A fixed focus lens

Abstract

The application discloses a fixed-focus lens, which 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 arranged in sequence along an optical axis from an object plane to an image plane; the first lens is a double-concave plastic aspheric lens with negative focal power; 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 a convex surface; the fifth lens is a double-convex plastic aspheric lens with positive focal power; the sixth lens is a double-concave plastic aspheric lens with negative focal power; the seventh lens is a double-convex plastic aspheric lens with positive focal power; and the eighth lens is a center-convex-center-concave plastic aspheric lens with negative focal power. The fixed-focus lens can realize clear imaging under a 1 / 1.8" target surface and has the advantages of a large aperture and high image quality.

Description

Technical Field

[0001] The present invention relates to the field of optical device technology, and in particular to a fixed-focus lens. Background Technology

[0002] With the increasing popularity of security monitoring facilities, the market demands higher and higher requirements for security monitoring lenses. Fixed-focus lenses, as the mainstream products in the security industry, are highly sought after by the market. Meanwhile, 1 / 1.8″ chips are becoming more widely used, and the requirements for the size, aperture, and operating environment of the lenses that are paired with them are becoming increasingly stringent.

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

[0004] This invention provides a fixed-focus lens that can achieve clear imaging at a 1 / 1.8″ target surface, with the advantages of large aperture and high image quality, making it suitable for security applications in more situations.

[0005] This application provides a fixed-focus lens, including a first lens, a second lens, an aperture stop, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, and an eighth lens arranged sequentially along the optical axis from the object plane to the image plane;

[0006] Along the optical axis from the object plane to the image plane, the first lens is a negative optical power biconcave plastic aspherical lens; the second lens is a negative optical power concave-convex plastic aspherical lens; the third lens is a positive optical power convex-concave plastic aspherical lens; the fourth lens is a positive optical power glass spherical lens with a convex second surface; the fifth lens is a positive optical power biconvex plastic aspherical lens; the sixth lens is a negative optical power biconcave plastic aspherical lens; the seventh lens is a positive optical power biconvex plastic aspherical lens; and the eighth lens is a negative optical power central convex-central 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, which is also the largest aperture among all lenses in the entire fixed-focus lens; the total optical 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 fourth lens has a refractive index of nd4 and an Abbe number of 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 relationship:

[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 sagitta 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 also includes a flat glass plate located in the optical path between the eighth lens and the image plane.

[0024] The fixed-focus lens provided in this application embodiment employs seven plastic aspherical lenses and one glass spherical lens, arranged sequentially along the optical axis from the object plane to the image plane: a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, and an eighth lens. By rationally setting the number of lenses in the fixed-focus lens and the combination relationship of the optical power of each lens, clear imaging can be achieved at a 1 / 1.8″ target surface. It has the advantages of large aperture and high image quality, making it suitable for security use needs in more situations. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the structure of a fixed-focus lens provided in Embodiment 1 of this application;

[0026] Figure 2 An axial aberration curve of a fixed-focus lens provided in Embodiment 1 of this application;

[0027] Figure 3 A ray fan pattern for a fixed-focus lens provided in Embodiment 1 of this application;

[0028] Figure 4 A transverse chromatic aberration diagram of a fixed-focus lens provided in Embodiment 1 of this application;

[0029] Figure 5 This is a schematic diagram of the structure of a fixed-focus lens provided in Embodiment 2 of this application;

[0030] Figure 6 An axial aberration curve of a fixed-focus lens provided in Embodiment 2 of this application;

[0031] Figure 7 This is a ray fan pattern of a fixed-focus lens provided in Embodiment 2 of this application;

[0032] Figure 8 A transverse chromatic aberration diagram of a fixed-focus lens provided in Embodiment 2 of this application;

[0033] Figure 9 This is a schematic diagram of the structure of a fixed-focus lens provided in Embodiment 3 of this application;

[0034] Figure 10 An axial aberration curve of a fixed-focus lens provided in Embodiment 3 of this application;

[0035] Figure 11 This is a ray fan pattern of a fixed-focus lens provided in Embodiment 3 of this application;

[0036] Figure 12 This is a chromatic aberration diagram of a fixed-focus lens provided in Embodiment 3 of this application. Detailed Implementation

[0037] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the application and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present application, not the entire structure.

