Imaging optical system for industrial visual inspection

Abstract

The invention provides an imaging optical system for industrial visual inspection, which is characterized in that a first lens is mainly composed of nine lenses and has focal power, the object side surface of the first lens is a convex surface, and the image side surface of the first lens is a concave surface; the second lens has focal power; the third lens has focal power; the fourth lens has focal power; the fifth lens has positive focal power; the sixth lens has focal power, and the object side surface of the sixth lens is a convex surface; the seventh lens has focal power, and the object side surface of the seventh lens is a concave surface; the eighth lens has focal power; and the ninth lens has positive focal power, the image side surface of the ninth lens is a convex surface, and through the combination design of nine lenses and the reasonable configuration of the refractive power and the surface type of each lens, high-resolution imaging under a compact structure and a large aperture is realized, the aberration correction capability is particularly enhanced, and a relatively high MTF value is ensured in the whole zoom range. Accuracy and reliability of industrial detection are remarkably improved, and the system has the advantages of zooming, low distortion and low cost.

Description

Technical field

[0001] This application is achieved through the following technical solutions: 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 order from the object plane side to the image plane side along the optical axis; The first lens has optical power, an object-side surface thereof is convex, and an image-side surface thereof 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 refractive power; The sixth lens has optical power and its object-side surface is convex; The seventh lens has optical power and its object side surface is concave; The eighth lens has optical power; The ninth lens has positive refractive power and its image-side surface is convex; The sixth lens and the seventh lens constitute a cemented lens; the F number of the imaging optical system satisfies: F≤2.5; and the total length TTL of the imaging optical system satisfies: TTL≤60.0 mm.

[0002] 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 surface of the first lens, TTL is the on-axis distance from the object side surface 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.

[0003] 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 surface of the first lens to the imaging surface.

[0004] 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.

[0005] 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.

[0006] 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.

[0007] 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 surface of the first lens, R2 is the curvature radius of the image side surface of the first lens, R3 is the curvature radius of the object side surface of the second lens, R4 is the curvature radius of the image side surface of the second lens, R18 is the curvature radius of the image side surface of the ninth lens, and f is the effective focal length of the optical imaging system.

[0008] An imaging optical system for industrial vision inspection as described above, 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 surface of the optical system in the optical axis direction.

[0009] An imaging optical system for industrial vision inspection as described above, 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.

[0010] An imaging optical system for industrial vision inspection as described above, the aperture stop of the system is located between the fifth lens and the sixth lens.

[0011] 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 light weight.

Description of the Drawings

[0012] Figure 1 It is a schematic structural diagram of the optical imaging lens in Embodiment 1; Figure 2 [[ID=SS]]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 axial chromatic aberration, astigmatism, and distortion curves of the optical imaging lens of Example 3; Figure 7 is a schematic structural diagram of the optical imaging lens of Example 4; Figure 8 axial chromatic aberration, astigmatism, and distortion curves of the optical imaging lens of Example 4. [Specific implementation method] In order to make the technical problems, technical solutions and beneficial effects solved by this application more clearly understood, this application is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0013] See also Figures 1 to 8 An imaging optical system for industrial visual inspection, 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 STO, a sixth lens E6, a seventh lens E7, an eighth lens E8, a ninth lens E9, and an infrared filter E10 in order from the object side to the image side along the optical axis; The first lens E1 has optical power, an object-side surface S1 of the lens is convex, and an image-side surface S2 of the lens is concave; The second lens E2 has an optical power; The third lens E3 has an optical power; The fourth lens E4 has an optical power; The fifth lens E5 has positive refractive power; The sixth lens E6 has an 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 an optical power; The ninth lens element E9 has positive refractive power, and its image-side surface S17 is convex; The sixth lens E6 and the seventh lens E7 form a cemented lens; the F number of the imaging optical system satisfies: F≤2.5; and the total length TTL of the imaging optical system satisfies: TTL≤60.0 mm.

