Industrial double-telecentric lens and optical system for visual inspection of large-size element

Abstract

The invention relates to an industrial double telecentric lens and optical system for visual inspection of large-size elements, in a front lens group, a first lens is a plano-convex lens and has positive focal power, a second lens is a convex meniscus lens and has positive focal power, a third lens is a plano-concave lens and has positive focal power, and a fourth lens is a concave meniscus lens and has negative focal power; the third lens and the fourth lens are glued to form a first doublet lens group; in the middle lens group, a fifth lens is a thick concave meniscus lens and has negative focal power, a sixth lens is a thin concave meniscus lens and has negative focal power, and a diaphragm is arranged on a light path between the sixth lens and a seventh lens; in the rear lens group, the seventh lens is a plano-convex lens and has positive focal power, the eighth lens is a plano-concave lens and has negative focal power, the eighth lens and the ninth lens are cemented to form a second doublet lens group, the ninth lens is a biconvex lens and has positive focal power, and the tenth lens is a plano-convex lens and has positive focal power. The high-performance compact design is realized through the middle lens group, and the total length of the lens is greatly reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical lens imaging, and in particular relates to an industrial bi-telecentric lens and an optical system for visual inspection of large-size components. Background Art

[0002] Bi-telecentric lenses, with their unique optical path design, play a key role in machine vision inspection. Their core principle is to converge light from an object into parallel beams through the front lens. After passing through an aperture, they are focused by the rear lens onto a photoelectric sensor to form an image. Bi-telecentric lenses are widely used in industries involving machine vision inspection, such as electronics, machinery manufacturing, and industrial automation, primarily for detecting millimeter-level defects, dimensional deviations, and surface flaws.

[0003] Current bi-telecentric lenses mostly use a double Gaussian structure and its deformation structure. When the field of view increases, to ensure that larger workpieces can be effectively projected onto the imaging surface while maintaining image clarity and consistency, it is usually necessary to increase the working distance on the object side. As the field of view increases, the lens will introduce more off-axis aberrations, which deteriorates the image quality. To improve the aberrations, the traditional solution uses multiple lenses for group correction, which increases the overall length of the lens and the size of the system. In addition, the current bi-telecentric lenses with high resolution and low distortion performance still have the problem of small linear field of view on the object side and low magnification. As the size of industrial components increases, multiple scanning is often required, resulting in low inspection efficiency. Ultimately, the bi-telecentric lens has problems with the field of view, resolution, image quality, total lens length and magnification performance.

[0004] Therefore, as the size of industrial components increases, the demand for large field of view, high magnification, high resolution and imaging quality is becoming increasingly urgent. At the same time, the lens must be compact to adapt to complex installation environments. Summary of the Invention

[0005] To address the aforementioned problems in the prior art, the present invention provides an industrial bi-telecentric lens and optical system for visual inspection of large-sized components. The technical problems to be solved by the present invention are achieved through the following technical solutions:

[0006] The present invention provides an industrial bi-telecentric lens for visual inspection of large-size components, comprising: a front lens group, a middle lens group, and a rear lens group, wherein the front lens group comprises a first lens, a second lens, a third lens, and a fourth lens arranged in sequence from the object side to the image side, the first lens is a plano-convex lens with positive focal power, the second lens is a convex meniscus lens with positive focal power, the third lens is a plano-concave lens with positive focal power, the fourth lens is a concave meniscus lens with negative focal power, and the third lens and the fourth lens are cemented to form a first doublet lens group; the middle lens group comprises a fifth lens, a sixth lens arranged in sequence from the object side to the image side and an aperture, the fifth lens is a thick concave meniscus lens with negative focal power, the sixth lens is a thin concave meniscus lens with negative focal power, and the aperture is arranged behind the sixth lens; the rear lens group includes a seventh lens, an eighth lens, a ninth lens and a tenth lens arranged in sequence from the object side to the image side, the seventh lens is a plano-convex lens with positive focal power, the aperture is arranged before the seventh lens, the eighth lens is a plano-concave lens with negative focal power, the eighth lens and the ninth lens are cemented to form a second doublet lens group, the ninth lens is a biconvex lens with positive focal power, and the tenth lens is a plano-convex lens with positive focal power.

[0007] In one embodiment of the present invention, the air gap between the first lens and the second lens ranges from 17.5 to 24.5 mm; the air gap between the second lens and the first doublet lens group ranges from 2.0 to 4.0 mm; and the air gap between the first doublet lens group and the fifth lens ranges from 34.0 to 41.0 mm.

[0008] In one embodiment of the present invention, the air gap between the fifth lens and the sixth lens is in the range of 9.0 to 11.0 mm; the air gap between the sixth lens and the aperture is in the range of 2.5 to 4.5 mm; and the air gap between the aperture and the seventh lens is in the range of 1.5 to 3.5 mm.

[0009] In one embodiment of the present invention, the air gap between the seventh lens and the second doublet lens group is in the range of 0.1 to 0.2 mm; the air gap between the second doublet lens group and the tenth lens is in the range of 0.1 to 0.2 mm.

