A dual-telecentric lens and optical device

Abstract

The application provides a double-telecentric lens and an optical device, wherein the first lens group, the second lens group, the third lens group and the fourth lens group of the double-telecentric lens are symmetrically arranged on both sides of an aperture diaphragm to form a near double-Gaussian structure, thereby effectively correcting aberrations such as spherical aberration and distortion, reducing the incidence angle of light on the surface of each lens, reducing the sensitivity of the system tolerance, and improving the assembly yield of the optical system. In addition, by setting the aperture diaphragm as a variable diaphragm including at least a first aperture and a second aperture, the double-telecentric lens with high double-telecentricity under green light and red light double-band illumination is realized.

Description

Technical Field

[0001] This application relates to the field of optical device technology, and more specifically, to a double telecentric lens and optical device. Background Technology

[0002] With the rapid development of machine vision technology, dual telecentric lenses have demonstrated unique advantages in industrial applications such as precision defect detection and high-precision dimensional measurement due to their low distortion, large depth of field, and magnification that does not change with object distance or image distance. Especially in the field of precision machining, as the requirements for inspection accuracy continue to increase, the market demand for high-resolution, high-quality dual telecentric lenses continues to grow, demonstrating enormous market potential.

[0003] However, commonly available dual telecentric lenses with -1X magnification, coaxial illumination, and white light band generally suffer from insufficient resolution, making it difficult to meet the needs of high-precision detection scenarios. Furthermore, traditional dual telecentric lenses typically only exhibit ideal telecentric characteristics at a single dominant wavelength. When the object being detected requires dual-band illumination, they cannot simultaneously guarantee the telecentric effect at both wavelengths, which to some extent limits their application in the field of multispectral detection. Utility Model Content

[0004] In order to at least overcome the above-mentioned deficiencies in the prior art, the purpose of this utility model is to provide a dual telecentric lens, comprising a first lens group, a second lens group, an aperture stop, a third lens group, and a fourth lens group arranged sequentially from the object side to the image side along the optical axis; the first lens group and the second lens group are nearly symmetrically distributed with respect to the aperture stop and the third and fourth lens groups, wherein the nearly symmetrical distribution is a double Gaussian distribution. The first lens group has positive optical power; the second lens group has negative optical power; the third lens group has positive optical power; and the fourth lens group has positive optical power. The aperture stop includes a variable aperture, comprising at least a first aperture suitable for green light of a first set wavelength to pass through and a second aperture suitable for red light of a second set wavelength to pass through; The dual telecentric lenses satisfy the following relationship: -0.019<F1 / F<-0.01; 0.02<F2 / F<0.1; -0.26<F3 / F<-0.19; -0.019<F4 / F<-0.012 Wherein, F, F1, F2, F3 and F4 are the total focal length of the double telecentric lens, the focal length of the first lens group, the focal length of the second lens group, the focal length of the third lens group and the focal length of the fourth lens group, respectively.

[0005] In one possible implementation, the first lens group includes a first lens and a second lens arranged sequentially from the object side to the image side along the optical axis, with the first lens and the second lens being nearly symmetrically distributed. Preferably, the object-side surface of the first lens is concave, the image-side surface is convex, and the refractive index is 1.87 < n1 < 1.97; Preferably, the object side of the second lens is convex, the image side is concave, and the refractive index is 1.8 < n2 < 1.89.

[0006] In one possible implementation, the second lens group includes a first cemented lens, a second cemented lens, a seventh lens, and a third cemented lens arranged sequentially along the optical axis from the object side to the image side; The first cemented lens includes a third lens and a fourth lens; Preferably, the object side of the third lens is concave, the image side is concave, and the refractive index is 1.75 < n3 < 1.85; Preferably, the fourth lens has a convex object side and a concave image side, and a refractive index of 1.61 < n3 < 1.71; The second cemented lens includes a fifth lens, a sixth lens, and a seventh lens; Preferably, the object-side surface of the fifth lens is convex, the image-side surface is convex, and the refractive index is 1.56 < n5 < 1.67; Preferably, the object side of the sixth lens is concave, the image side is convex, and the refractive index is 1.73 < n6 < 1.83; Preferably, the object side of the seventh lens is convex, the image side is convex, and the refractive index is 1.56 < n7 < 1.67; The third cemented lens includes an eighth lens and a ninth lens; Preferably, the object-side surface of the eighth lens is convex, the image-side surface is convex, and the refractive index is 1.65 < n8 < 1.75; Preferably, the object side of the ninth lens is concave, the image side is concave, and the refractive index is 1.7 < n9 < 1.8.

