Machine vision optical system and applied machine vision lens thereof

Abstract

The invention provides a machine vision optical system and a machine vision lens using the same, the machine vision optical system is mainly composed of seven lenses, the object plane side of the first lens is a convex surface, the image plane side is a concave surface and has focal power, the object plane side of the second lens is a convex surface, the image plane side is a concave surface and has negative focal power, and the object plane side of the second lens is a convex surface. The object plane side of the third lens is a concave surface, the image plane side of the third lens is a convex surface, and the focal power is negative; the object plane side and the image plane side of the fourth lens are convex surfaces, and the focal power is positive; the object plane side of the fifth lens is a convex surface, the image plane side of the fifth lens is a concave surface, and the focal power is positive; the object plane side of the sixth lens is a convex surface, the image plane side of the sixth lens is a concave surface, and the focal power is negative; the object plane side and the image plane side of the seventh lens are both convex surfaces, the focal power is positive, the number of the lenses is reasonable, through reasonable distribution of the focal power of the lenses, the image quality of the lens is improved, meanwhile, the lens is made to be lighter, the design requirements for high image quality and light weight in the field of industrial automatic online recognition and detection can be effectively met, and the application range is wide. And the device is suitable for being used in environments with ultra-short object distance of 100mm and multiple object distances.

Description

Technical Field

[0001] This application relates to the field of optical imaging, and in particular to a machine vision optical system and a machine vision lens applied thereto. Background Art

[0002] At present, camera modules are widely used in industrial automation such as online identification and detection. The resolution of existing optical lenses is average, the resolution at close range is poor or the number of lenses is large, resulting in a complex structure and high cost, making it difficult to meet the needs of users.

[0003] Therefore, how to enable machine vision lenses to balance high image quality and light weight to meet the performance requirements of industrial automation online identification and detection has become the goal pursued by everyone. Summary of the Invention

[0004] This application aims to provide a machine vision optical system that can effectively meet the high image quality and light weight design requirements in the field of industrial automation online identification and detection, and is suitable for use in ultra-close object distances of 100 mm and multi-object distance environments.

[0005] To achieve the above object, the present invention adopts the following technical solutions: A machine vision optical system is composed of a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, and a seventh lens in sequence along the optical axis from the object plane to the image plane; The object plane side of the first lens is convex, and the image plane side is concave, and it has a focal power; The object plane side of the second lens is convex, and the image plane side is concave, and its focal power is negative; The object plane side of the third lens is concave, and the image plane side is convex, and its focal power is negative; The object plane side and the image plane side of the fourth lens are both convex, and its focal power is positive; The object plane side of the fifth lens is convex, and the image plane side is concave, and its focal power is positive; The object plane side of the sixth lens is convex, and the image plane side is concave, and its focal power is negative; The object plane side and the image plane side of the seventh lens are both convex, and its focal power is positive.

[0006] On the other hand, an embodiment of this application also provides a machine vision lens, which at least includes an optical lens, and the above-mentioned machine vision optical system is installed in the optical lens.

[0007] Compared with the prior art, the beneficial effects of this application are as follows: The present invention provides a machine vision optical system and a machine vision lens applied thereto, which mainly consist of 7 lenses. The number of lenses is reasonable, reducing the number of lenses. By reasonably distributing the lens focal power, the image quality of the lens is improved, and at the same time, the lens is made lighter, which can effectively meet the design requirements of high image quality and light weight in the field of industrial automation online identification and detection, and is suitable for use in an ultra-short object distance of 100 mm and a multi-object distance environment. Brief Description of the Drawings

[0008] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for use in the description of the embodiments.

