An imaging optical system for industrial vision inspection

Abstract

The application provides an imaging optical system for industrial visual detection, which is mainly composed of nine lenses, a first lens with optical power, a convex object side and a concave image side, a second lens with optical power, a third lens with optical power, a fourth lens with optical power, a fifth lens with positive optical power, a sixth lens with optical power, a convex object side, a seventh lens with optical power, a concave object side, an eighth lens with optical power, and a ninth lens with positive optical power, a convex image side. Through reasonable configuration of nine lens combinations, lens power and surface type, high-resolution imaging is realized under the compact structure of TTL≤60mm and the large aperture of F≤2.5, the aberration correction ability is particularly strengthened, the MTF value is high in the whole zoom range, the accuracy and reliability of industrial detection are significantly improved, and the imaging optical system has the characteristics of zoom, low distortion and low cost.

Description

[Technical Field] This application belongs to the field of optical imaging technology, specifically relating to an imaging optical system for industrial visual inspection. [Background Technology] Industrial vision inspection systems are placing increasingly stringent demands on the performance of optical lenses. Modern industrial inspection not only requires optical lenses to possess high resolution and high-magnification zoom capabilities, but also to meet the need for compact design to adapt to installation in confined spaces. However, existing industrial zoom lenses generally suffer from insufficient aberration correction and image plane drift during zooming when achieving high-magnification zoom, leading to a decrease in inspection accuracy. To obtain better image quality, traditional industrial zoom lenses typically compensate for aberration changes during zooming by increasing the number of lens groups. However, this also results in problems such as excessive lens size and weight, making it difficult to meet the miniaturization and lightweight requirements of modern industrial equipment. [Utility Model Content] To address the problem of excessively large lens size and weight caused by increasing the number of lenses to maintain high-resolution imaging in existing technologies, this application provides an imaging optical system for industrial vision inspection.

[0004] This application is achieved through the following technical solution: An imaging optical system for industrial visual inspection is characterized in that it is composed of a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an eighth lens, and a ninth lens in sequence along the optical axis from the object plane side to the image plane side. The first lens has optical power, and its object side is convex and its image side is concave. The second lens has optical power; The third lens has optical power; The fourth lens has optical power; The fifth lens has positive optical power; The sixth lens has optical power and its object side is convex. The seventh lens has optical power and its object side is concave. The eighth lens has optical power; The ninth lens has positive optical power and its image-side surface is convex. The sixth and seventh lenses constitute a bonding lens; the F-number of the imaging optical system satisfies: F≤2.5; the total length TTL of the imaging optical system satisfies: TTL≤60.0mm.

[0005] An imaging optical system for industrial vision inspection as described above, the imaging optical system satisfies the following relationship: 0.2° / mm < FOV / (DT11 × TTL / ImgH) < 1.4° / mm; where FOV is half of the maximum field angle of the imaging optical system, DT11 is the maximum effective radius of the object side of the first lens, TTL is the on-axis distance from the object side of the first lens to the imaging surface, and ImgH is half of the diagonal length of the effective pixel area on the imaging surface.

[0006] An imaging optical system for industrial vision inspection as described above, the imaging optical system satisfies the following relationship: 1.1 < (F × f × ImgH) / TTL < 2.6; where F is the F-number of the optical imaging lens, f is the effective focal length of the optical imaging system, ImgH is half of the diagonal length of the effective pixel area on the imaging surface, and TTL is the on-axis distance from the object side of the first lens to the imaging surface.

[0007] An imaging optical system for industrial vision inspection as described above, the imaging optical system satisfies the following relationship: 0.2 < ∣f1 + f2∣ / ∣f1 - f2∣ < 2.2; where f1 is the effective focal length of the first lens and f2 is the effective focal length of the second lens.

[0008] An imaging optical system for industrial vision inspection as described above, the imaging optical system satisfies the following relationship: 0.6 < ∣(f4 - f5) / (f4 + f5)∣ < 3.2; where f4 is the effective focal length of the fourth lens and f5 is the effective focal length of the fifth lens.

[0009] An imaging optical system for industrial vision inspection as described above, the imaging optical system satisfies the following relationship: 0 < (f - f12) / f < 2.1; where f12 is the effective combined focal length of the first lens and the second lens, and f is the effective focal length of the optical imaging system.

[0010] An imaging optical system for industrial vision inspection as described above, the imaging optical system satisfies the following relationship: 1.1 < (R1 + R2) / R2 < 2.8; 0.5 < (R3 + R4) / R3 < 1.9; 0.3 < f / ∣R18∣ < 1.5; Where R1 is the curvature radius of the object side of the first lens, R2 is the curvature radius of the image side of the first lens, R3 is the curvature radius of the object side of the second lens, R4 is the curvature radius of the image side of the second lens, R18 is the curvature radius of the image side of the ninth lens, and f is the effective focal length of the optical imaging system.

[0011] An imaging optical system for industrial vision inspection as described above, and this imaging optical system satisfies the following relationship: 2.0 < BFL / (T12 + T23) < 3.7; where T12 is the air gap between the first lens and the second lens on the optical axis, T23 is the air gap between the second lens and the third lens on the optical axis, and BFL is the shortest distance from the image side of the ninth lens to the imaging plane of the optical system in the direction of the optical axis.

[0012] An imaging optical system for industrial vision inspection as described above, and this imaging optical system satisfies the following relationship: 1.2 < (CT8 + CT9) / EPD < 3.9; where EPD is the entrance pupil diameter of the optical imaging system, CT8 is the central thickness of the eighth lens on the optical axis, and CT9 is the central thickness of the ninth lens on the optical axis.

