Telecentric lens group and measuring equipment

Abstract

The invention relates to an optical element technology, and discloses a telecentric lens group and measuring equipment. The telecentric lens group comprises a front group lens, a rear group lens, and a diaphragm arranged between the front group lens and the rear group lens. The front group lens is provided with a first lens, a second lens, a third lens, a fourth lens, a fifth lens and a beam splitter prism in sequence from an object space to an image space; the rear group lens is provided with a sixth lens, a seventh lens, an eighth lens and a ninth lens from the object space to the image space in sequence; the second lens and the third lens are combined to form a balsaming lens, and the fourth lens and the fifth lens are combined to form a balsaming lens; the combined focal length of the front group of lenses is fixed, and the rear group of lenses with different combined focal lengths are matched to form telecentric lens groups with different magnifications. The invention aims to provide a telecentric lens with good optical performance and relatively high magnification so as to meet the precision detection requirement of a machine vision system.

Description

Technical Field

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

[0002] With the development of industrial automation and the popularization of machine vision, industrial lenses are widely used in defect detection, dimension 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 changes in object distance do not affect the magnification of the image.

[0003] At present, with the increasing demand for optical measurement in integrated circuits, semiconductors, transistors, etc., the requirements for lenses are becoming higher and higher in addition to the high precision and miniaturization required for measuring equipment to reduce costs. Therefore, there is an urgent need for telecentric lenses with good optical performance and high magnification to meet the precision detection of machine vision systems.

[0004] The above contents are only used to assist in understanding the technical solution of the present application and do not constitute an admission that the above contents are prior art. Summary of the invention

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

[0006] To achieve the above-mentioned purpose, the present application provides a telecentric lens group, comprising a front lens group and a rear lens group, and an aperture arranged between the front lens group and the rear lens group; in the front lens group, a first lens, a second lens, a third lens, a fourth lens, a fifth lens and a beam splitter prism are arranged in sequence from the object side to the image side; in the rear lens group, a sixth lens, a seventh lens, an eighth lens and a ninth lens are arranged in sequence 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 optical power; the second lens, the fifth lens, the seventh lens, and the ninth lens have negative optical 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 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.

[0010] To achieve the above-mentioned purpose, the present application also provides a measuring device, which includes a camera module and a computing module, and the camera module is communicatively connected with the computing module; the camera module is provided with the telecentric lens group as described above.

[0011] The telecentric lens group and measuring equipment provided in this application, the telecentric lens combines multiple advantages such as precise light control, cemented lens optimization, flexible magnification adjustment and design optimization, so that the telecentric lens group has significant improvements in imaging quality, flexibility, cost-effectiveness and application diversity. It has good optical performance and high magnification, and provides a feasible solution for large field of view, high-resolution imaging and low-cost visual inspection needs, thereby meeting the precision inspection needs of machine vision systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is a schematic diagram of the structure of a telecentric lens assembly in one embodiment of the present application;

[0013] Figure 2 Another schematic diagram of the structure of a telecentric lens assembly in one embodiment of the present application;

[0014] Figure 3 This is the MTF diagram of the telecentric lens set with a magnification of 2.0x for this application;

[0015] Figure 4 This is the axial aberration diagram of the telecentric lens set with a magnification of 2.0x in this application;

[0016] Figure 5 This is the distortion diagram of the telecentric lens set with a magnification of 2.0x in this application;

[0017] Figure 6 This is the MTF diagram of the telecentric lens set with a magnification of 1.5x for this application;

[0018] Figure 7 This is the axial aberration diagram of the telecentric lens set with a magnification of 1.5x in this application;

[0019] Figure 8 This is the distortion diagram of the telecentric lens set with a magnification of 1.5x in this application;

[0020] Fig. 9 This is the MTF diagram of the telecentric lens set with a magnification of 1.2x for this application;

[0021] Fig.10 This is the axial aberration diagram of the telecentric lens set with a magnification of 1.2x in this application;

[0022] Fig.11 This is the distortion diagram of the telecentric lens set with a magnification of 1.2x in this application.

[0023] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0024] The embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present application, and should not be construed as limiting the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0025] In addition, if the description of "first", "second", etc. is involved in this application, it is only used for descriptive purposes (such as for distinguishing the same or similar features), and cannot be understood as indicating or suggesting their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in this field to implement. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by this application.

[0026] Reference Figure 1 or Figure 2 In one 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 sequence 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 sequence 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 lens group, an aperture STO and a rear lens group are sequentially arranged from the object side to the image side.