[0010] In one embodiment of the present invention, the thickness of the fifth lens is less than or equal to the curvature radius thereof.

[0011] In one embodiment of the present invention, the diaphragm is an aperture diaphragm, and the aperture height of the aperture diaphragm is 7.0806 mm.

[0012] In one embodiment of the present invention, the total length of the industrial bi-telecentric lens used for visual inspection of large-sized components is no more than 250 mm, and the size of its object-side linear field of view is no less than 150 mm.

[0013] In one embodiment of the present invention, the lenses in the industrial bi-telecentric lens for visual inspection of large-size components are all spherical glass lenses, and the maximum aperture of all the lenses is no more than 158 mm.

[0014] In one embodiment of the present invention, the radius of the object surface of the first lens is in the range of 182.5000 to 192.5000 mm, the thickness is in the range of 22.0 to 29.0 mm, and the radius of the image side surface of the first lens is in the range of -4255.0000 to -4245.0000 mm; the radius of the object surface of the second lens is in the range of 73.0000 to 80.0000 mm, the thickness is in the range of 22.5 to 29.5 mm, and the radius of the image side surface of the second lens is in the range of 274.8000 to 284.8000 mm; the radius of the object surface of the third lens is in the range of 370.3000 to 380 .3000mm, the thickness range is 11.5~13.5mm, the radius range of the image side of the third lens is 63.0000~70.0000mm; the radius range of the object surface of the fourth lens is 63.0000~70.0000mm, the thickness range is 16.5~23.5mm, the radius range of the image side of the fourth lens is 34.0000~41.0000mm; the radius range of the object surface of the fifth lens is 16.5000~23.5000mm, the thickness range is 14.5~21.5mm, the radius range of the image side of the fifth lens is 8.0000~1 0.0000mm; the radius range of the object surface of the sixth lens is 16.0000~23.0000mm, the thickness range is 2.5~4.5mm, the radius range of the image side surface of the sixth lens is 11.0000~12.0000mm; the radius range of the object surface of the seventh lens is 115.5000~125.5000mm, the thickness range is 16.5~23.5mm, the radius of the image side surface of the seventh lens is -25.0000~-18.0000mm; the radius range of the object surface of the eighth lens is 135.0000~145.0000mm, the thickness range is The radius range of the image side surface of the eighth lens is 2.0~4.0mm, and the radius range of the image side surface of the eighth lens is 20.0000~27.0000mm; the radius range of the object surface of the ninth lens is 20.0000~27.0000mm, and the thickness range is 11.0~13.0mm, and the radius range of the image side surface of the ninth lens is -47.5000~-40.5000mm; the radius range of the object surface of the tenth lens is 23.5000~30.5000mm, and the thickness range is 13.0~15.0mm, and the radius range of the image side surface of the tenth lens is 201.5000~211.5000mm.

[0015] The present invention also provides an optical system comprising the above-mentioned industrial bi-telecentric lens for visual inspection of large-size components.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] The industrial bi-telecentric lens for visual inspection of large-size components of the present invention adopts a structure of a front lens group, a middle lens group and a rear lens group. The front lens group introduces negative coma, and the rear lens group introduces positive coma. The two compensate each other to eliminate coma. The middle lens group is composed of a thick concave meniscus lens, a thin concave meniscus lens and an aperture. The thick concave meniscus lens can compress the space of the front lens group, the thin concave meniscus lens further fine-tunes the light path, and the aperture is used to fix the optimal light passing area. The synergistic effect of the three realizes a high-performance compact design, greatly reduces the total lens length of the industrial bi-telecentric lens, and achieves better image quality and resolution with a smaller aperture. At the same time, it also broadens the field of view and brightness. Through the wide field of view coverage, it can be flexibly integrated into a variety of usage scenarios, from the size detection of key parts of large-scale mechanical assembly to precise component defect detection, all of which can meet the requirements of the industrial bi-telecentric lens for telecentricity, high resolution, low distortion, and low chromatic aberration.

[0018] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the following preferred embodiments are specifically cited and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 1 is a schematic structural diagram of an industrial bi-telecentric lens for visual inspection of large-size components provided by an embodiment of the present invention;

[0020] Figure 2 This is a spot diagram of an industrial bi-telecentric lens for visual inspection of large-sized components provided by an embodiment of the present invention;

[0021] Figure 3 is an optical transfer function diagram of an industrial bi-telecentric lens for visual inspection of large-size components provided by an embodiment of the present invention;

[0022] Figure 4 This is a geometric distortion diagram of an industrial bi-telecentric lens for visual inspection of large-size components provided by an embodiment of the present invention;

[0023] Figure 5 This is an optical transfer function diagram of an industrial bi-telecentric lens for visual inspection of large-size components provided by an embodiment of the present invention at -10°C;

[0024] Figure 6 2 is an optical transfer function diagram of an industrial bi-telecentric lens for visual inspection of large-size components at 20°C provided by an embodiment of the present invention;

[0025] Figure 7 Graph showing the optical transfer function at 50°C of an industrial bi-telecentric lens for visual inspection of large-sized components provided by an embodiment of the present invention;

[0026] Figure 8 This is a geometric distortion diagram of an industrial bi-telecentric lens for visual inspection of large-size components provided by an embodiment of the present invention at -10°C;

[0027] Figure 9 This is a geometric distortion diagram of an industrial bi-telecentric lens for visual inspection of large-size components at 20°C provided by an embodiment of the present invention;

[0028] Figure 10 This is a geometric distortion diagram of an industrial bi-telecentric lens for visual inspection of large-size components provided by an embodiment of the present invention at 50°C.