[0009] Figure 1 It is a schematic structural diagram of the optical system or camera lens in Embodiment 1 of the present application; Figure 2 It is an optical path diagram of the optical system or camera lens in Embodiment 1 of the present application at a main object distance of 200 mm; Figure 3 It is an MTF curve diagram of the optical system or camera lens in Embodiment 1 of the present application at a main object distance of 200 mm; Figure 4 It is a lateral chromatic aberration diagram of the optical system or camera lens in Embodiment 1 of the present application at a main object distance of 200 mm; Figure 5 It is a field curvature and distortion curve diagram of the optical system or camera lens in Embodiment 1 of the present application at a main object distance of 200 mm; Figure 6 It is an optical path diagram of the optical system or camera lens in Embodiment 1 of the present application at an optimal object distance of 300 mm; Figure 7 It is an MTF curve diagram of the optical system or camera lens in Embodiment 1 of the present application at an optimal object distance of 300 mm; Figure 8 It is a lateral chromatic aberration diagram of the optical system or camera lens in Embodiment 1 of the present application at an optimal object distance of 300 mm; Figure 9 It is a field curvature and distortion curve diagram of the optical system or camera lens in Embodiment 1 of the present application at an optimal object distance of 300 mm; Figure 10 It is an optical path diagram of the optical system or camera lens in Embodiment 1 of the present application at a short object distance of 100 mm; Figure 11 It is an MTF curve diagram of the optical system or camera lens in Embodiment 1 of the present application at a short object distance of 100 mm; Figure 12 It is a lateral chromatic aberration diagram of the optical system or camera lens in Embodiment 1 of the present application at a short object distance of 100 mm; Figure 13It is the field curvature and distortion curve graph of the optical system or camera lens in Embodiment 1 of the present application at a near object distance of 100 mm; Figure 14 It is the optical path diagram of the optical system or camera lens in Embodiment 1 of the present application at an infinite object distance; Figure 15 It is the MTF curve graph of the optical system or camera lens in Embodiment 1 of the present application at an infinite object distance; Figure 16 It is the lateral chromatic aberration graph of the optical system or camera lens in Embodiment 1 of the present application at an infinite object distance; Figure 17 It is the field curvature and distortion curve graph of the optical system or camera lens in Embodiment 1 of the present application at an infinite object distance; Figure 18 It is the structural schematic diagram of the optical system or camera lens in Embodiment 2 of the present application; Figure 19 It is the optical path diagram of the optical system or camera lens in Embodiment 2 of the present application at a main object distance of 200 mm; Figure 20 It is the MTF curve graph of the optical system or camera lens in Embodiment 2 of the present application at a main object distance of 200 mm; Figure 21 It is the lateral chromatic aberration graph of the optical system or camera lens in Embodiment 2 of the present application at a main object distance of 200 mm; Figure 22 It is the field curvature and distortion curve graph of the optical system or camera lens in Embodiment 2 of the present application at a main object distance of 200 mm; Figure 23 It is the optical path diagram of the optical system or camera lens in Embodiment 2 of the present application at an optimal object distance of 300 mm; Figure 24 It is the MTF curve graph of the optical system or camera lens in Embodiment 2 of the present application at an optimal object distance of 300 mm; Figure 25 It is the lateral chromatic aberration graph of the optical system or camera lens in Embodiment 2 of the present application at an optimal object distance of 300 mm; Figure 26 It is the field curvature and distortion curve graph of the optical system or camera lens in Embodiment 2 of the present application at an optimal object distance of 300 mm; Figure 27 It is the optical path diagram of the optical system or camera lens in Embodiment 2 of the present application at a near object distance of 100 mm; Figure 28 It is the MTF curve graph of the optical system or camera lens in Embodiment 2 of the present application at a near object distance of 100 mm; Figure 29 It is the lateral chromatic aberration graph of the optical system or camera lens in Embodiment 2 of the present application at a near object distance of 100 mm; Figure 30It is the graph of field curvature and distortion of the optical system or camera lens in Embodiment 2 of the present application at a near object distance of 100 mm; Figure 31 It is the optical path diagram of the optical system or camera lens in Embodiment 2 of the present application at an infinite object distance; Figure 32 It is the MTF curve graph of the optical system or camera lens in Embodiment 2 of the present application at an infinite object distance; Figure 33 It is the lateral chromatic aberration graph of the optical system or camera lens in Embodiment 2 of the present application at an infinite object distance; Figure 34 It is the graph of field curvature and distortion of the optical system or camera lens in Embodiment 2 of the present application at an infinite object distance; Figure 35 It is the structural schematic diagram of the optical system or camera lens in Embodiment 3 of the present application; Figure 36 It is the optical path diagram of the optical system or camera lens in Embodiment 3 of the present application at a main object distance of 200 mm; Figure 37 It is the MTF curve graph of the optical system or camera lens in Embodiment 3 of the present application at a main object distance of 200 mm; Figure 38 It is the lateral chromatic aberration graph of the optical system or camera lens in Embodiment 3 of the present application at a main object distance of 200 mm; Figure 39 It is the graph of field curvature and distortion of the optical system or camera lens in Embodiment 3 of the present application at a main object distance of 200 mm; Figure 40 It is the optical path diagram of the optical system or camera lens in Embodiment 3 of the present application at an optimal object distance of 300 mm; Figure 41 It is the MTF curve graph of the optical system or camera lens in Embodiment 3 of the present application at an optimal object distance of 300 mm; Figure 42 It is the lateral chromatic aberration graph of the optical system or camera lens in Embodiment 3 of the present application at an optimal object distance of 300 mm; Figure 43 It is the graph of field curvature and distortion of the optical system or camera lens in Embodiment 3 of the present application at an optimal object distance of 300 mm; Figure 44 It is the optical path diagram of the optical system or camera lens in Embodiment 3 of the present application at a near object distance of 100 mm; Figure 45 It is the MTF curve graph of the optical system or camera lens in Embodiment 3 of the present application at a near object distance of 100 mm; Figure 46 It is the lateral chromatic aberration graph of the optical system or camera lens in Embodiment 3 of the present application at a near object distance of 100 mm; Figure 47It is the field curvature and distortion curve graph of the optical system or camera lens in Embodiment 3 of the present application at a near object distance of 100 mm; Figure 48 It is the optical path diagram of the optical system or camera lens in Embodiment 3 of the present application at an infinite object distance; Figure 49 It is the MTF curve graph of the optical system or camera lens in Embodiment 3 of the present application at an infinite object distance; Figure 50 It is the lateral chromatic aberration graph of the optical system or camera lens in Embodiment 3 of the present application at an infinite object distance; Figure 51 It is the field curvature and distortion curve graph of the optical system or camera lens in Embodiment 3 of the present application at an infinite object distance. Detailed implementation manners