[0014] An imaging optical system for industrial vision inspection in the present application achieves 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 enhances 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 zooming, low distortion, and low cost, fully meeting the stringent requirements of the industrial automation inspection field for high performance, miniaturization, and lightweight.

[0015] Further, as a preferred implementation manner rather than a limitation of this solution, 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 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.

[0016] 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 of the effective pixel area on the imaging surface ImgH, the system achieves reasonable field of view coverage and good imaging uniformity while maintaining a compact structure. By defining 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 falls below the lower limit, while ensuring the wide-angle performance of the optical system, DT11*TTL / IamgH further increases, hindering the optical lens's ability to meet the requirements of miniaturization and a large target area. When the relationship exceeds the upper limit, while ensuring the wide-angle performance of the optical system, the front aperture of the optical system is excessively compressed, making it difficult for the imaging system to achieve good imaging resolution. When the FOV / (DT11×TTL / ImgH) value is less than 0.2° / mm, while the optical system's wide-angle characteristics are maintained, the increase in DT11×TTL / ImgH hinders the miniaturization of the optical lens and the expansion of the target area. When this value exceeds 1.4° / mm, while wide-angle characteristics are still maintained, the excessive compression of the optical system's front aperture reduces imaging resolution. Therefore, by controlling this value between 0.2° / mm and 1.4° / mm, it is possible to maintain wide-angle characteristics while ensuring miniaturization and a large target area of ​​the optical lens, while also providing good imaging resolution. This design limits the maximum angle of incidence of the light beam within the system, avoiding distortion, astigmatism, and field of view obstruction caused by excessively tilted imaging at the edge, and effectively controlling the field of view curvature and relative illumination degradation. By setting this parameter range, the system can maintain high-resolution imaging performance in a compact structure, enhancing installation flexibility in confined spaces and enhancing the system's comprehensive coverage of industrial target surfaces.

[0017] Furthermore, as a preferred embodiment of the present invention but not a limitation, the imaging optical system satisfies the following relationship: 1.1<(F×f×ImgH) / TTL<2.6; wherein 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 plane, and TTL is the on-axis distance from the object side S1 of the first lens E1 to the imaging plane.

[0018] In this embodiment, by controlling the ratio between the F-number, effective focal length f, half the diagonal length of the imaging plane ImgH, and the total system length TTL, a coordinated optimization of the system's luminous flux, imaging size, focal length, and structural compactness is achieved. This reflects how the system can accommodate a sufficiently large imaging plane within a limited total TTL length while maintaining a large aperture, low F-number, and a 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 plane to the axial distance from the object side of the first lens to the imaging plane of the optical imaging system, aberrations can be ensured to be within the correctable range, reducing design complexity. When the ratio is below the lower limit of the relationship, while ensuring a large aperture, the total optical length of the optical system is further increased, which is not conducive to 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 angle range of the optical lens, and sufficient object space information cannot be obtained, which affects the image quality of the optical lens. This enables the system to maintain a 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 obstruction and incomplete field of view caused by too short TTL, or structural redundancy and mechanical layout difficulties caused by too long TTL.

[0019] Furthermore, as a preferred embodiment of the present invention but not a limitation, the imaging optical system satisfies the following relationship: 0.2<|f1+f2| / |f1−f2|<2.2; wherein f1 is the effective focal length of the first lens E1, and f2 is the effective focal length of the second lens E2.