[0007] In one possible implementation, the third lens group includes a fourth cemented lens arranged nearly symmetrically with respect to the third cemented lens about the aperture stop; The fourth cemented lens includes a tenth lens and an eleventh lens arranged sequentially along the optical axis from the object side to the image side; Preferably, the object side of the tenth lens is concave, the image side is convex, and the refractive index is 1.9 < n10 < 2.0; Preferably, the object side of the eleventh lens is concave, the image side is convex, and the refractive index is 1.65 < n11 < 1.75.

[0008] In one possible implementation, the fourth lens group includes a fifth cemented lens, a fourteenth lens, and a fifteenth lens arranged sequentially along the optical axis from the object side to the image side; The fifth cemented lens includes the twelfth and thirteenth lenses; Preferably, the object side of the twelfth lens is convex, the image side is convex, and the refractive index is 1.73 < n12 < 1.82; Preferably, the object side of the thirteenth lens is concave, the image side is convex, and the refractive index is 1.55 < n13 < 1.65; Preferably, the fourteenth lens has a convex object side and a concave image side, and its refractive index is 1.88 < n13 < 1.93; Preferably, the object side of the fifteenth lens is convex, the image side is concave, and the refractive index is 1.68 < n13 < 1.73.

[0009] In one possible implementation, the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the seventh lens, the eighth lens, the ninth lens, the tenth lens, the eleventh lens, the twelfth lens, the thirteenth lens, the fourteenth lens, and the fifteenth lens are spherical lenses.

[0010] In one possible implementation, the materials of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the seventh lens, the eighth lens, the ninth lens, the tenth lens, the eleventh lens, the twelfth lens, the thirteenth lens, the fourteenth lens, and the fifteenth lens include glass.

[0011] In one possible implementation, along the optical axis, the distance from the aperture stop to the image side of the ninth lens is 3.2 mm to 4 mm, and the distance from the aperture stop to the object side of the tenth lens is 13 mm to 13.9 mm. The aperture stop has a first aperture diameter of 22mm to 22.8mm and a second aperture diameter of 25.2mm to 26mm.

[0012] In one possible implementation, the dual telecentric lenses satisfy the following relationship: -0.27<F1 / F2<-0.18; -4.1<F3 / F2<-3.1; -0.3<F4 / F2<-0.22 Wherein, F1, F2, F3 and F4 are the focal lengths of the first lens group, the second lens group, the third lens group and the fourth lens group, respectively.

[0013] This application also provides an optical device, including any of the aforementioned telecentric lenses.

[0014] Compared with the prior art, this application has the following beneficial effects: This invention provides a double telecentric lens and optical device. By nearly symmetrically distributing the first, second, third, and fourth lens groups on both sides of the aperture stop, a near-double Gaussian structure is formed, effectively correcting aberrations such as spherical aberration and distortion. Simultaneously, it reduces the incident angle of light on each lens surface, lowers system tolerance sensitivity, and improves the assembly yield of the optical system. Furthermore, by setting the aperture stop as a variable stop including at least a first and a second aperture, a double telecentric lens with high telecentricity under both green and red light dual-band illumination is achieved. Attached Figure Description

[0015] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings required in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this utility model and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a schematic diagram of the structure of the dual telecentric lens provided in this embodiment; Figure 2 This is a schematic diagram of the modulation transfer function of the dual telecentric lens under green light illumination provided in this embodiment; Figure 3 This is a schematic diagram of the modulation transfer function of the dual telecentric lens under red illumination provided in this embodiment; Figure 4 This is a schematic diagram of a dot pattern under green light illumination from a dual telecentric lens provided in this embodiment; Figure 5 This is a schematic diagram of a dot array under red light illumination from a dual telecentric lens provided in this embodiment; Figure 6 This is a schematic diagram of field curvature and distortion under green light illumination from a dual telecentric lens provided in this embodiment; Figure 7 This is a schematic diagram of field curvature and distortion under red light illumination from a dual telecentric lens provided in this embodiment.