[0010] The present application provides a machine vision optical system, which sequentially consists of a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a stop STO, a fifth lens L5, a sixth lens L6, a seventh lens L7, and a filter L8 along the optical axis from the object plane to the image plane; the object plane side of the first lens L1 is convex, and the image plane side is concave, and it has a focal power; the object plane side of the second lens L2 is convex, and the image plane side is concave, and its focal power is negative; the object plane side of the third lens L3 is concave, and the image plane side is convex, and its focal power is negative; the object plane side and the image plane side of the fourth lens L4 are both convex, and its focal power is positive; the object plane side of the fifth lens L5 is convex, and the image plane side is concave, and its focal power is positive; the object plane side of the sixth lens L6 is convex, and the image plane side is concave, and its focal power is negative; the object plane side and the image plane side of the seventh lens L7 are both convex, and its focal power is positive.

[0011] The optical system of the embodiment of the present application is mainly composed of 7 lenses. The number of lenses is reasonable, reducing the number of lenses. By reasonably distributing the focal power of the lenses, the image quality of the lens is improved, and at the same time, the lens is made lighter, which can effectively meet the design requirements of high image quality and light weight in the field of industrial automation online recognition and detection, and is suitable for use in the environment of an ultra - near object distance of 100 mm and multiple object distances.

[0012] Further, as a preferred embodiment of the present invention rather than a limitation, the second lens and the third lens are aspherical lenses; the radius of curvature R4 of the image side of the second lens, the radius of curvature R5 of the object side of the third lens, and the radius of curvature R6 of the image side of the third lens satisfy: -1.25 ≤ R4 / (R5 + R6) ≤ -0.25; by reasonably controlling the ratio of the radius of curvature of the object side of the second lens to the sum of the radii of curvature of the object side and the image side of the third lens within a certain range, the axial aberration generated by the imaging optical system can be effectively balanced. Further preferably, it satisfies: the radius of curvature R3 of the object side of the second lens and the radius of curvature R4 of the image side of the second lens satisfy: 0 ≤ R3 / (R3 + R4) ≤ 0.65; the radius of curvature R5 of the object side of the third lens and the radius of curvature R6 of the image side of the third lens satisfy: 0.58 ≤ R6 / (R5 + R6) ≤ 0.72. By controlling the R values of the object and image sides of the second lens and the third lens within a reasonable range, the field curvature can be effectively corrected, the imaging quality of the system can be improved. Preferably, the second lens and the third lens are made of high-transmission plastic aspherical optical lenses, reducing the number of lenses, improving the image quality of the lens, and making the lens lighter.