[0029] Reference numerals: 1 - first lens; 2 - second lens; 3 - third lens; 4 - fourth lens; 5 - fifth lens; 6 - sixth lens; 7 - seventh lens; 8 - eighth lens; 9 - ninth lens; 10 - tenth lens. DETAILED DESCRIPTION

[0030] In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined purpose of the invention, the following is a detailed description of an industrial bi-telecentric lens and optical system for visual inspection of large-size components proposed in accordance with the present invention, in combination with the accompanying drawings and specific implementation methods.

[0031] The aforementioned and other technical contents, features, and effects of the present invention are clearly presented in the following detailed description of the specific embodiments in conjunction with the accompanying drawings. Through the description of the specific embodiments, a deeper and more specific understanding of the technical means and effects adopted by the present invention to achieve the intended purpose can be obtained. However, the accompanying drawings are provided for reference and illustration purposes only and are not intended to limit the technical solutions of the present invention.

[0032] Example 1

[0033] The first aspect of the present invention provides an industrial bi-telecentric lens for visual inspection of large-sized components, such as Figure 1 As shown, Figure 1 The figure is a schematic structural diagram of an industrial bi-telecentric lens for visual inspection of large-size components provided by an embodiment of the present invention.

[0034] In this embodiment, an industrial bi-telecentric lens for visual inspection of large-size components includes: a front lens group, a middle lens group, and a rear lens group, wherein the front lens group includes a first lens 1, a second lens 2, a third lens 3, and a fourth lens 4 arranged in sequence from the object side to the image side, the first lens 1 is a plano-convex lens with positive focal power, the second lens 2 is a convex meniscus lens with positive focal power, the third lens 3 is a plano-concave lens with positive focal power, the fourth lens 4 is a concave meniscus lens with negative focal power, and the third lens 3 and the fourth lens 4 are cemented to form a first double cemented lens. The central lens group includes, from object to image, a fifth lens element 5, a sixth lens element 6, and an aperture. The fifth lens element 5 is a thick concave meniscus lens with negative focal power, while the sixth lens element 6 is a thin concave meniscus lens with negative focal power. The aperture is positioned after the sixth lens element 6 and before the seventh lens element 7, i.e., located in the optical path between the sixth and seventh lenses 6 and 7. The combination of the thick and thin meniscus lenses and the aperture effectively corrects aberrations, optimizes telecentricity on the object and image sides, controls the angle of incidence of light, and reduces chromatic aberration and distortion. Controlling field brightness through the aperture improves optical transmission efficiency, ensuring high resolution and uniform imaging, making it particularly suitable for applications such as high-precision measurement and industrial inspection. The rear lens group includes a seventh lens 7, an eighth lens 8, a ninth lens 9 and a tenth lens 10 arranged in order from the object side to the image side. The seventh lens 7 is a plano-convex lens with positive focal power, the eighth lens 8 is a plano-concave lens with negative focal power, the eighth lens 8 and the ninth lens 9 are cemented together to form a second doublet lens group, the ninth lens 9 is a biconvex lens with positive focal power, and the tenth lens 10 is a plano-convex lens with positive focal power.

[0035] The principle is that the industrial double telecentric lens of the present invention uses a double Gaussian deformation structure as the initial structure, adds a convex meniscus lens (second lens 2) and a plano-convex lens (first lens 1) to the front lens group, and the middle lens group is composed of a thick concave meniscus lens (fifth lens 5), a thin concave meniscus lens (sixth lens 6) and an aperture; the rear lens group is composed of two plano-convex lenses (seventh lens 7 and tenth lens 10) and a group of doublet lenses (eighth lens 8 and ninth lens 9). The convex meniscus lens (second lens 2) can effectively compensate for the field curvature of the system and make the image plane flatter. In conjunction with the positive lens in the double Gaussian structure, it can reduce the spherical aberration offset of the edge light. The positive focal length dominated by the convex surface can enhance the overall convergence ability of the system and shorten the focal length. The concave meniscus lens (fourth lens 4) can effectively control the refraction of light, has the effect of correcting aberrations (chromatic aberration and distortion) and optimizing imaging quality. It can also improve the symmetry of the optical system, reduce spherical aberration and coma, thereby optimizing the compactness of the optical system and making the system design more efficient. The first double cemented lens group and the second double cemented lens group can correct chromatic aberration, reduce spherical aberration, and improve imaging quality; therefore, the industrial double telecentric lens structure of the present invention has the advantages of compact structure and smaller size compared to traditional double telecentric lenses.