[0017] Icons: O - Object plane; A - First lens group; B - Second lens group; C - Third lens group; D - Fourth lens group; S - Aperture stop; I - Image plane; L1 - First lens; L2 - Second lens; L3 - Third lens; L4 - Fourth lens; L5 - Fifth lens; L6 - Sixth lens; L7 - Seventh lens; L8 - Eighth lens; L9 - Ninth lens; L10 - Tenth lens; L11 - Eleventh lens; L12 - Twelfth lens; L13 - Thirteenth lens; L14 - Fourteenth lens; L15 - Fifteenth lens. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0019] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0020] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0021] In the description of this application, it should be noted that the terms "upper," "lower," etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product is in use. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this application. In addition, the terms "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0022] Furthermore, terms such as "horizontal," "vertical," and "sag" do not imply that components must be absolutely horizontal or suspended, but rather that they can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal relative to "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0023] In the description of this application, it should also be noted that, unless otherwise expressly specified and limited, the terms "set up," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0024] It should be noted that, where there is no conflict, different features in the embodiments of this application can be combined with each other.

[0025] This utility model provides a double telecentric lens; please refer to [reference needed]. Figure 1 It includes a first lens group A, a second lens group B, an aperture stop S, a third lens group C, and a fourth lens group D arranged sequentially from the object side to the image side along the optical axis; the first lens group A and the second lens group B are nearly symmetrically distributed with respect to the aperture stop S, the third lens group C, and the fourth lens group D, wherein the nearly symmetrical distribution is a double Gaussian distribution.

[0026] In this embodiment, a near-double Gaussian optical structure is formed by distributing the first lens group A, the second lens group B, the third lens group C, and the fourth lens group D of the double telecentric lens in a near-symmetrical manner on both sides of the aperture stop S. The symmetrical distribution of the near-double Gaussian optical structure effectively corrects various aberrations such as spherical aberration, coma, astigmatism, field curvature, and distortion, making it particularly suitable for optical systems with large fields of view and high resolution. By reducing the incident angle of light on the lens surface, this structure not only reduces light loss and stray light but also improves image contrast and sharpness. Simultaneously, the symmetrical design significantly reduces the sensitivity of the optical system to component processing and assembly errors, improving system stability and assembly yield, thereby reducing production costs. Furthermore, the near-double Gaussian structure achieves a compact optical system design while ensuring high performance, making it suitable for space-constrained applications.

[0027] The first lens group A has positive optical power; the second lens group B has negative optical power; the third lens group C has positive optical power; and the fourth lens group D has positive optical power.

[0028] The aperture stop S includes a variable aperture, comprising at least a first aperture suitable for green light of a first set wavelength to pass through and a second aperture suitable for red light of a second set wavelength to pass through.

[0029] In this embodiment, by setting a first aperture and a second aperture, high dual telecentricity of both green and red light bands can be achieved simultaneously. For example, a first set wavelength of 500nm~550nm is set for the green light band, and a second set wavelength of 600nm~650nm is set for the red light band, thereby achieving dual-band illumination under the aforementioned wavelengths.

[0030] The dual telecentric lenses satisfy the following relationship: -0.019<F1 / F<-0.01; 0.02<F2 / F<0.1; -0.26<F3 / F<-0.19; -0.019<F4 / F<-0.012 Wherein, F, F1, F2, F3 and F4 are the total focal length of the double telecentric lens, the focal length of the first lens group A, the focal length of the second lens group B, the focal length of the third lens group C and the focal length of the fourth lens group D, respectively.

[0031] In one possible implementation, the first lens group A includes a first lens L1 and a second lens L2 arranged sequentially along the optical axis from the object side to the image side, with the first lens L1 and the second lens L2 being nearly symmetrically distributed.

[0032] In this embodiment, the first lens L1 and the second lens L2 adopt a near-symmetrical design, which balances the refraction path of light and reduces the angle of incident light as it passes through the lens. A smaller incident angle not only reduces reflection and refraction losses on the lens surface but also reduces aberrations such as spherical aberration and coma introduced by excessively large light angles. Simultaneously, the near-symmetrical design makes the propagation of light more uniform throughout the system, further optimizing the aberration correction effect.

[0033] Optionally, the object-side surface of the first lens L1 is concave, the image-side surface is convex, and the refractive index is 1.87 < n1 < 1.97.