[0013] Further, as a preferred embodiment of the present invention rather than a limitation, each lens of the optical system satisfies the following conditions: f1 < 38.9 mm; -61.5 mm < f2 < -5.8 mm; -45.2 mm < f3 < -25.6 mm; 11.5 mm < f4 < 21.4 mm; 18.0 mm < f5 < 74.0 mm; -28.1 mm < f6 < -17.9 mm; 11.7 mm < f7 < 19.8 mm; where f1 is the focal length of the first lens, f2 is the focal length of the second lens, f3 is the focal length of the third lens, f4 is the focal length of the fourth lens, f5 is the focal length of the fifth lens, f6 is the focal length of the sixth lens, and f7 is the focal length of the seventh lens. In this application, by restricting the effective focal lengths of each lens within a reasonable range, the spherical aberration of the system is finely adjusted and controlled, the distortion of the system is controlled, the lens aberration is optimized, the imaging quality analysis performance is improved, and the field curvature of the system is improved.

[0014] Furthermore, the refractive index Nd1 and Abbe number Vd1 of the first lens L1 satisfy: 1.61 < Nd1 < 1.85, 42 < Vd1 < 57; the refractive index Nd2 and Abbe number Vd2 of the second lens L2 satisfy: 1.51 < Nd2 < 1.89, 20 < Vd2 < 57; the refractive index Nd3 and Abbe number Vd3 of the third lens L3 satisfy: 1.51 < Nd3 < 1.59, 52 < Vd3 < 57; the refractive index Nd4 and Abbe number Vd4 of the fourth lens L4 satisfy: 1.41 < Nd4 < 1.61, 87 < Vd4 < 92; the refractive index Nd5 and Abbe number Vd5 of the fifth lens L5 satisfy: 1.45 < Nd5 < 1.59, 51 < Vd5 < 59; the refractive index Nd6 and Abbe number Vd6 of the sixth lens L6 satisfy: 1.57 < Nd6 < 1.91, 21 < Vd6 < 25; the refractive index Nd7 and Abbe number Vd7 of the seventh lens L7 satisfy: 1.36 < Nd7 < 1.57, 76 < Vd7 < 95; by controlling the refractive index and Abbe number of each lens material within a reasonable range, this design can effectively reduce chromatic aberration, optimize lens aberration, and thus effectively improve the imaging quality of the system.

[0015] Furthermore, as a preferred embodiment of the present invention rather than a limitation, the optical system satisfies the following condition: 2.6 < TTL / D < 3.5, where TTL is the total length of the system and D is the aperture of the objective lens. This setting is beneficial to realizing the miniaturization of the lens. When the value of the above relational expression is less than 2.6, the aberration balance at the long focal end of the optical lens is limited, and it is difficult to improve the resolution. When the value of the above relational expression is greater than 3.5, the volume of the optical lens increases, the zoom efficiency decreases, and the cost increases. When the above relational expression is satisfied, the optical lens has high performance in terms of small volume, high resolution, low cost, and zoom efficiency.

[0016] Furthermore, as a preferred embodiment of the present invention rather than a limitation, the fifth lens, the sixth lens, and the seventh lens form a focusing group that can move together along the optical axis for focusing. The back focal length of the optical system > 10 mm, and the focusing structure is simple and has low weight. By adopting the single-group internal focusing method for focusing, the weight of the focusing group is reduced, ensuring that the lens has high imaging quality in different focusing states.

[0017] Furthermore, as a preferred embodiment of the present invention rather than a limitation, the total length of the optical system satisfies the following condition: 45 mm ≤ TTL ≤ 55 mm. This design can reduce the optical total length, making the lens miniaturized, and enabling the miniaturized wide-angle lens to have greater competitiveness in the market.