[0036] Specifically, the first lens 1 has a first object-side surface facing the object side and a first image-side surface facing the image side; the second lens 2 has a second object-side surface facing the object side and a second image-side surface facing the image side; the third lens 3 has a third object-side surface facing the object side and a third image-side surface facing the image side; the fourth lens 4 has a fourth object-side surface facing the object side and a fourth image-side surface facing the image side; the fifth lens 5 has a fifth object-side surface facing the object side and a fifth image-side surface facing the image side; the sixth lens 6 has a sixth object-side surface facing the object side and a sixth image-side surface facing the image side; an aperture is arranged on the optical path between the sixth lens 6 and the seventh lens 7; the seventh lens 7 has a seventh object-side surface facing the object side and a seventh image-side surface facing the image side; the eighth lens 8 has an eighth object-side surface facing the object side and an eighth image-side surface facing the image side; the ninth lens 9 has a ninth object-side surface facing the object side and a ninth image-side surface facing the image side; the tenth lens 10 has a tenth object-side surface facing the object side and a tenth image-side surface facing the image side, and the side surfaces of the above lenses are all spherical.

[0037] In an optional embodiment, the air gap between the first lens 1 and the second lens 2 ranges from 17.5 to 24.5 mm; the air gap between the second lens 2 and the first doublet lens group ranges from 2.0 to 4.0 mm; the air gap between the first doublet lens group and the fifth lens 5 ranges from 34.0 to 41.0 mm; the air gap between the fifth lens 5 and the sixth lens 6 ranges from 9.0 to 11.0 mm; the air gap between the sixth lens 6 and the aperture ranges from 2.5 to 4.5 mm; the air gap between the aperture and the seventh lens 7 ranges from 1.5 to 3.5 mm; the air gap between the seventh lens 7 and the second doublet lens group ranges from 0.1 to 0.2 mm; and the air gap between the second doublet lens group and the tenth lens 10 ranges from 0.1 to 0.2 mm. For example, the air gap between the first lens 1 and the second lens 2 is 21 mm, the air gap between the second lens 2 and the first doublet lens is 3.1 mm, the air gap between the first doublet lens and the fifth lens 5 is 37.6 mm, and the air gap between the fifth lens 5 and the sixth lens 6 is 10 mm. The air gap between the sixth lens 6 and the aperture is 3.5 mm, the air gap between the aperture and the seventh lens 7 is 2.4 mm, the air gap between the seventh lens 7 and the second doublet lens group is 0.1 mm, and the air gap between the second doublet lens group and the tenth lens 10 is 0.1 mm.

[0038] In an optional embodiment, the radius of the object surface of the first lens 1 is in the range of 182.5000 to 192.5000 mm, the thickness is in the range of 22.0 to 29.0 mm, and the radius of the image side surface of the first lens 1 is in the range of -4255.0000 to -4245.0000 mm; the radius of the object surface of the second lens 2 is in the range of 73.0000 to 80.0000 mm, the thickness is in the range of 22.5 to 29.5 mm, and the radius of the image side surface of the second lens 2 is in the range of 274.8000 to 284.8000 mm; the radius of the object surface of the third lens 3 is in the range of 370.3000 to 380. 3000mm, thickness range is 11.5~13.5mm, the radius range of the image side surface of the third lens 3 is 63.0000~70.0000mm; the radius range of the object surface of the fourth lens 4 is 63.0000~70.0000mm, thickness range is 16.5~23.5mm, the radius range of the image side surface of the fourth lens 4 is 34.0000~41.0000mm; the radius range of the object surface of the fifth lens 5 is 16.5000~23.5000mm, thickness range is 14.5~21.5mm, the radius range of the image side surface of the fifth lens 5 is 8.0000~10 .0000mm; the radius of the object surface of the sixth lens 6 is in the range of 16.0000~23.0000mm, the thickness range is 2.5~4.5mm, the radius range of the image side surface of the sixth lens 6 is 11.0000~12.0000mm; the radius of the object surface of the seventh lens 7 is in the range of 115.5000~125.5000mm, the thickness range is 16.5~23.5mm, the radius of the image side surface of the seventh lens 7 is -25.0000~-18.0000mm; the radius of the object surface of the eighth lens 8 is in the range of 135.0000~145.0000mm, the thickness range is The radius of the image side surface of the eighth lens element 8 is in the range of 2.0 to 4.0 mm, and the radius of the image side surface of the eighth lens element 8 is in the range of 20.0000 to 27.0000 mm; the radius of the object surface of the ninth lens element 9 is in the range of 20.0000 to 27.0000 mm, and the thickness is in the range of 11.0 to 13.0 mm, and the radius of the image side surface of the ninth lens element 9 is in the range of -47.5000 to -40.5000 mm; the radius of the object surface of the tenth lens element 10 is in the range of 23.5000 to 30.5000 mm, and the thickness is in the range of 13.0 to 15.0 mm, and the radius of the image side surface of the tenth lens element 10 is in the range of 201.5000 to 211.5000 mm.