[0020] In this embodiment, controlling this ratio prevents the two lenses from having too close a focal length, which could result in an excessively short equivalent focal length of the front group, a distorted field of view, or excessive convergence power, leading to uncontrollable aberrations and an increased compensation burden on subsequent lens groups. It also prevents excessive reverse distribution of refractive power, which could lead to excessive deflection of the principal ray, causing image plane drift or sudden changes in the system pupil position. By properly controlling the focal length ratio of the first and second lenses, the optical system can achieve a wide field of view while also achieving high imaging resolution. If the ratio exceeds the upper limit of the relationship, the refractive power of the first and second lenses is insufficient, making it difficult for wide-angle light to enter the optical system, which is detrimental to expanding the field of view of the optical system. If the ratio falls below the lower limit, the refractive power of the first and second lenses is too strong, which could easily produce strong astigmatism and chromatic aberration, detrimental to high-resolution imaging. By maintaining the ratio between 0.2 and 2.2, the front lens assembly ensures moderate focusing power and aberration adjustment flexibility, creating favorable incident light conditions and beam structure stability for subsequent lens designs, improving the image quality consistency and center-to-edge MTF balance of the entire system. In a specific embodiment, when |f1+f2| / |f1−f2| exceeds 2.2, the refractive power of the first and second lens elements is insufficient, making it difficult for wide-angle light to enter the optical system, which is not conducive to expanding the field of view. When this value is below 0.2, the refractive power of the first and second lens elements is too strong, which easily produces strong astigmatism and chromatic aberration, which is not conducive to high-resolution imaging.

[0021] Furthermore, as a preferred embodiment of this solution but not a limitation, the imaging optical system satisfies the following relationship: 0.6<|(f4−f5) / (f4+f5)|<3.2; wherein f4 is the effective focal length of the fourth lens element E4, and f5 is the effective focal length of the fifth lens element E5.

[0022] In this embodiment, the focal length ratio of the fourth lens element, E4, to the total refractive power is constrained, thereby regulating the beam reconstruction and aberration neutralization effects of these two key middle lens elements during zooming. By rationally controlling the focal length ratio of the third and fourth lenses, the power difference between adjacent lenses is kept within an optimal balance range, effectively suppressing higher-order aberrations such as field curvature, astigmatism, and spherical aberration caused by sudden changes in power, thereby improving system imaging quality. Below the lower limit of the relationship, the power difference between adjacent lenses is too small, weakening aberration correction capabilities; exceeding the upper limit results in excessive light deflection angles, resulting in difficult-to-correct higher-order aberrations. This ratio, by reflecting the relative refractive power asymmetry between f4 and f5, ensures that the middle optical structure not only effectively shapes, expands, or compresses beams, but also compensates for higher-order aberrations. This plays a crucial role in correcting optical defects such as field curvature, coma, and asymmetric distortion. If this ratio is too small, indicating similar focal lengths between the two lenses, the system's ability to control the principal ray is weak, easily leading to blurred images in the middle section and uneven brightness at the edges of the field of view. Conversely, if the ratio is too large, it may cause optical axis offset or image plane drift, exacerbating aberration accumulation. Therefore, controlling it within the range of 0.6 to 3.2 is ideal for balancing beam correction capability and optical structure stability. In terms of operating principle, E4 and E5 are typically configured as a negative-positive or positive-positive combination, respectively, forming the key aberration control unit or quasi-zoom unit. This achieves step-by-step compensation of multi-order aberrations while maintaining the TTL total length constraint, contributing significantly to improved peripheral image quality in large field of view systems.

[0023] Furthermore, as a preferred embodiment of this solution but not a limitation, the imaging optical system satisfies the following relationship: 0<(f−f12) / f<2.1; wherein 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.

[0024] In this embodiment, by regulating the difference between the combined focal length f12 of the front lens group and the total focal length f of the system, the front lens group is ensured to provide sufficient primary focus and aberration pre-correction within the imaging path while not excessively dominating the overall optical path structure, thereby providing 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 lens groups to the effective focal length of the optical lens, the focal power of the first, second, and rear lens groups is properly distributed. This balances the internal aberrations of the optical lens while maintaining a compact design. This helps adjust the field curvature and astigmatism at the edge of the optical lens, ensuring the best imaging quality 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, so as to avoid the front group forming a quasi-primary mirror structure, resulting in the rear group losing adjustment space, thus causing problems such as fixed image plane, limited zoom range, and unadjustable distortion; and 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, resulting in the main light being highly divergent in the system, thereby increasing the pressure on the rear group to compensate for aberrations, chromatic aberrations, field curvature, etc.

