Telecentric lens and measuring device

Abstract

The application relates to an optical element technology and discloses a telecentric lens set and a measuring device. The telecentric lens set comprises a front lens set and a rear lens set and a diaphragm arranged between the front lens set and the rear lens set; the front lens set is sequentially provided with a first lens, a second lens, a third lens, a fourth lens, a fifth lens and a light splitting prism from an object side to an image side; the rear lens set is sequentially provided with a sixth lens, a seventh lens, an eighth lens and a ninth lens from the object side to the image side; the second lens and the third lens are combined into a cemented lens, and the fourth lens and the fifth lens are combined into a cemented lens; the combined focal length of the front lens set is fixed, and the rear lens set with different combined focal lengths is matched to form telecentric lens sets with different magnification ratios. The application aims to provide a telecentric lens with good optical performance and high magnification ratio to meet the precise detection requirements of a machine vision system.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of optical elements, in particular to a telecentric lens group and a measuring device. BACKGROUND

[0002] With the development of industrial automation and the popularization of machine vision applications, industrial lenses are widely used in defect detection, size measurement, security monitoring and other fields. Among them, telecentric lenses are widely used in precision measurement, non-contact optical measurement and other fields due to their unique technical advantage that object distance changes do not affect the magnification of the image.

[0003] At present, with the increasing demand for optical measurement in integrated circuits, semiconductors, transistors and other aspects, the measuring device requires high precision, miniaturization and cost reduction, and the requirements for the lens are also increasing. Therefore, there is an urgent need for telecentric lenses with good optical performance and high magnification to meet the precision detection requirements of machine vision systems.

[0004] The above content is only used to assist in understanding the technical solutions of the present application and does not represent the acknowledgement of the above content as prior art. SUMMARY

[0005] The main purpose of the present application is to provide a telecentric lens group and a measuring device, which aims to provide a telecentric lens with good optical performance and high magnification to meet the precision detection requirements of machine vision systems.

[0006] To achieve the above purpose, the present application provides a telecentric lens group, which comprises a front group lens and a rear group lens, and a diaphragm arranged between the front group lens and the rear group lens; in the front group lens, a first lens, a second lens, a third lens, a fourth lens, a fifth lens and a light splitting prism are arranged in order from the object side to the image side; in the rear group lens, a sixth lens, a seventh lens, an eighth lens and a ninth lens are arranged in order from the object side to the image side;

[0007] Among them, the first lens, the third lens, the fourth lens, the sixth lens and the eighth lens have positive refractive power; the second lens, the fifth lens, the seventh lens and the ninth lens have negative refractive power;

[0008] The second lens and the third lens are combined into a cemented lens, and the fourth lens and the fifth lens are combined into a cemented lens.

[0009] The combined focal length of the front group lens is fixed, and the rear group lens with different combined focal lengths is matched to form a telecentric lens group with different magnifications.

[0010] To achieve the above object, the application further provides a measuring device, comprising a camera module and an operation module, and the camera module is in communication connection with the operation module; the camera module is provided with the telecentric lens group as described above.

[0011] The telecentric lens group and the measuring device provided by the application have multiple advantages of precise light control, optimized cemented lens, flexible magnification adjustment and design optimization, so that the telecentric lens group has significant improvement in imaging quality, flexibility, cost-effectiveness and application diversity, has good optical performance and high magnification, provides a feasible solution for large field of view, high resolution imaging and low cost visual detection demand, so as to meet the precision detection demand of the machine vision system. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 It is an architecture schematic diagram of the telecentric lens group in an embodiment of the application.

[0013] Figure 2 It is another architecture schematic diagram of the telecentric lens group in an embodiment of the application.

[0014] Figure 3 It is an MTF diagram of the telecentric lens group with a magnification of 2.0x in the application.

[0015] Figure 4 It is an axial aberration diagram of the telecentric lens group with a magnification of 2.0x in the application.

[0016] Figure 5 It is a distortion diagram of the telecentric lens group with a magnification of 2.0x in the application.

[0017] Figure 6 It is an MTF diagram of the telecentric lens group with a magnification of 1.5x in the application.

[0018] Figure 7 It is an axial aberration diagram of the telecentric lens group with a magnification of 1.5x in the application.