[0038] Figure 1 This is a schematic diagram of a fixed-focus lens provided in Embodiment 1 of this application. Figure 1As shown, the fixed-focus lens 100 provided in this application embodiment 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 sequentially along the optical axis from the object plane to the image plane. Along the optical axis from the object plane to the image plane, the first lens 11 is a negative optical power biconcave plastic aspherical lens; the second lens 12 is a negative optical power concave-convex plastic aspherical lens; the third lens 13 is a positive optical power convex-concave plastic aspherical lens; the fourth lens 14 is a positive optical power glass spherical lens with a convex second surface; the fifth lens 15 is a positive optical power biconvex plastic aspherical lens; the sixth lens 16 is a negative optical power biconcave plastic aspherical lens; the seventh lens 17 is a positive optical power biconvex plastic aspherical lens; and the eighth lens 18 is a negative optical power central convex-central concave plastic aspherical lens.

[0039] Optical power is equal to the difference between the convergence of light beams at the image plane and the convergence of light beams at the image plane. It characterizes the ability of an optical system to deflect light rays. The larger the absolute value of optical power, the stronger the ability to bend light rays; the smaller the absolute value of optical power, the weaker the ability to bend light rays. When optical power is positive, the refraction of light rays is converging; when optical power is negative, the refraction of light rays is diverging. Optical power can be used to characterize a single refractive surface of a lens (i.e., one surface of the lens), a single lens, or a system formed by multiple lenses (i.e., a lens group).

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

[0041] Reference Figure 1As shown, the surface of the lens closest to the object plane M1 is the object-side surface, and the surface of the lens closest to the image plane M2 is the image-side surface. The object-side surface of the first lens 11 is concave, and the image-side surface of the first lens 120 is concave, forming a double-concave surface. The object-side surface of the second lens 12 is concave, and the image-side surface of the second lens 120 is convex, forming a concave-convex surface. The object-side surface of the third lens 13 is convex, and the image-side surface of the third lens 13 is concave, forming a convex-concave surface. The object-side surface of the fourth lens 14 is flat. Lens 14 has a convex image-side surface, resulting in a plano-convex shape; lens 15 has a convex object-side surface and a convex image-side surface, resulting in a biconvex shape; lens 16 has a concave object-side surface and a concave image-side surface, resulting in a biconcave shape; lens 17 has a convex object-side surface and a convex image-side surface, resulting in a biconvex shape; and lens 18 has a centrally convex object-side surface and a centrally concave image-side surface, resulting in a centrally convex-centrally concave shape. By combining the surface shapes of these lenses, not only can optical power be rationally allocated, but space can also be effectively saved, expanding the lens's application scenarios.

[0042] The first lens 11, with its double concave surface, and the second lens 12, with its concave-convex surface, form a lens with negative optical power. This ensures that light has a larger aperture before entering the stop STO, thereby increasing the lens's aperture. By placing the stop STO in the optical path between the second lens 12 and the third lens 13, the propagation angle of light can be limited, the propagation direction of the beam can be adjusted, and the incident angle of light can be adjusted, which helps to improve the lens's image quality. At the same time, the third lens 13, with its convex-concave surface, and the fourth lens 14, with its second convex surface, form two lens groups with positive optical power. The two work together to ensure that light passes smoothly through the stop STO, which can avoid stray light such as reflections at the stop STO position and adjust the lens's aberrations to a certain extent, ensuring the lens's aberration balance and stable high and low temperature performance.

[0043] Furthermore, the biconvex type of the fifth lens 15, the biconcave type of the sixth lens 16, and the biconvex 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 light passing through the aperture STO, allowing light to pass through smoothly and ensuring that the lens can form a clear image under a 1 / 1.8″ target surface.

[0044] Considering that the cost of plastic lenses is much lower than that of glass lenses, 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 arrangement satisfies the requirement of high lens resolution while reducing costs. Furthermore, considering that glass is more stable than plastic in high and low temperature environments, the fourth lens 14 is a glass aspherical lens. Placing the fourth lens 14 near the aperture ST0 effectively corrects off-axis image quality and on-axis chromatic aberration while ensuring focus stability at high and low temperatures.