[0031] In the field of optics, the object side (also called the object side) and the image side (also called the image side) refer to two different areas in the optical system, which are used to describe the different positions and directions of light in the process of propagating from the object to the image. In the optical system, the object side usually refers to the side where the light propagates from the object plane OBJ to the optical system. The light undergoes refraction, reflection, etc. in this area to form the incident end of the optical system; the image side refers to the area where the light is gathered and imaged after being modulated by the optical system. The light forms the final image in this area, that is, the image plane IMG.

[0032] The front lens is located at the starting point of the optical path and is responsible for the initial focusing, splitting and adjustment of the incident light to form an intermediate image. The light is initially shaped and modulated through the refraction, scattering and combination of the front lens.

[0033] The aperture STO is located between the front lens group and the rear lens group, and it plays a role in limiting the angle of incident light and reducing scattered interference in the optical system. The aperture STO will filter out some non-main light, avoid interference and stray light, and ensure the clarity and quality of the image.

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

[0035] Optionally, 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 prism BS are sequentially arranged from the object side to the image side.

[0036] Among them, the beam splitter BS is mainly used to separate, deflect or refract the incident light according to the wavelength or direction to achieve the light splitting effect. When the incident light passes through the beam splitter BS, due to the different refractive indices of light of different wavelengths in the medium, the light is dispersed to different degrees. This phenomenon is called the dispersion effect, which enables the beam splitter BS to separate the different wavelength components in the incident light. The beam splitter BS can be divided into different types according to its structure and working principle, such as faceted beam splitter BS, prism spectrometer, 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 refractive power; the second lens L2, the fifth lens L5, the seventh lens L7, and the ninth lens L9 have negative refractive power.

[0038] It should be noted that the main difference between positive and negative power lies in the focusing properties of optical elements: positive power means that the lens has the ability to focus light into a real image, while negative power means that the lens has the ability to diverge light into a virtual image. Among them, a lens with positive power is used to focus light to a focal point to achieve real image formation, such as a convex lens; a lens with negative power is used to make divergent light produce a virtual image, such as a concave lens.

[0039] There is a certain distance between the first lens L1 and the second lens L2, and 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 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, and the eighth lens L8 can be combined with the ninth lens L9 to form a cemented lens, or the eighth lens L8 can also be at a certain distance from the ninth lens L9.

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

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

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

[0043] (3) Adjusting optical parameters: By selecting lenses of different materials, curvature radii and thicknesses for bonding, the focal length, magnification and other parameters of the optical system can be changed to achieve customized optical design requirements.

[0044] (4) Reduce the gap and alignment problems between optical components: Glued lenses can reduce the gap and alignment errors between components and improve the stability and accuracy of the optical system.

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

[0046] Optionally, in a telecentric lens group, the combined focal length of the front lens group is fixed, while the combined focal length of the rear lens group can be changed accordingly according to the usage requirements of the telecentric lens group, thereby forming a telecentric lens group with different magnifications, such as the magnification of the telecentric lens group can be 2.0x, 1.5x, 1.2x, etc.

[0047] Optionally, in the front lens group, the design parameters related to each lens and the beam splitter prism BS can be set so that the combined focal length of the front lens group reaches a fixed value fA; and on the premise that the combined focal length of the front lens group is fA, the combined focal length fB of the rear lens group is adjusted (this can be achieved by adjusting the relevant design parameters of each lens in the rear lens group), thereby forming a telecentric lens group with different magnifications.

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

[0049] By replacing the rear lens group without changing the front lens group to meet different magnification requirements, the system design is optimized and the cost-effectiveness is improved, which also reduces the maintenance and upgrade costs of the telecentric lens group.

[0050] This design method can meet the needs of large field of view and high-precision optical detection at the same time, making the telecentric lens group perform well in different scenarios. Whether it is necessary to quickly scan large area images or require fine detection at high resolution, the telecentric lens group can meet the requirements.

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

[0052] In general, by sharing the front lens and randomly matching different rear lens groups to achieve different magnifications, the versatility and practicality of the telecentric lens group are met, 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 the large field of view, high-resolution imaging and low-cost requirements of the telecentric lens group.

[0053] In one embodiment, a telecentric lens combines multiple advantages such as precise light control, cemented lens optimization, flexible magnification adjustment, and design optimization, so that the telecentric lens group has significant improvements in imaging quality, flexibility, cost-effectiveness, and application diversity. It has good optical performance and high magnification, and provides a feasible solution for large field of view, high-resolution imaging, and low-cost visual inspection needs, thereby meeting the precision inspection needs of machine vision systems.

