5.505575131E-09 9.400223730E-10 S3 1.371934014E-06 3.586324276E-07 -2.859689231E-08 5.597782570E-10 S4 2.558901833E-05 -2.554269773E-06 1.135216905E-07 -4.368127040E-10 S6 6.533742125E-07 -4.551657755E-09 -8.468014647E-10 4.180280441E-11 S7 2.806479698E-07 -1.080075466E-09 -7.751007608E-11 2.766513974E-12 S10 2.141065724E-06 -1.338697074E-07 2.693022171E-09 -3.433405498E-12 S11 7.192621512E-07 -4.276550646E-08 8.604094170E-10 -1.008098654E-12 S12 4.210545329E-07 3.673373168E-08 -1.367608027E-09 7.684306751E-13 S13 5.078427491E-06 -9.805207008E-08 5.998357608E-10 -1.250964563E-11 S14 3.854399884E-07 5.213473394E-09 2.470332415E-11 -6.446538936E-12 S15 3.276746803E-07 -2.688542248E-08 6.421363002E-10 -2.401909077E-12 S16 -4.320737633E-07 5.742576059E-09 4.373390354E-10 -3.836642014E-12 S17 -2.031280736E-07 1.593227853E-08 -4.268709135E-10 4.474737332E-12

[0115] Among them, -4.184916896E-07 in Table 6 means that the coefficient a10 of the surface with surface number S1 is -4.184916896*10 -7 , and so on.

[0116] In Embodiment 3 of the present application, the aspherical lens of the fixed-focus lens 300 satisfies the following formula:

[0117]

[0118] where Z is the axial distance from the surface at a position perpendicular to the optical axis with a height of r along the optical axis direction to the vertex of the surface; c represents the curvature at the vertex of the aspherical surface; a4, a6, a8, a10, a12, a14, a16 are the high-order aspherical coefficients of the fourth, sixth, eighth, tenth, twelfth, fourteenth, and sixteenth orders of the corresponding aspherical surface, and a i r i combine to form the high-order terms of the corresponding aspherical surface; k is the conic coefficient; where the units of Z, r, and c are all mm.

[0119] The fixed-focus lens 300 of Embodiment 3 has achieved the following technical indicators:

[0120] The focal length f of the fixed-focus lens 300 is 4.9098 mm, and the f-number F / # is 1.081162.

[0121] Furthermore, multiple performance tests were conducted on the fixed-focus lens 300 provided in Embodiment 3, and the test results are as follows:

[0122] Figure 10 This is the axial aberration curve diagram of a fixed-focus lens provided in Embodiment 3 of the present application. As Figure 10 shown, the vertical direction is the normalized aperture, 0 indicates on the optical axis, and the vertex in the vertical direction represents the maximum pupil radius; the horizontal direction represents the offset relative to the ideal focus, with the unit of millimeters (mm). Different linear curves in the figure represent different wavelengths of the system imaging. From Figure 10 it can be seen that the axial aberrations of different wavelengths from 0 to 1.0 normalized aperture are all controlled within the range of (-0.02 mm, +0.02 mm), indicating that the spherical aberration of the fixed-focus lens 300 provided in Embodiment 3 of the present application has been well controlled and can meet the requirements of wide-spectrum applications.

[0123] Figure 11 This is the ray fan diagram of a fixed-focus lens provided in Embodiment 3 of the present application. The ray fan diagram is one of the commonly used evaluation methods by current optical designers. As Figure 11 shown, in a single figure, the abscissa is the normalized beam aperture, and the ordinate is the lateral aberration. Ideally, each curve should completely coincide with the horizontal axis. At this time, all rays in the field of view are focused at the same point on the image plane; the ordinate in a single image can also represent the maximum dispersion range of the beam on the ideal image plane. The ray fan diagram can not only reflect the monochromatic aberration of different wavelengths but also represent the magnitude of the lateral chromatic aberration. From Figure 11It can be seen that this optical system is well approximated to the abscissa at each wavelength in each field of view, indicating that the vertical aberration at each wavelength is well corrected. In addition, the curves of each color do not show obvious dispersion, indicating that this optical system also has good correction for chromatic aberration, thus ensuring the imaging requirement of clear imaging in the full wavelength band of the fixed-focus lens 300 provided in the third embodiment.