[0039] For example, the radius of the object side of the first lens 1 is 187.7189 mm, the thickness is 25.50 mm, and the radius of the image side of the first lens is -4250.5269 mm; the radius of the object side of the second lens 2 is 76.9379 mm, the thickness is 26.00 mm, and the radius of the image side of the second lens 2 is 279.7966 mm; the radius of the object side of the third lens 3 is 375.2637 mm, the thickness is 12.50 mm, and the radius of the image side of the third lens 3 is 66. The object side radius of the fourth lens 4 is 66.6512 mm, the thickness is 20.00 mm, and the image side radius of the fourth lens 4 is 37.7956 mm. The object side radius of the fifth lens 5 is 20.1060 mm, the thickness is 18.00 mm, and the image side radius of the fifth lens 5 is 9.1188 mm. The object side radius of the sixth lens 6 is 20.1611 mm, the thickness is 3.50 mm, and the image side radius of the sixth lens 6 is 11.9434 mm. The object-side radius of the seventh lens element 7 is 120.9355 mm, and the thickness is 20.00 mm. The image-side radius of the seventh lens element 7 is -21.6310 mm. The object-side radius of the eighth lens element 8 is 140.0311 mm, and the thickness is 3.00 mm. The image-side radius of the eighth lens element 8 is 23.5717 mm. The object-side radius of the ninth lens element 9 is 23.5717 mm, and the thickness is 12.00 mm. The image-side radius of the ninth lens element 9 is -43.9218 mm. The object-side radius of the tenth lens element 10 is 27.0007 mm, and the thickness is 14.00 mm. The image-side radius of the tenth lens element 10 is 206.6199 mm.

[0040] In an optional embodiment, in an optional embodiment, the middle lens group of the industrial double telecentric lens for visual inspection of large-size components of the present invention adopts a combination of a thick concave meniscus lens, a thin concave meniscus lens and an aperture, which can effectively correct aberrations, optimize telecentricity, control the light propagation path, and reduce light scattering and reflection, thereby achieving higher resolution and imaging quality. This design not only simplifies the optical system, but also reduces the total length of the optical system, optimizes the installation and use performance, and can also reduce costs. It is suitable for application scenarios that require field of view brightness uniformity and high imaging accuracy. However, the thickness of the thick concave meniscus lens should not be greater than its curvature radius. This is because if the thickness of the meniscus lens is greater than its curvature radius, it will lead to increased optical aberrations (such as spherical aberration, astigmatism, chromatic aberration), enhanced diffraction effects and reduced system resolution; it will also increase the difficulty of processing, and may therefore cause lens deformation, unstable focal length, and increased weight and volume. Therefore, the thickness of the fifth lens 5 should be less than or equal to its curvature radius.

[0041] In an optional embodiment, the diaphragm is an aperture diaphragm. Exemplarily, the aperture height of the aperture diaphragm may be 7.0806 mm.

[0042] In an optional embodiment, the lenses in the industrial bi-telecentric lens for visual inspection of large-size components of the present invention are all spherical glass lenses, and the maximum aperture of all lenses is no more than 158 mm, which is conducive to reducing the overall size of the inspection equipment. Specifically, the first lens 1 can be a plano-convex lens made of H-ZLAF69, the second lens 2 can be a convex meniscus lens made of H-LAK52, the third lens 3 can be a plano-concave lens made of H-ZF6, the fourth lens 4 can be a concave meniscus lens made of H-LAF2, the fifth lens 5 can be a thick concave meniscus lens made of H-ZK21, the sixth lens 6 can be a thin concave meniscus lens made of H-BAK7, the seventh lens 7 can be a plano-convex lens made of H-LAF 50B, the eighth lens 8 can be a plano-concave lens made of H-ZLAF90, the ninth lens 9 can be a biconvex lens made of H-ZPK1A, and the tenth lens 10 can be a plano-convex lens made of H-ZPK7. The aperture is arranged on the optical path between the sixth lens 6 and the seventh lens 7, and the aperture height of the aperture can be 7.0806 mm. Preferably, the lenses in the industrial bi-telecentric lens of the present invention can all be made of environmentally friendly glass materials that do not contain lead, arsenic, cadmium, or radioactive elements. Furthermore, all lenses are made of domestic environmentally friendly glass, reducing the cost of the lens.

[0043] For example, the total length of the industrial bi-telecentric lens for visual inspection of large-sized components of the present invention is not more than 250mm, and the size of its object-side linear field of view is not less than 150mm. The optimized length makes it easy to install and use, which is conducive to reducing the size of the entire inspection equipment. Preferably, the object-side linear field of view of the industrial bi-telecentric lens of the present invention is 150mm, the aperture number F / # is equal to 2.7, the total length of the lens is 249.3mm, the maximum lens aperture is 158mm, and the magnification is -0.1 x , telecentricity is less than 0.2°, geometric distortion is less than 0.1%, and MTF is greater than 0.3 at 200lp / mm. It can achieve high imaging resolution under a large field of view, and has good brightness, imaging quality and telecentricity. The large field of view coverage allows it to be flexibly integrated into a variety of usage scenarios. The Airy disk radius of the bi-telecentric lens of the present invention is 1.936μm, which can capture the details of tiny objects or defects and is suitable for high-precision detection tasks such as electronic components, semiconductor chips, micro-mechanical components, etc.

