A low-distortion, high-pixel, large-surface machine vision lens

Abstract

The present invention discloses a low-distortion, high-pixel, large-target machine vision lens, comprising a front lens group and a rear lens group arranged in sequence from the object side to the image side along the optical axis, wherein the front lens group comprises a first convex-concave structure glass spherical lens with positive focal power, a second convex-concave structure glass spherical lens with positive focal power, a third convex-concave structure glass spherical lens with negative focal power, a fourth convex-concave structure glass spherical lens with negative focal power, a concave-convex structure glass spherical lens with positive focal power, and a first biconvex structure glass spherical lens with positive focal power, which are arranged in sequence from the object side to the image side along the optical axis; and the rear lens group comprises a fifth convex-concave structure glass spherical lens with negative focal power, and a second biconvex structure glass spherical lens with positive focal power, which are arranged in sequence from the object side to the image side along the optical axis. The lens of the present invention meets the requirements of high-pixel and large-target surface, and has a wide working distance range, good and stable analytical performance, and small distortion in each section of the system.

Description

Technical Field

[0001] The present application belongs to the technical field of optical lenses, and specifically relates to a low-distortion, high-pixel, large-surface machine vision lens. Background Art

[0002] Generally, machine vision lenses have strict requirements on distortion, especially those used for size detection. In addition, some machine vision lenses require a variable working distance, which requires that the resolution and other performance of the lens be stable under a wide range of object distances. In addition, the resolution and other performance must also perform well under temperature changes.

[0003] For example, the prior art document with patent application number 201621237304.0 discloses a low-distortion close-range athermal machine vision lens, which uses 8 lenses and has an aperture of 2.08, and has a high cost-effectiveness. However, the MTF of the lens at 200lp / mm spatial frequency at an object distance of 600mm is 0.4 at the center and about 0.3 at the periphery, and the resolution performance needs to be improved. For another example, the document with patent application number 201711004527.1 discloses a 25mm industrial lens with optical compensation function, which has good resolution performance, but uses 9 lenses, and the cost-effectiveness needs to be improved. Summary of the invention

[0004] The present application provides a low-distortion, high-pixel, large-target-area machine vision lens, which meets the requirements of high-pixel, large-target-area, and has a wide working distance range, good and stable resolution performance, and small distortion in each section of the system.

[0005] In order to achieve the above purpose, the technical solution adopted by this application is:

[0006] A low-distortion, high-pixel, large-target-area machine vision lens, comprising a front lens group and a rear lens group arranged in sequence from the object side to the image side along the optical axis, wherein the front lens group comprises a first convex-concave structure glass spherical lens L1 with positive focal power, a second convex-concave structure glass spherical lens L2 with positive focal power, a third convex-concave structure glass spherical lens L3 with negative focal power, a fourth convex-concave structure glass spherical lens L4 with negative focal power, a concave-convex structure glass spherical lens L5 with positive focal power, and a first biconvex structure glass spherical lens L6 with positive focal power, which are arranged in sequence from the object side to the image side along the optical axis;

[0007] The rear lens group includes a fifth convex-concave structure glass spherical lens L7 with negative optical power and a second biconvex structure glass spherical lens L8 with positive optical power, which are arranged in sequence from the object side to the image side along the optical axis.

[0008] Preferably, a diaphragm is provided between the third convex-concave structure glass spherical lens L3 and the fourth convex-concave structure glass spherical lens L4.

[0009] Preferably, the fourth convex-concave structure glass spherical lens L4 and the convex-concave structure glass spherical lens L5 are glued together to form a glued lens.

[0010] Preferably, the following relationship is satisfied between the fifth convex-concave structure glass spherical lens L7 and the second biconvex structure glass spherical lens L8: -1.22 < f7 / f8 < -1.12, where f7 represents the focal length of the fifth convex-concave structure glass spherical lens L7, and f8 represents the focal length of the second biconvex structure glass spherical lens L8.