[0013] An imaging optical system for industrial vision inspection as described above, and the aperture stop of this system is located between the fifth lens and the sixth lens.

[0014] Compared with the prior art, the present application has the following advantages: An imaging optical system for industrial vision inspection of the present application realizes high-resolution imaging under a compact structure with TTL ≤ 60 mm and a large aperture with F ≤ 2.5 through the combined design of nine lenses and the reasonable configuration of the refractive power and surface shape of each lens. This system particularly strengthens the aberration correction ability, ensures a high MTF value throughout the zoom range, significantly improves the accuracy and reliability of industrial inspection, and has the characteristics of zoom, low distortion, and low cost, fully meeting the stringent requirements of the industrial automation inspection field for high performance, miniaturization, and lightweight.

Description of the Drawings

[0016] Figure 1 It is a schematic structural diagram of the optical imaging lens in Embodiment 1; Figure 2 It is the axial chromatic aberration, astigmatism, and distortion curves of the optical imaging lens in Embodiment 1; Figure 3 It is a schematic structural diagram of the optical imaging lens in Embodiment 2; Figure 4 It is the axial chromatic aberration, astigmatism, and distortion curves of the optical imaging lens in Embodiment 2; Figure 5 It is a schematic structural diagram of the optical imaging lens in Embodiment 3; Figure 6 The on-axis chromatic aberration, astigmatism, and distortion curves of the optical imaging lens in Example 3 are shown. Figure 7 This is a schematic diagram of the optical imaging lens in Embodiment 4; Figure 8 These are the on-axis chromatic aberration, astigmatism, and distortion curves of the optical imaging lens in Example 4.

Detailed Implementation Methods

[0018] Please see Figures 1 to 8 An imaging optical system for industrial visual inspection is characterized in that it is composed of a first lens E1, a second lens E2, a third lens E3, a fourth lens E4, a fifth lens E5, an aperture stop STO, a sixth lens E6, a seventh lens E7, an eighth lens E8, a ninth lens E9, and an infrared filter E10, arranged sequentially along the optical axis from the object plane side to the image plane side. The first lens E1 has optical power, its object side S1 is convex, and its image side S2 is concave. The second lens E2 has optical power; The third lens E3 has optical power; The fourth lens E4 has optical power; The fifth lens E5 has positive optical power; The sixth lens E6 has optical power, and its object side surface S11 is convex. The seventh lens E7 has optical power, and its object side surface S12 is concave. The eighth lens E8 has optical power; The ninth lens E9 has positive optical power and its image-side surface S17 is convex. The sixth lens E6 and the seventh lens E7 constitute a bonding lens; the F-number of the imaging optical system satisfies: F≤2.5; the total length TTL of the imaging optical system satisfies: TTL≤60.0mm.

[0019] An imaging optical system for industrial vision inspection of the present application realizes high-resolution imaging under a compact structure with TTL ≤ 60 mm and a large aperture with F ≤ 2.5 through the combined design of nine lenses and the reasonable configuration of the refractive power and surface shape of each lens. The system particularly strengthens the aberration correction ability, ensures a high MTF value throughout the zoom range, significantly improves the accuracy and reliability of industrial inspection, and has the characteristics of zoom, low distortion, and low cost, fully meeting the stringent requirements of the industrial automation inspection field for high performance, miniaturization, and lightweight.

[0020] Further, as a preferred implementation manner rather than a limitation of this solution, the imaging optical system satisfies the following relational expression: 0.2° / mm < FOV / (DT11 × TTL / ImgH) < 1.4° / mm; where FOV is half of the maximum field angle of the imaging optical system, DT11 is the maximum effective radius S1 of the object side surface of the first lens E1, TTL is the axial distance from the object side surface S1 of the first lens E1 to the imaging surface, and ImgH is half of the diagonal length of the effective pixel area on the imaging surface.

[0021] In this embodiment, by comprehensively constraining the maximum field of view (FOV), the maximum effective radius DT11 of the first lens object side, the total system length (TTL), and the diagonal length ImgH of the effective pixel area of ​​the imaging surface, the system achieves reasonable field of view coverage and good imaging uniformity while maintaining a compact structure. By limiting the relationship between half the diagonal length of the effective pixel area on the imaging surface, the maximum effective radius of the first lens object side, the on-axis distance from the first lens object side to the imaging surface, and the on-axis distance from the first lens object side to the imaging surface, aberrations are ensured to be within a correctable range, reducing design complexity. When the relationship is below the lower limit, DT11*TTL / IamgH further increases while ensuring a wide-angle optical system, which is not conducive to the optical lens meeting the characteristics of miniaturization and large target area; when the relationship exceeds the upper limit, the front aperture of the optical system is excessively compressed while ensuring a wide-angle optical system, making it difficult for the imaging system to obtain good imaging resolution. When the FOV / (DT11×TTL / ImgH) value is below 0.2° / mm, although the wide-angle characteristics of the optical system are guaranteed, an increase in DT11×TTL / ImgH will hinder the miniaturization and large target area of ​​the optical lens. When the value exceeds 1.4° / mm, although the wide-angle characteristics are still guaranteed, the excessive compression of the front aperture of the optical system will reduce the imaging resolution. Therefore, by controlling this value between 0.2° / mm and 1.4° / mm, the miniaturization and large target area characteristics of the optical lens can be guaranteed while maintaining the wide-angle characteristics, and good imaging resolution can be provided. This design limits the maximum incident angle of the beam within the system, avoiding distortion, astigmatism, and field-of-view obstruction caused by excessive tilting imaging in the edge areas, and effectively controlling the decrease in field curvature and relative illumination. By setting this parameter range, the system can maintain high-resolution imaging performance in a miniaturized structure, improving the flexibility of installation and use in confined spaces and the system's comprehensive coverage of industrial target surfaces.