[0019] Figure 8 It is a distortion diagram of the telecentric lens group with a magnification of 1.5x in the application.

[0020] Figure 9 It is an MTF diagram of the telecentric lens group with a magnification of 1.2x in the application.

[0021] Figure 10 It is an axial aberration diagram of the telecentric lens group with a magnification of 1.2x in the application.

[0022] Figure 11 It is a distortion diagram of the telecentric lens group with a magnification of 1.2x in the application.

[0023] The objectives, functional characteristics and advantages of the present application will be further described with reference to the embodiments in conjunction with the accompanying drawings. DETAILED DESCRIPTION

[0024] Embodiments of the present application are described in detail below with reference to examples thereof shown in the accompanying drawings, wherein the same or similar components or components having the same or similar functions are denoted throughout by the same or similar reference numerals. The embodiments described below by reference to the accompanying drawings are exemplary and are intended to explain the present application, and cannot be understood as limiting the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative labor fall within the scope of protection of the present application.

[0025] In addition, if the description of "first", "second" and the like is involved in the present application, it is only for the purpose of description (such as for distinguishing the same or similar features), and cannot be understood as indicating or implying the relative importance of the indicated technical features or implicitly indicating the number of the indicated technical features. Therefore, the features limited by "first", "second" can explicitly or implicitly include at least one of the features. In addition, the technical solutions of various embodiments can be combined with each other, but it must be based on the fact that the technical solutions can be realized by those of ordinary skill in the art. When the combination of technical solutions appears to be contradictory or unachievable, it should be considered that the combination of technical solutions does not exist, and is not within the scope of protection required by the present application.

[0026] Reference Figure 1 Or Figure 2 In an embodiment, the telecentric lens group includes a front lens group and a rear lens group, and a stop STO arranged between the front lens group and the rear lens group; in the front lens group, a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5 and a beam splitter BS are arranged in order from the object side to the image side; in the rear lens group, a sixth lens L6, a seventh lens L7, an eighth lens L8 and a ninth lens L9 are arranged in order from the object side to the image side;

[0027] Among them, the first lens L1, the third lens L3, the fourth lens L4, the sixth lens L6 and the eighth lens L8 have positive refractive power; the second lens L2, the fifth lens L5, the seventh lens L7 and the ninth lens L9 have negative refractive power;

[0028] The second lens L2 and the third lens L3 are combined into a cemented lens, and the fourth lens L4 and the fifth lens L5 are combined into a cemented lens;

[0029] The combined focal length of the front lens group is fixed, and the rear lens group with different combined focal lengths is matched to form a telecentric lens group with different magnifications.

[0030] In this embodiment, in the telecentric lens group, a front group lens, a stop STO and a rear group lens are sequentially arranged from the object side to the image side.

[0031] In the field of optics, the object side (also known as the object side) and the image side (also known as the image side) refer to two different regions in an optical system, respectively describing the different positions and directions of light propagation from the object to the imaging process. In the optical system, the object side usually represents the side where the light propagates from the object plane OBJ to the optical system, and the light is refracted, reflected, etc. in this area to form the entrance end of the optical system; the image side represents the area where the light is collected and imaged after being modulated by the optical system, and the light forms the final image in this area, i.e. the image plane IMG.

[0032] Among them, the front group lens is located at the starting point of the optical path, responsible for the initial focusing, splitting and adjustment of the incident light, forming an intermediate image. Through the refraction, scattering and combination of the front group lens, the light is preliminarily shaped and modulated.

[0033] Among them, the stop STO is located between the front group lens and the rear group lens, which plays a role in limiting the angle of incident light and reducing scattering interference in the optical system. The stop STO will filter out some non-main light to avoid interference and stray light effects, ensuring the clarity and quality of the image.

[0034] Among them, the rear group lens is immediately behind the stop STO, responsible for further adjusting, focusing and imaging the light, and finally focusing the light onto the image plane IMG to form a clear image. The rear group lens, through its specific optical parameters, performs the final shaping and modulation of the light, ensuring the accuracy and clarity of the image.

[0035] Optionally, in the front group lens, a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5 and a light splitting prism BS are sequentially arranged from the object side to the image side.