[0045] Furthermore, when combined with the central convex-central concave aspherical lens of the eighth lens 18, the residual advanced aberrations of the lens can be eliminated as much as possible, and the image quality can be improved while expanding the lens target surface (size), so as to meet the usage requirements in more situations.

[0046] Furthermore, glass and plastic can compensate for each other, effectively balancing the expansion and contraction of the lens front and rear ends under temperature changes. This helps improve the overall high and low temperature performance of the lens. Using a combination of glass and plastic lenses in the lens can better balance the lens resolution under high and low temperature conditions. At the same time, using a reasonable combination of glass lenses can also have a good effect on correcting lens aberrations. Using the above materials can ensure that the lens has good resolution within the range of -40 to 80℃, meeting the application requirements of various security environments.

[0047] It should be noted that the materials of the above-mentioned 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. This application does not elaborate on or limit these materials.

[0048] Reference Figure 1 As shown in the embodiments of this application, each lens of the fixed-focus lens can be fixed in a lens barrel and sealed or vacuum-sealed. The user fixes each lens to ensure the stability and clarity of each lens surface and to ensure image quality. Each lens will not be shown in detail in the embodiments of this application.

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

[0050] Optionally, the fixed-focus lens 100 may also include a flat glass CG disposed 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. The imaging chip is used to convert the light signals collected by the fixed-focus lens into electrical signals, thereby ensuring the imaging effect of the fixed-focus lens.

[0051] Furthermore, by rationally setting one or more parameters such as the radius of curvature, center thickness, focal length, refractive index, and Abbe number of the lens, it is possible to achieve a low-cost fixed-focus lens design that is small in size and has a large aperture.

[0052] Optional, 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 negative optical power. The combination of negative optical power of the two lenses can diverge light, expand the beam aperture before the light enters the aperture stop STO, increase the amount of light entering the optical fiber into the aperture stop STO, and adapt to the clear imaging of fixed-focus lenses in dark or low-light environments, thereby expanding the security application environment of the lens.

[0054] Optional, continue to refer to Figure 1 As shown, the maximum aperture of the first lens 11 is Φ, which is also the largest aperture among all lenses in the entire fixed-focus lens 100; the total optical length of the fixed-focus lens 100 is TTL, which satisfies the following relationship: 0.49 < Φ / TTL < 0.52.

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

[0056] Optional, 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, the ratio of the focal length f4 of the fourth lens 14 to the focal length f of the fixed-focus lens 100 meets this range setting, which can achieve a reasonable match between the optical power of the fourth lens 14 and other lenses, allowing light to pass through the lens more smoothly, and to a large extent correcting the impact of the lens's advanced aberrations on image quality, thereby improving image sharpness.

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

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

[0060] Specifically, the fourth lens 14 is a glass spherical lens. Glass lenses offer a wide range of choices for refractive index and Abbe number combinations. By appropriately matching the refractive index nd4 and Abbe number vd4 of the fourth lens 14, chromatic aberration of the lens can be corrected to a significant extent. This also facilitates its combination with other lenses to achieve a near-cemented effect, thus reducing chromatic aberration. For example, the third lens 13 and the fourth lens 14 can be fitted together.

[0061] Optional, 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 these glass lenses together ensures good resolution within the stated temperature range, expanding the lens's application range. When light passes through the aperture stop STO and enters the third lens 13 and the fourth lens 14, setting the sum of the focal lengths f3 and f4 of the third lens 13 within the aforementioned range provides a relatively large focal length, which facilitates light convergence to the fifth lens 15. This avoids excessive pressure on the rear lenses during chromatic aberration, aberration correction, and angle of incidence correction, reducing the difficulty of lens manufacturing. Furthermore, using a plastic aspherical lens for the third lens 13 also helps in correcting the aforementioned aberrations.