[0022] Furthermore, as a preferred embodiment of this solution and not a limitation thereof, the imaging optical system satisfies the following relationship: 1.1 < (F × f × ImgH) / TTL < 2.6; where F is the F-number of the optical imaging lens, f is the effective focal length of the optical imaging system, ImgH is half the diagonal length of the effective pixel area on the imaging surface, and TTL is the on-axis distance from the object side surface S1 of the first lens E1 to the imaging surface.

[0023] In this embodiment, by controlling the ratio between the F-number, effective focal length f, half the diagonal length of the imaging surface ImgH, and the total system length TTL, the synergistic optimization of system luminous flux, imaging size, focal length, and structural compactness is achieved. This reflects how the system can accommodate a sufficiently large imaging surface within a limited TTL length while maintaining a large aperture, low F-number, and reasonable focal length, thereby ensuring that the imaging system has good luminous flux capture capability and high spatial resolution. By limiting the aperture, effective focal length, and the ratio of half the diagonal length of the effective pixel area on the imaging surface to the on-axis distance from the object side of the first lens to the imaging surface, aberrations can be kept within a correctable range, reducing design complexity. When the ratio is below the lower limit of the relationship, the total optical length of the optical system further increases while ensuring a large aperture, which is not conducive to the miniaturization of the optical system; when the ratio is above the upper limit of the relationship, it is not conducive to meeting the field of view range of the optical lens, and insufficient object space information cannot be obtained, affecting the image quality of the optical lens. This allows the system to maintain good signal-to-noise ratio and contrast in low-light environments, making it particularly suitable for visual inspection tasks under low-light conditions in industrial environments. By setting this parameter range, the imbalance between TTL and imaging optical performance is limited, avoiding image plane occlusion and incomplete field of view due to excessively short TTL, or structural redundancy and mechanical arrangement difficulties due to excessively long TTL.

[0024] Furthermore, as a preferred embodiment of this solution and not a limitation thereof, the imaging optical system satisfies the following relationship: 0.2 < |f1+f2| / |f1−f2| < 2.2; where f1 is the effective focal length of the first lens E1 and f2 is the effective focal length of the second lens E2.

[0025] In this embodiment, controlling this ratio avoids the two lenses having excessively similar focal lengths, which could lead to an excessively short equivalent focal length in the front group combination, field distortion, or excessively strong convergence, resulting in uncontrollable aberrations and an increased burden on subsequent lens group compensation. It also prevents excessively large reverse distribution of refractive power, which could cause excessive deflection of the principal ray, leading to image plane drift or abrupt changes in the system's pupil position. By reasonably controlling the focal length ratio of the first and second lenses, the optical system can achieve a large field of view while also obtaining high imaging resolution. If the ratio exceeds the upper limit of the formula, the refractive power of the first and second lenses is insufficient, making it difficult for large-angle light rays to enter the optical system, thus hindering the expansion of the field of view. If the ratio is below the lower limit, the refractive power of the first and second lenses is too strong, easily producing strong astigmatism and chromatic aberration, which is detrimental to high-resolution imaging characteristics. By maintaining a value between 0.2 and 2.2, the front lens assembly is ensured to possess adequate focusing capability and aberration adjustment flexibility, creating favorable incident light conditions and beam structure stability for subsequent lens design, thereby improving the overall system's image quality consistency and center-to-edge MTF balance. In a specific embodiment, when |f1+f2| / |f1−f2| exceeds 2.2, the refractive power of the first and second lenses is insufficient, making it difficult to allow large-angle light rays to enter the optical system, which is detrimental to expanding the field of view; while when this value is below 0.2, the refractive power of the first and second lenses is too strong, easily producing strong astigmatism and chromatic aberration, which is detrimental to high-resolution imaging characteristics.

[0026] Furthermore, as a preferred embodiment of this solution and not a limitation, the imaging optical system satisfies the following relationship: 0.6 < |(f4−f5) / (f4+f5) | < 3.2; where f4 is the effective focal length of the fourth lens E4 and f5 is the effective focal length of the fifth lens E5.

[0027] In this embodiment, the focal length ratio between the fourth lens E4 and the fifth lens E5 is primarily used to constrain the relative ratio between their focal length differences and total refractive power, thereby regulating the beam reconstruction and aberration neutralization effects of these two key mid-section lenses during zooming. By rationally controlling the focal length ratio of the third and fourth lenses, the optical power difference between adjacent lenses is kept within the optimal balance range, effectively suppressing higher-order aberrations such as field curvature, astigmatism, and spherical aberration caused by abrupt changes in optical power, thus improving the system's imaging quality. Below the lower limit of the relation, the optical power difference between adjacent lenses is too small, weakening the aberration correction capability; above the upper limit, it leads to excessive light deflection angles, generating higher-order aberrations that are difficult to correct. This ratio reflects the relative refractive power asymmetry between f4 and f5, ensuring that the mid-section optical structure, while effectively shaping, expanding, or compressing the beam, also possesses higher-order aberration compensation capabilities, especially playing a decisive role in correcting optical defects such as field curvature, coma, and asymmetric distortion. If this ratio is too small, it indicates that the focal lengths of the two lenses are similar, resulting in weak system control over the principal ray and a tendency for blurred mid-range imaging and uneven brightness at the edges of the field of view. Conversely, if the ratio is too large, it may cause optical axis shift or image plane drift, exacerbating aberration accumulation. Therefore, controlling it within the range of 0.6 to 3.2 is an ideal choice for balancing beam correction capability and optical structure stability. In terms of working principle, E4 and E5 are usually configured as a negative-positive combination or a positive-positive combination, respectively, forming a key aberration control unit or quasi-zoom unit. Under the constraint of the total TTL length, they achieve step-by-step compensation of multi-order aberrations, especially contributing significantly to the improvement of peripheral imaging quality in large field-of-view systems.