[0018] Further, as a preferred embodiment rather than a limitation of the present invention, the objective lens aperture D of the optical system satisfies the following condition: 13 mm ≤ D ≤ 30 mm. By controlling the objective lens aperture of the optical imaging lens, it helps to improve the light source energy reception ability of the lens, obtain as much object-side information as possible, and thus obtain imaging information with higher brightness and resolution.

[0019] Specifically, as a preferred embodiment rather than a limitation of the present invention, Figure 1 FIG. shows a schematic structural diagram of an optical imaging lens according to Embodiment 1 of the present application. The image circle is 11.4 mm, compatible with 2 / 3" Φ11.2 mm CMOS chips, 1 / 1.7" Φ9.3 mm CMOS chips, and 1 / 1.8" Φ9.0 mm CMOS chips. The working distance is from 100 mm to infinity, the focal length is 11.8 - 12.3 mm, the field of view range is 48.3° - 51°; the objective lens aperture is 15 mm; the working wavelength is in the visible light band of 0.449 μm - 0.68 μm; the total system length is 50 mm, the focusing group is the rear group, and the back focal length is greater than 10 mm; As Figure 1 As shown, along the optical axis from the object plane to the image plane, it is successively composed of a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a stop STO, a fifth lens L5, a sixth lens L6, a seventh lens L7, and a filter L8; the object-side of the first lens L1 is convex, and the image-side is concave, and its optical power is negative; the object-side of the second lens L2 is convex, and the image-side is concave, and its optical power is negative; the object-side of the third lens L3 is concave, and the image-side is convex, and its optical power is negative; the object-side and the image-side of the fourth lens L4 are both convex, and its optical power is positive; the object-side of the fifth lens L5 is convex, and the image-side is concave, and its optical power is positive; the object-side of the sixth lens L6 is convex, and the image-side is concave, and its optical power is negative; the object-side and the image-side of the seventh lens L7 are both convex, and its optical power is positive; the light from the object sequentially passes through each surface and finally forms an image on the imaging plane.

[0020] Table 1 shows the surface types, curvature radii, thicknesses, and materials of each lens of the optical imaging lens in Embodiment 1. Among them, the units of the curvature radius and the thickness are both millimeters (mm): Table 1: Basic parameters of the optical system in Embodiment 1

[0021] In the above Table 1, any one of the object-side and the image-side of the second lens L2, the third lens L3, and the fifth lens L5 is an aspherical surface. The surface types of each aspherical lens can be defined by, but not limited to, the following aspherical formula:

[0022] Wherein, x is the distance from the corresponding point on the aspherical surface to the plane tangent to the surface vertex, h is the distance from the corresponding point on the aspherical surface to the optical axis, c is the curvature of the aspherical vertex, k is the conic coefficient, and Ai is the coefficient corresponding to the i-th high-order term in the aspherical surface formula. Table 2 gives the conic coefficients and high-order term coefficients A4, A6, A8, A10, A12, A14 of each aspherical surface that can be used in Example 1.

[0023] Table 2: Aspherical-related values of the lens surface in Example 1

[0024] Figure 2 Shows the optical path diagram at the main object distance of 200 mm in Example 1, Figure 3 Shows the MTF curve, Figure 4 Shows the lateral chromatic aberration, Figure 5 Shows the astigmatism and distortion curves.

[0025] Figure 6 Shows the optical path diagram at the optimal object distance of 300 mm in Example 1, Figure 7 Shows the MTF curve, Figure 8 Shows the lateral chromatic aberration, Figure 9 Shows the astigmatism and distortion curves.

[0026] Figure 10 Shows the optical path diagram at the near object distance of 100 mm in Example 1, Figure 11 Shows the MTF curve, Figure 12 Shows the lateral chromatic aberration, Figure 13 Shows the astigmatism and distortion curves.

[0027] Figure 14 Shows the optical path diagram at the infinite object distance in Example 1, Figure 15 Shows the MTF curve, Figure 16 Shows the lateral chromatic aberration, Figure 17 Shows the astigmatism and distortion curves.

[0028] From Figure 2-17 It can be seen that the optical lens given in Example 1 can achieve good imaging quality and is suitable for use in an environment with an ultra-near object distance of 100 mm and multiple object distances.