[0034] Optionally, the object-side surface of the second lens L2 is convex, the image-side surface is concave, and the refractive index is 1.8 < n2 < 1.89.

[0035] In one possible implementation, the second lens group B includes a first cemented lens, a second cemented lens, a seventh lens L7, and a third cemented lens arranged sequentially along the optical axis from the object side to the image side.

[0036] The first cemented lens includes a third lens L3 and a fourth lens L4.

[0037] Optionally, the object side of the third lens L3 is concave, the image side is concave, and the refractive index is 1.75 < n3 < 1.85.

[0038] Optionally, the fourth lens L4 has a convex object side and a concave image side, with a refractive index of 1.61 < n3 < 1.71.

[0039] The second cemented lens includes a fifth lens L5, a sixth lens L6, and a seventh lens L7.

[0040] Optionally, the object-side surface of the fifth lens L5 is convex, the image-side surface is convex, and the refractive index is 1.56 < n5 < 1.67.

[0041] Optionally, the object side of the sixth lens L6 is concave, the image side is convex, and the refractive index is 1.73 < n6 < 1.83.

[0042] Optionally, the object-side surface of the seventh lens L7 is convex, the image-side surface is convex, and the refractive index is 1.56 < n7 < 1.67.

[0043] The third cemented lens includes an eighth lens L8 and a ninth lens L9.

[0044] Optionally, the object-side surface of the eighth lens L8 is convex, the image-side surface is convex, and the refractive index is 1.65 < n8 < 1.75.

[0045] Optionally, the object side of the ninth lens L9 is concave, the image side is concave, and the refractive index is 1.7 < n9 < 1.8.

[0046] In one possible implementation, the third lens group C includes a fourth cemented lens arranged nearly symmetrically with respect to the third cemented lens about the aperture stop S.

[0047] In this embodiment, since the near-symmetric and symmetrical structures achieve optical path balance in the optical system, the near-symmetrical distribution of the third and fourth cemented lenses with respect to the aperture stop S effectively reduces system aberrations. The near-symmetric distribution ensures that light rays propagate uniformly between the third and fourth cemented lenses after passing through the aperture stop S, thereby reducing aberrations introduced by asymmetric light paths, such as spherical aberration, coma, and astigmatism.

[0048] The fourth cemented lens includes a tenth lens L10 and an eleventh lens L11 arranged sequentially along the optical axis from the object side to the image side.

[0049] Optionally, the object side of the tenth lens L10 is concave, the image side is convex, and the refractive index is 1.9 < n10 < 2.0.

[0050] Optionally, the object-side surface of the eleventh lens L11 is concave, the image-side surface is convex, and the refractive index is 1.65 < n11 < 1.75.

[0051] In one possible implementation, the fourth lens group D includes a fifth cemented lens, a fourteenth lens L14, and a fifteenth lens L15 arranged sequentially along the optical axis from the object side to the image side.

[0052] The fifth cemented lens includes the twelfth lens L12 and the thirteenth lens L13.

[0053] Optionally, the object side of the twelfth lens L12 is convex, the image side is convex, and the refractive index is 1.73 < n12 < 1.82.

[0054] Optionally, the object-side surface of the thirteenth lens L13 is concave, the image-side surface is convex, and the refractive index is 1.55 < n13 < 1.65.

[0055] Optionally, the fourteenth lens L14 has a convex object side and a concave image side, with a refractive index of 1.88 < n13 < 1.93.

[0056] Optionally, the object-side surface of the fifteenth lens L15 is convex, the image-side surface is concave, and the refractive index is 1.68 < n13 < 1.73.

[0057] In this embodiment, a total of 10 lenses are used, which reduces the number of lenses while ensuring the performance of the optical system parameters, thereby effectively reducing manufacturing costs.

[0058] Specifically, please refer to Table 1 below, which shows a set of actual design parameters for the dual telecentric lens provided in the embodiments of this application.

[0059] Table 1. Parameters of the dual telecentric lenses provided in the embodiments of this application.