[0063] Optional, 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, the fifth lens 15, sixth lens 16, and seventh lens 17 are all made of plastic aspherical lenses. After the light passes through the third lens 13 and fourth lens 14 to eliminate certain aberrations, the aspherical lens L5 can eliminate higher-order aberrations and residual spherical aberrations that the front-end lenses have not eliminated. When combined with the sixth lens 16 and seventh lens 17, which are also aspherical lenses, the remaining higher-order aberrations can be eliminated to the greatest extent. In addition, this combination of optical power allows light to pass smoothly through the rear of the lens. At the same time, the reasonable combination of the optical power of the fifth lens 15, sixth lens 16, and seventh lens 17 can also keep the angle of the principal ray within a suitable range, and can also adjust the height of the intersection point between the principal ray of the maximum field of view and the image plane at the rear of the optical system, adapting to various chips and saving lens costs on the other hand.

[0066] Optional, 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 relationship:

[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 are plastic aspherical lenses. The third lens 13 uses a positive optical power to better converge light at the front of the lens and reduce pressure at the back. The eighth lens 18 uses a negative optical power to allow light to smoothly reach the chip target surface after correcting various aberrations. Using lenses with this combination of optical power allows light to pass smoothly through the entire lens, avoiding excessive and difficult-to-correct aberrations.

[0069] Optional, continue to refer to Figure 1 As shown, along the optical axis from the object plane to the image plane, the maximum sagitta 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 passes 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 higher-order aberrations and residual spherical aberrations that were not eliminated at the front end. In addition, by setting the ratio of the maximum sag SAG of the eighth lens 18 to the maximum aperture Φ to be within the range of 0.13 to 0.17, the height of the intersection point between the principal ray of the maximum field of view and the image plane can be adjusted at the rear of the optical system, adapting to various chips, increasing the application range, and saving lens costs.

[0072] As one possible implementation, 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 Embodiment 1 of this application. Table 2 shows the aspherical coefficient values ​​of the aspherical lens in the fixed-focus lens 100 provided in Embodiment 1 of this application.

[0073] Table 1 Design values ​​of optical physical parameters for fixed-focus lenses

[0074]

[0075] In Table 1, the surface numbers are assigned according to the surface sequence of each lens. For example, surfaces S1 and S2 are the object-side and image-side surfaces of the first lens 11, respectively; surfaces S3 and S4 are the object-side and image-side surfaces of the second lens 12, respectively; and so on. “STO” represents the aperture stop of a fixed-focus lens. The radius of curvature R represents the curvature of the corresponding lens surface. A positive value indicates that the surface bends towards the image plane, and a negative value indicates that the surface bends towards the object plane. “INF” indicates that the surface is a plane with an infinite radius of curvature. The thickness T represents the central axial distance from the current surface to the next surface. The units for both the radius of curvature and the thickness are millimeters (mm). The refractive index Nd represents the ability of the material between the current surface and the next surface to deflect light. A blank space indicates that the current position is air with a refractive index of 1.

[0076] Table 2 Aspherical coefficients of fixed-focus lenses

[0077] 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 Face 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] In Table 2, -4.064858918E-07 indicates that the coefficient a10 for surface number S1 is -4.064858918*10. -7 And so on.

[0079] In Embodiment 1 of this application, the aspherical lens of the fixed-focus lens 100 satisfies the following formula:

[0080]

[0081] Where Z is the axial distance from the vertex of the surface at a position perpendicular to the optical axis at a height r along the optical axis; c represents the curvature at the vertex of the aspherical surface; a4, a6, a8, a10, a12, a14, and a16 are the fourth, sixth, eighth, tenth, twelfth, fourteenth, and sixteenth order higher-order aspherical coefficients corresponding to the aspherical surface, and a i r i The terms are combined to form higher-order terms for the corresponding aspherical surfaces; k is the conic coefficient; where Z, r, and c are all in mm.

[0082] The fixed-focus lens 100 in this embodiment achieves the following technical specifications:

[0083] The focal length of the 100mm prime lens is f: 4.9097mm, and the aperture is f / #: 1.08178.