[0029] Specifically, as another preferred embodiment of the present invention rather than a limitation, Figure 18The figure shows a schematic structural diagram of an optical imaging lens according to Embodiment 2 of the present application. The image circle is 11.4 mm, compatible with 2 / 3" Φ11.2 mm CMOS chips, 1 / 1.7" Φ9.3 mm CMOS chips, and 1 / 1.8" Φ9.0 mm CMOS chips. The working distance is from 100 mm to infinity, the focal length is 11.8 - 12.3 mm, the field of view range is 44.3° - 50°; the objective aperture is 15 mm; the working wavelength is in the visible light band of 0.449 μm - 0.68 μm; the total system length is 50 mm, the focusing group is the rear group, and the back focal length is greater than 10 mm; As Figure 18 shown, along the optical axis from the object plane to the image plane, it is successively composed of a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a stop STO, a fifth lens L5, a sixth lens L6, a seventh lens L7, and a filter L8; the object side of the first lens L1 is convex and the image side is concave, and its optical power is positive; the object side of the second lens L2 is convex and the image side is concave, and its optical power is negative; the object side of the third lens L3 is concave and the image side is convex, and its optical power is negative; the object side and the image side of the fourth lens L4 are both convex, and its optical power is positive; the object side of the fifth lens L5 is convex and the image side is concave, and its optical power is positive; the object side of the sixth lens L6 is convex and the image side is concave, and its optical power is negative; the object side and the image side of the seventh lens L7 are both convex, and its optical power is positive; the light from the object sequentially passes through each surface and finally forms an image on the imaging surface.

[0030] Table 3 shows the surface types, curvature radii, thicknesses, and materials of the lenses of the optical imaging lens in Embodiment 2, where the units of the curvature radius and thickness are both millimeters (mm): Table 3: Basic parameters of the optical system in Embodiment 2

[0031] In the above Table 3, any one of the object side and the image side of the second lens L2, the third lens L3, and the fifth lens L5 is an aspherical surface, and the surface shape of each aspherical lens can be defined by, but not limited to, the following aspherical formula:

[0032] where x is the distance from the corresponding point on the aspherical surface to the plane tangent to the surface vertex, h is the distance from the corresponding point on the aspherical surface to the optical axis, c is the curvature of the aspherical vertex, k is the conic coefficient, and Ai is the coefficient corresponding to the i-th high-order term in the aspherical surface formula. Table 4 gives the conic coefficients and high-order term coefficients A4, A6, A8, A10, A12 of the aspherical surfaces that can be used in Embodiment 2.

[0033] Table 4: Aspherical-related values of the lens surfaces in Embodiment 2

[0034] Figure 19 Shows the optical path diagram at the main object distance of 200 mm in Embodiment 2. Figure 20 Shows the MTF curve. Figure 21 Shows the lateral chromatic aberration. Figure 22 Shows the astigmatism and distortion curves.

[0035] Figure 23 Shows the optical path diagram at the optimal object distance of 300 mm in Embodiment 2. Figure 24 Shows the MTF curve. Figure 25 Shows the lateral chromatic aberration. Figure 26 Shows the astigmatism and distortion curves.

[0036] Figure 27 Shows the optical path diagram at the near object distance of 100 mm in Embodiment 2. Figure 28 Shows the MTF curve. Figure 29 Shows the lateral chromatic aberration. Figure 30 Shows the astigmatism and distortion curves.

[0037] Figure 31 Shows the optical path diagram at the infinite object distance in Embodiment 2. Figure 32 Shows the MTF curve. Figure 33 Shows the lateral chromatic aberration. Figure 34 Shows the astigmatism and distortion curves.

[0038] From Figure 19-34 It can be seen that the optical lens given in Embodiment 2 can achieve good imaging quality and is suitable for use in the environment of ultra - near object distance of 100 mm and multiple object distances.

[0039] Specifically, as another preferred embodiment of the present invention rather than a limitation, Figure 35 Shows the structural schematic diagram of the optical imaging lens according to Embodiment 3 of the present application. The image circle is 11.4 mm, compatible with 2 / 3” Φ11.2 mm CMOS chip, 1 / 1.7” Φ9.3 mm CMOS chip and 1 / 1.8” Φ9.0 mm CMOS chip. The working distance is from 100 mm to infinity, the focal length is 15.73~16.2 mm, the field of view range is 36°~40°; the objective aperture is 18 mm; the working wavelength is 0.449 μm~0.68 μm visible light band; the total system length is 53 mm, the focusing group is the rear group, and the back focal length is greater than 10 mm.