[0011] Preferably, the refractive index nd of the second biconvex structure glass spherical lens L8 is > 1.9.

[0012] Preferably, the focal length f of the low-distortion, high-pixel, large-format machine vision lens satisfies: 25 ≤ f ≤ 35.

[0013] Preferably, the aperture F# of the low-distortion, high-pixel, large-format machine vision lens satisfies: 1.82 ≤ F# ≤ 2.8.

[0014] Preferably, the distance between the front lens group and the rear lens group is 0.52 mm to 7.71 mm.

[0015] The low-distortion, high-pixel, large-format machine vision lens of the present application has a wide working distance range, is athermalized and can be used in various environments, and adopts an internal focusing method to ensure that the rear lens group does not collide with mechanical components and electronic components; the rear lens group consists of two lenses, which can ensure that the resolution performance of the lens remains stable when imaging and focusing at different object distances, and the distortion of each section can be ensured to be less than 0.2%, and the distortion at the main working distance is less than 0.1%; the lens consists of 8 lenses, and the overall cost performance of the lens is relatively high; at the same time, the requirements of high pixel and large format are achieved, and the requirements of ten million pixels and 1-inch format can be met. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a schematic structural diagram of the low-distortion, high-pixel, large-format machine vision lens of the present application;

[0017] Figure 2 is the normal temperature defocus curve diagram of Embodiment 1 of the present application;

[0018] Figure 3 is the low temperature defocus curve diagram of -30 degrees Celsius of Embodiment 1 of the present application;

[0019] Figure 4 is the high temperature defocus curve diagram of +70 degrees Celsius of Embodiment 1 of the present application;

[0020] Figure 5 This is a field curvature distortion diagram when the working object distance is 150 mm in Example 1 of the present application;

[0021] Figure 6 This is a field curvature distortion diagram when the working object distance is 300 mm in Example 1 of the present application;

[0022] Figure 7 This is a field curvature distortion diagram when the working object distance is 500 mm in Example 1 of the present application;

[0023] Figure 8 This is a field curvature distortion diagram when the working object is infinitely far away in Example 1 of the present application;

[0024] Fig. 9 This is the MTF diagram of Example 1 of the present application when the working object distance is 500 mm;

[0025] Fig.10 This is a normal temperature defocus curve diagram of Example 2 of the present application;

[0026] Fig.11 This is a low temperature defocus curve at -30 degrees Celsius of Example 2 of the present application;

[0027] Fig.12 This is a high temperature 70 degree defocus curve diagram of Example 2 of the present application;

[0028] Fig.13 This is a field curvature distortion diagram of Example 2 of the present application;

[0029] Fig.14 This is a normal temperature defocus curve diagram of Example 3 of the present application;

[0030] Fig.15 This is a low temperature defocus curve at -30 degrees Celsius of Example 3 of the present application;

[0031] Fig.16 This is a high temperature 70 degree defocus curve diagram of Example 3 of the present application;

[0032] Fig.17 This is a field curvature distortion diagram of Example 3 of the present application. DETAILED DESCRIPTION

[0033] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which this application belongs. The terms used in the description of this application herein are for the purpose of describing specific embodiments only and are not intended to limit this application.

[0035] As Figure 1 shown, in one embodiment, a machine vision lens with low distortion, high pixels, and a large target surface is provided, which includes a front lens group and a rear lens group arranged in sequence from the object side to the image side along the optical axis.

[0036] The front lens group includes a first convex-concave structure glass spherical lens L1 with positive optical power, a second convex-concave structure glass spherical lens L2 with positive optical power, a third convex-concave structure glass spherical lens L3 with negative optical power, a convex-concave structure glass spherical lens L4 with negative optical power, a convex-concave structure glass spherical lens L5 with positive optical power, and a first biconvex structure glass spherical lens L6 with positive optical power, which are arranged in sequence from the object side to the image side along the optical axis.

[0037] The rear lens group includes a fifth convex-concave structure glass spherical lens L7 with negative optical power and a second biconvex structure glass spherical lens L8 with positive optical power, which are arranged in sequence from the object side to the image side along the optical axis.