[0044] It is worth noting that the present invention adopts an overall symmetrical structure. The front lens group introduces negative coma, while the rear lens group introduces positive coma. The two compensate for each other and eliminate coma. The front lens group is composed of four lenses, including a doublet. The front lens group is equivalent to an object-side telecentric system, aiming to direct incident light from a large field of view into the aperture stop. The meniscus lens near the aperture stop effectively reduces aperture stop aberrations. The rear lens group is composed of a single lens and a doublet, which is equivalent to an image-side telecentric optical path, ultimately focusing light passing through the aperture stop onto the photoelectric sensor. It is suitable for photoelectric sensors with a target surface size of 1" and a pixel size of 3.2mm.

[0045] Furthermore, based on the traditional optical path structure of the object, front lens group, diaphragm, rear lens group, and image plane, the present invention forms a middle lens group of the lens structure by a thick concave meniscus lens (fifth lens 5), a thin concave meniscus lens (sixth lens 6), and a diaphragm, wherein the thick concave meniscus lens is used to expand the optical path and provide a more relaxed light incident condition for the diaphragm, thereby reducing vignetting; the thin concave meniscus lens is used to balance the optical focal length, thereby avoiding uneven image plane caused by excessive divergence of the thick lens; the front lens group space is compressed by the thick concave meniscus lens, the optical path is further fine-tuned by the thin concave meniscus lens, and the optimal light passing area is fixed by the diaphragm. The combination of the three realizes the compact design of the industrial double telecentric lens. Specifically, the middle lens group realizes the coordinated compensation of multiple aberrations through thick lens correction, thin lens fine tuning, and diaphragm screening. Finally, by accurately controlling the optical path and telecentricity, as well as the balance between high performance and compactness, the total length of the industrial double telecentric lens and the volume of the optical system are effectively reduced.

[0046] like Figure 2 As shown, Figure 2 This is a spot diagram for an industrial bi-telecentric lens for large-scale component visual inspection, provided by an embodiment of the present invention. The spot diagram represents the root mean square (RMS) value of the focused spot on the photoelectric sensor target surface for each field of view. A smaller RMS radius indicates better focusing. As can be seen from the figure, the optimized RMS radius of the focused spot for each field of view is approximately 1.8 mm to 2.8 mm, which is smaller than the pixel size of 3.2 mm.

[0047] like Figure 3 As shown, Figure 3 This is an optical transfer function diagram of an industrial bi-telecentric lens for large-size component visual inspection provided by an embodiment of the present invention. The optical transfer function MTF (Modulation Transfer Function) represents the imaging resolution capability of each field of view. Figure 3It can be seen that the transfer function of the entire field of view decreases smoothly and the OTF coefficient (Optical Transfer Function) at 200lp / mm is greater than 0.3, indicating that the industrial bi-telecentric lens of this embodiment can well match the industrial camera with a pixel size of 3.2mm, and has good contrast and imaging resolution.

[0048] like Figure 4 As shown, Figure 4 This is a geometric distortion diagram of an industrial bi-telecentric lens for large-size component visual inspection provided by an embodiment of the present invention. Geometric distortion represents the percentage difference between the actual image height and the ideal image height. Therefore, it only affects the shape of the image and has nothing to do with the imaging resolution. Figure 4 It can be seen that the distortion of the optimized bi-telecentric lens over the entire field of view is less than 0.1%.

[0049] Traditional optical lenses experience significant performance degradation and poor stability due to temperature rise caused by light source illumination or changes in ambient temperature. Therefore, the industrial bi-telecentric lens for large-scale component visual inspection in this embodiment optimizes its temperature performance through the optimized design of the air gap, ensuring excellent stability in various temperature environments.

[0050] like Figures 5 to 7 As shown, Figure 5 This is an optical transfer function diagram of an industrial bi-telecentric lens for visual inspection of large-size components provided by an embodiment of the present invention at -10°C; Figure 6 2 is an optical transfer function diagram of an industrial bi-telecentric lens for visual inspection of large-size components at 20°C provided by an embodiment of the present invention; Figure 7 This is a diagram of the optical transfer function of the industrial bi-telecentric lens for visual inspection of large-size components provided by an embodiment of the present invention at 50°C. As can be seen from the figure, in the environmental range of -10°C to 50°C, the optical transfer function MTF is greater than 0.23 at 156lp / mm. Therefore, the industrial bi-telecentric lens for visual inspection of large-size components provided by an embodiment of the present invention still has good MTF in a wider temperature range (-10°C to 50°C) and at high spatial frequencies to ensure sharp images and clear edges. This further indicates that the imaging quality of the lens remains stable in a wider temperature range (-10°C to 50°C), so it can be used in scenarios with high requirements for temperature adaptability, such as industrial inspection, aerospace, and infrared imaging.

