A fixed focus lens

Abstract

This invention discloses a fixed-focus lens, comprising: a first lens with negative optical power, a second lens with negative optical power, a third lens with negative optical power, a fourth lens with positive optical power, a fifth lens with positive optical power, a sixth lens with negative optical power, a seventh lens with positive optical power, an eighth lens with negative optical power, and a ninth lens with positive optical power, arranged sequentially along the optical axis from the object plane to the image plane; wherein the first, second, third, fourth, and fifth lenses are all glass spherical lenses; the sixth, seventh, eighth, and ninth lenses are all plastic aspherical lenses; the third and fourth lenses constitute a cemented lens; and the eighth and ninth lenses constitute a cemented lens. Using the above technical solution, the comprehensive performance requirements of high imaging quality, compact structure, large aperture, and ultra-wide field of view can be met.

Description

Technical Field

[0001] This invention relates to the field of lens technology, and more particularly to a fixed-focus lens. Background Technology

[0002] With the continuous advancement of science and technology and the continuous development of society, optical lenses have also developed rapidly in recent years. Optical imaging lenses are widely used in various fields such as smartphones, tablets, vehicle monitoring, security monitoring, drone aerial photography, machine vision systems, and video conferencing. Therefore, the requirements for optical imaging lenses are also getting higher and higher.

[0003] However, existing optical lenses still have shortcomings, such as the inability to simultaneously possess large aperture and wide field of view. Therefore, they need to be improved to meet usage requirements. Summary of the Invention

[0004] This invention provides a fixed-focus lens that combines imaging requirements, compact structure, large aperture, and ultra-wide field of view.

[0005] This invention provides a fixed-focus lens, comprising: a first lens having negative optical power, a second lens having negative optical power, a third lens having negative optical power, a fourth lens having positive optical power, a fifth lens having positive optical power, a sixth lens having negative optical power, a seventh lens having positive optical power, an eighth lens having negative optical power, and a ninth lens having positive optical power, arranged sequentially along the optical axis from the object plane to the image plane.

[0006] Wherein, the first lens, the second lens, the third lens, the fourth lens, and the fifth lens are all glass spherical lenses; the sixth lens, the seventh lens, the eighth lens, and the ninth lens are all plastic aspherical lenses;

[0007] The third lens and the fourth lens constitute a cemented lens; the eighth lens and the ninth lens constitute a cemented lens.

[0008] Optionally, the Abbe number Vd3 of the third lens can be in the range of: 44 < Vd3 < 99;

[0009] The Abbe number Vd4 of the fourth lens has the following range: 16 < Vd4 < 33.

[0010] Optionally, the Abbe number Vd5 of the fifth lens can be in the range of 32 < Vd5 < 60.

[0011] Optionally, the Abbe number of the eighth lens is less than the high Abbe number of the ninth lens.

[0012] Optionally, the refractive index Nd1 of the first lens can be in the range of 1.7 < Nd1 < 2.15.

[0013] The refractive index Nd2 of the second lens ranges from 1.65. <Nd2<2.1。

[0014] Optionally, the refractive index of the sixth lens is greater than that of the seventh lens.

[0015] Optionally, both the first lens and the second lens are meniscus lenses with a convex object side and a concave image side.

[0016] Among them, -0.74<(Φ1+Φ2) / Φ<-0.46;

[0017] Φ1 is the optical power of the first lens, Φ2 is the optical power of the second lens, and Φ is the optical power of the optical system of the fixed-focus lens.

[0018] Optionally, the third lens is a biconcave lens with both the object-side and image-side surfaces concave, and the fourth lens is a biconvex lens with both the object-side and image-side surfaces convex.

[0019] Among them, -0.40<Φ3 / Φ<-0.24, 0.32<Φ4 / Φ<0.51;

[0020] Φ3 is the optical power of the third lens, Φ4 is the optical power of the fourth lens, and Φ is the optical power of the optical system of the fixed-focus lens.

[0021] Optionally, 0.27≤Φ5 / Φ≤0.35;

[0022] Wherein, Φ5 is the optical power of the fifth lens, and Φ is the optical power of the fixed-focus lens optical system.

[0023] Optionally, the sixth lens is a meniscus lens with a concave object side and a convex image side, and the seventh lens is a biconvex lens with both the object side and the image side being convex.