[0038] In this embodiment, the rear lens group is composed of two lenses, which can ensure that the resolution performance remains stable and the distortion is small when the lens is focused at different object distances. The whole lens is composed of 8 lenses cooperating with each other, which can meet the requirements of high pixels and a large target surface while having a high cost performance.

[0039] To ensure the integrity of the lens, in one embodiment, a diaphragm is provided between the third convex-concave structure glass spherical lens L3 and the fourth convex-concave structure glass spherical lens L4.

[0040] In one embodiment, the fourth convex-concave structure glass spherical lens L4 and the convex-concave structure glass spherical lens L5 are glued together to form a glued lens.

[0041] In one embodiment, the following relationship is satisfied between the fifth convex-concave structure glass spherical lens L7 and the second biconvex structure glass spherical lens L8: -1.22 < f7 / f8 < -1.12, where f7 represents the focal length of the fifth convex-concave structure glass spherical lens L7, and f8 represents the focal length of the second biconvex structure glass spherical lens L8.

[0042] In one embodiment, the refractive index nd of the second biconvex structure glass spherical lens L8 > 1.9, and the second biconvex structure glass spherical lens L8 is made of a material with high refractive index and high dispersion.

[0043] In one embodiment, the focal length f of the low-distortion, high-pixel, large-target-area machine vision lens satisfies: 25≤f≤35.

[0044] In one embodiment, the aperture F# of the low-distortion, high-pixel, large-target-area machine vision lens satisfies: 1.82≤F#≤2.8.

[0045] In one embodiment, the distance between the front lens group and the rear lens group is 0.52 mm to 7.71 mm.

[0046] When focusing the machine vision lens in this embodiment, it is only necessary to move the front lens group and keep the rear lens group stationary.

[0047] The following is a further detailed description of the low distortion, high pixel, large target surface machine vision lens of the present application through examples:

[0048] Example 1

[0049] The lens of this embodiment is constructed with 8 lenses, and the optical parameters of the lens and each lens are as follows:

[0050] Table 1 Parameters of each lens in Example 1

[0051]

[0052]

[0053] In Table 1, L1R1 represents the object side mirror surface of the convex-concave structure glass spherical lens L1, and L1R2 represents the image side mirror surface of the convex-concave structure glass spherical lens L1; the rest are similar, and can be referred to Figure 1 Indications in. R represents the radius of curvature, nd represents the refractive index, and vd represents the Abbe number.

[0054] Table 2 Lens related parameters of Example 1

[0055] f F# TTL DFOV f7 f8 f7 / f8 25mm 1.82 40.7mm 45° -56.97 46.88 -1.21

[0056] In Table 2, f represents the focal length of the lens, F# represents the aperture number of the lens (abbreviated as aperture), TTL is the total optical length of the lens, DFOV is the maximum oblique field angle of the lens, f7 represents the focal length of the fifth convex-concave structure glass spherical lens L7, and f8 represents the focal length of the second double convex structure glass spherical lens L8.

[0057] Table 3 Focusing distance of the lens of Example 1 at different object distances

[0058] Object distance 150mm 300mm 500mm 1000mm ∞ L6 to L7 interval 5.468mm 2.928mm 1.95mm 1.237mm 0.523mm

[0059] The interval between L6 and L7 in Table 3 is the focusing distance between L6 and L7.

[0060] like Figure 2 to Figure 4Shown are the normal temperature defocus curve, the low temperature defocus curve of -30 degrees and the high temperature defocus curve of +70 degrees of the lens of Example 1 when the working object distance WD=500mm. It can be seen from the figure that when the lens of this embodiment is at a low temperature of -30 degrees and a high temperature of +70 degrees, the system defocus is controlled within 0.01mm, meeting the requirements of high resolution in a large temperature range.

