Industrial lenses

Abstract

The application discloses an industrial lens, which comprises, in sequence from the object side to the image side along the optical axis, a first lens with positive refractive power, the object side of which is convex; a second lens with positive refractive power, the object side of which is convex; a third lens with negative refractive power, the image side of which is concave; a fourth lens with positive refractive power; a fifth lens with negative refractive power, the object side of which is concave, and the image side of which is concave; a sixth lens with positive refractive power, the image side of which is convex; the number of lenses with refractive power in the industrial lens is six; and the industrial lens satisfies 1.61≤fa / fb≤4.22, wherein fa is the combined effective focal length of the first lens to the third lens, and fb is the combined effective focal length of the fourth lens to the sixth lens.

Description

Technical Field

[0001] This application relates to the field of imaging lens technology, and more specifically, to an industrial lens. Background Technology

[0002] Industrial lenses can be widely used in various barcode scanning applications in parking management, payment, industry, and logistics management. As the application fields of industrial lenses become more and more extensive, the market demand for industrial lenses is also increasing. However, existing industrial lenses generally suffer from the disadvantage of complex lens structure, making it difficult to ensure low lens cost, while also making it difficult to achieve indicators such as wide working distance range, high resolution, low distortion, and high illumination.

[0003] Therefore, in view of the shortcomings of the prior art, the present invention provides a high-performance industrial lens that, while satisfying the requirements of simple lens structure and low cost, still has a wide working object distance range, is suitable for large chip target surfaces, and takes into account high resolution and low distortion, and has high illumination in each field of view within the working object distance range of 40mm to infinity. Summary of the Invention

[0004] This application provides an industrial lens, which comprises, along the optical axis from the object side to the image side, the following elements in sequence: a first lens with positive optical power, the object side of which is convex; a second lens with positive optical power, the object side of which is convex; a third lens with negative optical power, the image side of which is concave; a fourth lens with positive optical power; a fifth lens with negative optical power, the object side of which is concave and the image side of which is concave; and a sixth lens with positive optical power, the image side of which is convex. The number of lenses with optical power in the industrial lens is six. The industrial lens satisfies the following condition: 1.61 ≤ fa / fb ≤ 4.22, where fa is the combined effective focal length of the first to third lenses, and fb is the combined effective focal length of the fourth to sixth lenses.

[0005] According to an exemplary embodiment of this application, the first lens image side of the industrial lens is convex, concave, or flat; the second lens image side is convex, concave, or flat; the third lens object side is convex, concave, or flat; the fourth lens object side is convex, concave, or flat, and its image side is convex; the sixth lens object side is convex, concave, or flat.

[0006] According to an exemplary embodiment of this application, the industrial lens includes an aperture stop located between a third lens and a fourth lens.

[0007] According to an exemplary embodiment of this application, the industrial lens satisfies at least one of the following conditions: 1.31≤fa / f≤2.78, 0.59≤fb / f≤0.90, where fa is the combined effective focal length of the first to third lenses, fb is the combined effective focal length of the fourth to sixth lenses, and f is the total effective focal length of the industrial lens.

[0008] According to an exemplary embodiment of this application, the industrial lens satisfies at least one of the following conditions: -9.55mm≤(f2+f3)*f23 / (f1+f2+f3)≤-2.77mm, 0.53≤((nd1+nd3) / nd2)*(f1+f3) / fa≤1.07, -1.01≤f23 / fa≤-0.23, where fa is the combined effective focal length of the first to third lenses, f23 is the combined effective focal length of the second to third lenses, f1 is the effective focal length of the first lens, f2 is the effective focal length of the second lens, f3 is the effective focal length of the third lens, nd1 is the refractive index of the first lens, nd2 is the refractive index of the second lens, and nd3 is the refractive index of the third lens.

[0009] According to an exemplary embodiment of this application, the industrial lens satisfies at least one of the following conditions: 0.62≤(f4+f5+f6) / fb≤1.11, -2.26≤(R32 / R51)*(f3 / f5)≤-0.13, -1.63≤R5n / f5≤-0.94, 0.36≤TCbn_max / fbn≤1.21, where f3 is the effective focal length of the third lens, f4 is the effective focal length of the fourth lens, and f5 is the effective focal length of the fifth lens. Where f6 is the effective focal length of the sixth lens, fb is the combined effective focal length of the fourth to sixth lenses, R32 is the radius of curvature of the image side of the third lens, R51 is the radius of curvature of the object side of the fifth lens, R5n is the minimum absolute value of the radius of curvature of the object side or image side of the fifth lens, TCbn_max is the maximum value of the center thickness of any one of the fourth, fifth, and sixth lenses, and fbn is the minimum absolute value of the effective focal length of any one of the fourth, fifth, and sixth lenses.

[0010] According to an exemplary embodiment of this application, the industrial lens satisfies at least one of the following conditions: 1.20≤(f1+f6) / f≤1.63, 4.61≤(R11+R21)*(f1+f2) / |R62*f6|≤9.04, 6.32mm -1 ≤(vd4+vd6) / f6≤10.05mm -1, 0.11≤(TCn_max-TCn_min) / TCn_sum≤0.17, where f1 is the effective focal length of the first lens, f2 is the effective focal length of the second lens, f6 is the effective focal length of the sixth lens, f is the total effective focal length of the industrial lens, R11 is the radius of curvature of the object side of the first lens, R21 is the radius of curvature of the object side of the second lens, R62 is the radius of curvature of the image side of the sixth lens, vd4 is the Abbe number of the fourth lens, vd6 is the Abbe number of the sixth lens, TCn_max is the maximum value of the center thickness of any lens from the first to the sixth lens, TCn_min is the minimum value of the center thickness of any lens from the first to the sixth lens, and TCn_sum is the sum of the center thicknesses of the lenses from the first to the sixth lens.

[0011] According to an exemplary embodiment of this application, the industrial lens satisfies at least one of the following conditions: 10.03mm≤fb*(TC4+TC5+TC6) / CTb≤14.15mm, 1.73≤CTb / CTa≤2.58, where fb is the combined effective focal length of the fourth to sixth lenses, TC4 is the center thickness of the fourth lens, TC5 is the center thickness of the fifth lens, TC6 is the center thickness of the sixth lens, CTa is the center distance from the object side of the first lens to the aperture plane, and CTb is the center distance from the aperture plane to the image side of the sixth lens.