[0024] Among them, 0.40<(Φ6+Φ7) / Φ<0.65;

[0025] Φ6 is the optical power of the sixth lens, Φ7 is the optical power of the seventh lens, and Φ is the optical power of the fixed-focus lens optical system.

[0026] Optional, -0.14 < Φ89 / Φ < -0.04;

[0027] Wherein, Φ89 is the optical power of the cemented lens formed by the eighth lens and the ninth lens, and Φ is the optical power of the optical system of the fixed-focus lens.

[0028] The technical solution of this invention rationally allocates the optical power of each lens by combining the positive and negative optical powers of each lens. Simultaneously, it sets the first to fifth lenses as glass spherical lenses and the sixth to ninth lenses as plastic aspherical lenses, employing a combination of five glass spherical lenses and four plastic aspherical lenses. This allows for effective aberration correction and ensures good image quality at a lower cost, while also meeting the requirements of a large aperture, a wide field of view, and a small overall optical system length. It can be paired with a 4MP, 1 / 2.9-inch chip, enabling its application in a wider range of fields. Furthermore, by forming cemented lenses with the third and fourth lenses, and with the eighth and ninth lenses, it facilitates the correction of field curvature while meeting the requirements of a large aperture, thus satisfying the demand for high-definition imaging quality. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the structure of a fixed-focus lens provided by the present invention;

[0030] Figure 2 yes Figure 1 A schematic diagram of the spherical aberration curve of a fixed-focus lens is shown.

[0031] Figure 3 This is a schematic diagram of another fixed-focus lens provided by the present invention;

[0032] Figure 4 yes Figure 3 A schematic diagram of the spherical aberration curve of a fixed-focus lens is shown.

[0033] Figure 5 This is a schematic diagram of the structure of another fixed-focus lens provided by the present invention;

[0034] Figure 6 yes Figure 5 A schematic diagram of the spherical aberration curve of a fixed-focus lens is shown.

[0035] Figure 7 This is a schematic diagram of the structure of another fixed-focus lens provided by the present invention;

[0036] Figure 8 yes Figure 7 The diagram shows the spherical aberration curve of a fixed-focus lens. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be fully described below with reference to the accompanying drawings of the embodiments of this invention through specific implementation methods. Obviously, the described embodiments are only some, not all, embodiments of this invention. Various modifications and variations can be made to this invention without departing from the spirit or scope of this invention, which will be obvious to those skilled in the art. Therefore, this invention is intended to cover modifications and variations of this invention that fall within the scope of the corresponding claims (the claimed technical solutions) and their equivalents.

[0038] Furthermore, the terms "first," "second," and similar terms used in the embodiments of this disclosure do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similarly, terms such as "an," "one," or "the" do not indicate a quantity limitation, but rather indicate the presence of at least one. Terms such as "including" or "comprising" mean that the element or object preceding the word encompasses the elements or objects listed after the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are only used to indicate relative positional relationships, and these relative positional relationships may change accordingly when the absolute position of the described object changes. In addition, descriptions of "same" or "equal" in the embodiments of this disclosure do not mean that two objects are completely equal in size or shape; they are allowed to be approximately the same or approximately equal within a certain error range.

[0039] It should be noted that the implementation methods provided in the embodiments of the present invention can be combined with each other without contradiction.

[0040] Figure 1 This is a schematic diagram of the structure of a fixed-focus lens provided in an embodiment of the present invention, as shown below. Figure 1 As shown, the fixed-focus lens provided in this embodiment of the invention includes: a first lens 10 with negative optical power, a second lens 20 with negative optical power, a third lens 30 with negative optical power, a fourth lens 40 with positive optical power, a fifth lens 50 with positive optical power, a sixth lens 60 with negative optical power, a seventh lens 70 with positive optical power, an eighth lens 80 with negative optical power, and a ninth lens 90 with positive optical power, arranged sequentially along the optical axis from the object plane to the image plane; wherein, the first lens 10, the second lens 20, the third lens 30, the fourth lens 40, and the fifth lens 50 are all glass spherical lenses; the sixth lens 60, the seventh lens 70, the eighth lens 80, and the ninth lens 90 are all plastic aspherical lenses; the third lens 30 and the fourth lens 40 constitute a cemented lens; the eighth lens 80 and the ninth lens 90 constitute a cemented lens.

[0041] Optical power is equal to the difference between the convergence of the image-side beam and the convergence of the object-side beam; it characterizes the ability of an optical system to deflect light rays. The larger the absolute value of the optical power, the stronger the bending ability of light rays; the smaller the absolute value, the weaker the bending ability. When the optical power is positive, the refraction of light rays is converging; when the 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).