[0124] Figure 12 This is the vertical chromatic aberration diagram of a fixed-focus lens provided in the third embodiment of the present application. As Figure 12 shown, the vertical direction represents the normalization of the aperture, 0 represents on the optical axis, and the vertex in the vertical direction represents the maximum pupil radius; the main wavelength is 546.074 nm, and the horizontal direction represents the offset relative to the main wavelength, with the unit of micrometer (um). From Figure 12 it can be seen that the vertical chromatic aberration of different wavelengths is controlled within a reasonable range, indicating that the vertical chromatic aberration of the fixed-focus lens 300 provided in the third embodiment of the present application is well controlled and can meet the wide-spectrum application requirements of the full wavelength band.

[0125] Note that the above is only the preferred embodiment of the present application and the technical principles applied. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein. Various obvious changes, re-adjustments, and substitutions can be made by those skilled in the art without departing from the protection scope of the present invention. Therefore, although the present invention has been described in 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, a second lens, an aperture, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens and an eighth lens which are arranged in sequence from the object plane to the image plane along the optical axis; Along the direction from the object plane to the image plane of the optical axis, the first lens is a double concave plastic aspheric lens with negative optical power; the second lens is a concave-convex plastic aspheric lens with negative optical power; the third lens is a convex-concave plastic aspheric lens with positive optical power; the fourth lens is a glass spherical lens with positive optical power and the second surface is convex; the fifth lens is a double convex plastic aspheric lens with positive optical power; the sixth lens is a double concave plastic aspheric lens with negative optical power; the seventh lens is a double convex plastic aspheric lens with positive optical power; the eighth lens is a central convex-central concave plastic aspheric lens with negative optical power.

2. The fixed-focus lens according to claim 1, characterized in that: The focal length of the first lens is f1, the focal length of the second lens is f2, and the focal length of the fixed-focus lens is f, satisfying the following relationship: -6.19<(f1+f2) / f<-5.

27.

3. The fixed-focus lens according to claim 1, characterized in that: The maximum aperture of the first lens is Φ, which is the largest aperture among all lenses of the fixed-focus lens; the total optical length of the fixed-focus lens is TTL, which satisfies the following relationship: 0.49<Φ / TTL<0.

52.

4. The fixed-focus lens according to claim 1, characterized in that: The focal length of the fourth lens is f4, and the focal length of the fixed-focus lens is f, satisfying the following relationship: 1.90≤f4 / f≤3.

16.

5. The fixed-focus lens according to claim 1, wherein: The focal length of the third lens is f3, the focal length of the fourth lens is f4, and the focal length of the fixed-focus lens is f, satisfying the following relationship: 5.95<(f3+f4) / f<6.

85.

6. The fixed-focus lens according to claim 1, wherein: The refractive index of the fourth lens is nd4, the Abbe number is vd4, and meets the following requirements: 1.43≤nd4≤1.80;37.00≤vd4≤94.

50.

7. The fixed-focus lens according to claim 1, wherein: The focal length of the fifth lens is f5, the focal length of the sixth lens is f6, the focal length of the seventh lens is f7, and the focal length of the fixed-focus lens is f, satisfying the following relationship: 1.59<(f5+f6+f7) / f<2.

12.

8. The fixed-focus lens according to claim 1, wherein: The focal length of the third lens is f3, the focal length of the eighth lens is f8, and the focal length of the fixed-focus lens is f, which satisfies the following relationship: 3.53 <f3 / f<4.95;-6.22<f8 / f<-2.92。 9. The fixed-focus lens according to claim 1, wherein: Along the direction from the object plane to the image plane of the optical axis, the maximum sag of the second surface of the eighth lens is SAG; the maximum aperture of the eighth lens is Φ, satisfying the following relationship: 0.13 <SAG / Φ<0.17。 10. The fixed-focus lens according to claim 1, wherein: It also includes a flat glass, which is located in the optical path between the eighth lens and the image plane.

Images