[0061] like Figures 5 to 8 The figures show the field curvature distortion diagrams of the lens of Example 1 at different working object distances. It can be seen from the figures that from the object distance of 150mm to infinity, the distortion of each section of the system is less than 0.2%, and the distortion of the main working object distance is less than 0.1%, which meets the requirement of low distortion. In addition, the distortion fluctuations at different object distances are relatively stable, and the distortion of the main working object distance is relatively smaller.

[0062] Fig. 9 This is the MTF diagram of the lens of Example 1 when the working object distance WD=500mm. It can be seen from the figure that the lens of this embodiment uses only 8 lenses, and the aperture can reach 1.82. Under this condition, the resolution performance can reach 0.45 at the center of the MTF of 200lp / mm spatial frequency at an object distance of 500mm, and about 0.35 at the periphery, which has good and stable resolution performance.

[0063] It can be seen that the machine vision lens of this embodiment has high resolution within a large temperature range, good and stable resolution performance, and small distortion in each segment.

[0064] Example 2

[0065] The lens of this embodiment is constructed with 8 lenses, and the optical parameters of the lens and each lens are as follows:

[0066] Table 4 Parameters of each lens in Example 2

[0067]

[0068] In Table 4, L1R1 represents the mirror surface on the object side of the convex-concave structure glass spherical lens L1, and L1R2 represents the mirror surface on the image side of the convex-concave structure glass spherical lens L1; the rest are similar. R represents the radius of curvature, nd represents the refractive index, and vd represents the Abbe number.

[0069] Table 5 Lens related parameters of Example 2

[0070] f F# TTL DFOV f7 f8 f7 / f8 25mm 2.8 38.3mm 38.6° -48.54 39.75 -1.22

[0071] In Table 5, f represents the focal length of the lens, F# represents the aperture number of the lens (abbreviated as aperture), TTL is the total optical length of the lens, DFOV is the maximum oblique field angle of the lens, f7 represents the focal length of the fifth convex-concave structure glass spherical lens L7, and f8 represents the focal length of the second double convex structure glass spherical lens L8.

[0072] Table 6 Focusing distance of the lens of Example 2 at different object distances

[0073]

[0074]

[0075] The interval between L6 and L7 in Table 6 is the focusing distance between L6 and L7.

[0076] like Figure 10 to Figure 13 The figures show the defocus curve at room temperature, the defocus curve at low temperature of -30 degrees, the defocus curve at high temperature of 70 degrees, and the field curvature distortion diagram of the lens of Example 2 when the working object distance WD=500mm. It can be seen from the figure that the system distortion of the lens of this embodiment is less than 0.2%, and the system defocus is controlled within 0.01mm at low temperature of -30 degrees and high temperature of 70 degrees. It can be seen that the lens of this embodiment has low distortion and good resolution performance.

[0077] Example 3

[0078] The lens of this embodiment is constructed with 8 lenses, and the optical parameters of the lens and each lens are as follows:

[0079] Table 7 Parameters of each lens in Example 2

[0080]

[0081] In Table 7, L1R1 represents the mirror surface on the object side of the convex-concave structure glass spherical lens L1, and L1R2 represents the mirror surface on the image side of the convex-concave structure glass spherical lens L1; the rest are similar. R represents the radius of curvature, nd represents the refractive index, and vd represents the Abbe number.

[0082] Table 8 Lens related parameters of Example 3

[0083]

[0084] In Table 8, f represents the focal length of the lens, F# represents the aperture number of the lens (abbreviated as aperture), TTL is the total optical length of the lens, DFOV is the maximum oblique field angle of the lens, f7 represents the focal length of the fifth convex-concave structure glass spherical lens L7, and f8 represents the focal length of the second double convex structure glass spherical lens L8.

[0085] Table 9 Focusing distance of the lens of Example 3 at different object distances

[0086] Object distance 150mm 300mm 500mm 1000mm ∞ L6 to L7 interval 7.71mm 4.88mm 3.13mm 1.88mm 0.79mm

[0087] The interval between L6 and L7 in Table 9 is the focusing distance between L6 and L7.