[0025] Furthermore, as a preferred embodiment of this solution but 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; Among them, R1 is the curvature radius of the object-side surface S1 of the first lens E1, R2 is the curvature radius of the image-side surface S2 of the first lens E1, R3 is the curvature radius of the object-side surface S3 of the second lens E2, R4 is the curvature radius of the image-side surface S4 of the second lens E2, R18 is the curvature radius of the image-side surface S17 of the ninth lens E9, and f is the effective focal length of the optical imaging system.

[0026] 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 beneficial to restrict the bending degree of the object side of the ninth lens, allowing more light to enter the optical system. At the same time, it is also beneficial to reasonably distribute the refractive power of the optical system and correct 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 between the 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 high-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 regulation 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.

[0027] Further, as a preferred implementation manner of this solution rather than a limitation, 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 E'9 to the imaging surface of the optical system in the optical axis direction.

[0028] In this embodiment, when the above-mentioned conditional equation is met, the optical back focus is controlled within a reasonable range, effectively ensuring the matching between the camera image and the image sensor, and thus ensuring the compatibility of the optical system with 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 assembly, avoids light interference caused by the two lenses being too close together, reduces lens sensitivity, and mitigates ghost image energy between the first and second lenses, thereby improving the image quality of the lens. The ratio between the sum of the air spacings between the front lens groups (T12 and T23) and the back focus length (BFL) of the system is regulated, thereby achieving optimal placement of the imaging plane and controlling image quality stability while maintaining a compact system structure. This ratio, based on the optical path structure, constrains the proportion of the front air spacing in the overall system optical path, ensuring that light beams have a sufficient and orderly convergence trend after passing through the front group, providing favorable incident conditions for the middle and rear lens groups, and avoiding excessive divergence or paraxial tilted light rays that can lead to aberration accumulation, blur at the edge of the field of view, and reduced relative illumination.

[0029] Furthermore, as a preferred embodiment of this solution but not a limitation, the imaging optical system satisfies the following relationship: 1.2<(CT8+CT9) / EPD<3.9; wherein EPD is the entrance pupil diameter of the optical imaging system, CT8 is the center thickness of the eighth lens element E8 on the optical axis, and CT9 is the center thickness of the ninth lens element E9 on the optical axis.

[0030] In this embodiment, by limiting the range of the above sub-equation, the center thickness of the eighth and ninth lenses is ensured to be moderate, facilitating lens processing and assembly. Below the lower limit of the relationship, the eighth and ninth lenses are too thin, potentially leading to processing difficulties and lens distortion, which in turn affects lens image quality. Above the upper limit, the risk of ghosting increases for the eighth and ninth lenses, hindering the reduction of optical system distortion and field curvature, and thus, improving lens image quality. This helps reduce the overall system thickness while ensuring excellent focusing capability and marginal light flux transmission efficiency in the middle and rear lens groups, effectively suppressing image vignetting and improving brightness uniformity. Furthermore, by rationally designing the center thickness ratio of E8 and E9, image quality at wide apertures can be improved while maintaining accurate control of the chief ray tilt angle. In particular, during focusing, the angle of incidence of the chief ray on the focal plane is closer to vertical, significantly reducing off-axis aberrations caused by image plane tilt, such as field curvature and astigmatism, enabling high resolution and sharpness even in the peripheral areas of the system.

[0031] Furthermore, as a preferred embodiment of this solution but not a limitation, the system aperture STO is located between the fifth lens E5 and the sixth lens E6.

[0032] Specifically, as a preferred embodiment of the present invention but not limiting, Figure 1 FIG. 1 shows a schematic structural diagram of an optical imaging lens according to Example 1 of the present application. Figure 1 As shown, the optical imaging lens according to an exemplary embodiment of the present application includes, in order from the object side to the image side along the optical axis: a first lens E1, a second lens E2, a third lens E3, a fourth lens E4, a fifth lens E5, 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.

[0033] 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 element E9 has positive refractive power, with a convex object-side surface S16 and a convex image-side surface S17. The filter E10 has an object-side surface S18 and an image-side surface S19. Light from an object passes through surfaces S1 through S19 in sequence and is ultimately imaged on imaging surface S20.