[0012] According to an exemplary embodiment of this application, the industrial lens satisfies at least one of the following conditions: 1.78≤fa / fb≤3.84, 1.45≤fa / f≤2.53, 0.65≤fb / f≤0.82, -0.92≤f23 / fa≤-0.26, -8.69mm≤(f2+f3)*f23 / (f1+f2+f3)≤-3.07mm, 0.68≤(f4+f5+f6) / fb≤0.94, -2.06≤(R32 / R51)*(f3 / f5)≤ -0.24, -1.44≤R5n / f5≤-1.00, 0.58≤((nd1+nd3) / nd2)*(f1+f3) / fa≤0.98, 1.31≤(f1+f6) / f≤1.48, 5.11≤(R11+ R21)*(f1+f2) / |R62*f6|≤8.23,11.23mm≤fb*(TC4+TC5+TC6) / CTb≤12.87mm,0.40≤TCbn_max / fbn≤1.11,7.03mm -1 ≤(vd4+vd6) / f6≤9.14mm -1, 0.11≤(TCn_max-TCn_min) / TCn_sum≤0.16, 1.92≤CTb / CTa≤2.35, where fa is the combined effective focal length of the first to third lenses, fb is the combined effective focal length of the fourth to sixth lenses, f is the total effective focal length of the industrial lens, f23 is the combined effective focal length of the second to third lenses, f1 is the effective focal length of the first lens, f2 is the effective focal length of the second lens, f3 is the effective focal length of the third lens, f4 is the effective focal length of the fourth lens, f5 is the effective focal length of the fifth lens, f6 is the effective focal length of the sixth lens, R11 is the radius of curvature of the object-side surface of the first lens, R21 is the radius of curvature of the object-side surface of the second lens, R32 is the radius of curvature of the image-side surface of the third lens, R51 is the radius of curvature of the object-side surface of the fifth lens, R62 is the radius of curvature of the image-side surface of the sixth lens, and R5n is the absolute value of the radius of curvature of the object-side or image-side surface of the fifth lens. The minimum value of , nd1 is the refractive index of the first lens, nd2 is the refractive index of the second lens, nd3 is the refractive index of the third lens, vd4 is the Abbe number of the fourth lens, vd6 is the Abbe number of the sixth lens, TC4 is the center thickness of the fourth lens, TC5 is the center thickness of the fifth lens, TC6 is the center thickness of the sixth lens, TCbn_max is the maximum value of the center thickness of any one of the fourth, fifth and sixth lenses, fbn is the minimum absolute value of the effective focal length of any one of the fourth, fifth and sixth lenses, TCn_max is the maximum value of the center thickness of any one of the first to sixth lenses, TCn_min is the minimum value of the center thickness of any one of the first to sixth lenses, TCn_sum is the sum of the center thicknesses of the first to sixth lenses, CTa is the center distance from the object side of the first lens to the aperture plane, and CTb is the center distance from the aperture plane to the image side of the sixth lens.

[0013] The industrial lens of this application, by reasonably setting the number of lenses (e.g., six) and rationally allocating the relationship between the optical power, lens surface shape and lens parameters of each lens, makes the industrial lens provided by this application have the characteristics of simple structure, low cost and wide working object distance range (WD≥40mm), which can be adapted to large chip target surfaces (1 / 1.8” chip), while taking into account high resolution, low distortion (optical distortion |DIS|≤0.65%), and high relative illumination (relative illumination>88%) in each field of view in the working object distance range from 40mm to infinity. Attached Figure Description

[0014] Other features, objects, and advantages of this application will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0015] Figure 1This is a schematic diagram of the structure of an industrial lens according to Embodiment 1 of this application;

[0016] Figure 2 This is a distortion curve diagram of an industrial lens according to Embodiment 1 of this application;

[0017] Figure 3 This is a schematic diagram of the structure of an industrial lens according to Embodiment 2 of this application;

[0018] Figure 4 This is a distortion curve diagram of an industrial lens according to Embodiment 2 of this application;

[0019] Figure 5 This is a schematic diagram of the structure of an industrial lens according to Embodiment 3 of this application;

[0020] Figure 6 This is a distortion curve diagram of an industrial lens according to Embodiment 3 of this application;

[0021] Figure 7 This is a schematic diagram of the structure of an industrial lens according to Embodiment 4 of this application;

[0022] Figure 8 This is a distortion curve diagram of an industrial lens according to Embodiment 4 of this application. Detailed Implementation

[0023] To better understand this application, various aspects of this application will be described in more detail with reference to the accompanying drawings. It should be understood that these detailed descriptions are merely illustrative of exemplary embodiments of this application and are not intended to limit the scope of this application in any way. Throughout the specification, the same reference numerals refer to the same elements. The expression "and / or" includes any and all combinations of one or more of the associated listed items.

[0024] It should be noted that in this specification, the terms "first," "second," "third," etc., are used only to distinguish one feature from another and do not imply any limitation on the features. Therefore, without departing from the teachings of this application, the first lens discussed below may also be referred to as the second lens or the third lens.

[0025] In the accompanying drawings, the thickness, size, and shape of the lenses have been slightly exaggerated for ease of illustration. Specifically, the shapes of the spherical or aspherical surfaces shown in the drawings are illustrated by way of example. That is, the shapes of the spherical or aspherical surfaces are not limited to those shown in the drawings. The drawings are for illustrative purposes only and are not strictly to scale.

[0026] In this article, the paraxial region refers to the region near the optical axis. If the lens surface is convex and the location of the convexity is not defined, it means that the lens surface is convex at least in the paraxial region; if the lens surface is concave and the location of the concaveness is not defined, it means that the lens surface is concave at least in the paraxial region. The surface of each lens closest to the subject is called the object-side surface of the lens, and the surface of each lens closest to the imaging plane is called the image-side surface of the lens.

[0027] It should also be understood that the terms "comprising," "having," "including," etc., when used in this specification, indicate the presence of the stated features, elements, and / or components, but do not exclude the presence or addition of one or more other features, elements, components, and / or combinations thereof. Furthermore, when a statement such as "at least one of..." appears after a list of listed features, it modifies the entire list of features, not individual elements in the list. Additionally, when describing embodiments of this application, the word "may" is used to indicate "one or more embodiments of this application." And the term "exemplary" is intended to refer to an example or illustration.