[0051] like Figures 8 to 10 As shown, Figure 8 This is a geometric distortion diagram of an industrial bi-telecentric lens for visual inspection of large-size components provided by an embodiment of the present invention at -10°C; Figure 9This is a geometric distortion diagram of an industrial bi-telecentric lens for visual inspection of large-size components at 20°C provided by an embodiment of the present invention; Figure 10 This figure shows the geometric distortion of an industrial bi-telecentric lens for large-scale component visual inspection at 50°C, provided by an embodiment of the present invention. Temperature changes affect the lens material's thermal expansion coefficient or refractive index (dn / dT), thereby altering image aberrations. As can be seen in the figure, the optical distortion of the industrial bi-telecentric lens for large-scale component visual inspection, provided by an embodiment of the present invention, is less than 0.1% within an ambient temperature range of -10°C to 50°C, demonstrating the lens' high imaging geometric accuracy, temperature adaptability, and temperature reliability.

[0052] The industrial bi-telecentric lens for visual inspection of large-size components of the present invention adopts a structure of a front lens group, a middle lens group and a rear lens group. The front lens group introduces negative coma, and the rear lens group introduces positive coma. The two compensate each other to eliminate coma. The middle lens group is composed of a thick concave meniscus lens, a thin concave meniscus lens and an aperture. The thick concave meniscus lens can compress the space of the front lens group, the thin concave meniscus lens further fine-tunes the light path, and the aperture is used to fix the optimal light passing area. The synergistic effect of the three realizes a high-performance compact design, greatly reduces the total lens length of the industrial bi-telecentric lens, and achieves better image quality and resolution with a smaller aperture. At the same time, it also broadens the field of view and brightness. Through the wide field of view coverage, it can be flexibly integrated into a variety of usage scenarios, from the size detection of key parts of large-scale mechanical assembly to precise component defect detection, all of which can meet the requirements of the industrial bi-telecentric lens for telecentricity, high resolution, low distortion, and low chromatic aberration.

[0053] A second aspect of the present invention provides an optical system comprising the industrial bi-telecentric lens for visual inspection of large-sized components according to the first aspect.

[0054] In optical systems, the application of the industrial bi-telecentric lens used for visual inspection of large-size components in the first aspect offers significant advantages. Regarding imaging angle, its main advantages include: improved optical system structure; high imaging clarity and brightness facilitate highlighting contours and defect features, facilitating further extraction of texture features during visual inspection; optical distortion generated by the lens is within the range of -0.1% to 0.1%, and telecentricity is less than 0.2°. The bi-telecentric lens with low distortion and large depth of field makes it easier for edge detection algorithms to extract shape features; adding double-cemented lens groups on both sides of the aperture eliminates vertical chromatic aberration in the off-axis field of view, making it easier to extract color features when used with convolutional neural networks; and an object-side line field of view of 150mm, which can improve inspection efficiency. Therefore, when applied to visual inspection, the feature extraction effect is more obvious, further improving the accuracy of size and defect detection.

[0055] It should be noted that the optical system provided in the second aspect of the present invention has similar beneficial effects as the industrial bi-telecentric lens of the first aspect. Therefore, for any technical details not disclosed therein, reference can be made to the description of the first aspect for understanding.

[0056] It should be noted that, in this document, relational terms such as first and second are used solely to distinguish one entity or operation from another, and do not necessarily require or imply any actual relationship or order between these entities or operations. Furthermore, the terms "comprise," "include," or any other variations thereof are intended to encompass non-exclusive inclusion, such that an article or device comprising a list of elements includes not only those elements but also other elements not explicitly listed. Without further limitation, an element defined by the phrase "comprising a..." does not preclude the presence of additional identical elements in the article or device comprising the element. Terms such as "connected" or "connected" are not limited to physical or mechanical connections but may include electrical connections, whether direct or indirect. References to orientations or positional relationships, such as "upper," "lower," "left," and "right," are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate description and simplify the description of the present invention. They do not indicate or imply that the device or element referred to must have, be constructed, or operate in a specific orientation, and are therefore not to be construed as limiting the present invention.

[0057] The above is a further detailed description of the present invention in conjunction with specific preferred embodiments, and the specific implementation of the present invention should not be considered to be limited to these descriptions. For those skilled in the art of the present invention, without departing from the concept of the present invention, several simple deductions or substitutions can be made, which should be considered to fall within the scope of protection of the present invention.

Claims

1. An industrial bi-telecentric lens for visual inspection of large-size components, characterized in that: include: Front lens group, middle lens group and rear lens group, among which, The front lens group includes a first lens, a second lens, a third lens, and a fourth lens arranged in sequence from the object side to the image side, the first lens is a plano-convex lens with positive focal power, the second lens is a convex meniscus lens with positive focal power, the third lens is a plano-concave lens with positive focal power, and the fourth lens is a concave meniscus lens with negative focal power. The third lens and the fourth lens are cemented together to form a first doublet lens group; The middle lens group includes a fifth lens, a sixth lens, and an aperture arranged in sequence from the object side to the image side, the fifth lens being a thick concave meniscus lens with negative optical power, the sixth lens being a thin concave meniscus lens with negative optical power, and the aperture being disposed behind the sixth lens; The rear lens group includes a seventh lens, an eighth lens, a ninth lens, and a tenth lens arranged in sequence from the object side to the image side, the seventh lens is a plano-convex lens with positive focal power, the aperture is arranged in front of the seventh lens, the eighth lens is a plano-concave lens with negative focal power, the eighth lens and the ninth lens are cemented to form a second doublet lens group, the ninth lens is a biconvex lens with positive focal power, and the tenth lens is a plano-convex lens with positive focal power.