[0036] Among them, the light splitting prism BS is mainly used to separate, deflect or refract the incident light according to the wavelength or direction, realizing the light splitting effect. When the incident light passes through the light splitting prism BS, due to the different refractive indices of different wavelengths of light in the medium, the light is dispersed to different degrees, which is called chromatic dispersion effect, so that the light splitting prism BS can separate different wavelength components in the incident light. The light splitting prism BS can be divided into different types according to its structure and working principle, such as prismatic light splitting prism BS, prism light splitter, etc.

[0037] Among them, the first lens L1, the third lens L3, the fourth lens L4, the sixth lens L6 and the eighth lens L8 have positive focal power; the second lens L2, the fifth lens L5, the seventh lens L7 and the ninth lens L9 have negative focal power.

[0038] It should be noted that the main difference between positive and negative focal power is the focusing property of the optical element: positive focal power indicates that the lens has the ability to focus light into a real image, while negative focal power indicates that the lens has the ability to diverge light into a virtual image. Among them, the lens with positive focal power is used to focus light on the focal point to realize real image imaging, such as convex lens; the lens with negative focal power is used to make divergent light produce virtual image, such as concave lens.

[0039] Among them, there is a certain distance between the first lens L1 and the second lens L2, while the second lens L2 and the third lens L3 are combined into a cemented lens; there is a certain distance between the third lens L3 and the fourth lens L4, and then the fourth lens L4 and the fifth lens L5 are combined into a cemented lens; there is a certain distance between the fifth lens L5 and the beam splitter BS. There is a certain distance between the sixth lens L6 and the seventh lens L7, and there is a certain distance between the seventh lens L7 and the eighth lens L8, while the eighth lens L8 can be combined with the ninth lens L9 into a cemented lens, or the eighth lens L8 can be a certain distance from the ninth lens L9.

[0040] It should be noted that the cemented lens refers to the adhesion of two or more lenses to form a single component. The main functions of the cemented lens include the following points:

[0041] (1) Optimize optical performance: By cementing two lenses together, the air surface reflection and overlapping optical path difference between lenses can be reduced, thereby reducing the aberration of the optical system and improving the imaging quality.

[0042] (2) Simplify optical design: Cemented lenses can combine the functions of two lenses into one, simplifying the design and assembly process of the optical system.

[0043] (3) Adjust optical parameters: By selecting lenses with different materials, radii of curvature and thickness for cementing, the focal length, magnification and other parameters of the optical system can be changed to meet the customized optical design requirements.

[0044] (4) Reduce the gap and alignment problems between optical elements: Cemented lenses can reduce the gap and alignment errors between elements, improving the stability and precision of the optical system.

[0045] In this way, the telecentric lens group realizes precise control and imaging of light through the positive and negative focal powers of different lenses and the action of the beam splitter BS. The use of cemented lenses further optimizes the optical performance and design flexibility of the system.

[0046] Optionally, in the telecentric lens group, the combined focal length of the front group of lenses is fixed, and the combined focal length of the rear group of lenses can be changed accordingly according to the use requirements of the telecentric lens group, so as to form telecentric lens groups with different magnification ratios, such as 2.0x, 1.5x, 1.2x, etc.

[0047] Optionally, in the front group of lenses, the design parameters of each lens and the beam splitter BS can be set to make the combined focal length of the front group of lenses reach a fixed value fA; and under the premise that the combined focal length of the front group of lenses is fA, the value of the combined focal length fB of the rear group of lenses is adjusted (which can be achieved by adjusting the design parameters of each lens in the rear group of lenses), so as to form telecentric lens groups with different magnification ratios.

[0048] By sharing the front group of lenses and randomly matching different rear groups of lenses, the telecentric lens group can adjust the imaging magnification in real time according to the specific task requirements, easily switch between large field of view and high resolution imaging, and improve the applicability and practicality of the telecentric lens group.

[0049] By replacing the rear group of lenses without changing the front group of lenses to achieve different magnification ratios, the system design is optimized, the cost-effectiveness is improved, and the maintenance and upgrade costs of the telecentric lens group are reduced.

[0050] This design method can simultaneously meet the requirements of large field of view and high-precision optical detection, so that the telecentric lens group performs well in different scenarios. Whether it needs to quickly scan a large area of image or needs fine detection under high resolution, the telecentric lens group can meet the requirements.