[0042] Specifically, each of the lenses from the first lens 10 to the ninth lens 90 can be fixed in a lens barrel. Figure 1 (Not shown) By setting the optical power of the first lens 10 to a negative value, a larger field of view is achieved, and the object-side light rays can smoothly enter the subsequent optical system, reducing the proportion of higher-order aberrations. Setting the optical power of both the second lens 20 and the third lens 30 to negative values ​​effectively reduces the angle of deviation of the light rays passing through the first lens 10 after passing through the second lens 20 and the third lens 30, which is beneficial for correcting system aberrations. Setting the optical power of the fourth lens 40 and the fifth lens 50 to positive values ​​allows the light rays passing through the first lens 10, the second lens 20, and the third lens 30 to slowly transition to the subsequent optical system via the fourth lens 40 and the fifth lens 50. In this optical system, the system aberrations can be further corrected, which helps to reduce the assembly tolerances between lenses, simplify the assembly method of the entire optical system, and improve the assemblability of the entire optical system. By setting the optical power of the sixth lens 60 to a negative value, the optical power of the seventh lens 70 to a positive value, the optical power of the eighth lens 80 to a negative value, and the optical power of the ninth lens 90 to a positive value, the lenses with positive optical power cooperate with the lenses with negative optical power. This ensures that the light reaches the image plane smoothly while further correcting the system aberrations, so that high imaging quality can be achieved under ambient light of different brightness, while meeting the requirements of large aperture and large field of view.

[0043] Optionally, both the first lens 10 and the second lens 20 are meniscus lenses with a convex object-side surface and a concave image-side surface; where -0.74 < (Φ1 + Φ2) / Φ < -0.46; Φ1 is the optical power of the first lens 10, Φ2 is the optical power of the second lens 20, and Φ is the optical power of the fixed-focus lens optical system. This configuration allows object-side light rays to enter the fixed-focus lens optical system smoothly, enabling light to enter the third lens 30 at a smaller angle of incidence, reducing the proportion of higher-order aberrations, decreasing the aperture of the fixed-focus lens, and shortening the overall length of the fixed-focus lens optical system.

[0044] Optionally, the third lens 30 is a biconcave lens with both its object-side and image-side surfaces concave, and the fourth lens 40 is a biconvex lens with both its object-side and image-side surfaces convex; where -0.40 < Φ3 / Φ < -0.24, 0.32 < Φ4 / Φ < 0.51; Φ3 is the optical power of the third lens 30, Φ4 is the optical power of the fourth lens 40, and Φ is the optical power of the fixed-focus lens optical system. This configuration can further smooth out the angle of light deflection, giving the fixed-focus lens optical system a more relaxed tolerance, which is beneficial to improving production yield.

[0045] Optionally, 0.27 ≤ Φ5 / Φ ≤ 0.35; where Φ5 is the optical power of the fifth lens 50, and Φ is the optical power of the fixed-focus lens optical system. The fifth lens 50 is a biconvex lens with both its object-side and image-side surfaces being convex. This configuration facilitates the achievement of a large aperture in the system.

[0046] Optionally, the sixth lens 60 is a meniscus lens with a concave object side and a convex image side, and the seventh lens 70 is a biconvex lens with both object and image sides being convex; where 0.40 < (Φ6 + Φ7) / Φ < 0.65; Φ6 is the optical power of the sixth lens 60, Φ7 is the optical power of the seventh lens 70, and Φ is the optical power of the fixed-focus lens optical system. This configuration can effectively reduce aberrations, thereby obtaining high-definition image quality.

[0047] Optionally, when the fixed-focus lens also includes an aperture stop 100, the aperture stop 100 can be set in the optical path between the sixth lens 60 and the seventh lens 70. In this case, by setting the optical power of the sixth lens 60 and the seventh lens 70 to the above-mentioned range, the aberration at the aperture stop 100 can be effectively reduced, which is beneficial to obtaining high-definition image quality.

[0048] Optionally, -0.14 < Φ89 / Φ < -0.04; where Φ89 is the optical power of the cemented lens composed of the eighth lens 80 and the ninth lens 90, and Φ is the optical power of the fixed-focus lens optical system. This setting is beneficial for correcting chromatic aberration and distortion, thereby obtaining high-definition image quality.