2. The industrial bi-telecentric lens for visual inspection of large-size components according to claim 1, characterized in that: The air gap between the first lens and the second lens ranges from 17.5 to 24.5 mm; the air gap between the second lens and the first doublet lens group ranges from 2.0 to 4.0 mm; and the air gap between the first doublet lens group and the fifth lens ranges from 34.0 to 41.0 mm.

3. The industrial bi-telecentric lens for visual inspection of large-size components according to claim 1, characterized in that: The air gap between the fifth lens and the sixth lens is in the range of 9.0 to 11.0 mm; the air gap between the sixth lens and the aperture is in the range of 2.5 to 4.5 mm; and the air gap between the aperture and the seventh lens is in the range of 1.5 to 3.5 mm.

4. The industrial bi-telecentric lens for visual inspection of large-size components according to claim 1, characterized in that: The air gap between the seventh lens and the second doublet lens group is in the range of 0.1 to 0.2 mm; the air gap between the second doublet lens group and the tenth lens is in the range of 0.1 to 0.2 mm.

5. The industrial bi-telecentric lens for visual inspection of large-size components according to claim 1, characterized in that: The thickness of the fifth lens is less than or equal to the curvature radius of the fifth lens.

6. The industrial bi-telecentric lens for visual inspection of large-size components according to claim 1, characterized in that: The diaphragm is an aperture diaphragm, and the aperture height of the aperture diaphragm is 7.0806 mm.

7. The industrial bi-telecentric lens for visual inspection of large-size components according to claim 1, characterized in that: The total length of the industrial bi-telecentric lens used for visual inspection of large-size components shall not exceed 250mm, and the size of its object-side linear field of view shall not be less than 150mm.

8. The industrial bi-telecentric lens for visual inspection of large-size components according to claim 1, characterized in that: The lenses in the industrial bi-telecentric lens for visual inspection of large-size components are all spherical glass lenses, and the maximum aperture of all the lenses is no more than 158 mm.

9. The industrial bi-telecentric lens for visual inspection of large-size components according to claim 1, characterized in that: The radius of the object surface of the first lens is in the range of 182.5000 to 192.5000 mm, the thickness is in the range of 22.0 to 29.0 mm, and the radius of the image side of the first lens is in the range of -4255.0000 to -4245.0000 mm; the radius of the object surface of the second lens is in the range of 73.0000 to 80.0000 mm, the thickness is in the range of 22.5 to 29.5 mm, and the radius of the image side of the second lens is in the range of 274.8000 to 284.8000 mm. mm; the radius of the object surface of the third lens is in the range of 370.3000 to 380.3000 mm, the thickness is in the range of 11.5 to 13.5 mm, and the radius of the image side surface of the third lens is in the range of 63.0000 to 70.0000 mm; the radius of the object surface of the fourth lens is in the range of 63.0000 to 70.0000 mm, the thickness is in the range of 16.5 to 23.5 mm, and the radius of the image side surface of the fourth lens is in the range of 34.0000 to 41.0000 mm; The radius of the object surface of the fifth lens is in the range of 16.5000 to 23.5000 mm, the thickness is in the range of 14.5 to 21.5 mm, and the radius of the image side surface of the fifth lens is in the range of 8.0000 to 10.0000 mm; the radius of the object surface of the sixth lens is in the range of 16.0000 to 23.0000 mm, the thickness is in the range of 2.5 to 4.5 mm, and the radius of the image side surface of the sixth lens is in the range of 11.0000 to 12.0000 mm; The radius of the object surface of the seventh lens is in the range of 115.5000 to 125.5000 mm, the thickness is in the range of 16.5 to 23.5 mm, and the radius of the image side surface of the seventh lens is in the range of -25.0000 to -18.0000 mm; the radius of the object surface of the eighth lens is in the range of 135.0000 to 145.0000 mm, the thickness is in the range of 2.0 to 4.0 mm, and the radius of the image side surface of the eighth lens is in the range of 20.0000 to 27.0000 mm; The radius range of the physical surface of the ninth lens is 20.0000~27.0000mm, the thickness range is 11.0~13.0mm, and the radius range of the image side surface of the ninth lens is -47.5000~-40.5000mm; the radius range of the physical surface of the tenth lens is 23.5000~30.5000mm, the thickness range is 13.0~15.0mm, and the radius range of the image side surface of the tenth lens is 201.5000~211.5000mm.

10. An optical system, characterized in that: An industrial bi-telecentric lens for visual inspection of large-size components comprising the method described in any one of claims 1 to 9.

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