[0051] And by sharing the front group of lenses, the consistency and stability of the telecentric lens group can be maintained, and high imaging quality and precision can be maintained under different magnifications, ensuring the reliability of the imaging results.

[0052] In summary, by sharing the front group of lenses and randomly matching different rear groups of lenses to achieve different magnifications, the multifunctionality and practicality of the telecentric lens group are improved, the cost-effectiveness is improved, and the imaging quality and performance of the telecentric lens group are guaranteed. This design method provides a feasible solution for large field of view, high resolution imaging and low cost requirements of the telecentric lens group.

[0053] In an embodiment, the telecentric lens group combines multiple advantages such as precise light control, optimized cemented lenses, flexible magnification adjustment, and design optimization, so that the telecentric lens group has significant improvement in imaging quality, flexibility, cost-effectiveness and application diversity, has good optical performance and high magnification, provides a feasible solution for large field of view, high resolution imaging and low cost vision detection requirements, and meets the precise detection requirements of machine vision systems.

[0054] In an embodiment, on the basis of the above-mentioned embodiment, with reference to Figure 1 , the magnification of the telecentric lens group is 2.0x; the eighth lens L8 and the ninth lens L9 are combined into a cemented lens.

[0055] In the embodiment, the combined focal length of the front group lens is f A, the combined focal length of the rear group lens is f B, the focal length of the sixth lens L6 is fL6, the focal length of the seventh lens L7 is fL7, the focal length of the eighth lens L8 is fL8, the focal length of the ninth lens L9 is fL9, the focal length of the cemented lens combined by the eighth lens L8 and the ninth lens L9 is fL89, and the following relationships are satisfied:

[0056] 0.1<|f A / f B|<0.2 (further preferred range can be 0.11<|f A / f B|<0.15);

[0057] 0.1<|fL6 / f B|<0.3 (further preferred range can be 0.15<|fL6 / f B|<0.19);

[0058] 0<|fL7 / f B|<0.1 (further preferred range can be 0.03<|fL7 / f B|<0.05);

[0059] 0<|fL8 / f B|<0.2 (further preferred range can be 0.07<|fL8 / f B|<0.1);

[0060] 0<|fL9 / f B|<0.2;

[0061] 0.02<|fL89 / f B|<0.2 (further preferred range can be 0.09<|fL89 / f B|<0.12).

[0062] Optionally, the related parameters of the telecentric lens group include at least one of the following:

[0063] The object-side working distance is 111-113mm;

[0064] The maximum object-side field of view is φ9.6mm;

[0065] The object-side numerical aperture (NA) is 0.112;

[0066] The aperture is 9;

[0067] The maximum object-side telecentricity is 0.06°;

[0068] The object-image distance is 350mm;

[0069] The object-side optical resolution is 3um;

[0070] The maximum face size is φ19.2mm.

[0071] The setting of these parameters and relationships aims to ensure that the optical performance and imaging quality of the telecentric lens group meet specific requirements, and by designing the cemented lens and controlling the proportion of the focal lengths of each lens, the stability and flexibility of the system are improved. This design method can effectively optimize the imaging effect of the telecentric lens group, while meeting the requirements of 2.0x magnification and application needs.

[0072] Optionally, in the telecentric lens group with a magnification of 2.0x, the design parameters of the related optical elements are shown in Table 1:

[0073] Table 1:

[0074]

[0075]

[0076] Reference Figure 3 , Figure 3 is the MTF (Modulation Transfer Function) graph of the telecentric lens group with a magnification of 2.0x, indicating that the MTF of the full field of view approaches the diffraction limit, which is used to evaluate the imaging performance of the telecentric lens group, especially the spatial resolution. Here, the MTF graph represents the imaging quality of the telecentric lens group in the full field of view, and if the graph approaches the diffraction limit, it means that the system has good imaging ability at various spatial frequencies.

[0077] From the MTF graph, it can be observed that the contrast transfer of the telecentric lens group at different spatial frequencies, i.e. the performance of the telecentric lens group in preserving image details and clarity. It can be seen that the MTF curve of the telecentric lens group at different spatial frequencies is relatively close to 1 (i.e. close to the diffraction limit), indicating that the telecentric lens group can effectively transfer high spatial frequency details and achieve good imaging performance.