[0060] Under these actual design parameters, the focal length of the first lens L1 =145.864mm; Focal length of the second lens L2 =123.499mm; the focal length of the third lens L3 =-42.508mm; the focal length of the fourth lens L4 =101.744mm; the focal length of the fifth lens L5 =47.357mm; the focal length of the sixth lens L6 =-53.427mm; the focal length of the seventh lens L7 =72.842mm; the focal length of the eighth lens L8 =44.031mm; the focal length of the ninth lens L9 =-28.965mm; the focal length of the tenth lens L10 =62.321mm; the focal length of the eleventh lens L11 =-79.274mm; the focal length of the twelfth lens L12 =46.777mm; the focal length of the thirteenth lens L13 =-286.044mm; the focal length of the fourteenth lens L14 =67.554mm; the focal length of the fifteenth lens L15 =-35.865mm.

[0061] In this embodiment, the magnification of the provided dual telecentric lens is β=-1X, and the effective field of view on the object side is [missing information]. =4mm, effective field of view at the image side is =4mm; This dual telecentric lens can simultaneously achieve dual-band imaging in the green light band (500nm~550nm) and the red light band (600nm~650nm); the lens's numerical aperture NA in the green light band is 0.18, and in the red light band it is 0.2. At this point, according to the formula... =0.61λ / NA, where NA is the numerical aperture of the objective lens and λ is the lithography wavelength. The resolution of the dual telecentric lens provided in this embodiment can theoretically reach 1.8μm in both wavelength bands. The dual telecentric lens designed with the parameters described in Table 1 has an object distance of 92.87mm and an image distance of 31.27mm, which provides sufficient space for lens installation.

[0062] In one possible implementation, the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, the sixth lens L6, the seventh lens L7, the eighth lens L8, the ninth lens L9, the tenth lens L10, the eleventh lens L11, the twelfth lens L12, the thirteenth lens L13, the fourteenth lens L14, and the fifteenth lens L15 are spherical lenses.

[0063] In this embodiment, all lenses are spherical lenses, which have the advantages of low processing cost and high assembly efficiency. By rationally designing the curvature, thickness, and material combination of spherical lenses, aberrations such as spherical aberration, coma, and astigmatism can be effectively corrected to meet the requirements of high imaging quality. In addition, the optical performance of spherical lenses is stable and less affected by factors such as ambient temperature and humidity, which can ensure the stability of the optical system under complex working conditions.

[0064] In one possible implementation, the materials of the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, the sixth lens L6, the seventh lens L7, the eighth lens L8, the ninth lens L9, the tenth lens L10, the eleventh lens L11, the twelfth lens L12, the thirteenth lens L13, the fourteenth lens L14, and the fifteenth lens L15 include glass.

[0065] In this embodiment, domestically produced environmentally friendly glass is used as the lens material, which not only meets environmental protection requirements but also reduces material costs. At the same time, it takes into account both optical performance and economic benefits, making it more suitable for mass production and application.

[0066] Specifically, the material of the first lens L1 may include heavy flint glass, the material of the second lens L2 may include heavy flint glass, the material of the third lens L3 may include heavy flint glass, the material of the fourth lens L4 may include heavy barium flint glass, the material of the fifth lens L5 may include heavy phosphorus crown glass, the material of the sixth lens L6 may include heavy flint glass, the material of the seventh lens L7 may include heavy phosphorus crown glass, the material of the eighth lens L8 may include lanthanum crown glass, the material of the ninth lens L9 may include heavy flint glass, the material of the tenth lens L10 may include light heavy flint glass, the material of the eleventh lens L11 may include heavy flint glass, the material of the twelfth lens L12 may include lanthanum flint glass, the material of the thirteenth lens L13 may include heavy crown glass, the material of the fourteenth lens L14 may include heavy flint glass, and the material of the fifteenth lens L15 may include heavy flint glass.

[0067] In one possible implementation, along the optical axis, the distance from the aperture stop S to the image side of the ninth lens L9 is 3.2 mm to 4 mm, and the distance from the aperture stop S to the object side of the tenth lens L10 is 13 mm to 13.9 mm.

[0068] The aperture stop S has a first aperture diameter of 22mm to 22.8mm and a second aperture diameter of 25.2mm to 26mm.

[0069] In this embodiment, by setting the position of the aperture stop S and the size of the first and second apertures in this way, dual-band imaging of 500nm~550nm in the green light band and 600nm~650nm in the red light band can be achieved.