[0028] Unless otherwise specified, all terms used herein (including technical and scientific terms) shall have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. It should also be understood that terms (e.g., those defined in common dictionaries) shall be interpreted as having the meaning consistent with their meaning in the context of the relevant art and shall not be interpreted in an idealized or overly formalized sense, unless expressly so specified herein.

[0029] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0030] An industrial lens according to an exemplary embodiment of this application may include six lenses of optical power sequentially from the object side to the image side along the optical axis, namely a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and a sixth lens.

[0031] In an exemplary embodiment, the first lens of the industrial lens has positive optical power. The object-side surface of the first lens can be convex, and the image-side surface can be convex, concave, or flat. This arrangement can effectively converge incident light rays and diverge the large field of view light entering the optical system into the rear optical system, effectively increasing the light transmission and improving the illumination of the optical system.

[0032] In an exemplary embodiment, the second lens of the industrial lens has positive optical power. The object-side surface of the second lens can be convex, and the image-side surface can be convex, concave, or flat. The third lens of the industrial lens has negative optical power. The object-side surface of the third lens can be convex, concave, or flat, and the image-side surface can be concave. The second and third lenses can form a cemented doublet lens. This arrangement can reduce the angle of incidence of light between the second and third lenses, thereby effectively reducing the tolerance sensitivity between the second and third lenses and ensuring the production yield of the lens; at the same time, it makes the light transition smooth, effectively corrects spherical aberration, and can also correct on-axis chromatic aberration, improving the resolution of the lens.

[0033] In an exemplary embodiment, the fourth lens of the industrial lens has positive optical power. The object-side surface of the fourth lens can be convex, concave, or flat, while the image-side surface is convex. This configuration effectively controls the direction of light, allowing for a smooth transition of light rays, effectively reducing the tolerance sensitivity of the lens, and improving the quality of the lens. Simultaneously, the fourth lens can be made of a low Abbe number glass lens material, which, when combined with the third lens which also uses a low Abbe number glass lens material, helps to balance astigmatism and improve the resolving performance of the lens.

[0034] In an exemplary embodiment, the fifth lens of the industrial lens has negative optical power. The object-side surface of the fifth lens can be concave, and the image-side surface can also be concave. This arrangement helps to balance aberrations in the peripheral field of view of the industrial lens, while correcting distortion and achieving low distortion characteristics; it also effectively controls the light path, further elevating the light and contributing to a large target area for the lens.

[0035] In an exemplary embodiment, the sixth lens of the industrial lens has positive optical power. The object-side surface of the sixth lens can be convex, concave, or flat, while the image-side surface is convex. This arrangement effectively controls the light path, allowing the light to smoothly transition onto the image plane. It also effectively controls the exit angle of the light passing through the sixth lens, which is beneficial for matching the CRA chip and helps to achieve a large target area in the lens. Simultaneously, the sixth lens can be made of a high Abbe number glass lens material, which can be used in conjunction with a fifth lens made of a low Abbe number glass lens material. This combination of high and low Abbe number lens materials helps to correct chromatic aberration and field curvature in the optical system, improving the quality of the lens.

[0036] In the exemplary embodiment, since the curvature radii of the image-side surface of the first lens, the image-side surface of the second lens, the object-side surface of the fourth lens, and the object-side surface of the sixth lens are all relatively large, it is easy for the convex, flat, and concave surfaces to change or be finely adjusted. Generally, the impact on the overall technical effect of the optical system is small. Those skilled in the art can use the larger curvature radius of the surface as the optimization boundary condition. Obviously, no creative effort is required.

[0037] In an exemplary embodiment, the industrial lens satisfies: 1.61 ≤ fa / fb ≤ 4.22, where fa is the combined effective focal length of the first to third lenses, and fb is the combined effective focal length of the fourth to sixth lenses. By rationally allocating the ratio of the combined effective focal length of the first to third lenses to the combined effective focal length of the fourth to sixth lenses, it is beneficial to rationally configure the relationship between the combined effective focal lengths of the lenses before and after the aperture stop in the optical system. This helps ensure that the industrial lens achieves a wide working object distance range, effectively reduces chromatic aberration generated by the optical system, and effectively corrects distortion. This allows the industrial lens to achieve low distortion across the entire working object distance range from 40mm to infinity, while also maintaining high resolution. More specifically, the industrial lens may also satisfy 1.78 ≤ fa / fb ≤ 3.84.

[0038] In an exemplary embodiment, the industrial lens satisfies: 1.31 ≤ fa / f ≤ 2.78, where fa is the combined effective focal length of the first to third lenses, and f is the total effective focal length of the industrial lens. By reasonably controlling the ratio between the combined effective focal length of the first to third lenses and the total effective focal length of the industrial lens, the direction of light is effectively controlled, balancing the aberrations generated when light passes through the first to third lenses of the optical system, thus improving the imaging quality of the lens. Simultaneously, it also helps correct distortion, enabling the industrial lens to achieve low distortion and high resolution across the entire working object distance range from 40mm to infinity. More specifically, the industrial lens may also satisfy 1.45 ≤ fa / f ≤ 2.53.

[0039] In an exemplary embodiment, the industrial lens satisfies: 0.59 ≤ fb / f ≤ 0.90, where fb is the combined effective focal length of the fourth to sixth lenses, and f is the total effective focal length of the industrial lens. By reasonably controlling the ratio of the combined effective focal length of the fourth to sixth lenses to the total effective focal length of the industrial lens, chromatic aberration of the system can be effectively reduced, and lens resolution can be improved; at the same time, it also helps to correct distortion, enabling the industrial lens to achieve low distortion and high resolution across the entire working object distance range from 40mm to infinity. More specifically, the industrial lens may also satisfy 0.65 ≤ fb / f ≤ 0.82.

[0040] In an exemplary embodiment, the industrial lens satisfies: -1.01 ≤ f23 / fa ≤ -0.23, where fa is the combined effective focal length of the first to third lenses, and f23 is the combined effective focal length of the second to third lenses. By appropriately matching the ratio of the combined effective focal length of the second to third lenses to that of the first to third lenses, it is beneficial to control the light path, ensuring a smooth transition of light, effectively reducing the tolerance sensitivity between lenses, and helping to improve the lens production yield; at the same time, it can also balance overall aberrations and improve lens quality. More specifically, the industrial lens may also satisfy -0.92 ≤ f23 / fa ≤ -0.26.