[0078] Overall, the full field of view of the MTF graph approaching the diffraction limit is a good performance, meaning that the telecentric lens group has excellent imaging ability at a magnification of 2.0x, and can achieve high-quality imaging in the full field of view, preserving more detail information and clarity. This is very important for applications that require high resolution and fine imaging, and can improve the imaging performance and application value of the telecentric lens group.

[0079] Reference Figure 4 , Figure 4 is the axial aberration graph of the telecentric lens group with a magnification of 2.0x, and it can be seen that the axial chromatic aberration of the telecentric lens group provided in this embodiment is 0.1mm when the pupil is 0.7.

[0080] Axial chromatic aberration is an important performance parameter in optical systems, which describes the shift of the focal point position of the image under different wavelengths of light, leading to image blur or chromatic aberration phenomenon. When the pupil is 0.7, the axial chromatic aberration of the telecentric lens group is 0.1 mm, which means that the focal point position of the telecentric lens group shifts by 0.1 mm under different wavelengths of light, which is a relatively small value. Smaller axial chromatic aberration indicates that the telecentric lens group has better focusing performance under different wavelengths of light, which can reduce the image blur and color deviation caused by chromatic aberration, and improve the overall imaging quality.

[0081] For high-requirement imaging tasks, the control of axial chromatic aberration is very important, which can ensure that the telecentric lens group can provide clear and accurate imaging under different wavelengths of light, so as to meet the user's demand for image details and color accuracy.

[0082] Reference Figure 5 , Figure 5 is the distortion map of the telecentric lens group with a magnification of 2.0x, and the maximum distortion of the telecentric lens group is 0.067%.

[0083] Distortion is a common optical aberration in optical systems, which describes the image distortion caused by the shape or installation deviation of optical elements. The maximum distortion of the telecentric lens group is 0.067%, which means that the degree of distortion in the image is very small. Smaller distortion means that the telecentric lens group can accurately transmit and present the geometric shapes and lines in the image, maintaining the accuracy and reliability of the image.

[0084] For many applications, especially in fields requiring precise measurement and true scale, such as engineering measurement, medical imaging, etc., the control of distortion is crucial. The performance of the telecentric lens group with a maximum distortion of 0.067% indicates that the telecentric lens group performs well in image quality, and can provide almost distortion-free imaging, which helps to maintain the accuracy and reliability of the image.

[0085] In an embodiment, on the basis of the above-mentioned embodiments, with reference to Figure 1 , the magnification of the telecentric lens group is 1.5x; the eighth lens L8 and the ninth lens L9 are combined into a cemented lens.

[0086] In this embodiment, the combined focal length of the front group lens is f A, the combined focal length of the rear group lens is f B, the focal length of the sixth lens L6 is fL6, the focal length of the seventh lens L7 is fL7, the focal length of the eighth lens L8 is fL8, the focal length of the ninth lens L9 is fL9, and the focal length of the cemented lens combined by the eighth lens L8 and the ninth lens L9 is fL89, and the following relationship is satisfied:

[0087] 0.1<|f A / f B|<0.3 (further preferred range can be 0.19<|f A / f B|<0.23);

[0088] 0.1<|fL6 / f B|<0.5 (further preferred range can be 0.25<|fL6 / f B|<0.29);

[0089] 0<|fL7 / f B|<0.2 (further preferred range can be 0.04<|fL7 / f B|<0.08);

[0090] 0<|fL8 / f B|<0.2 (further preferred range can be 0.07<|fL8 / f B|<0.11);

[0091] 0<|fL9 / f B|<0.3;

[0092] 0.02<|fL89 / f B|<0.3 (further preferred range can be 0.09<|fL89 / f B|<0.13).

[0093] Optionally, the related parameters of the telecentric lens group include at least one of the following:

[0094] The object-side working distance is 111-113 mm;

[0095] The maximum object-side field of view is φ12.8 mm;

[0096] The object-side numerical aperture (NA) is 0.088;

[0097] The aperture is 8.5;

[0098] The maximum telecentricity of the object side is 0.008°;

[0099] The object-image distance is 330 mm;

[0100] The object-side optical resolution is 3.8 um;

[0101] The maximum image plane size is φ19.2 mm.