[0084] Furthermore, several performance tests were conducted on the fixed-focus lens 100 provided in Embodiment 1, and the specific test results are as follows:

[0085] Figure 2 This is a schematic diagram of an axial aberration curve provided in Embodiment 1 of this application. Figure 2 As shown, the vertical direction represents the normalized aperture, with 0 indicating the optical axis, and the vertical vertex representing the maximum pupil radius; the horizontal direction represents the offset relative to the ideal focal point, in millimeters (mm). Different linear curves in the figure represent different wavelengths of system imaging, determined by... Figure 2 It can be seen that the axial aberrations of the normalized apertures of different wavelengths from 0 to 1.0 are all controlled within the range of (-0.02 mm, +0.02 mm), indicating that the fixed-focus lens 100 provided in Embodiment 1 of this application has achieved good control of spherical aberration at each wavelength, which can meet the requirements of wide spectrum applications.

[0086] Figure 3 This is a schematic diagram of a ray fan plot provided in Embodiment 1 of this application. Ray fan plots are one of the commonly used evaluation methods by optical designers. Figure 3 As shown, in a single image, the horizontal axis represents the normalized beam aperture, and the vertical axis represents the transverse aberration. Ideally, each curve should perfectly coincide with the horizontal axis, in which case all rays in that field of view focus at the same point on the image plane; the vertical axis in a single image can also represent the maximum dispersion range of the beam on the ideal image plane. The fan plot can not only reflect monochromatic aberrations of different wavelengths but also the magnitude of transverse chromatic aberration. Figure 3 It can be seen that this optical system closely approximates the horizontal axis at all wavelengths in all fields of view, indicating that the transverse aberrations at each wavelength are well corrected. In addition, the curves of each color do not show significant dispersion, indicating that this optical system also has good correction for chromatic aberration, thus ensuring the imaging requirements of the fixed-focus lens 100 provided in Embodiment 1 to form a clear image across the entire wavelength range.

[0087] Figure 4 An axial chromatic aberration diagram of a fixed-focus lens provided in an embodiment of this application. For example... Figure 4 As shown, the vertical direction represents the normalized aperture, 0 indicates it is on the optical axis, and the vertex in the perpendicular direction represents the maximum pupil radius; the dominant wavelength is 546.074 nm, and the horizontal direction represents the offset relative to the dominant wavelength, in micrometers (µm). Figure 4It can be seen that the transverse chromatic aberration of different wavelengths is controlled within a reasonable range, indicating that the transverse chromatic aberration of the fixed-focus lens 100 provided in Embodiment 1 of this application is well controlled and can meet the requirements of wide-spectrum applications across the entire wavelength range.

[0088] In summary, the fixed-focus lens provided in Embodiment 1 of this application adopts a glass-plastic hybrid method, which can take into account the design requirements of small size, large aperture and low cost, and achieve large aperture, high image quality and clear imaging under a 1 / 1.8″ target surface, making it suitable for security use needs in more situations.

[0089] Example 2

[0090] Figure 5 This is a schematic diagram of a fixed-focus lens provided in Embodiment 2 of this application. Figure 5 As shown, the fixed-focus lens 200 provided in Embodiment 2 of this application includes a first lens 21, a second lens 22, an aperture stop 20, 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 sequentially along the optical axis from the object plane to the image plane; along the direction from the object plane to the image plane, the first lens 21 is a negative optical power biconcave plastic aspherical lens; the second lens 22 is a negative optical power concave-convex plastic aspherical lens. The first lens is a spherical lens; the second lens is a convex-concave plastic aspherical lens with positive optical power; the third lens 23 is a convex glass spherical lens with positive optical power and a second convex surface; the fourth lens 24 is a biconvex plastic aspherical lens with positive optical power; the fifth lens 25 is a biconvex plastic aspherical lens with positive optical power; the sixth lens 26 is a biconcave plastic aspherical lens with negative optical power; the seventh lens 27 is a biconvex plastic aspherical lens with positive optical power; and the eighth lens 28 is a centrally convex-centrally concave plastic aspherical lens with negative optical power.

[0091] As one possible implementation, 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 Embodiment 2 of this application. Table 4 shows the aspherical coefficient values ​​of the aspherical lenses in the fixed-focus lens 200 provided in Embodiment 2 of this application.