[0041] In an exemplary embodiment, the industrial lens satisfies: 0.53 ≤ ((nd1+nd3) / nd2)*(f1+f3) / fa ≤ 1.07, where f1 is the effective focal length of the first lens, f3 is the effective focal length of the third lens, fa is the combined effective focal length of the first to third lenses, nd1 is the refractive index of the first lens, nd2 is the refractive index of the second lens, and nd3 is the refractive index of the third lens. By satisfying this conditional relationship, it is beneficial to control the light path, ensuring a smooth transition of light, and helping to ensure that the industrial lens can effectively reduce the tolerance sensitivity between lenses and improve the lens production yield within a wide working object distance range from 40mm to infinity; at the same time, it can also balance overall aberrations and improve lens quality. More specifically, the industrial lens may also satisfy 0.58 ≤ ((nd1+nd3) / nd2)*(f1+f3) / fa ≤ 0.98.

[0042] In an exemplary embodiment, the industrial lens satisfies: -9.55mm ≤ (f2+f3)*f23 / (f1+f2+f3) ≤ -2.77mm, where f23 is the combined effective focal length of the second to third lenses, f1 is the effective focal length of the first lens, f2 is the effective focal length of the second lens, and f3 is the effective focal length of the third lens. By satisfying this conditional relationship, it is beneficial to control the light path, ensuring a smooth transition of light, effectively reducing the tolerance sensitivity between lenses, and helping to improve the lens production yield. Simultaneously, it can effectively balance the aberrations of the optical system, correct chromatic aberration, improve the color reproduction of the lens, and ensure the high quality of the lens. More specifically, the industrial lens may also satisfy -8.69mm ≤ (f2+f3)*f23 / (f1+f2+f3) ≤ -3.07mm.

[0043] In an exemplary embodiment, the industrial lens satisfies: 0.62 ≤ (f4 + f5 + f6) / fb ≤ 1.11, where f4 is the effective focal length of the fourth lens, f5 is the effective focal length of the fifth lens, f6 is the effective focal length of the sixth lens, and fb is the combined effective focal length of the fourth to sixth lenses. By satisfying this conditional relationship, it is beneficial to control the light path, ensuring a smooth transition of light, effectively balancing the aberrations of the optical system, and improving the lens's resolving performance. Simultaneously, it also ensures a smooth transition of light onto the image plane, effectively controlling the exit angle of light passing through the fourth to sixth lenses, which is beneficial for matching the chip CRA and helps achieve a large target area for the lens. More specifically, the industrial lens may also satisfy 0.68 ≤ (f4 + f5 + f6) / fb ≤ 0.94.

[0044] In an exemplary embodiment, the industrial lens satisfies: -2.26 ≤ (R32 / R51)*(f3 / f5) ≤ -0.13, where R32 is the radius of curvature of the image-side surface of the third lens, R51 is the radius of curvature of the object-side surface of the fifth lens, f3 is the effective focal length of the third lens, and f5 is the effective focal length of the fifth lens. By satisfying the above conditional relationship, it is beneficial to adjust the incident and exit angles of light rays before and after passing through the lenses of the aperture stop, effectively control the light trajectory, reduce tolerance sensitivity, and improve lens quality. More specifically, the industrial lens may also satisfy -2.06 ≤ (R32 / R51)*(f3 / f5) ≤ -0.24.

[0045] In an exemplary embodiment, the industrial lens satisfies: -1.63 ≤ R5n / f5 ≤ -0.94, where R5n is the minimum absolute value of the radius of curvature of the object-side or image-side surface of the fifth lens, and f5 is the effective focal length of the fifth lens. By controlling the ratio of the minimum absolute value of the radius of curvature of the object-side or image-side surface of the fifth lens to the effective focal length of the fifth lens, the light path can be effectively controlled, enabling the industrial lens to balance peripheral field aberrations and improve the lens's resolving performance across the entire working object distance range from 40mm to infinity; it can also further elevate the light source, contributing to a larger lens target area. More specifically, the industrial lens may also satisfy -1.44 ≤ R5n / f5 ≤ -1.00.

[0046] In an exemplary embodiment, the industrial lens satisfies the following condition: 10.03mm ≤ fb*(TC4+TC5+TC6) / CTb ≤ 14.15mm, where fb is the combined effective focal length of the fourth to sixth lenses, TC4 is the center thickness of the fourth lens, TC5 is the center thickness of the fifth lens, TC6 is the center thickness of the sixth lens, and CTb is the center distance from the aperture plane to the image-side plane of the sixth lens. By satisfying the above conditional relationship, higher-order aberrations generated when light passes through the first to third lenses are effectively corrected, field curvature and chromatic aberration are corrected, and the lens resolution quality is improved; it also helps to achieve a large lens surface area. More specifically, the industrial lens may also satisfy 11.23mm ≤ fb*(TC4+TC5+TC6) / CTb ≤ 12.87mm.

[0047] In an exemplary embodiment, the industrial lens satisfies: 0.36 ≤ TCbn_max / fbn ≤ 1.21, where TCbn_max is the maximum value of the center thickness of any one of the fourth, fifth, and sixth lenses, and fbn is the minimum absolute value of the effective focal length of any one of the fourth, fifth, and sixth lenses. Satisfying this conditional relationship helps correct chromatic aberration and field curvature in the optical system, while effectively controlling the light path, reducing tolerance sensitivity, and improving lens production yield. More specifically, the industrial lens may also satisfy 0.40 ≤ TCbn_max / fbn ≤ 1.11.

[0048] In an exemplary embodiment, the industrial lens satisfies: 1.20 ≤ (f1 + f6) / f ≤ 1.63, where f1 is the effective focal length of the first lens, f6 is the effective focal length of the sixth lens, and f is the total effective focal length of the industrial lens. By rationally controlling the ratio of the sum of the effective focal lengths of the first and sixth lenses to the effective focal length of the system, the incident and exit angles of light can be effectively controlled. This ensures that the light reaches the image plane smoothly across the entire working object distance range from 40mm to infinity, increasing the light transmission of the optical system and achieving high illumination. Simultaneously, it helps balance astigmatism and reduce distortion, achieving high resolution and low distortion characteristics. More specifically, the industrial lens may also satisfy 1.31 ≤ (f1 + f6) / f ≤ 1.48.