[0049] Continue to refer to Figure 1The first lens 10 to the fifth lens 50, a total of five lenses, are all glass spherical lenses, while the sixth lens 60 to the ninth lens 90, a total of four lenses, are all plastic aspherical lenses. The plastic aspherical lenses can be made of various plastics known to those skilled in the art, and the glass spherical lenses can be made of various types of glass known to those skilled in the art; this embodiment of the invention does not elaborate on or limit the materials used. Because glass spherical lenses have good surface smoothness, good light reflectivity, high impact resistance, and stable chemical properties, they are suitable for use in high and low temperature environments. Plastic aspherical lenses can correct aberrations such as field curvature, astigmatism, spherical aberration, and coma. Therefore, by using five glass spherical lenses and four plastic aspherical lenses, this embodiment of the invention ensures that the fixed-focus lens has high image quality while maintaining a low cost. Furthermore, because the two types of materials have a mutually compensating effect, the fixed-focus lens can still be used normally in high and low temperature environments.

[0050] Furthermore, the third lens 30 and the fourth lens 40 constitute a cemented lens, allowing the third lens 30 and the fourth lens 40 to be bonded together with glue, or supported by spacers or shims, resulting in a small air gap between the third lens 30 and the fourth lens 40; similarly, the eighth lens 80 and the ninth lens 90 constitute a cemented lens, allowing the eighth lens 80 and the ninth lens 90 to be bonded together with glue, or supported by spacers or shims, resulting in a small air gap between the eighth lens 80 and the ninth lens 90. Thus, by setting the third lens 30 and the fourth lens 40 as cemented lenses, and setting the eighth lens and the ninth lens as cemented lenses, it is beneficial to reduce the overall length of the optical system, allowing the fixed-focus lens to have a smaller overall length of the light system. At the same time, when adjacent lenses are cemented together, chromatic aberration can be minimized or eliminated, allowing various aberrations of the fixed-focus lens to be fully corrected. Under the premise of compact structure, resolution can be improved and optical performance optimized. In addition, when adjacent lenses are cemented together, light loss caused by light reflection between lenses can also be reduced, illumination can be increased, thereby improving image quality and image sharpness. Furthermore, the use of cemented lenses can also reduce the number of assembly parts between adjacent lenses, simplify the assembly process in the manufacturing process of fixed-focus lenses, reduce costs, and reduce tolerance sensitivity issues such as tilting / eccentricity of individual lenses during assembly.

[0051] Optionally, the Abbe number Vd3 of the third lens 30 has a range of 44 < Vd3 < 99; the Abbe number Vd4 of the fourth lens 40 has a range of 16 < Vd4 < 33.

[0052] Optionally, the Abbe number Vd5 of the fifth lens 50 can be in the range of 32 < Vd5 < 60.

[0053] Optionally, the Abbe number of the eighth lens 80 is less than the high Abbe number of the ninth lens 90.

[0054] 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.

[0055] In one embodiment, by setting the Abbe number Vd3 of the third lens 30 to 44-99 and the Abbe number Vd4 of the fourth lens 40 to 16-33, the third lens 30 has a higher Abbe number and the fourth lens 40 has a lower Abbe number. This allows the third lens 30 and the fourth lens 40 to work together to achieve high imaging quality while satisfying the requirements of a large aperture and a wide field of view.

[0056] In another embodiment, by setting the Abbe number Vd5 of the fifth lens 50 to 32-60, the chromatic aberration of the system can be effectively reduced, thereby obtaining high-definition image quality.

[0057] In another embodiment, by setting the Abbe number of the eighth lens 80 to be lower than the high Abbe number of the ninth lens 90, the eighth lens 80 can have a lower Abbe number while the ninth lens 90 can have a higher Abbe number. This can effectively reduce chromatic aberration and spherical aberration in the system, which is beneficial for achieving high-definition image quality.

[0058] Optionally, the refractive index Nd1 of the first lens 10 has a range of 1.7 < Nd1 < 2.15; the refractive index Nd2 of the second lens has a range of 1.65. <Nd2<2.1。

[0059] Optionally, the refractive index of the sixth lens 60 is greater than that of the seventh lens 70.

[0060] 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.

[0061] In one embodiment, by setting the refractive index Nd1 of the first lens 10 to 1.7 to 2.15 and the refractive index of the second lens 20 to 1.65 to 2.1, both the first lens 10 and the second lens 20 are made of high refractive index materials, which can better allow large-angle light to enter the third lens 30, which is beneficial to the realization of ultra-large field of view, and at the same time, it is beneficial to reduce the light transmission aperture of the fixed-focus lens and the overall length of the optical system.