[0028] Furthermore, as a preferred embodiment of this solution and not a limitation, the imaging optical system satisfies the following relationship: 0 < (f − f12) / f < 2.1; where f12 is the effective combined focal length of the first lens E1 and the second lens E2, and f is the effective focal length of the optical imaging system.

[0029] In this embodiment, by adjusting the difference between the combined focal length f12 of the front group and the total focal length f of the system, it is ensured that the front group provides sufficient primary focusing and aberration pre-correction in the imaging path without excessively dominating the entire optical path structure. This provides reasonable compensation space and focusing margin for the middle and rear lens groups. By constraining the ratio of the combined focal length of the first and second lenses to the effective focal length of the optical lens, the optical power distribution of the first, second, and rear lens groups can be properly managed. This not only satisfies the miniaturization design of the optical lens but also achieves a balance of internal aberrations, thereby helping to adjust the field curvature and astigmatism at the imaging edges of the optical lens and meeting the imaging quality requirements of the optical lens for the surrounding environment. The lower limit of this relationship is greater than zero, which means that f12 must not be equal to the total focal length f of the system. This is to avoid the front group forming a structure similar to a quasi-prime lens, which would cause the rear group to lose its adjustment space, resulting in problems such as fixed image plane, limited zoom range, and unadjustable distortion. The upper limit is set to 2.1, which effectively limits the decrease in the focal length ratio of the front group, preventing the front group from being too weak and causing the principal ray to diverge highly in the system, thereby increasing the pressure on the rear group to compensate for aberrations, chromatic aberration, field curvature, etc.

[0030] Furthermore, as a preferred embodiment of this solution and not a limitation, the imaging optical system satisfies the following relationship: 1.1 < (R1 + R2) / R2 < 2.8; 0.5 < (R³ + R⁴) / R³ < 1.9; 0.3 <f / ∣R18∣<1.5; Wherein, R1 is the radius of curvature of the object-side surface S1 of the first lens E1, R2 is the radius of curvature of the image-side surface S2 of the first lens E1, R3 is the radius of curvature of the object-side surface S3 of the second lens E2, R4 is the radius of curvature of the image-side surface S4 of the second lens E2, R18 is the radius of curvature of the image-side surface S17 of the ninth lens E9, and f is the effective focal length of the optical imaging system.

[0031] In this embodiment, 1.1 < (R1 + R2) / R2 < 2.8. By controlling the curvature radii of the object side and the image side of the first lens, the total deflection angles of the object side and the image side of the first lens at the marginal field can be reasonably controlled within a reasonable range, effectively reducing the sensitivity of the system; 0.5 < (R3 + R4) / R3 < 1.9. By restricting the ratio of the curvature radii of the object side and the image side of the second lens, the surface shape of the second lens will not be overly curved, and it has a high degree of freedom during the design process, which is conducive to better correcting the astigmatism and field curvature of the optical lens, reducing the risk of ghost images, and improving the imaging quality of the optical lens. In addition, it is also beneficial to the machinability of the second lens and reduces the difficulty of forming and assembling the second lens; 0.3 < f / |R18| < 1.5. By limiting the range of the above relationship, it is conducive to restricting the curvature degree of the object side of the ninth lens, allowing more light to enter the optical system. At the same time, it is also conducive to reasonably distributing the refractive power of the optical system and correcting the off-axis aberration of the optical system. Exceeding the upper limit of the relationship, the focal length of the optical system is too large, which is not conducive to achieving miniaturization characteristics; below the lower limit of the relationship, the curvature radius of the object side of the ninth lens is too small, and the image side of the ninth lens is overly curved, further increasing the risk of ghost images; The first lens E1 and the second lens E2 are located at the front end of the system and are important units that dominate the refraction direction of object-side light and preprocess primary aberrations. The setting of the curvature ratio relationship of its object and image sides not only affects the position of the refractive power center and the principal ray deflection angle of the single lens, but also directly determines the introduction or compensation direction of spherical aberration, coma, and field curvature; further, the reverse control relationship of the surface curvature of the second lens plays a role in compensating for the higher-order aberrations of the previous lens, ensuring that the front group still has strong wavefront control ability under the condition of limited overall thickness, and is particularly suitable for high MTF and high-contrast image output requirements. The third formula f / |R18| is between 0.3 and 1.5, mainly used to limit the proportional relationship between the effective focal length f of the entire system and the curvature radius of the image side of the ninth lens, so as to optimize the back focal length BFL of the system on the premise of keeping the TTL unchanged. This parameter not only ensures the full-link aberration balance ability of the optical system from front-end focusing to back-end imaging, but also provides a refined curvature distribution control mechanism for achieving the comprehensive goals of large aperture, high resolution, low distortion, and structural compactness, effectively solving the core problems such as poor marginal image quality, too long back focal length, and difficult distortion suppression existing in traditional systems.