[0040] As Figure 35As shown in the figure, along the optical axis from the object plane to the image plane, there are successively a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a stop STO, a fifth lens L5, a sixth lens L6, a seventh lens L7, and a filter L8; the object side of the first lens L1 is convex and the image side is concave, and its optical power is negative; the object side of the second lens L2 is convex and the image side is concave, and its optical power is negative; the object side of the third lens L3 is concave and the image side is convex, and its optical power is negative; the object side and the image side of the fourth lens L4 are both convex, and its optical power is positive; the object side of the fifth lens L5 is convex and the image side is concave, and its optical power is positive; the object side of the sixth lens L6 is convex and the image side is concave, and its optical power is negative; the object side and the image side of the seventh lens L7 are both convex, and its optical power is positive; the light from the object sequentially passes through each surface and finally forms an image on the imaging plane.

[0041] Table 5 shows the surface types, radii of curvature, thicknesses, and materials of the lenses of the optical imaging lens of Example 3, where the units of the radius of curvature and the thickness are both millimeters (mm): Table 5: Basic parameters of the optical system of Example 3

[0042] In the above Table 6, any one of the object side and the image side of the third lens L3, the fifth lens L5, and the sixth lens L6 is an aspherical surface, and the surface shape of each aspherical lens can be defined by, but not limited to, the following aspherical formula:

[0043] Among them, x is the distance from the corresponding point on the aspherical surface to the plane tangent to the surface vertex, h is the distance from the corresponding point on the aspherical surface to the optical axis, c is the curvature of the aspherical vertex, k is the conic coefficient, and Ai is the coefficient corresponding to the i-th high-order term in the aspherical surface formula. Table 2 gives the conic coefficients and high-order term coefficients A4, A6, A8, A10, A12, A14, and A16 of the aspherical surfaces that can be used in Example 1.

[0044] Table 6: Aspherical-related values of the lens surfaces of Example 3

[0045] Figure 36 Shows the optical path diagram at the main object distance of 200 mm in Example 3, Figure 37 Shows the MTF curve, Figure 38 Shows the lateral chromatic aberration, Figure 39 Shows the astigmatism and distortion curves.

[0046] Figure 40 Shows the optical path diagram at the optimal object distance of 300 mm in Example 3, Figure 41shows the MTF curve, Figure 42 shows the lateral chromatic aberration, Figure 43 shows the astigmatism and distortion curves.

[0047] Figure 44 shows the optical path diagram at a near object distance of 100 mm in Embodiment 3, Figure 45 shows the MTF curve, Figure 46 shows the lateral chromatic aberration, Figure 47 shows the astigmatism and distortion curves.

[0048] Figure 48 shows the optical path diagram at an infinite object distance in Embodiment 3, Figure 49 shows the MTF curve, Figure 50 shows the lateral chromatic aberration, Figure 51 shows the astigmatism and distortion curves.

[0049] It can be seen from Figure 36-51 that the optical lens given in Embodiment 3 can achieve good imaging quality and is suitable for use in environments with an ultra - near object distance of 100 mm and multiple object distances.

[0050] In Embodiments 1 - 3, the basic data is as shown in Table 7 below: Table 7 Basic Data of Embodiments 1 - 3

[0051] In Embodiments 1 - 3, the conditional expressions are as shown in Table 8 below: Table 8 Conditional Expressions of Embodiments 1 - 3

[0052] A camera lens includes at least an optical lens, and the above - mentioned machine vision optical system is installed inside the optical lens. An embodiment of the present invention provides a camera lens, which is mainly composed of 7 lenses. The number of lens elements is reasonable, reducing the number of lenses. By reasonably distributing the lens focal power, the image quality of the lens is improved, and at the same time, the lens is made lighter. It can effectively meet the design requirements of high image quality and light weight in the field of industrial automation online recognition and detection, and is suitable for use in environments with an ultra - near object distance of 100 mm and multiple object distances.