[0049] In an exemplary embodiment, the industrial lens satisfies: 4.61 ≤ (R11 + R21) * (f1 + f2) / |R62 * f6| ≤ 9.04, where R11 is the radius of curvature of the object-side surface of the first lens, R21 is the radius of curvature of the object-side surface of the second lens, R62 is the radius of curvature of the image-side surface of the sixth lens, f1 is the effective focal length of the first lens, f2 is the effective focal length of the second lens, and f6 is the effective focal length of the sixth lens. By satisfying the above conditional relationship, it is beneficial to adjust the incident and exit angles of light rays before and after passing through the lenses of the aperture stop, effectively control the light trajectory, reduce tolerance sensitivity, and improve lens quality. More specifically, the industrial lens may also satisfy 5.11 ≤ (R11 + R21) * (f1 + f2) / |R62 * f6| ≤ 8.23.

[0050] In an exemplary embodiment, the industrial lens meets the following requirement: 6.32mm. -1 ≤(vd4+vd6) / f6≤10.05mm -1 Where vd4 is the Abbe number of the fourth lens, vd6 is the Abbe number of the sixth lens, and f is the total effective focal length of the industrial lens. A reasonable allocation of the sum of the Abbe numbers of the glass materials of the fourth and sixth lenses, along with the ratio of the effective focal length of the sixth lens, is beneficial for correcting chromatic aberration and effectively controlling the exit angle of light, allowing the light to reach the image plane smoothly, which is conducive to achieving large target surface imaging. For example, the industrial lens can also meet the requirements of 7.03mm... -1 ≤(vd4+vd6) / f6≤9.14mm -1 .

[0051] In an exemplary embodiment, the industrial lens satisfies: 0.11 ≤ (TCn_max - TCn_min) / TCn_sum ≤ 0.17, where TCn_max is the maximum center thickness of any one of the first to sixth lenses, TCn_min is the minimum center thickness of any one of the first to sixth lenses, and TCn_sum is the sum of the center thicknesses of the first to sixth lenses. By satisfying the above conditional relationship, high resolution can be achieved while also compressing the lens volume and reducing its weight to a certain extent, thus realizing the characteristic of lens miniaturization. For example, the industrial lens may also satisfy 0.11 ≤ (TCn_max - TCn_min) / TCn_sum ≤ 0.16.

[0052] In an exemplary embodiment, the industrial lens satisfies: 1.73 ≤ CTb / CTa ≤ 2.58, where CTa is the center distance from the object side of the first lens to the center of the aperture, and CTb is the center distance from the aperture to the image side of the sixth lens. Reasonably controlling the ratio of the center distance from the aperture to the image side of the sixth lens to the center distance from the object side of the first lens to the aperture helps ensure that the industrial lens achieves a wide working object distance range, effectively balancing aberrations generated within the working object distance range of 40mm to infinity, minimizing the overall blur diameter, and thus optimizing resolution. Exemplarily, the industrial lens may also satisfy 1.92 ≤ CTb / CTa ≤ 2.35.

[0053] In an exemplary embodiment, each of the first to sixth lenses in the industrial lens of this application can be a spherical lens or an aspherical lens. This application does not specifically limit the number of spherical and aspherical lenses as needed. When image quality is a primary concern, the number of aspherical lenses can be increased, or even all lenses can be aspherical. An aspherical lens is characterized by a continuously changing curvature from its center to its periphery. Unlike a spherical lens, which has a constant curvature from its center to its periphery, an aspherical lens has better radius of curvature characteristics, offering advantages in improving distortion and astigmatism. Using aspherical lenses can minimize aberrations that occur during imaging, thereby improving the image quality of the lens. However, those skilled in the art should understand that the lens surface type constituting the industrial lens can be changed to obtain the various results and advantages described in this specification without departing from the technical solutions claimed in this application. As an example, the first to sixth lenses in this application are all spherical lenses.

[0054] Those skilled in the art will understand that plastics have a large temperature coefficient of refractive index (dn / dt) and anomalous dispersion. A suitable amount of plastic material is beneficial for high and low temperature balance, but excessive plastic lenses are detrimental to system stability. Optical lenses made of glass can suppress the shift in back focus of the optical lens due to temperature changes, thereby improving system stability. Simultaneously, using glass avoids lens blurring caused by high and low temperature variations in the operating environment, thus preventing problems affecting normal lens use. Using glass also facilitates heat-free lens operation. Furthermore, using glass can better correct system chromatic aberration, improve lens resolution, and reduce ghosting. As an example, the first to sixth lenses in this application are all made of glass, which is beneficial for balancing the high and low temperature performance of industrial lenses, achieving high imaging quality within the range of -30℃ to +70℃; it also helps control light path, reducing tolerance sensitivity while achieving large target surface imaging.

[0055] The industrial lens of this application may further include an aperture stop for limiting the light beam. The aperture stop helps to concentrate the light entering the optical lens, reduce the maximum aperture of the optical lens, and decrease the assembly sensitivity of the optical system. Simultaneously, it effectively balances overall aberrations, especially spherical aberration and coma, to further improve the imaging quality of the optical lens. It should be noted that the aperture stop can be positioned between or to one side of any lens, depending on actual needs. For example, the aperture stop is positioned between the third and fourth lenses.

[0056] The industrial lens of this application may also include a filter having an object-side side and an image-side side, and / or a protective glass having an object-side side and an image-side side. The filter can be used to correct color deviation, and the protective glass can be used to protect the image sensor chip located at the imaging plane.

[0057] The image height H corresponding to the maximum field of view of the industrial lens in this application meets the following requirements: 8.81mm ≤ H ≤ 9.6mm. It can be matched with a 1 / 1.8” chip size to achieve large target surface imaging.

[0058] The working object distance range of the industrial lens in this application can meet the requirement of WD≥40mm. This allows for a wide working object distance range for the lens.

[0059] The industrial lens of this application has excellent resolution. At a spatial frequency of 125 lp / mm, the MTF value of the center field of view at all object distances is above 0.26; and the relative illumination value of the entire field of view at all object distances is above 88%.

[0060] However, those skilled in the art will understand that the number of lenses constituting the industrial lens can be varied to obtain the various results and advantages described herein without departing from the technical solutions claimed in this application. For example, although six lenses are described as an example in the embodiments, the industrial lens is not limited to including six lenses. If desired, the industrial lens may also include other numbers of lenses.

[0061] The following describes specific embodiments of industrial lenses applicable to the above-described embodiments with reference to the accompanying drawings.