[0102] These parameters and relationships are set to ensure that the optical performance and imaging quality of the telecentric lens group meet specific requirements, and by designing the cemented lens and controlling the focal length ratio of each lens, the stability and flexibility of the system are improved. This design method can effectively optimize the imaging effect of the telecentric lens group, while meeting the requirements of 1.5x magnification and application requirements.

[0103] Optionally, in the telecentric lens group with a magnification of 1.5x, the design parameters of the related optical elements are shown in Table Two:

[0104] Table Two:

[0105]

[0106]

[0107] Referring to Figure 6 , Figure 6 The MTF graph of the telecentric lens group with a magnification of 1.5x shows that the MTF of the full field of view approaches the diffraction limit, which is used to evaluate the imaging performance of the telecentric lens group, especially the spatial resolution capability. Here, the MTF graph represents the imaging quality of the telecentric lens group in the full field of view range, and it can be observed that the contrast transfer of the telecentric lens group at different spatial frequencies. It can be seen that the MTF curve of the telecentric lens group at different spatial frequencies is relatively close to 1 (i.e. close to the diffraction limit), indicating that the telecentric lens group can effectively transfer high spatial frequency details and achieve good imaging performance.

[0108] Overall, the full field of view of the MTF graph approaches the diffraction limit, which is a good performance, indicating that the telecentric lens group has excellent imaging capability at a magnification of 1.5x, and can achieve high-quality imaging in the full field of view range, retaining more detail information and clarity. This is very important for applications that require high resolution and fine imaging, which can improve the imaging performance and application value of the telecentric lens group.

[0109] Referring to Figure 7 , Figure 7 The axial aberration graph of the telecentric lens group with a magnification of 1.5x is shown in Figure 8, which shows that the axial chromatic aberration of the telecentric lens group is 0.07mm when the pupil is 0.7.

[0110] When the pupil is 0.7, the axial chromatic aberration of the telecentric lens group is 0.07mm, which means that the focal position offset of the telecentric lens group under different wavelengths of light is 0.07mm, which is a relatively small value. Smaller axial chromatic aberration indicates that the telecentric lens group has better focusing performance under different wavelengths of light, which can reduce the image blur and color shift problems caused by chromatic aberration and improve the overall imaging quality.

[0111] For high-demand imaging tasks, the control of axial chromatic aberration is very important, which can ensure that the telecentric lens group can provide clear and accurate imaging under different wavelengths of light, thereby meeting the user's demand for image details and color accuracy.

[0112] Referring to Figure 8 , Figure 8 The distortion graph of the telecentric lens group with a magnification of 1.5x is shown in Figure 9, which shows that the maximum distortion of the telecentric lens group is 0.056%.

[0113] The maximum distortion of the telecentric lens group is 0.056%, which means that the degree of distortion present in the image is very small. Smaller distortion means that the telecentric lens group can accurately transmit and present the geometric shapes and lines in the image, maintaining the accuracy and reliability of the image. The performance of the telecentric lens group with a maximum distortion of 0.056% indicates that it performs well in terms of image quality, providing almost distortion-free imaging, which helps to maintain the accuracy and reliability of the image.

[0114] In an embodiment, on the basis of the above-mentioned embodiments, with reference to Figure 2 , the magnification of the telecentric lens group is 1.2x; and there is a certain interval between the eighth lens L8 and the ninth lens L9.

[0115] In this embodiment, the combined focal length of the front group lens is f A, the combined focal length of the rear group lens is f B, the focal length of the sixth lens L6 is fL6, the focal length of the seventh lens L7 is fL7, the focal length of the eighth lens L8 is fL8, and the focal length of the ninth lens L9 is fL9, and the following relationships are satisfied:

[0116] 0.1<|f A / f B|<0.5 (further preferred range can be 0.3<|f A / f B|<0.4);

[0117] 0.1<|fL6 / f B|<0.6 (further preferred range can be 0.22<|fL6 / f B|<0.27);

[0118] 0.01<|fL7 / f B|<0.3 (further preferred range can be 0.1<|fL7 / f B|<0.13);

[0119] 0.01<|fL8 / f B|<0.3 (further preferred range can be 0.1<|fL8 / f B|<0.15);

[0120] 0.01<|fL9 / f B|<0.3 (further preferred range can be 0.12<|fL9 / f B|<0.17).