[0034] Figure 2 The following graphs show the axial chromatic aberration, astigmatism, and distortion curves of the optical imaging lens of Example 1. Axial chromatic aberration indicates the deviation of light of different wavelengths from the focal point after passing through the lens; astigmatism indicates meridional and sagittal image curvature; and distortion indicates the magnitude of distortion at different image heights.

[0035] The optical imaging lens provided in Example 1 can achieve good imaging quality.

[0036] Table 1 shows the surface type, curvature radius, thickness, and material of each lens of the optical imaging lens system of Example 1, where the units of curvature radius and thickness are both in millimeters (mm). Table 1: Basic parameters of the optical system of Example 1

[0037] In Table 1, both the object-side surface and the image-side surface of the eighth lens element E8 are Q-type aspherical surfaces. The surface shape of each aspherical lens element can be defined by, but not limited to, the following aspherical surface formula:

[0038] Where Z is the distance from the corresponding point on the aspheric surface to the plane tangent to the vertex of the surface, r is the radial coordinate of the aspheric surface, c is the curvature of the aspheric vertex, K is the conic coefficient, Am is the aspheric coefficient, rmax is the maximum radial radius coordinate, and u = r / rmax. Table 2 shows the conic coefficients and higher-order coefficients A4, A6, A8, A10, A12, A14, A16, A18, and A20 for various aspheric surfaces that can be used in the first embodiment.

[0039] Table 2: Aspheric surface related values ​​of the lens surface of Example 1

[0040] Specifically, as a preferred embodiment of the present invention but not limiting, Figure 3 FIG. 1 shows a schematic structural diagram of an optical imaging lens according to the second embodiment of the present application. Figure 3 As shown, the optical imaging lens according to an exemplary embodiment of the present application includes, in order from the object side to the image side along the optical axis: a first lens E1, a second lens E2, a third lens E3, a fourth lens E4, a fifth lens E5, 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.

[0041] The first lens E1 has positive focal power, with its object-side surface S1 being convex and its image-side surface S2 being concave. The second lens E2 has negative focal power, with its object-side surface S3 being convex and its image-side surface S4 being concave. The third lens E3 has negative focal power, with its object-side surface S5 being convex and its image-side surface S6 being concave. The fourth lens E4 has negative focal power, with its object-side surface S7 being convex and its image-side surface S8 being concave. The fifth lens E5 has positive focal power, with its object-side surface S9 being convex and its image-side surface S10 being convex. The sixth lens E6 has positive focal power, with its object-side surface S11 being convex and its image-side surface S12 being convex. The seventh lens E7 has negative focal power, with its object-side surface S12 being concave and its image-side surface S13 being concave. The eighth lens E8 has positive focal power, with its object-side surface S14 being concave and its image-side surface S15 being convex. The ninth lens element E9 has positive refractive power, with a concave object-side surface S16 and a convex image-side surface S17. The filter E10 has an object-side surface S18 and an image-side surface S19. Light from an object passes through surfaces S1 through S19 in sequence and is ultimately imaged on imaging surface S20.

[0042] Figure 4 The following graphs show the axial chromatic aberration, astigmatism, and distortion curves of the optical imaging lens of Example 2. Axial chromatic aberration indicates the deviation of light of different wavelengths from the focal point after passing through the lens; astigmatism indicates meridional and sagittal image curvature; and distortion indicates the magnitude of distortion at different image heights, demonstrating excellent imaging quality.

[0043] Table 3 shows the surface type, curvature radius, thickness, and material of each lens of the optical imaging lens system of Example 2, where the units of curvature radius and thickness are both millimeters (mm).