[0062] Example 1

[0063] Figure 1 A schematic diagram of the structure of an industrial lens according to Embodiment 1 of this application is shown. Figure 1 As shown, the industrial lens includes, in sequence from the object side to the image side along the optical axis, a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, and a sixth lens L6.

[0064] The first lens L1 has positive optical power, with its object side S1 being convex and its image side S2 being concave.

[0065] The second lens L2 has positive optical power, with its object side S3 being convex and its image side S4 being concave.

[0066] The third lens L3 has negative optical power, with its object side S4 being convex and its image side S5 being concave.

[0067] The fourth lens L4 has positive optical power, and its object side S6 is convex, and its image side S7 is convex.

[0068] The fifth lens L5 has negative optical power, and its object side S8 is concave, as is its image side S9.

[0069] The sixth lens L6 has positive optical power, and its object side S10 is convex, and its image side S11 is convex.

[0070] The second lens L2 and the third lens L3 together form a cemented doublet lens.

[0071] Industrial lenses also include an aperture stop STO, which can be positioned between the third lens L3 and the fourth lens L4. It should be noted that surfaces S1 to S11 are... Figure 1 Not shown in the image.

[0072] Table 1 shows the basic parameters of the industrial lens of Example 1, where the units for radius of curvature and thickness / distance are millimeters (mm).

[0073] Table 1

[0074]

[0075]

[0076] In Embodiment 1, the object-side surface and image-side surface of all lenses from the first lens to the sixth lens are spherical.

[0077] In this embodiment 1, the industrial lens exhibits a central field-of-view MTF value above 0.28 at a spatial frequency of 125 lp / mm and working object distances from 40 mm to infinity. Furthermore, the MTF curve decreases smoothly and uniformly from the center to the edge of the field of view, indicating that the industrial lens has good imaging quality and good detail resolution. In addition, the minimum relative illumination of the industrial lens is 90% at working object distances from 40 mm to infinity, indicating that the industrial lens has high relative illumination.

[0078] Figure 2 The distortion curve of the industrial lens of Example 1 is shown, which represents the maximum optical distortion value corresponding to the working object distance from 40mm to infinity. It can be seen from the figure that the absolute value of the optical distortion at the edge field of view of Example 1 is 0.53% (reference wavelength 0.546nm). According to... Figure 2As can be seen, the industrial lens given in Example 1 has the characteristics of low distortion and can achieve good imaging quality.

[0079] Example 2

[0080] Figure 3 A schematic diagram of the structure of an industrial lens according to Embodiment 2 of this application is shown. Figure 3 As shown, the industrial lens includes, in sequence from the object side to the image side along the optical axis, a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, and a sixth lens L6.

[0081] The first lens L1 has positive optical power, with its object side S1 being convex and its image side S2 being concave.

[0082] The second lens L2 has positive optical power, with its object side S3 being convex and its image side S4 being concave.

[0083] The third lens L3 has negative optical power, with its object side S4 being convex and its image side S5 being concave.

[0084] The fourth lens L4 has positive optical power, and its object side S6 is convex, and its image side S7 is convex.

[0085] The fifth lens L5 has negative optical power, and its object side S8 is concave, as is its image side S9.

[0086] The sixth lens L6 has positive optical power, and its object side S10 is convex, and its image side S11 is convex.

[0087] The second lens L2 and the third lens L3 together form a cemented doublet lens.

[0088] Industrial lenses also include an aperture stop STO, which can be positioned between the third lens L3 and the fourth lens L4. It should be noted that surfaces S1 to S11 are... Figure 3 Not shown in the image.

[0089] Table 2 shows the basic parameters of the industrial lens of Example 2, where the units for radius of curvature and thickness / distance are millimeters (mm).

[0090] Table 2

[0091]

[0092] In Embodiment 2, the object-side surface and image-side surface of all lenses from the first lens to the sixth lens are spherical.

[0093] In this embodiment 2, the industrial lens exhibits a central field-of-view MTF value above 0.30 at a spatial frequency of 125 lp / mm and working object distances from 40 mm to infinity. Furthermore, the MTF curve decreases smoothly and uniformly from the center to the edge of the field of view, indicating that the industrial lens has good imaging quality and good detail resolution. In addition, the minimum relative illumination of the industrial lens is 91% at working object distances from 40 mm to infinity, indicating that the industrial lens has high relative illumination.

[0094] Figure 4 The distortion curve of the industrial lens of Example 2 is shown, representing the maximum optical distortion at working object distances from 40mm to infinity. As can be seen from the graph, the absolute value of optical distortion at the edge field of view in Example 2 is 0.65% (reference wavelength 0.546nm). According to... Figure 4 As can be seen, the industrial lens given in Example 2 has the characteristics of low distortion and can achieve good imaging quality.

[0095] Example 3

[0096] Figure 5 A schematic diagram of the structure of an industrial lens according to Embodiment 3 of this application is shown. Figure 5 As shown, the industrial lens includes, in sequence from the object side to the image side along the optical axis, a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, and a sixth lens L6.

[0097] The first lens L1 has positive optical power, with its object side S1 being convex and its image side S2 being concave.

[0098] The second lens L2 has positive optical power, and its object side S3 is convex, while its image side S4 is convex.

[0099] The third lens L3 has negative optical power, and its object side S4 is concave, as is its image side S5.

[0100] The fourth lens L4 has positive optical power, with its object side S6 being concave and its image side S7 being convex.

[0101] The fifth lens L5 has negative optical power, and its object side S8 is concave, as is its image side S9.

[0102] The sixth lens L6 has positive optical power, with its object side S10 being concave and its image side S11 being convex.

[0103] The second lens L2 and the third lens L3 together form a cemented doublet lens.

[0104] Industrial lenses also include an aperture stop STO, which can be positioned between the third lens L3 and the fourth lens L4. It should be noted that surfaces S1 to S11 are... Figure 5 Not shown in the image.

[0105] Table 3 shows the basic parameters of the industrial lens of Example 3, where the units for radius of curvature and thickness / distance are millimeters (mm).

[0106] Table 3

[0107]

[0108] In Embodiment 3, the object-side surface and image-side surface of all lenses from the first lens to the sixth lens are spherical.