[0032] Further, as a preferred implementation manner rather than a limitation of this solution, the imaging optical system satisfies the following relationship: 2.0 < BFL / (T12 + T23) < 3.7; where, T12 is the air gap between the first lens E1 and the second lens E2 on the optical axis, T23 is the air gap between the second lens E2 and the third lens E3 on the optical axis, and BFL is the shortest distance from the image side of the ninth lens E9 to the imaging surface of the optical system in the optical axis direction.

[0033] In this embodiment, when the above-mentioned conditions are met, by controlling the optical back focal length within a reasonable range, the matching degree between the camera image and the image sensor is effectively ensured, guaranteeing the compatibility between the optical system and the image sensor. Simultaneously, the on-axis distances between the first and second lenses, as well as between the second and third lenses, are controlled. This facilitates the assembly process, avoids light interference caused by two lenses being too close, reduces lens sensitivity, weakens ghost energy between the first and second lenses, and improves the lens's imaging quality. The ratio between the total air gaps (T12 and T23) between the front lens groups and the system's back focal length (BFL) is adjusted to achieve a reasonable arrangement of the imaging plane and control of image quality stability while maintaining a compact system structure. This ratio, based on the optical path structure, constrains the proportion of the front air gap in the entire system's optical path, ensuring that the light beam has a sufficient and orderly converging tendency after passing through the front group, providing good incident conditions for the middle and rear lens groups, and avoiding excessive divergence or paraxial tilted light that leads to aberration accumulation, blurred field edges, and decreased relative illumination.

[0034] Furthermore, as a preferred embodiment of this solution and not a limitation thereof, the imaging optical system satisfies the following relationship: 1.2 < (CT8 + CT9) / EPD < 3.9; where EPD is the entrance pupil diameter of the optical imaging system, CT8 is the center thickness of the eighth lens E8 on the optical axis, and CT9 is the center thickness of the ninth lens E9 on the optical axis.

[0035] In this embodiment, by limiting the range of the above-mentioned sub-formula, it is possible to ensure that the center thickness of the eighth and ninth lenses is not too thin, which is beneficial to the lens processing and assembly process. If the thickness is below the lower limit of the formula, the eighth and ninth lenses will be too thin, which can easily lead to processing difficulties and lens deformation, thus affecting the image quality of the lens. If the thickness exceeds the upper limit of the formula, the ghosting risk of the eighth and ninth lenses will increase, and it will not be conducive to reducing the distortion and field curvature of the optical system, which is not conducive to improving the image quality of the lens. This helps to ensure that the system has good focusing ability and edge light flux transmission efficiency in the middle and rear lens groups while compressing the overall system thickness, effectively suppressing the vignetting phenomenon at the image edge and improving the brightness uniformity of the image field. In addition, by reasonably designing the center thickness combination ratio of E8 and E9, the image quality of the system under large aperture conditions can be improved while maintaining the control accuracy of the principal ray tilt angle. In particular, when focusing, the incident angle of the principal ray focal plane is closer to vertical, which is conducive to significantly reducing off-axis aberrations caused by image plane tilt, such as field curvature and astigmatism, so that the system also has high resolution and sharpness in the edge area.

[0036] Furthermore, as a preferred embodiment of this solution and not a limitation, the system aperture STO is located between the fifth lens E5 and the sixth lens E6.

[0037] Specifically, this is a preferred embodiment of the present invention and not a limitation thereof. Figure 1 A schematic diagram of the structure of an optical imaging lens according to Embodiment 1 of this application is shown. Figure 1 As shown, the optical imaging lens according to an exemplary embodiment of this application includes, in sequence along the optical axis from the object side to the image side: a first lens E1, a second lens E2, a third lens E3, a fourth lens E4, a fifth lens E5, a STO, a sixth lens E6, a seventh lens E7, an eighth lens E8, a ninth lens E9, an infrared filter E10, and an imaging surface S20.

[0038] The first lens E1 has negative optical power, with its object-side surface S1 being convex and its image-side surface S2 being concave. The second lens E2 has negative optical power, with its object-side surface S3 being concave and its image-side surface S4 being concave. The third lens E3 has negative optical power, with its object-side surface S5 being convex and its image-side surface S6 being concave. The fourth lens E4 has positive optical power, with its object-side surface S7 being concave and its image-side surface S8 being convex. The fifth lens E5 has positive optical power, with its object-side surface S9 being convex and its image-side surface S10 being concave. The sixth lens E6 has positive optical power, with its object-side surface S11 being convex and its image-side surface S12 being convex. The seventh lens E7 has negative optical power, with its object-side surface S12 being concave and its image-side surface S13 being concave. The eighth lens E8 has positive optical power, with its object-side surface S14 being convex and its image-side surface S15 being convex. The ninth lens E9 has positive optical power, with its object-side surface S16 being convex and its image-side surface S17 being convex. The filter E10 has an object-side surface S18 and an image-side surface S19. Light from the object passes sequentially through each surface S1 to S19 and is finally imaged on the imaging surface S20.