[0062] In another embodiment, by setting the refractive index of the sixth lens 60 to be greater than that of the seventh lens 70, the sixth lens 60 can be made of a material with a higher refractive index, while the seventh lens 70 can be made of a material with a lower refractive index. The combination of the refractive indices of the sixth lens 60 and the seventh lens 70 can further reduce the aberrations of the system, which is beneficial to achieving high-definition image quality.

[0063] Optionally, the fixed-focus lens may also include a filter 110, which may be disposed on the image plane side of the ninth lens. The filter 110 can filter out unwanted stray light, thereby improving the image quality of the fixed-focus lens. For example, the filter 110 can filter out infrared light during the day to improve the image quality of the fixed-focus lens. At the same time, the filter 100 can also protect the imaging sensor.

[0064] This invention, through the rational allocation of the optical power, Abbe number, and refractive index of each lens, and by setting the first to fifth lenses as glass spherical lenses and the sixth to ninth lenses as plastic aspherical lenses (i.e., using a mixture of five glass spherical lenses and four plastic aspherical lenses), and by forming cemented lenses with the third and fourth lenses and with the eighth and ninth lenses, achieves excellent aberration correction at a lower cost. This is beneficial for correcting field curvature of the system, ensuring high-definition imaging quality, while also meeting the requirements of a large aperture, a large field of view, and a small overall optical system length. It can be paired with a 4MP, 1 / 2.9-inch chip, making it applicable to a wider range of fields.

[0065] The following describes in further detail, with reference to the accompanying drawings, specific embodiments of a fixed-focus lens applicable to the above-described embodiments.

[0066] In one feasible embodiment, Table 1 details a feasible implementation method. Figure 1 The specific optical and physical parameters of the fixed-focus lens are shown.

[0067] Table 1. Design of optical physical parameters for a fixed-focus lens

[0068]

[0069] The fixed-focus lens in this embodiment has a focal length f of 1.76mm and an aperture number F# of 1.06.

[0070] Table 2 shows the design parameters of each lens in a fixed-focus lens, including surface type, radius of curvature, thickness, and material, corresponding to those in Table 1.

[0071] Table 2. Parameter Design of Each Lens in a Fixed-Focus Lens

[0072]

[0073] The fixed-focus lens provided in this embodiment includes a first lens 10, a second lens 20, a third lens 30, a fourth lens 40, a fifth lens 50, a sixth lens 60, an aperture stop 100, a seventh lens 70, an eighth lens 80, a ninth lens 90, and a filter 110 arranged sequentially from the object side to the image side along the optical axis. The surface numbers in Table 2 are assigned according to the surface sequence of each lens. "STO" represents the aperture stop of a fixed-focus lens; "IMA" represents the image plane of a fixed-focus lens; the radius of curvature represents the curvature of the lens surface, with a positive value indicating that the surface bends towards the image plane and a negative value indicating that the surface bends towards the object plane, where "Infinity" indicates that the surface is flat and the radius of curvature is infinite; the thickness represents the central axial distance between the current surface and the next surface; the refractive index represents the ability of the material between the current surface and the next surface to deflect light, with a blank space indicating that the current position is air and the refractive index is 1; the Abbe number represents the dispersion characteristics of the material between the current surface and the next surface, with a blank space indicating that the current position is air; half-aperture represents the light-gathering ability of the lens at its maximum aperture; and the k-value represents the magnitude of the conic coefficient of the aspherical surface.

[0074] In this embodiment, the aspherical conic coefficient of the fixed-focus lens can be defined by the following aspherical formula, but is not limited to the following representation:

[0075] ;

[0076] Where z is the axial sagitta in the Z direction of the aspherical surface; r is the height of the aspherical surface; c is the curvature of the fitted sphere, which is numerically the reciprocal of the radius of curvature; k is the coefficient of the fitted cone; A, B, C, D, E and F are the coefficients of the 4th, 6th, 8th, 10th, 12th and 14th order terms of the aspherical polynomial, respectively.

[0077] Table 3 Aspherical coefficients of a fixed-focus lens

[0078]

[0079] Where 1.617661E-02 indicates that the coefficient A of surface number S10 is 1.617661 × 10 -2 .