[0121] Optionally, the related parameters of the telecentric lens group include at least one of the following:

[0122] The object side working distance is 111-113mm;

[0123] The maximum object side field of view is φ16mm;

[0124] The object side numerical aperture is 0.07;

[0125] The aperture is 8.5;

[0126] The maximum telecentricity on the object side is 0.015°;

[0127] The object-image distance is 322 mm;

[0128] The optical resolution on the object side is 4.75 um;

[0129] The maximum image plane size is φ19.2 mm.

[0130] These parameters and relationships are set to ensure that the optical performance and imaging quality of the telecentric lens group meet specific requirements, and by designing the cemented lens and controlling the proportion of the focal length of each lens, the stability and flexibility of the system are improved. This design method can effectively optimize the imaging effect of the telecentric lens group, while meeting the magnification requirement of 1.2x and application requirements.

[0131] Optionally, in the telecentric lens group with a magnification of 1.2x, the design parameters of the related optical elements are shown in Table Three:

[0132] Table Three:

[0133]

[0134]

[0135] Reference Figure 9 , Figure 9 is the MTF graph of the telecentric lens group with a magnification of 1.2x, indicating that the MTF of the full field of view approaches the diffraction limit, which is used to evaluate the imaging performance of the telecentric lens group, especially the spatial resolution. The full field of view of the MTF graph approaches the diffraction limit, which is a good performance, meaning that the telecentric lens group has excellent imaging ability at a magnification of 1.2x, and can achieve high-quality imaging in the full field of view, retaining more detail information and clarity. This is very important for applications that require high resolution and fine imaging, which can improve the imaging performance and application value of the telecentric lens group.

[0136] Reference Figure 10 , Figure 10 is the axial aberration graph of the telecentric lens group with a magnification of 1.2x, which shows that the axial chromatic aberration of the telecentric lens group provided in this embodiment is 0.07 mm when the pupil is 0.7. When the pupil is 0.7, the axial chromatic aberration of the telecentric lens group is 0.07 mm, which means that the focal position offset of the telecentric lens group under different wavelengths of light is 0.07 mm, which is a relatively small value. Smaller axial chromatic aberration indicates that the telecentric lens group has better focusing performance under different wavelengths of light, which can reduce the image blur and color shift problems caused by chromatic aberration and improve the overall imaging quality.

[0137] Reference Figure 11 , Figure 11The figure is the distortion chart of the telecentric lens group with a magnification of 1.2x. It can be seen that the maximum distortion of the telecentric lens group is 0.051%. The maximum distortion of the telecentric lens group is 0.051%, which means that the degree of distortion present in the image is very small. Smaller distortion means that the telecentric lens group can accurately transmit and present the geometric shapes and lines in the image, maintaining the accuracy and reliability of the image. The performance of the telecentric lens group with a maximum distortion of 0.051% indicates that it performs well in terms of image quality, providing almost distortion-free imaging, which helps to maintain the accuracy and reliability of the image.

[0138] Alternatively, the preferred values of the related lens group parameters of the telecentric lens group with magnifications of 2.0x, 1.5x, and 1.2x are shown in Table Four below:

[0139] Table Four:

[0140] Relationship and parameters Magnification 2.0x Magnification 1.5x Magnification 1.2x |f A / f B| 0.139 0.213 0.35 |fL6 / f B| 0.181 0.279 0.253 |fL7 / f B| 0.046 0.064 0.115 |fL8 / f B| 0.05 0.054 0.113 |fL9 / f B| 0.082 0.089 0.147 |fL89 / f B| 0.113 0.114 - Object-side numerical aperture 0.112 0.088 0.07

[0141] The preferred values of the above-mentioned related lens group parameters can optimize the imaging effect of the telecentric lens group at the corresponding magnification.

[0142] The present application further proposes a measuring device, which comprises a camera module and an operation module, and the camera module and the operation module are in communication connection; wherein the camera module is provided with a telecentric lens group, and the specific structure of the telecentric lens group is referred to the above-mentioned embodiments. Since the measuring device adopts all the technical solutions of the above-mentioned embodiments, it at least has all the technical effects brought by the technical solutions of the above-mentioned embodiments, which will not be repeated here.

[0143] It should be noted that in this document, the terms "include", "contain" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, device, article or method including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such process, device, article or method. Without more limitations, the element defined by the statement "including a" does not exclude the presence of another identical element in the process, device, article or method including the element.