[0044] Table 3: Basic parameters of the optical system of Example 2

[0045] In Table 3, both the object-side surface and the image-side surface of the eighth lens element E8 are Q-type aspherical surfaces. The surface shape of each aspherical lens element can be defined by, but not limited to, the following aspherical surface formula:

[0046] Where Z is the distance from the corresponding point on the aspheric surface to the plane tangent to the vertex of the surface, r is the radial coordinate of the aspheric surface, c is the curvature of the aspheric vertex, K is the conic coefficient, Am is the aspheric coefficient, rmax is the maximum radial radius coordinate, and u = r / rmax. Table 4 shows the conic coefficients and higher-order coefficients A4, A6, A8, A10, A12, A14, A16, A18, and A20 for various aspheric surfaces that can be used in the second embodiment.

[0047] Table 4: Aspheric surface related values ​​of the lens surface of Example 2

[0048] Specifically, as a preferred embodiment of the present invention but not limiting, Figure 5 A schematic structural diagram of an optical imaging lens according to a third embodiment of the present application is shown.

[0049] like Figure 5 As shown, the optical imaging lens according to an exemplary embodiment of the present application includes, in order from the object side to the image side along the optical axis: 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.

[0050] The first lens E1 has negative refractive power, an object-side surface S1 thereof is convex, and an image-side surface S2 thereof is concave.

[0051] The second lens E2 has positive refractive power, its object-side surface S3 is concave, and its image-side surface S4 is convex.

[0052] The third lens E3 has positive refractive power, its object-side surface S5 is concave, and its image-side surface S6 is convex.

[0053] The fourth lens element E4 has negative refractive power, and its object-side surface S7 is convex, and its image-side surface S8 is concave.

[0054] The fifth lens E5 has positive refractive power, its object-side surface S9 is concave, and its image-side surface S10 is convex.

[0055] The sixth lens E6 has negative refractive power, its object-side surface S11 is convex, and its image-side surface S12 is concave.

[0056] The seventh lens E7 has positive refractive power, its object-side surface S12 is concave, and its image-side surface S13 is convex.

[0057] The eighth lens E8 has negative refractive power, its object-side surface S14 is convex, and its image-side surface S15 is concave.

[0058] The ninth lens element E9 has positive refractive power, and its object-side surface S16 and image-side surface S17 are convex.

[0059] The filter E10 has an object-side surface S18 and an image-side surface S19 .

[0060] Light from an object passes 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 surfaces S1 to S19 of the infrared filter E10 in sequence and is finally imaged on the imaging surface S20.

[0061] Figure 6 The graph shows the axial chromatic aberration, astigmatism and distortion curves of the optical imaging lens of Example 3.

[0062] Axial chromatic aberration refers to the deviation of light of different wavelengths from the focal point after passing through the lens; Astigmatism refers to meridional image curvature and sagittal image curvature; Distortion refers to the distortion value corresponding to different image heights.

[0063] The optical imaging lens provided in Example 3 can achieve good imaging quality.

[0064] Table 5 shows the surface type, curvature radius, thickness, and material of each lens of the optical imaging lens system of Example 3, where the units of curvature radius and thickness are both millimeters (mm).

[0065] Table 5: Basic parameters of the optical system of Example 3

[0066] In Table 6, both the object-side surface and the image-side surface of the eighth lens element E8 are Q-type aspherical surfaces. The surface shape of each aspherical lens element can be defined by, but not limited to, the following aspherical surface formula:

[0067] Where Z is the distance from the corresponding point on the aspheric surface to the plane tangent to the vertex of the surface, r is the radial coordinate of the aspheric surface, c is the curvature of the aspheric vertex, K is the conic coefficient, Am is the aspheric coefficient, rmax is the maximum radial radius coordinate, and u = r / rmax. Table 4 shows the conic coefficients and higher-order coefficients A4, A6, A8, A10, A12, A14, A16, A18, and A20 for various aspheric surfaces that can be used in the third embodiment.

[0068] Table 6: Aspheric surface related values ​​of the lens surface of Example 3

[0069] Specifically, as a preferred embodiment of the present invention but not limiting, Figure 7 A schematic structural diagram of an optical imaging lens according to a fourth embodiment of the present application is shown.