[0070] In one possible implementation, the dual telecentric lenses satisfy the following relationship: -0.27<F1 / F2<-0.18; -4.1<F3 / F2<-3.1; -0.3<F4 / F2<-0.22 Wherein, F1, F2, F3 and F4 are the focal lengths of the first lens group A, the second lens group B, the third lens group C and the fourth lens group D, respectively.

[0071] Based on the aforementioned solution, please refer to Figure 2 and Figure 3 This allows for the creation of telecentric lenses with modulation transfer function (MTF) ≥ 0.2@470lp / mm@525nm and MTF ≥ 0.2@430lp / mm@630nm.

[0072] Please refer to Figure 4 and Figure 5 The diagrams show point arrays under green and red illumination of the dual telecentric lens in this embodiment. The size of the blur spots in the central and peripheral fields of view is small, the energy concentration of on-axis and off-axis points is high, and the aberration correction effect is good.

[0073] Please refer to Figure 6 and Figure 7 In the green light band, the distortion rate of the dual telecentric lens provided in this application embodiment is ≤0.0024%, and the distortion amount is ≤0.048μm, which is less than 1 / 10 of the system resolution; in the red light band, the distortion rate is ≤0.0029%, and the distortion amount is ≤0.058μm, which is also better than 1 / 10 of the system resolution. This ensures the high-precision imaging capability of the dual telecentric lens under dual-band illumination and meets the optical performance requirements of low distortion in industrial inspection.

[0074] Please refer to Figure 6 and Figure 7 The telecentric lens provided in this application has a field curvature of ≤0.0059mm in the green light band and ≤0.0070mm in the red light band. This low field curvature characteristic ensures the flatness of the imaging plane throughout the entire field of view and reduces image quality degradation at the edges of the field of view caused by field curvature.

[0075] The dual telecentric lens provided in this application has an object-side working distance (Lwo) ranging from 95mm to 101mm and an image-side working distance (Lwi) ranging from 12mm to 12.5mm. This allows the lens to have reasonable working distances in both the object and image sides, which can not only adapt to the installation and inspection needs of different objects in various industrial inspection scenarios, but also provide a flexible spatial layout for the integration of imaging equipment.

[0076] It is worth noting that near the aperture stop S, the double telecentric lens may also include a filter to achieve the filtering function of red and green light.

[0077] Based on the same concept, this application also provides an optical device including any of the aforementioned dual telecentric lenses. Since the aforementioned dual telecentric lenses have advantages such as large numerical aperture, high resolution, low distortion, compatibility with dual-band illumination, and -1X imaging, the optical device integrating the dual telecentric lens can also meet the requirements of high-precision applications such as high-resolution machine vision industrial inspection.

[0078] In summary, this application provides a double telecentric lens and optical device. By symmetrically distributing the first lens group A, the second lens group B, the third lens group C, and the fourth lens group D on both sides of the aperture stop S, a near-double Gaussian structure is formed, effectively correcting aberrations such as spherical aberration and distortion. Simultaneously, it reduces the incident angle of light on each lens surface, lowers system tolerance sensitivity, and improves the assembly yield of the optical system. Furthermore, by setting the aperture stop S as a variable stop including at least a first aperture and a second aperture, a double telecentric lens with high telecentricity under both green and red light dual-band illumination is achieved.

[0079] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0080] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A double telecentric lens, characterized in that, The system includes a first lens group, a second lens group, an aperture stop, a third lens group, and a fourth lens group arranged sequentially from the object side to the image side along the optical axis. The first and second lens groups are nearly symmetrically distributed with respect to the aperture stop, and the nearly symmetrical distribution is a double Gaussian distribution. The first lens group has positive optical power; the second lens group has negative optical power; the third lens group has positive optical power; and the fourth lens group has positive optical power. The aperture stop includes a variable aperture, comprising at least a first aperture suitable for green light of a first set wavelength to pass through and a second aperture suitable for red light of a second set wavelength to pass through; The dual telecentric lenses satisfy the following relationship: -0.019<F1 / F<-0.01; 0.02<F2 / F<0.1; -0.26<F3 / F<-0.19; -0.019<F4 / F<-0.012 Wherein, F, F1, F2, F3 and F4 are the total focal length of the double telecentric lens, the focal length of the first lens group, the focal length of the second lens group, the focal length of the third lens group and the focal length of the fourth lens group, respectively.