[0039] Figure 2 The on-axis chromatic aberration, astigmatism, and distortion curves of the optical imaging lens of Embodiment 1 are shown. On-axis chromatic aberration represents the deviation of the focal point of light of different wavelengths after passing through the lens; astigmatism represents the curvature of the meridional image plane and the sagittal image plane; distortion represents the magnitude of distortion corresponding to different image heights.

[0040] The optical imaging lens given in Example 1 can achieve good imaging quality.

[0041] Table 1 shows the surface type, radius of curvature, thickness and material of each lens of the optical imaging lens in Embodiment 1, wherein the units of radius of curvature and thickness are millimeters (mm). Table 1: Basic Parameters of the Optical System in Example 1

[0042] In Table 1, the object-side and image-side surfaces of the eighth lens E8 are both Q-type aspherical surfaces. The surface shape of each aspherical lens can be defined using, but is not limited to, the following aspherical formulas:

[0043] Where Z is the distance from the corresponding point on the aspherical surface to the plane tangent to the vertex of the surface, r is the radial coordinate of the aspherical surface, c is the curvature of the vertex of the aspherical surface, K is the conic coefficient, Am is the aspherical coefficient, rmax is the maximum value of the radial radius coordinate, and u = r / rmax. Table 2 gives the conic coefficients and higher-order coefficients A4, A6, A8, A10, A12, A14, A16, A18, and A20 of each aspherical surface that can be used in the first embodiment.

[0044] Table 2: Aspherical Correlation Values ​​of Lens Surface in Example 1

[0045] Specifically, this is a preferred embodiment of the present invention and not a limitation thereof. Figure 3 A schematic diagram of the structure of an optical imaging lens according to Embodiment 2 of this application is shown. Figure 3 As shown, the optical imaging lens according to an exemplary embodiment of this application includes, in sequence along the optical axis from the object side to the image side: a first lens E1, a second lens E2, a third lens E3, a fourth lens E4, a fifth lens E5, a STO, a sixth lens E6, a seventh lens E7, an eighth lens E8, a ninth lens E9, an infrared filter E10, and an imaging surface S20.

[0046] The first lens E1 has positive optical power, with its object-side surface S1 being convex and its image-side surface S2 being concave. The second lens E2 has negative optical power, with its object-side surface S3 being convex and its image-side surface S4 being concave. The third lens E3 has negative optical power, with its object-side surface S5 being convex and its image-side surface S6 being concave. The fourth lens E4 has negative optical power, with its object-side surface S7 being convex and its image-side surface S8 being concave. The fifth lens E5 has positive optical power, with its object-side surface S9 being convex and its image-side surface S10 being convex. The sixth lens E6 has positive optical power, with its object-side surface S11 being convex and its image-side surface S12 being convex. The seventh lens E7 has negative optical power, with its object-side surface S12 being concave and its image-side surface S13 being concave. The eighth lens E8 has positive optical power, with its object-side surface S14 being concave and its image-side surface S15 being convex. The ninth lens E9 has positive optical power, with its object-side surface S16 being concave and its image-side surface S17 being convex. The filter E10 has an object-side surface S18 and an image-side surface S19. Light from the object passes sequentially through each surface S1 to S19 and is finally imaged on the imaging surface S20.

[0047] Figure 4The on-axis chromatic aberration, astigmatism, and distortion curves of the optical imaging lens of Embodiment 2 are shown. On-axis chromatic aberration indicates the deviation of the focal point of light of different wavelengths after passing through the lens; astigmatism indicates the curvature of the meridional image plane and the sagittal image plane; distortion indicates the magnitude of distortion at different image heights, resulting in good imaging quality.

[0048] Table 3 shows the surface type, radius of curvature, thickness, and material of each lens in the optical imaging lens of Embodiment 2, wherein the units for radius of curvature and thickness are millimeters (mm).

[0049] Table 3: Basic Parameters of the Optical System in Example 2

[0050] In Table 3, the object-side and image-side surfaces of the eighth lens E8 are both Q-type aspherical surfaces. The surface shape of each aspherical lens can be defined using, but is not limited to, the following aspherical formulas:

[0051] Where Z is the distance from the corresponding point on the aspherical surface to the plane tangent to the vertex of the surface, r is the radial coordinate of the aspherical surface, c is the curvature of the vertex of the aspherical surface, K is the conic coefficient, Am is the aspherical coefficient, rmax is the maximum value of the radial radius coordinate, and u = r / rmax. Table 4 gives the conic coefficients and higher-order coefficients A4, A6, A8, A10, A12, A14, A16, A18, and A20 of each aspherical surface that can be used in the second embodiment.

[0052] Table 4: Aspherical Correlation Values ​​of Lens Surface in Example 2

[0053] Specifically, this is a preferred embodiment of the present invention and not a limitation thereof. Figure 5 A schematic diagram of the structure of an optical imaging lens according to Embodiment 3 of this application is shown.

[0054] like Figure 5 As shown, the optical imaging lens according to an exemplary embodiment of this application comprises, in sequence along the optical axis from the object side to the image side: First lens E1, second lens E2, third lens E3, fourth lens E4, fifth lens E5, STO, sixth lens E6, seventh lens E7, eighth lens E8, ninth lens E9, infrared filter E10 and imaging surface S20.

[0055] The first lens E1 has negative optical power, with its object side S1 being convex and its image side S2 being concave.

[0056] The second lens E2 has positive optical power, with its object side S3 being concave and its image side S4 being convex.

[0057] The third lens E3 has positive optical power, with its object side S5 being concave and its image side S6 being convex.

[0058] The fourth lens E4 has negative optical power, with its object side S7 being convex and its image side S8 being concave.