[0070] like Figure 7 As shown, the optical imaging lens according to an exemplary embodiment of the present application includes, in order from the object side to the image side along the optical axis: a first lens E1, a second lens E2, a third lens E3, a fourth lens E4, a fifth lens E5, 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.

[0071] The first lens E1 has positive focal power, with its object-side surface S1 being convex and its image-side surface S2 being concave. The second lens E2 has negative focal power, with its object-side surface S3 being convex and its image-side surface S4 being concave. The third lens E3 has negative focal power, with its object-side surface S5 being convex and its image-side surface S6 being concave. The fourth lens E4 has negative focal power, with its object-side surface S7 being concave and its image-side surface S8 being concave. The fifth lens E5 has positive focal power, with its object-side surface S9 being convex and its image-side surface S10 being convex. The sixth lens E6 has positive focal power, with its object-side surface S11 being convex and its image-side surface S12 being convex. The seventh lens E7 has negative focal power, with its object-side surface S12 being concave and its image-side surface S13 being concave. The eighth lens E8 has positive focal power, with its object-side surface S14 being convex and its image-side surface S15 being convex. The ninth lens element E9 has positive refractive power, with a convex object-side surface S16 and a convex image-side surface S17. The filter E10 has an object-side surface S18 and an image-side surface S19. Light from an object passes through surfaces S1 through S19 in sequence and is ultimately imaged on imaging surface S20.

[0072] Figure 8The following plots show the axial chromatic aberration, astigmatism, and distortion of the optical imaging lens of Example 4. Axial chromatic aberration indicates the deviation of light of different wavelengths from the focal point after passing through the lens; astigmatism indicates meridional and sagittal image curvature; and distortion indicates the magnitude of distortion at different image heights. This lens exhibits excellent imaging quality.

[0073] Table 7 shows the surface type, curvature radius, thickness, and material of each lens of the optical imaging lens system of Example 4, where the units of curvature radius and thickness are both millimeters (mm).

[0074] Table 7: Basic parameters of the optical system of Example 4

[0075] In Table 7, both the object-side surface and the image-side surface of the eighth lens element E8 are Q-type aspherical surfaces. The surface shape of each aspherical lens element can be defined by, but not limited to, the following aspherical surface formula:

[0076] Where Z is the distance from the corresponding point on the aspheric surface to the plane tangent to the vertex of the surface, r is the radial coordinate of the aspheric surface, c is the curvature of the aspheric vertex, K is the conic coefficient, Am is the aspheric coefficient, rmax is the maximum radial radius coordinate, and u = r / rmax. Table 4 shows the conic coefficients and higher-order coefficients A4, A6, A8, A10, A12, A14, A16, A18, and A20 for various aspheric surfaces that can be used in the first embodiment.

[0077] Table 8: Aspheric surface related values ​​of the lens surface of Example 4

[0078] In Examples 1-4, the basic data are shown in Table 9 below: Table 9: Basic data of Examples 1-4

[0079] In Examples 1-4, each conditional formula satisfies the following conditions as shown in Table 10: Table 10: The conditional formulas of Examples 1-4 satisfy the conditions in the following table

[0080] The working principle of this embodiment is as follows: This application presents an imaging optical system for industrial visual inspection. Through a nine-lens design and the rational configuration of each lens' refractive power and surface shape, it achieves high-resolution imaging with a compact TTL ≤ 60mm and a large aperture of F ≤ 2.5. This system features enhanced aberration correction capabilities, ensuring high MTF values ​​throughout the entire zoom range, significantly improving the accuracy and reliability of industrial inspection. Its zoom, low distortion, and low cost characteristics fully meet the stringent requirements of industrial automated inspection for high performance, miniaturization, and lightweighting.

[0081] The above are implementation methods provided in conjunction with specific content, and the specific implementation of this application is not limited to these descriptions. Any method structure that is similar to the method structure of this application, or any technical deduction or replacement based on the concept of this application, should be considered as 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 surface of the optical system in the optical axis direction.

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

Images