2. The double telecentric lens according to claim 1, characterized in that, The first lens group includes a first lens and a second lens arranged sequentially from the object side to the image side along the optical axis, with the first lens and the second lens being nearly symmetrically distributed; The object-side surface of the first lens is concave, the image-side surface is convex, and the refractive index is 1.87 < n1 < 1.97; The object-side surface of the second lens is convex, the image-side surface is concave, and the refractive index is 1.8 < n2 < 1.

89.

3. The dual telecentric lens according to claim 2, characterized in that, The second lens group includes a first cemented lens, a second cemented lens, a seventh lens, and a third cemented lens arranged sequentially along the optical axis from the object side to the image side; The first cemented lens includes a third lens and a fourth lens; The object side of the third lens is concave, the image side is concave, and the refractive index is 1.75 < n3 < 1.85; The fourth lens has a convex object side and a concave image side, with a refractive index of 1.61 < n3 < 1.

71. The second cemented lens includes a fifth lens, a sixth lens, and a seventh lens; The fifth lens has a convex object side and a convex image side, and its refractive index is 1.56 < n5 < 1.

67. The sixth lens has a concave side surface and a convex side surface, with a refractive index of 1.73 < n6 < 1.83; The seventh lens has a convex object side and a convex image side, and its refractive index is 1.56 < n7 < 1.

67. The third cemented lens includes an eighth lens and a ninth lens; The eighth lens has a convex object side and a convex image side, and its refractive index is 1.65 < n8 < 1.

75. The ninth lens has a concave object side and a concave image side, and its refractive index is 1.7 < n9 < 1.

8.

4. The double telecentric lens according to claim 3, characterized in that, The third lens group includes a fourth cemented lens that is nearly symmetrically arranged with respect to the aperture stop with respect to the third cemented lens; The fourth cemented lens includes a tenth lens and an eleventh lens arranged sequentially along the optical axis from the object side to the image side; The tenth lens has a concave side surface and a convex side surface, with a refractive index of 1.9 < n10 < 2.0; The eleventh lens has a concave object side and a convex image side, with a refractive index of 1.65 < n11 < 1.

75.

5. The dual telecentric lens according to claim 4, characterized in that, The fourth lens group includes a fifth cemented lens, a fourteenth lens, and a fifteenth lens arranged sequentially from the object side to the image side along the optical axis; The fifth cemented lens includes the twelfth and thirteenth lenses; The twelfth lens has a convex object side and a convex image side, and its refractive index is 1.73 < n12 < 1.

82. The thirteenth lens has a concave object side and a convex image side, with a refractive index of 1.55 < n13 < 1.

65. The fourteenth lens has a convex object side and a concave image side, with a refractive index of 1.88 < n13 < 1.93; The fifteenth lens has a convex object side and a concave image side, with a refractive index of 1.68 < n13 < 1.

73.

6. The dual telecentric lens according to claim 5, characterized in that, The first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the seventh lens, the eighth lens, the ninth lens, the tenth lens, the eleventh lens, the twelfth lens, the thirteenth lens, the fourteenth lens, and the fifteenth lens are spherical lenses.

7. The dual telecentric lens according to claim 5, characterized in that, The materials of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the seventh lens, the eighth lens, the ninth lens, the tenth lens, the eleventh lens, the twelfth lens, the thirteenth lens, the fourteenth lens, and the fifteenth lens include glass.

8. The dual telecentric lens according to claim 5, characterized in that, Along the optical axis, the distance from the aperture stop to the image side of the ninth lens is 3.2mm~4mm, and the distance from the aperture stop to the object side of the tenth lens is 13mm~13.9mm; The aperture stop has a first aperture diameter of 22mm to 22.8mm and a second aperture diameter of 25.2mm to 26mm.

9. The double telecentric lens according to claim 1, characterized in that, The dual telecentric lenses satisfy the following relationship: -0.27<F1 / F2<-0.18; -4.1<F3 / F2<-3.1; -0.3<F4 / F2<-0.22 Wherein, F1, F2, F3 and F4 are the focal lengths of the first lens group, the second lens group, the third lens group and the fourth lens group, respectively.

10. An optical device, characterized in that, Includes the telecentric lens as described in any one of claims 1 to 9.

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