[0059] The fifth lens E5 has positive optical power, with its object side S9 being concave and its image side S10 being convex.

[0060] The sixth lens E6 has negative optical power, with its object side S11 being convex and its image side S12 being concave.

[0061] The seventh lens E7 has positive optical power, with its object side S12 being concave and its image side S13 being convex.

[0062] The eighth lens E8 has negative optical power, with its object side S14 being convex and its image side S15 being concave.

[0063] The ninth lens E9 has positive optical power, and its object side S16 is convex, and its image side S17 is convex.

[0064] The filter E10 has an object side surface S18 and an image side surface S19.

[0065] Light from the object passes sequentially through the first lens E1, the second lens E2, the third lens E3, the fourth lens E4, the fifth lens E5, STO, the sixth lens E6, the seventh lens E7, the eighth lens E8, the ninth lens E9, and the various surfaces S1 to S19 of the infrared filter E10, and is finally imaged on the imaging surface S20.

[0066] Figure 6 The on-axis chromatic aberration, astigmatism, and distortion curves of the optical imaging lens of Embodiment 3 are shown.

[0067] On-axis chromatic aberration indicates the deviation of the focal point of light of different wavelengths after passing through the lens; Astigmatism represents the curvature of the meridional image plane and the curvature of the sagittal image plane; Distortion represents the magnitude of distortion at different image heights.

[0068] The optical imaging lens given in Example 3 can achieve good imaging quality.

[0069] Table 5 shows the surface type, radius of curvature, thickness, and material of each lens in the optical imaging lens of Embodiment 3, wherein the units for radius of curvature and thickness are millimeters (mm).

[0070] Table 5: Basic Parameters of the Optical System in Example 3

[0071] In Table 6, the object-side and image-side surfaces of the eighth lens E8 are both Q-type aspherical surfaces. The surface shape of each aspherical lens can be defined using, but is not limited to, the following aspherical formulas:

[0072] Where Z is the distance from the corresponding point on the aspherical surface to the plane tangent to the vertex of the surface, r is the radial coordinate of the aspherical surface, c is the curvature of the vertex of the aspherical surface, K is the conic coefficient, Am is the aspherical coefficient, rmax is the maximum value of the radial radius coordinate, and u = r / rmax. Table 4 gives the conic coefficients and higher-order coefficients A4, A6, A8, A10, A12, A14, A16, A18, and A20 of each aspherical surface that can be used in the third embodiment.

[0073] Table 6: Aspherical Correlation Values ​​of Lens Surface in Example 3

[0074] Specifically, this is a preferred embodiment of the present invention and not a limitation thereof. Figure 7 A schematic diagram of the structure of an optical imaging lens according to Embodiment 4 of this application is shown.

[0075] like Figure 7 As shown, the optical imaging lens according to an exemplary embodiment of this application includes, in sequence along the optical axis from the object side to the image side: a first lens E1, a second lens E2, a third lens E3, a fourth lens E4, a fifth lens E5, a STO, a sixth lens E6, a seventh lens E7, an eighth lens E8, a ninth lens E9, an infrared filter E10, and an imaging surface S20.

[0076] The first lens E1 has positive optical power, with its object-side surface S1 being convex and its image-side surface S2 being concave. The second lens E2 has negative optical power, with its object-side surface S3 being convex and its image-side surface S4 being concave. The third lens E3 has negative optical power, with its object-side surface S5 being convex and its image-side surface S6 being concave. The fourth lens E4 has negative optical power, with its object-side surface S7 being concave and its image-side surface S8 being concave. The fifth lens E5 has positive optical power, with its object-side surface S9 being convex and its image-side surface S10 being convex. The sixth lens E6 has positive optical power, with its object-side surface S11 being convex and its image-side surface S12 being convex. The seventh lens E7 has negative optical power, with its object-side surface S12 being concave and its image-side surface S13 being concave. The eighth lens E8 has positive optical power, with its object-side surface S14 being convex and its image-side surface S15 being convex. The ninth lens E9 has positive optical power, with its object-side surface S16 being convex and its image-side surface S17 being convex. The filter E10 has an object-side surface S18 and an image-side surface S19. Light from the object passes sequentially through each surface S1 to S19 and is finally imaged on the imaging surface S20.

[0077] Figure 8The on-axis chromatic aberration, astigmatism, and distortion curves of the optical imaging lens of Embodiment 4 are shown. On-axis chromatic aberration represents the deviation of the focal point of light of different wavelengths after passing through the lens; astigmatism represents the curvature of the meridional and sagittal image planes; distortion represents the magnitude of distortion at different image heights. Good image quality is achieved.

[0078] Table 7 shows the surface type, radius of curvature, thickness, and material of each lens in the optical imaging lens of Embodiment 4, wherein the units for radius of curvature and thickness are millimeters (mm).

[0079] Table 7: Basic Parameters of the Optical System in Example 4

[0080] In Table 7, the object-side and image-side surfaces of the eighth lens E8 are both Q-type aspherical surfaces. The surface shape of each aspherical lens can be defined using, but is not limited to, the following aspherical formulas:

[0081] Where Z is the distance from the corresponding point on the aspherical surface to the plane tangent to the vertex of the surface, r is the radial coordinate of the aspherical surface, c is the curvature of the vertex of the aspherical surface, K is the conic coefficient, Am is the aspherical coefficient, rmax is the maximum value of the radial radius coordinate, and u = r / rmax. Table 4 gives the conic coefficients and higher-order coefficients A4, A6, A8, A10, A12, A14, A16, A18, and A20 of each aspherical surface that can be used in the first embodiment.