[0080] Figure 2 yes Figure 1 The diagram shows a schematic of the spherical aberration curve for a fixed-focus lens. (See attached diagram.) Figure 2 The axial aberration curves shown have the following dimensions: the vertical direction represents the normalized aperture (0 indicates on the optical axis), and the vertical vertex represents 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 the system imaging, determined by... Figure 2It can be seen that the axial aberrations of different wavelengths are all controlled within the range of (-0.05mm, +0.05mm), indicating that the spherical aberration of this fixed-focus lens is well controlled at each wavelength, which can meet the requirements of wide-spectrum applications.

[0081] In another feasible embodiment, Figure 3 This is a schematic diagram of another fixed-focus lens provided in an embodiment of the present invention. Table 4 describes in detail another feasible implementation. Figure 3 The specific optical and physical parameters of the fixed-focus lens are shown.

[0082] Table 4. Another optical physical parameter design for fixed-focus lenses

[0083]

[0084] The fixed-focus lens in this embodiment has a focal length f of 1.74mm and an aperture number F# of 1.06.

[0085] Table 5 shows the design parameters of each lens in another fixed-focus lens corresponding to Table 4, including surface type, radius of curvature, thickness, and material.

[0086] Table 5. Another parameter design for each lens in a fixed-focus lens.

[0087]

[0088] The fixed-focus lens provided in this embodiment includes a first lens 10, a second lens 20, a third lens 30, a fourth lens 40, a fifth lens 50, a sixth lens 60, an aperture stop 100, a seventh lens 70, an eighth lens 80, a ninth lens 90, and a filter 110 arranged sequentially from the object side to the image side along the optical axis. The surface numbers in Table 5 are assigned according to the surface sequence of each lens. "STO" represents the aperture stop of a fixed-focus lens; "IMA" represents the image plane of a fixed-focus lens; the radius of curvature represents the curvature of the lens surface, with a positive value indicating that the surface bends towards the image plane and a negative value indicating that the surface bends towards the object plane, where "Infinity" indicates that the surface is flat and the radius of curvature is infinite; the thickness represents the central axial distance between the current surface and the next surface; the refractive index represents the ability of the material between the current surface and the next surface to deflect light, with a blank space indicating that the current position is air and the refractive index is 1; the Abbe number represents the dispersion characteristics of the material between the current surface and the next surface, with a blank space indicating that the current position is air; half-aperture represents the light-gathering ability of the lens at its maximum aperture; and the k-value represents the magnitude of the conic coefficient of the aspherical surface.

[0089] In this embodiment, the aspherical conic coefficient of the fixed-focus lens can be defined by the following aspherical formula, but is not limited to the following representation:

[0090] ;

[0091] Where z is the axial sagitta in the Z direction of the aspherical surface; r is the height of the aspherical surface; c is the curvature of the fitted sphere, which is numerically the reciprocal of the radius of curvature; k is the coefficient of the fitted cone; A, B, C, D, E and F are the coefficients of the 4th, 6th, 8th, 10th, 12th and 14th order terms of the aspherical polynomial, respectively.

[0092] Table 6 Aspherical coefficients of another type of fixed-focus lens

[0093]

[0094] Where 1.630638E-02 indicates that the coefficient A of surface number S10 is 1.630638 × 10 -2 .

[0095] Figure 4 yes Figure 3 The diagram shows a schematic of the spherical aberration curve for a fixed-focus lens. (See attached diagram.) Figure 4 The axial aberration curves shown have the following dimensions: the vertical direction represents the normalized aperture (0 indicates on the optical axis), and the vertical vertex represents 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 the system imaging, determined by... Figure 4 It can be seen that the axial aberrations of different wavelengths are all controlled within the range of (-0.05mm, +0.05mm), indicating that the spherical aberration of this fixed-focus lens is well controlled at each wavelength, which can meet the requirements of wide-spectrum applications.

[0096] In yet another feasible embodiment, Figure 5 This is a schematic diagram of another fixed-focus lens provided in the embodiments of the present invention. Table 7 describes in detail another feasible implementation method. Figure 5 The specific optical and physical parameters of the fixed-focus lens are shown.

[0097] Table 7 Another optical physical parameter design for fixed-focus lenses

[0098]

[0099] The fixed-focus lens in this embodiment has a focal length f of 2.06mm and an aperture number F# of 1.05.

[0100] Table 8 shows the design parameters of the surface type, radius of curvature, thickness, and material of each lens in another type of fixed-focus lens, corresponding to Table 7.