[0144] The above-mentioned is only the preferred embodiment of the present application, and does not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation using the content of the specification and drawings, or direct or indirect application in other related technical fields, is also included in the patent protection scope of the present application.

Claims

1. A telecentric lens group characterized by, The telecentric lens group comprises a front group lens and a rear group lens, and a diaphragm arranged between the front group lens and the rear group lens; the front group lens is composed of a first lens, a second lens, a third lens, a fourth lens, a fifth lens and a light splitting prism arranged in sequence from an object side to an image side; the rear group lens is composed of a sixth lens, a seventh lens, an eighth lens and a ninth lens arranged in sequence from the object side to the image side; The first lens, the third lens, the fourth lens, the sixth lens and the eighth lens have positive focal lengths; the second lens, the fifth lens, the seventh lens and the ninth lens have negative focal lengths; The second lens and the third lens are combined into a cemented lens, and the fourth lens and the fifth lens are combined into a cemented lens; The combined focal length of the front group lens is fixed, and the rear group lens with different combined focal lengths is matched to form telecentric lens groups with different magnifications; The combined focal length of the front group lens is f A, the combined focal length of the rear group lens is f B, the focal length of the sixth lens is fL6, the focal length of the seventh lens is fL7, the focal length of the eighth lens is fL8, and the focal length of the ninth lens is fL9; When the magnification of the telecentric lens group is 2.0x, the eighth lens and the ninth lens are combined into a cemented lens, the focal length of the cemented lens combined by the eighth lens and the ninth lens is fL89, and the following relationships are satisfied: 0.1<|f A / f B|<0.2, 0.1<|fL6 / f B|<0.3, 0<|fL7 / f B|<0.1, 0<|fL8 / f B|<0.2, 0<|fL9 / f B|<0.2, and 0.02<|fL89 / f B|<0.2; Or, when the magnification of the telecentric lens group is 1.5x, the eighth lens and the ninth lens are combined into a cemented lens, the focal length of the cemented lens combined by the eighth lens and the ninth lens is fL89, and the following relationships are satisfied: 0.1<|f A / f B|<0.3, 0.1<|fL6 / f B|<0.5, 0<|fL7 / f B|<0.2, 0<|fL8 / f B|<0.2, 0<|fL9 / f B|<0.3, and 0.02<|fL89 / f B|<0.3; Or, when the magnification of the telecentric lens group is 1.2x, the following relationships are satisfied: 0.1<|f A / f B|<0.5, 0.1<|fL6 / f B|<0.6, 0.01<|fL7 / f B|<0.3, 0.01<|fL8 / f B|<0.3, and 0.01<|fL9 / f B|<0.

3.

2. The telecentric lens according to claim 1, wherein The related parameters of the telecentric lens group include at least one of the following: The object side working distance is 111-113mm; The maximum image plane size is φ19.2mm.

3. The telecentric lens according to claim 1 or 2, wherein The magnification of the telecentric lens group is 2.0x; the related parameters of the telecentric lens group include at least one of the following: The maximum object side field of view is φ9.6mm; The object side numerical aperture is 0.112; The aperture is 9; The maximum object telecentricity is 0.06°; The object-image distance is 350mm; The object optical resolution is 3um.

4. The telecentric lens according to claim 1 or 2, wherein The magnification of the telecentric lens group is 1.5x; the related parameters of the telecentric lens group include at least one of the following: The maximum object field of view is φ12.8mm; The object numerical aperture is 0.088; The aperture is 8.5; The maximum object telecentricity is 0.008°; The object-image distance is 330mm; The object optical resolution is 3.8um.

5. The telecentric lens according to claim 1 or 2, wherein The magnification of the telecentric lens group is 1.2x; the related parameters of the telecentric lens group include at least one of the following: The maximum object field of view is φ16mm; The object numerical aperture is 0.07; The aperture is 8.5; The maximum object telecentricity is 0.015°; The object-image distance is 322mm; The object optical resolution is 4.75um.

6. A measuring device, characterized by The measuring device comprises a camera module and an operation module, and the camera module is in communication connection with the operation module; the camera module is provided with the telecentric lens group according to any one of claims 1-5.

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