[0082] Table 8: Aspherical Correlation Values ​​of Lens Surface in Example 4

[0083] The basic data for Examples 1-4 are shown in Table 9 below: Table 9: Basic Data for Examples 1-4

[0084] In Examples 1-4, the conditions that satisfy the following table are shown in Table 10: Table 10: Conditions in Examples 1-4 satisfy the conditions in the table below.

[0085] The working principle of this embodiment is as follows: This application discloses an imaging optical system for industrial vision inspection. Through a nine-lens combination design and a rational configuration of the refractive power and surface shape of each lens, it achieves high-resolution imaging with a compact structure of TTL≤60mm and a large aperture of F≤2.5. This system particularly enhances aberration correction capabilities, ensuring a high MTF value throughout the zoom range, significantly improving the accuracy and reliability of industrial inspection. It features zoom capability, low distortion, and low cost, fully meeting the stringent requirements of high performance, miniaturization, and lightweight design in the field of industrial automation inspection.

[0086] The above are implementation methods provided in conjunction with specific content, and it is not intended that the specific implementation of this application is limited to these descriptions. Any methods or structures that are similar to those of this application, or any technical deductions or substitutions made based on the concept of this application, should be considered within the scope of protection of this application.

Claims

1. An imaging optical system for industrial visual inspection, characterized in that, It is composed of a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an eighth lens, and a ninth lens in sequence from the object side to the image side along the optical axis; The first lens has a focal power, its object side is convex, and its image side is concave; The second lens has a focal power; The third lens has a focal power; The fourth lens has a focal power; The fifth lens has a positive focal power; The sixth lens has a focal power, and its object side is convex; The seventh lens has a focal power, and its object side is concave; The eighth lens has a focal power; The ninth lens has a positive focal power, and its image side is convex; Among them, the sixth lens and the seventh lens form a cemented lens; the F-number of the imaging optical system satisfies: F ≤ 2.5; the total length TTL of the imaging optical system satisfies: TTL ≤ 60.0 mm.

2. The imaging optical system for industrial visual inspection according to claim 1, characterized in that, The imaging optical system satisfies the following relationship: 0.2° / mm < FOV / (DT11 × TTL / ImgH) < 1.4° / mm; where FOV is half of the maximum field angle of the imaging optical system, DT11 is the maximum effective radius of the object side of the first lens, TTL is the on-axis distance from the object side of the first lens to the imaging surface, and ImgH is half of the diagonal length of the effective pixel area on the imaging surface.

3. The imaging optical system for industrial visual inspection according to claim 1, characterized in that, The imaging optical system satisfies the following relationship: 1.1 < (F × f × ImgH) / TTL < 2.6; where F is the F-number of the optical imaging lens, f is the effective focal length of the optical imaging system, ImgH is half of the diagonal length of the effective pixel area on the imaging surface, and TTL is the on-axis distance from the object side of the first lens to the imaging surface.

4. The imaging optical system for industrial visual inspection according to claim 1, characterized in that, The imaging optical system satisfies the following relationship: 0.2 < ∣f1 + f2∣ / ∣f1 - f2∣ < 2.2; where f1 is the effective focal length of the first lens and f2 is the effective focal length of the second lens.

5. The imaging optical system for industrial visual inspection according to claim 1, characterized in that, The imaging optical system satisfies the following relationship: 0.6 < ∣(f4 - f5) / (f4 + f5)∣ < 3.2; where f4 is the effective focal length of the fourth lens and f5 is the effective focal length of the fifth lens.

6. The imaging optical system for industrial visual inspection according to claim 1, characterized in that, The imaging optical system satisfies the following relationship: 0 < (f - f12) / f < 2.1; where f12 is the effective combined focal length of the first lens and the second lens, and f is the effective focal length of the optical imaging system.

7. The imaging optical system for industrial visual inspection according to claim 1, characterized in that, The imaging optical system satisfies the following relationship: 1.1 < (R1 + R2) / R2 < 2.8; 0.5 < (R3 + R4) / R3 < 1.9; 0.3 < f / ∣R18∣ < 1.5; Among them, R1 is the curvature radius of the object side of the first lens, R2 is the curvature radius of the image side of the first lens, R3 is the curvature radius of the object side of the second lens, R4 is the curvature radius of the image side of the second lens, R18 is the curvature radius of the image side of the ninth lens, and f is the effective focal length of the optical imaging system.

8. The imaging optical system for industrial visual inspection according to claim 1, characterized in that, The imaging optical system satisfies the following relationship: 2.0 < BFL / (T12 + T23) < 3.7; where T12 is the air gap between the first lens and the second lens on the optical axis, T23 is the air gap between the second lens and the third lens on the optical axis, and BFL is the shortest distance from the image side of the ninth lens to the imaging plane of the optical system in the optical axis direction.

9. An imaging optical system for industrial visual inspection according to claim 1, characterized in that, The imaging optical system satisfies the following relationship: 1.2 < (CT8 + CT9) / EPD < 3.9; where EPD is the entrance pupil diameter of the optical imaging system, CT8 is the central thickness of the eighth lens on the optical axis, and CT9 is the central thickness of the ninth lens on the optical axis.

10. An imaging optical system for industrial visual inspection according to claim 1, characterized in that, The stop of the system is located between the fifth lens and the sixth lens.

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