[0092] Table 3 Design values ​​of optical physical parameters for fixed-focus lenses

[0093]

[0094] In Table 3, the surface numbers are assigned according to the surface sequence of each lens. For example, surfaces S1 and S2 are the object-side and image-side surfaces of the first lens 21, respectively; surfaces S3 and S4 are the object-side and image-side surfaces of the second lens 22, respectively; and so on. “STO” represents the aperture stop of a fixed-focus lens. The radius of curvature R represents the curvature of the corresponding lens surface. A positive value indicates that the surface bends towards the image plane, and a negative value indicates that the surface bends towards the object plane. “INF” indicates that the surface is a plane with an infinite radius of curvature. The thickness T represents the central axial distance between the current surface and the next surface. The units for both the radius of curvature and the thickness are millimeters (mm). The refractive index Nd represents the ability of the material between the current surface and the next surface to deflect light. A blank space indicates that the current position is air with a refractive index of 1.

[0095] Table 4 Aspherical coefficient of fixed-focus lenses

[0096] 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 Face 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] In Table 4, -4.184916896E-07 indicates that the coefficient a10 for surface number S1 is -4.184916896*10. -7 And so on.

[0098] In Embodiment 2 of this application, the aspherical lens of the fixed-focus lens 200 satisfies the following formula:

[0099]

[0100] Where Z is the axial distance from the vertex of the surface at a position perpendicular to the optical axis at a height r along the optical axis; c represents the curvature at the vertex of the aspherical surface; a4, a6, a8, a10, a12, a14, and a16 are the fourth, sixth, eighth, tenth, twelfth, fourteenth, and sixteenth order higher-order aspherical coefficients corresponding to the aspherical surface, and a i r i The terms are combined to form higher-order terms for the corresponding aspherical surfaces; k is the conic coefficient; where Z, r, and c are all in mm.

[0101] The fixed-focus lens 200 in this second embodiment achieves the following technical specifications:

[0102] The 200mm prime lens has a focal length of f / 4.9098mm and an aperture of f / #1.08020.

[0103] Furthermore, several performance tests were conducted on the fixed-focus lens 200 provided in Embodiment 2, and the specific test results are as follows:

[0104] Figure 6 This is an axial aberration curve diagram of a fixed-focus lens provided in Embodiment 2 of this application. Figure 6As shown, the vertical direction represents the normalized aperture, with 0 indicating the optical axis, and the vertical vertex representing the maximum pupil radius; the horizontal direction represents the offset relative to the ideal focal point, in millimeters (mm). Different linear curves in the figure represent different wavelengths of system imaging, determined by... Figure 6 It can be seen that the axial aberrations of the normalized apertures of different wavelengths from 0 to 1.0 are all controlled within the range of (-0.02 mm, +0.02 mm), indicating that the fixed-focus lens 200 provided in Embodiment 2 of this application has achieved good control of spherical aberration at each wavelength, which can meet the requirements of wide spectrum applications.

[0105] Figure 7 This is a ray fan diagram of a fixed-focus lens provided in Embodiment 2 of this application. Ray fan diagrams are one of the commonly used evaluation methods by optical designers. For example... Figure 7 As shown, in a single image, the horizontal axis represents the normalized beam aperture, and the vertical axis represents the transverse aberration. Ideally, each curve should perfectly coincide with the horizontal axis, in which case all rays in that field of view focus at the same point on the image plane; the vertical axis in a single image can also represent the maximum dispersion range of the beam on the ideal image plane. The fan plot can not only reflect monochromatic aberrations of different wavelengths but also the magnitude of transverse chromatic aberration. Figure 7 It can be seen that this optical system closely approximates the horizontal axis at all wavelengths in all fields of view, indicating that the transverse aberrations at each wavelength are well corrected. In addition, the curves of each color do not show significant dispersion, indicating that this optical system also has good correction for chromatic aberration, thereby ensuring the imaging requirements of the fixed-focus lens 200 provided in Embodiment 2 to achieve clear images across the entire wavelength range.