[0101] Table 8. Another parameter design for each lens in a fixed-focus lens.

[0102]

[0103] The fixed-focus lens provided in this embodiment includes a first lens 10, a second lens 20, a third lens 30, a fourth lens 40, a fifth lens 50, a sixth lens 60, an aperture stop 100, a seventh lens 70, an eighth lens 80, a ninth lens 90, and a filter 110 arranged sequentially from the object side to the image side along the optical axis. The surface numbers in Table 8 are assigned according to the surface sequence of each lens. "STO" represents the aperture stop of a fixed-focus lens; "IMA" represents the image plane of a fixed-focus lens; the radius of curvature represents the curvature of the lens surface, with a positive value indicating that the surface bends towards the image plane and a negative value indicating that the surface bends towards the object plane, where "Infinity" indicates that the surface is flat and the radius of curvature is infinite; the thickness represents the central axial distance between the current surface and the next surface; the refractive index represents the ability of the material between the current surface and the next surface to deflect light, with a blank space indicating that the current position is air and the refractive index is 1; the Abbe number represents the dispersion characteristics of the material between the current surface and the next surface, with a blank space indicating that the current position is air; half-aperture represents the light-gathering ability of the lens at its maximum aperture; and the k-value represents the magnitude of the conic coefficient of the aspherical surface.

[0104] In this embodiment, the aspherical conic coefficient of the fixed-focus lens can be defined by the following aspherical formula, but is not limited to the following representation:

[0105] ;

[0106] Where z is the axial sagitta in the Z direction of the aspherical surface; r is the height of the aspherical surface; c is the curvature of the fitted sphere, which is numerically the reciprocal of the radius of curvature; k is the coefficient of the fitted cone; A, B, C, D, E and F are the coefficients of the 4th, 6th, 8th, 10th, 12th and 14th order terms of the aspherical polynomial, respectively.

[0107] Table 9 Aspherical coefficients of another type of fixed-focus lens

[0108]

[0109] Where 1.652120E-02 indicates that the coefficient A of surface number S10 is 1.652120 × 10 -2 .

[0110] Figure 6 yes Figure 5 The diagram shows a schematic of the spherical aberration curve for a fixed-focus lens. (See attached diagram.) Figure 5The axial aberration curves shown have the following dimensions: the vertical direction represents the normalized aperture (0 indicates on the optical axis), and the vertical vertex represents 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 the system imaging, determined by... Figure 6 It can be seen that the axial aberrations of different wavelengths are all controlled within the range of (-0.05mm, +0.05mm), indicating that the spherical aberration of this fixed-focus lens is well controlled at each wavelength, which can meet the requirements of wide-spectrum applications.

[0111] In yet another feasible embodiment, Figure 7 This is a schematic diagram of another fixed-focus lens provided in the embodiments of the present invention. Table 10 describes in detail another feasible implementation method. Figure 7 The specific optical and physical parameters of the fixed-focus lens are shown.

[0112] Table 10 Another optical physical parameter design for fixed-focus lenses

[0113]

[0114] The fixed-focus lens in this embodiment has a focal length f of 1.85mm and an aperture number F# of 1.06.

[0115] Table 11 shows the design parameters of the surface type, radius of curvature, thickness, and material of each lens in another type of fixed-focus lens, corresponding to Table 10.

[0116] Table 11 Another parameter design for each lens in a fixed-focus lens

[0117]

[0118] The fixed-focus lens provided in this embodiment includes a first lens 10, a second lens 20, a third lens 30, a fourth lens 40, a fifth lens 50, a sixth lens 60, an aperture stop 100, a seventh lens 70, an eighth lens 80, a ninth lens 90, and a filter 110 arranged sequentially from the object side to the image side along the optical axis. The surface numbers in Table 11 are assigned according to the surface sequence of each lens. "STO" represents the aperture stop of a fixed-focus lens; "IMA" represents the image plane of a fixed-focus lens; the radius of curvature represents the curvature of the lens surface, with a positive value indicating that the surface bends towards the image plane and a negative value indicating that the surface bends towards the object plane. "Infinity" indicates that the surface is flat and the radius of curvature is infinite; the thickness represents the central axial distance between the current surface and the next surface; the refractive index represents the ability of the material between the current surface and the next surface to deflect light, with a blank space indicating that the current position is air and the refractive index is 1; the Abbe number represents the dispersion characteristics of the material between the current surface and the next surface, with a blank space indicating that the current position is air; half-aperture represents the light-gathering ability of the lens at its maximum aperture; and the k-value represents the magnitude of the conic coefficient of the aspherical surface.