[0109] In this embodiment 3, the industrial lens exhibits a central field-of-view MTF value above 0.28 at a spatial frequency of 125 lp / mm and working object distances from 40 mm to infinity. Furthermore, the MTF curve decreases smoothly and uniformly from the center to the edge of the field of view, indicating that the industrial lens has good imaging quality and good detail resolution. In addition, the minimum relative illumination of the industrial lens is 92% at working object distances from 40 mm to infinity, indicating that the industrial lens has high relative illumination.

[0110] Figure 6 The distortion curve of the industrial lens of Example 3 is shown, representing the maximum optical distortion at working object distances from 40mm to infinity. The graph shows that the absolute value of optical distortion at the edge field of view in Example 3 is 0.59% (reference wavelength 0.546nm). According to... Figure 6 As can be seen, the industrial lens given in Example 3 has the characteristics of low distortion and can achieve good imaging quality.

[0111] Example 4

[0112] Figure 7 A schematic diagram of the structure of an industrial lens according to Embodiment 4 of this application is shown. Figure 7 As shown, the industrial lens includes, in sequence from the object side to the image side along the optical axis, a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, and a sixth lens L6.

[0113] The first lens L1 has positive optical power, with its object side S1 being convex and its image side S2 being concave.

[0114] The second lens L2 has positive optical power, and its object side S3 is convex, while its image side S4 is convex.

[0115] The third lens L3 has negative optical power, and its object side S4 is concave, as is its image side S5.

[0116] The fourth lens L4 has positive optical power, and its object side S6 is convex, and its image side S7 is convex.

[0117] The fifth lens L5 has negative optical power, and its object side S8 is concave, as is its image side S9.

[0118] The sixth lens L6 has positive optical power, and its object side S10 is convex, and its image side S11 is convex.

[0119] The second lens L2 and the third lens L3 together form a cemented doublet lens.

[0120] Industrial lenses also include an aperture stop STO, which can be positioned between the third lens L3 and the fourth lens L4. It should be noted that surfaces S1 to S11 are... Figure 7 Not shown in the image.

[0121] Table 4 shows the basic parameters of the industrial lens of Example 4, where the units for radius of curvature and thickness / distance are millimeters (mm).

[0122] Table 4

[0123]

[0124] In embodiment 4, the object-side surface and image-side surface of all lenses from the first lens to the sixth lens are spherical.

[0125] In this embodiment 4, the industrial lens exhibits a central field-of-view MTF value above 0.28 at a spatial frequency of 125 lp / mm and working object distances from 40 mm to infinity. Furthermore, the MTF curve decreases smoothly and uniformly from the center to the edge of the field of view, indicating that the industrial lens has good imaging quality and good detail resolution. In addition, the minimum relative illumination of the industrial lens is 91% at working object distances from 40 mm to infinity, indicating that the industrial lens has high relative illumination.

[0126] Figure 8 The distortion curve of the industrial lens of Example 4 is shown, representing the maximum optical distortion at working object distances from 40mm to infinity. The graph shows that the absolute value of optical distortion at the edge field of view in Example 4 is 0.58% (reference wavelength 0.546nm). According to... Figure 8 As can be seen, the industrial lens given in Example 4 has the characteristics of low distortion and can achieve good imaging quality.

[0127] In summary, the industrial lenses in Examples 1 to 4 satisfy the relationships shown in Table 5. In Table 5, parameters nd1, nd2, nd3, vd4, and vd6 have no units, while the units for the remaining parameters are millimeters (mm).

[0128] Table 5

[0129] Conditional / Example 1 2 3 4 f 21.890 21.950 21.950 21.950 fa / fb 3.835 1.784 3.232 3.306 fa / f 2.526 1.454 2.179 2.249 fb / f 0.659 0.815 0.674 0.680 f23 / fa -0.261 -0.919 -0.302 -0.302 (f2+f3)*f23 / (f1+f2+f3) -3.500 -8.682 -3.073 -3.097 (f4+f5+f6) / fb 0.845 0.684 0.939 0.906 (R32 / R51)*(f3 / f5) -0.558 -2.059 -0.243 -0.329 R5n / f5 -1.251 -1.436 -1.040 -1.094 ((nd1+nd3) / nd2)*(f1+f3) / fa 0.585 0.974 0.680 0.674 (f1+f6) / f 1.329 1.478 1.382 1.369 (R11+R21)*(f1+f2) / |R62*f6| 6.506 8.221 5.119 5.606 fb*(TC4+TC5+TC6) / CTb 11.563 12.863 11.235 11.410 TCbn_max / fbn 0.773 1.102 0.483 0.565 (vd4+vd6) / f6 9.137 8.667 7.025 7.449 (TCn_max-TCn_min) / TCn_sum 0.141 0.155 0.119 0.132 CTb / CTa 1.927 2.347 2.020 2.029

[0130] The above description is merely a preferred embodiment of this application and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of the invention involved in this application is not limited to technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the inventive concept. For example, technical solutions formed by substituting the above features with (but not limited to) technical features with similar functions disclosed in this application.

Claims

1. An industrial lens characterized in that, in order from the object side to the image side along the optical axis, comprising: a first lens with positive refractive power, whose object side surface is convex; a second lens with positive refractive power, whose object side surface is convex; a third lens with negative refractive power, whose image side surface is concave; a fourth lens with positive refractive power; a fifth lens with negative refractive power, whose object side surface is concave and whose image side surface is concave; a sixth lens with positive refractive power, whose image side surface is convex; the number of lenses with refractive power in the industrial lens is six; and the industrial lens satisfies: 1.61≤fa / fb≤4.22, 0.59≤fb / f≤0.90, wherein fa is the combined effective focal length of the first lens to the third lens, fb is the combined effective focal length of the fourth lens to the sixth lens, and f is the total effective focal length of the industrial lens.

2. The industrial lens according to claim 1, wherein the image side surface of the first lens is convex or concave or planar; the image side surface of the second lens is convex or concave or planar; the object side surface of the third lens is convex or concave or planar; the object side surface of the fourth lens is convex or concave or planar and the image side surface is convex; the object side surface of the sixth lens is convex or concave or planar.

3. The industrial lens of claim 1, wherein, the industrial lens comprises a diaphragm, which is located between the third lens and the fourth lens.

4. The industrial lens according to claim 1 or 2, characterized in that, the industrial lens satisfies the following conditional expression: 1.31≤fa / f≤2.

78.