[0053] The above - mentioned is only the preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A machine vision optical system is composed of a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, and a seventh lens in sequence along the optical axis from the object surface to the image surface. It is characterized in that: The object side of the first lens is convex, and the image side is concave, and it has a focal power. The object side of the second lens is convex, and the image side is concave, and its focal power is negative. The object side of the third lens is concave, and the image side is convex, and its focal power is negative. Both the object side and the image side of the fourth lens are convex, and its focal power is positive. The object side of the fifth lens is convex, and the image side is concave, and its focal power is positive. The object side of the sixth lens is convex, and the image side is concave, and its focal power is negative. Both the object side and the image side of the seventh lens are convex, and its focal power is positive. The radius of curvature R4 of the image side of the second lens, the radius of curvature R5 of the object side of the third lens, and the radius of curvature R6 of the image side of the third lens satisfy: -1.25 ≤ R4 / (R5 + R6) ≤ -0.

25.

2. The machine vision optical system according to claim 1, wherein: The radius of curvature R3 of the object side of the second lens and the radius of curvature R4 of the image side of the second lens satisfy: 0 ≤ R3 / (R3 + R4) ≤ 0.

65.

3. The machine vision optical system according to claim 1, wherein: The radius of curvature R5 of the object side of the third lens and the radius of curvature R6 of the image side of the third lens satisfy: 0.58 ≤ R6 / (R5 + R6) ≤ 0.

72.

4. The machine vision optical system according to any one of claims 1-3, characterized in that: Each lens of this optical system satisfies the following conditions: f1 < 38.9 mm; -61.5 mm < f2 < -5.8 mm; -45.2 mm < f3 < -25.6 mm; 11.5 mm < f4 < 21.4 mm; 18.0 mm < f5 < 74.0 mm; -28.1 mm < f6 < -17.9 mm; 11.7 mm < f7 < 19.8 mm; Among them, f1 is the focal length of the first lens, f2 is the focal length of the second lens, f3 is the focal length of the third lens, f4 is the focal length of the fourth lens, f5 is the focal length of the fifth lens, f6 is the focal length of the sixth lens, and f7 is the focal length of the seventh lens.

5. The machine vision optical system according to any one of claims 1 to 3, characterized in that: This optical system satisfies the following conditions: 1.61 < Nd1 < 1.85, 42 < Vd1 < 57; 1.51 < Nd2 < 1.89, 20 < Vd2 < 57; 1.51 < Nd3 < 1.59, 52 < Vd3 < 57; 1.41 < Nd4 < 1.61, 87 < Vd4 < 92; 1.45 < Nd5 < 1.59, 51 < Vd5 < 59; 1.57 < Nd6 < 1.91, 21 < Vd6 < 25; 1.36 < Nd7 < 1.57, 76 < Vd7 < 95; Wherein, Nd1 is the refractive index of the first lens, Vd1 is the Abbe number of the first lens; Nd2 is the refractive index of the second lens, Vd2 is the Abbe number of the second lens; Nd3 is the refractive index of the third lens, Vd3 is the Abbe number of the third lens; Nd4 is the refractive index of the fourth lens, Vd4 is the Abbe number of the fourth lens; Nd5 is the refractive index of the fifth lens, Vd5 is the Abbe number of the fifth lens; Nd6 is the refractive index of the sixth lens, Vd6 is the Abbe number of the sixth lens, Nd7 is the refractive index of the seventh lens, and Vd7 is the Abbe number of the seventh lens.

6. The machine vision optical system according to any one of claims 1-3, characterized in that: The optical system satisfies the following condition: 2.6 < TTL / D < 3.5, where TTL is the total length of the system and D is the aperture of the objective lens.

7. The machine vision optical system according to any one of claims 1-3, characterized in that: The second lens and the third lens are aspherical lenses.

8. The machine vision optical system according to any one of claims 1-3, characterized in that: The system aperture stop is located between the fourth lens and the fifth lens.

9. The machine vision optical system according to any one of claims 1-3, characterized in that: The fifth lens, the sixth lens, and the seventh lens form a focusing group that can move together along the optical axis for focusing.

10. A machine vision lens, at least comprising an optical lens, characterized in that: The machine vision optical system according to any one of claims 1-9 is installed in the optical lens.

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