[0119] In this embodiment, the aspherical conic coefficient of the fixed-focus lens can be defined by the following aspherical formula, but is not limited to the following representation:

[0120] ;

[0121] Where z is the axial sagitta in the Z direction of the aspherical surface; r is the height of the aspherical surface; c is the curvature of the fitted sphere, which is numerically the reciprocal of the radius of curvature; k is the coefficient of the fitted cone; A, B, C, D, E and F are the coefficients of the 4th, 6th, 8th, 10th, 12th and 14th order terms of the aspherical polynomial, respectively.

[0122] Table 12 Aspherical coefficients of another type of fixed-focus lens

[0123]

[0124] Where 1.522184E-02 indicates that the coefficient A of surface number S10 is 1.522184 × 10 -2 .

[0125] Figure 8 yes Figure 7 The diagram shows a schematic of the spherical aberration curve for a fixed-focus lens. (See attached diagram.) Figure 8 The axial aberration curves shown have the following dimensions: the vertical direction represents the normalized aperture (0 indicates on the optical axis), and the vertical vertex represents 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 the system imaging, determined by... Figure 8It can be seen that the axial aberrations of different wavelengths are all controlled within the range of (-0.05mm, +0.05mm), indicating that the spherical aberration of this fixed-focus lens is well controlled at each wavelength, which can meet the requirements of wide-spectrum applications.

[0126] Note that the above description is merely a preferred embodiment of the present invention and the technical principles employed. 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, include: The fixed-focus lens comprises nine lenses of optical power arranged sequentially along the optical axis from the object plane to the image plane: a first lens with negative optical power, a second lens with negative optical power, a third lens with negative optical power, a fourth lens with positive optical power, a fifth lens with positive optical power, a sixth lens with negative optical power, a seventh lens with positive optical power, an eighth lens with negative optical power, and a ninth lens with positive optical power. Wherein, the first lens, the second lens, the third lens, the fourth lens, and the fifth lens are all glass spherical lenses; the sixth lens, the seventh lens, the eighth lens, and the ninth lens are all plastic aspherical lenses; The third lens and the fourth lens constitute a cemented lens; the eighth lens and the ninth lens constitute a cemented lens; The first lens and the second lens are both meniscus lenses with a convex object side and a concave image side; the third lens is a double concave lens with both the object side and the image side being concave; the fourth lens is a double convex lens with both the object side and the image side being convex; the sixth lens is a meniscus lens with a concave object side and a convex image side; and the seventh lens is a double convex lens with both the object side and the image side being convex. Among them, -0.56≤(Φ1+Φ2) / Φ<-0.46, -0.40<Φ3 / Φ<-0.24, 0.32<Φ4 / Φ<0.5 1, 0.27≤Φ5 / Φ≤0.35, 0.40<(Φ6+Φ7) / Φ≤0.52, -0.14<Φ89 / Φ<-0.04; Φ1 is the optical power of the first lens, Φ2 is the optical power of the second lens, Φ3 is the optical power of the third lens, Φ4 is the optical power of the fourth lens, Φ5 is the optical power of the fifth lens, Φ6 is the optical power of the sixth lens, Φ7 is the optical power of the seventh lens, Φ89 is the optical power of the cemented lens composed of the eighth and ninth lenses, and Φ is the optical power of the optical system of the fixed-focus lens.

2. The fixed-focus lens according to claim 1, characterized in that, The Abbe number Vd3 of the third lens ranges from 44 to 69.

9. The Abbe number Vd4 of the fourth lens has the following range: 16 < Vd4 < 33.

3. The fixed-focus lens according to claim 1, characterized in that, The Abbe number Vd5 of the fifth lens has a range of 32 < Vd5 < 60.

4. The fixed-focus lens according to claim 1, characterized in that, The Abbe number of the eighth lens is less than that of the ninth lens.

5. The fixed-focus lens according to claim 1, characterized in that, The refractive index Nd1 of the first lens has a range of 1.7 < Nd1 < 2.15; The refractive index Nd2 of the second lens ranges from 1.

65. <Nd2<2.1。 6. The fixed-focus lens according to claim 1, characterized in that, The refractive index of the sixth lens is greater than that of the seventh lens.

Images