5. The industrial lens according to claim 1 or 2, characterized in that, the industrial lens satisfies at least one of the following conditional expressions: -1.01≤f23 / fa≤-0.23, -9.55mm≤(f2+f3)*f23 / (f1+f2+f3)≤-2.77mm, 0.53≤((nd1+nd3) / nd2)*(f1+f3) / fa≤1.07, wherein f23 is the combined effective focal length of the second lens to the third lens, f1 is the effective focal length of the first lens, f2 is the effective focal length of the second lens, f3 is the effective focal length of the third lens, nd1 is the refractive index of the first lens, nd2 is the refractive index of the second lens, and nd3 is the refractive index of the third lens.

6. The industrial lens according to claim 1 or 2, characterized in that, the industrial lens satisfies at least one of the following conditional expressions: 0.62≤(f4+f5+f6) / fb≤1.11, -2.26≤(R32 / R51)*(f3 / f5)≤-0.13, -1.63≤R5n / f5≤-0.94, 0.36≤TCbn_max / fbn≤1.21, wherein f3 is an effective focal length of the third lens, f4 is an effective focal length of the fourth lens, f5 is an effective focal length of the fifth lens, f6 is an effective focal length of the sixth lens, R32 is a curvature radius of an image side surface of the third lens, R51 is a curvature radius of an object side surface of the fifth lens, R5n is a minimum value of an absolute value of a curvature radius of the object side surface or the image side surface of the fifth lens, TCbn_max is a maximum value of a central thickness of any one of the fourth lens, the fifth lens and the sixth lens, and fbn is a minimum value of an absolute value of an effective focal length of any one of the fourth lens, the fifth lens and the sixth lens.

7. The industrial lens according to claim 1 or 2, characterized in that, The industrial lens satisfies at least one of the following conditional expressions: 1.20 ≤ (f1+f6) / f ≤ 1.63, 4.61 ≤ (R11+R21)*(f1+f2) / |R62*f6| ≤ 9.04, 6.32 mm -1 ≤ (vd4 + vd6) / f6 ≤ 10.05 mm -1 , 0.11 ≤ (TCn_max-TCn_min) / TCn_sum ≤ 0.17, wherein f1 is an effective focal length of the first lens, f2 is an effective focal length of the second lens, f6 is an effective focal length of the sixth lens, R11 is a curvature radius of an object side surface of the first lens, R21 is a curvature radius of an object side surface of the second lens, R62 is a curvature radius of an image side surface of the sixth lens, vd4 is an Abbe number of the fourth lens, vd6 is an Abbe number of the sixth lens, TCn_max is a maximum value of a central thickness of any one of the first lens to the sixth lens, TCn_min is a minimum value of a central thickness of any one of the first lens to the sixth lens, and TCn_sum is a sum of central thicknesses of the lenses among the first lens to the sixth lens.

8. The industrial lens of claim 3, wherein, The industrial lens satisfies at least one of the following conditional expressions: 10.03 mm ≤ fb*(TC4+TC5+TC6) / CTb ≤ 14.15 mm, 1.73 ≤ CTb / CTa ≤ 2.58, wherein TC4 is a central thickness of the fourth lens, TC5 is a central thickness of the fifth lens, TC6 is a central thickness of the sixth lens, CTa is a central distance from the object side surface of the first lens to the diaphragm surface, and CTb is a central distance from the diaphragm surface to the image side surface of the sixth lens.

9. The industrial lens according to claim 1 or 2, characterized in that, The industrial lens satisfies at least one of the following conditional expressions: 1.78 ≤ fa / fb ≤ 3.84, 1.45 ≤ fa / f ≤ 2.53, 0.65 ≤ fb / f ≤ 0.82, -0.92 ≤ f23 / fa ≤ -0.26, -8.69 mm ≤ (f2+f3)*f23 / (f1+f2+f3) ≤ -3.07 mm, 0.68 ≤ (f4+f5+f6) / fb ≤ 0.94, -2.06 ≤ (R32 / R51)*(f3 / f5) ≤ -0.24, -1.44 ≤ R5n / f5 ≤ -1.00, 0.58 ≤ ((nd1+nd3) / nd2)*(f1+f3) / fa ≤ 0.98, 1.31 ≤ (f1+f6) / f ≤ 1.48, 5. 11≤(R11+R21)*(f1+f2) / |R62*f6|≤8.23, 0.40≤TCbn_max / fbn≤1.11, 7.03 mm -1 ≤ (vd4 + vd6) / f6 ≤ 9.14 mm -1 , 0.11≤(TCn_max-TCn_min) / TCn_sum≤0.16, wherein f23 is the combined effective focal length of the second lens to the third lens, f1 is the effective focal length of the first lens, f2 is the effective focal length of the second lens, f3 is the effective focal length of the third lens, f4 is the effective focal length of the fourth lens, f5 is the effective focal length of the fifth lens, f6 is the effective focal length of the sixth lens, R11 is the radius of curvature of the object side surface of the first lens, R21 is the radius of curvature of the object side surface of the second lens, R32 is the radius of curvature of the image side surface of the third lens, R51 is the radius of curvature of the object side surface of the fifth lens, R62 is the radius of curvature of the image side surface of the sixth lens, R5n is the minimum value of the absolute value of the radius of curvature of the object side surface or the image side surface of the fifth lens, nd1 is the refractive index of the first lens, nd2 is the refractive index of the second lens, nd3 is the refractive index of the third lens, vd4 is the Abbe number of the fourth lens, vd6 is the Abbe number of the sixth lens, TCbn_max is the maximum value of the central thickness of any one of the fourth lens, the fifth lens and the sixth lens, fbn is the minimum value of the absolute value of the effective focal length of any one of the fourth lens, the fifth lens and the sixth lens, TCn_max is the maximum value of the central thickness of any one of the first lens to the sixth lens, TCn_min is the minimum value of the central thickness of any one of the first lens to the sixth lens, TCn_sum is the sum of the central thickness of the lenses of the first lens to the sixth lens.

10. The industrial lens of claim 3, wherein, The industrial lens satisfies at least one of the following conditional expressions: 11.23mm≤fb*(TC4+TC5+TC6) / CTb≤12.87mm, 1.92≤CTb / CTa≤2.35, wherein TC4 is the central thickness of the fourth lens, TC5 is the central thickness of the fifth lens, TC6 is the central thickness of the sixth lens, CTa is the center distance from the object side surface of the first lens to the diaphragm surface, CTb is the center distance from the diaphragm surface to the image side surface of the sixth lens.

Images