[0088] like Figure 14 to Figure 17The figures show the defocus curve at room temperature, the defocus curve at low temperature of -30 degrees, the defocus curve at high temperature of 70 degrees, and the field curvature distortion diagram of the lens of Example 3 when the working object distance WD=500mm. It can be seen from the figure that the system distortion of the lens of this embodiment is less than 0.2%, and the system defocus is controlled within 0.01mm at low temperature of -30 degrees and high temperature of 70 degrees. It can be seen that the lens of this embodiment has low distortion and good resolution performance.

[0089] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0090] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the attached claims.

Claims

1. A low-distortion, high-pixel, large-surface machine vision lens, comprising a front lens group and a rear lens group arranged in sequence from the object side to the image side along the optical axis, characterized in that: The front lens group includes a glass spherical lens L1 with positive focal power, a glass spherical lens L2 with positive focal power, a glass spherical lens L3 with negative focal power, a glass spherical lens L4 with negative focal power, a glass spherical lens L5 with positive focal power, and a glass spherical lens L6 with positive focal power, which are arranged in sequence from the object side to the image side along the optical axis; the glass spherical lens L4 and the glass spherical lens L5 are glued together to form a glued lens; The rear lens group includes a glass spherical lens L7 with negative optical power and a glass spherical lens L8 with positive optical power, which are arranged in sequence from the object side to the image side along the optical axis; Among them, the surface shapes of the glass spherical lens L1 to the glass spherical lens L8 are biconvex, convex-concave, convex-concave, biconcave, biconvex, biconvex, convex-concave and convex-concave, and the curvature radius of the mirror surface on the object side of the glass spherical lens L1 to the glass spherical lens L8 is 28.85mm, 12.5mm, 119.8mm, -9.03mm, 55.08mm, 51.15mm, 25.06mm and 25.36mm respectively, and the curvature radius of the mirror surface on the image side of the glass spherical lens L1 to the glass spherical lens L8 is -183.07mm, 22.9mm, 9.08mm, 55.08mm, -13.13mm, -29.08mm, 15.2mm and 79.6mm respectively; Alternatively, the surface shapes of the glass spherical lens L1 to the glass spherical lens L8 are convex-concave, convex-concave, convex-concave, concave-convex, concave-convex, biconvex, convex-concave and convex-concave, and the curvature radii of the mirror surfaces on the object side of the glass spherical lens L1 to the glass spherical lens L8 are 34.4 mm, 8.72 mm, 24.08 mm, -5.76 mm, -20.13 mm, 225.58 mm, 41.65 mm and 26.85 mm, respectively, and the curvature radii of the mirror surfaces on the image side of the glass spherical lens L1 to the glass spherical lens L8 are 116.99 mm, 25.05 mm, 7.08 mm, -20.13 mm, -8.25 mm, -21.59 mm, 19.56 mm and 184.26 mm, respectively; Alternatively, the surface shapes of the glass spherical lens L1 to the glass spherical lens L8 are convex-concave, convex-concave, convex-concave, concave-convex, concave-convex, concave-convex, convex-concave and convex-concave, respectively, and the curvature radius of the mirror surface on the object side of the glass spherical lens L1 to the glass spherical lens L8 is 23.35mm, 10.81mm, 35.96mm, -8.35mm, -21.31mm, -1159mm, 114.24mm and 32.62mm respectively, and the curvature radius of the mirror surface on the image side of the glass spherical lens L1 to the glass spherical lens L8 is 59.04mm, 44.65mm, 7.83mm, -21.31mm, -13.35mm, -15.21mm, 24.8mm and 242.95mm respectively.

2. The low-distortion, high-pixel, large-target-area machine vision lens according to claim 1, characterized in that: An aperture is provided between the glass spherical lens L3 and the glass spherical lens L4.

3. The low-distortion, high-pixel, large-target-area machine vision lens according to claim 1, characterized in that: The refractive index of the glass spherical lens L8 is nd=1.77.

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