[0106] Figure 8 This is a chromatic aberration diagram of a fixed-focus lens provided in Embodiment 2 of this application. For example... Figure 8 As shown, the vertical direction represents the normalized aperture, 0 indicates it is on the optical axis, and the vertex in the perpendicular direction represents the maximum pupil radius; the dominant wavelength is 546.074 nm, and the horizontal direction represents the offset relative to the dominant wavelength, in micrometers (µm). Figure 8 It can be seen that the chromatic aberration of the vertical axis at different wavelengths is controlled within a reasonable range, indicating that the chromatic aberration of the fixed-focus lens 200 provided in Embodiment 2 of this application is well controlled and can meet the requirements of wide-spectrum applications across the entire wavelength range.

[0107] Example 3

[0108] Figure 5 This is a schematic diagram of a fixed-focus lens provided in Embodiment 3 of this application. Figure 5As shown, the fixed-focus lens 200 provided in Embodiment 3 of this application includes a first lens 31, a second lens 32, an aperture stop 30, 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 sequentially along the optical axis from the object plane to the image plane; along the direction from the object plane to the image plane, the first lens 31 is a negative optical power biconcave plastic aspherical lens; the second lens 32 is a negative optical power concave-convex plastic aspherical lens. Spherical lens; third lens 33 is a positive power convex-concave plastic aspherical lens; fourth lens 34 is a positive power glass spherical lens with a convex second surface; fifth lens 35 is a positive power biconvex plastic aspherical lens; sixth lens 36 is a negative power biconcave plastic aspherical lens; seventh lens 37 is a positive power biconvex plastic aspherical lens; eighth lens 38 is a negative power central convex-central concave plastic aspherical lens.

[0109] As one possible implementation, Table 5 shows the optical physical parameters of the first to eighth lenses in the fixed-focus lens provided in Embodiment 3 of this application. Table 6 shows the aspherical coefficient values ​​of the aspherical lenses in the fixed-focus lens 300 provided in Embodiment 3 of this application.

[0110] Table 5 Design values ​​of optical physical parameters for fixed-focus lenses

[0111]

[0112] In Table 5, the surface numbers are assigned according to the surface sequence of each lens. For example, surfaces S1 and S2 are the object-side and image-side surfaces of the first lens 31, respectively; surfaces S3 and S4 are the object-side and image-side surfaces of the second lens 32, respectively; and so on. “STO” represents the aperture stop of a fixed-focus lens. The radius of curvature R represents the curvature of the corresponding lens surface. A positive value indicates that the surface bends towards the image plane, and a negative value indicates that the surface bends towards the object plane. “INF” indicates that the surface is a plane with an infinite radius of curvature. The thickness T represents the central axial distance from the current surface to the next surface. The units for both the radius of curvature and the thickness are millimeters (mm). The refractive index Nd represents the ability of the material between the current surface and the next surface to deflect light. A blank space indicates that the current position is air with a refractive index of 1.

[0113] Table 6 Aspherical coefficients of fixed-focus lenses

[0114] 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 Face 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] In Table 6, -4.184916896E-07 indicates that the coefficient a10 for surface number S1 is -4.184916896*10. -7 And so on.

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

[0117]

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

[0119] The fixed-focus lens 300 in this third embodiment achieves the following technical specifications:

[0120] The 300mm prime lens has a focal length of f / 4.9098mm and an aperture of f / #1.081162.

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

[0122] Figure 10 This is an axial aberration curve diagram of a fixed-focus lens provided in Embodiment 3 of this application. Figure 10 As shown, the vertical direction represents the normalized aperture, with 0 indicating the optical axis, and the vertical vertex representing the maximum pupil radius; the horizontal direction represents the offset relative to the ideal focal point, in millimeters (mm). Different linear curves in the figure represent different wavelengths of system imaging, determined by... Figure 10 It can be seen that the axial aberrations of the normalized apertures of different wavelengths from 0 to 1.0 are all controlled within the range of (-0.02 mm, +0.02 mm), indicating that the fixed-focus lens 300 provided in Embodiment 3 of this application has achieved good control of spherical aberration at each wavelength, which can meet the requirements of wide spectrum applications.

[0123] Figure 11 This is a ray fan diagram of a fixed-focus lens provided in Embodiment 3 of this application. Ray fan diagrams are one of the commonly used evaluation methods by optical designers. For example... Figure 11 As shown, in a single image, the horizontal axis represents the normalized beam aperture, and the vertical axis represents the transverse aberration. Ideally, each curve should perfectly coincide with the horizontal axis, in which case all rays in that field of view focus at the same point on the image plane; the vertical axis in a single image can also represent the maximum dispersion range of the beam on the ideal image plane. The fan plot can not only reflect monochromatic aberrations of different wavelengths but also the magnitude of transverse chromatic aberration. Figure 11It can be seen that this optical system closely approximates the horizontal axis at all wavelengths in all fields of view, indicating that the transverse aberrations at each wavelength are well corrected. In addition, the curves of each color do not show significant dispersion, indicating that this optical system also has good correction for chromatic aberration, thereby ensuring the imaging requirements of the fixed-focus lens 300 provided in Embodiment 3 to achieve clear images across the entire wavelength range.

[0124] Figure 12 This is a chromatic aberration diagram of a fixed-focus lens provided in Embodiment 3 of this application. For example... Figure 12 As shown, the vertical direction represents the normalized aperture, 0 indicates it is on the optical axis, and the vertex in the perpendicular direction represents the maximum pupil radius; the dominant wavelength is 546.074 nm, and the horizontal direction represents the offset relative to the dominant wavelength, in micrometers (µm). Figure 12 It can be seen that the chromatic aberration of the vertical axis at different wavelengths is controlled within a reasonable range, indicating that the chromatic aberration of the fixed-focus lens 300 provided in Embodiment 3 of this application is well controlled and can meet the requirements of wide-spectrum applications across the entire wavelength range.

[0125] Note that the above are merely preferred embodiments and the technical principles employed in this application. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, and substitutions can be made without departing from the scope of protection 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, and may include many other equivalent embodiments without departing from the concept of the present invention, the scope of which is determined by the scope of the appended claims.

Claims

1. A fixed-focus lens, characterized in that, The fixed-focus lens comprises a first lens, a second lens, an aperture stop, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, and an eighth lens arranged sequentially along the optical axis from the object plane to the image plane; the fixed-focus lens has eight lenses with optical power. Along the optical axis from the object plane to the image plane, the first lens is a negative optical power biconcave plastic aspherical lens; the second lens is a negative optical power concave-convex plastic aspherical lens; the third lens is a positive optical power convex-concave plastic aspherical lens; the fourth lens is a positive optical power glass spherical lens with a convex second surface; the fifth lens is a positive optical power biconvex plastic aspherical lens; the sixth lens is a negative optical power biconcave plastic aspherical lens; the seventh lens is a positive optical power biconvex plastic aspherical lens; and the eighth lens is a negative optical power central convex-central concave plastic aspherical lens. The first lens has a focal length of f1, the second lens has a focal length of f2, and the fixed-focus lens has a focal length of f, satisfying the following relationship: ； The third lens has a focal length of f3, the fourth lens has a focal length of f4, the eighth lens has a focal length of f8, and the fixed-focus lens has a focal length of f, satisfying the following relationship: ； ； ； ； The fourth lens has a refractive index of nd4 and an Abbe number of vd4, and satisfies the following requirements: ； 。 2. The fixed-focus lens according to claim 1, characterized in that, The maximum aperture of the first lens is [value], and it is the largest aperture among all lenses in the entire fixed-focus lens; the total optical length of the fixed-focus lens is TTL, satisfying the following relationship: 。 3. The fixed-focus lens according to claim 1, characterized in that, The fifth lens has a focal length of f5, the sixth lens has a focal length of f6, the seventh lens has a focal length of f7, and the fixed-focus lens has a focal length of f, satisfying the following relationship: 。 4. The fixed-focus lens according to claim 1, characterized in that, Along the optical axis from the object plane to the image plane, the maximum sagitta of the second surface of the eighth lens is SAG; the maximum aperture of the eighth lens is... It satisfies the following relationship: 。 5. The fixed-focus lens according to claim 1, characterized in that, It also includes a flat glass plate, which is located in the optical path between the eighth lens and the image plane.

Images