[0054] In one embodiment, based on the above embodiment, referring 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 this embodiment, the combined focal length of the front lens group is fA, the combined focal length of the rear lens group is fB, 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 formed by the eighth lens L8 and the ninth lens L9 is fL89, and the following relationship is satisfied:

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

[0057] 0.1<|fL6 / fB|<0.3 (a further preferred range may be 0.15<|fL6 / fB|<0.19);

[0058] 0<|fL7 / fB|<0.1 (a further preferred range may be 0.03<|fL7 / fB|<0.05);

[0059] 0<|fL8 / fB|<0.2 (a further preferred range may be 0.07<|fL8 / fB|<0.1);

[0060] 0<|fL9 / fB|<0.2;

[0061] 0.02<|fL89 / fB|<0.2 (a further preferred range may be 0.09<|fL89 / fB|<0.12).

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

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

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

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

[0066] The aperture is 9;

[0067] The maximum telecentricity of the object space is 0.06°;

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

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

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

[0071] The setting of these parameters and relationships is designed to ensure that the optical performance and imaging quality of the telecentric lens group meet specific requirements, and the stability and flexibility of the system are improved through the design of the cemented lens and the proportional control of the focal length of each lens. This design method can effectively optimize the imaging effect of the telecentric lens group while meeting the 2.0x magnification requirement and application needs.

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

[0073] Table 1:

[0074]

[0075]

[0076] Reference Figure 3 , Figure 3 This is the MTF (Modulation Transfer Function) diagram of the telecentric lens group with a magnification of 2.0x, indicating that the MTF of the full field of view is close to the diffraction limit, which is used to evaluate the imaging performance of the telecentric lens group, especially the spatial resolution. Here, the MTF diagram shows the imaging quality of the telecentric lens group in the full field of view. If the diagram is close to the diffraction limit, it means that the system has good imaging capabilities at all spatial frequencies.

[0077] Through the MTF graph, we can observe the contrast transmission of the telecentric lens group at different spatial frequencies, that is, the performance of the telecentric lens group in retaining 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 (that is, close to the diffraction limit), indicating that the telecentric lens group can effectively transmit high spatial frequency details and achieve good imaging performance.

[0078] In general, the MTF graph is close to the diffraction limit in the full field of view, which is a good performance, which means that the telecentric lens group has excellent imaging capabilities at a magnification of 2.0x, 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, and can improve the imaging performance and application value of the telecentric lens group.

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

[0080] Axial chromatic aberration is an important performance parameter in optical systems. It describes the offset of the focus position of the image under different wavelengths of light, resulting in image blur or chromatic aberration. When the pupil is 0.7, the axial chromatic aberration of the telecentric lens group is 0.1mm, which means that under different wavelengths of light, the focus position offset of the telecentric lens group is 0.1mm, 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 image blur and color deviation problems caused by chromatic aberration and improve the overall imaging quality.

[0081] For demanding imaging tasks, the control of axial chromatic aberration is very important to ensure that the telecentric lens group can provide clear and accurate imaging under different wavelengths of light, thereby meeting the user's needs for image detail and color accuracy.

[0082] Reference Figure 5 , Figure 5 This is the distortion diagram of the telecentric lens group with a magnification of 2.0x. It can be seen that 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 components. The maximum distortion of the telecentric lens group is 0.067%, which means that the 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 those that require precise measurement and true proportions, such as engineering measurement, medical imaging, etc., distortion control is critical. The maximum distortion of the telecentric lens group is 0.067%, indicating that the telecentric lens group performs well in image quality and can provide almost distortion-free imaging, helping to maintain image accuracy and reliability.

[0085] In one embodiment, based on the above embodiment, referring 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 lens group is fA, the combined focal length of the rear lens group is fB, 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 formed 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 (a further preferred range may be 0.19<|f A / f B|<0.23);

[0088] 0.1<|fL6 / fB|<0.5 (a further preferred range may be 0.25<|fL6 / fB|<0.29);

[0089] 0<|fL7 / fB|<0.2 (a further preferred range may be 0.04<|fL7 / fB|<0.08);

[0090] 0<|fL8 / fB|<0.2 (a further preferred range may be 0.07<|fL8 / fB|<0.11);

[0091] 0<|fL9 / fB|<0.3;

[0092] 0.02<|fL89 / fB|<0.3 (a further preferred range may be 0.09<|fL89 / fB|<0.13).

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

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

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

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

[0097] The aperture is 8.5;

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

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

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

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

[0102] The setting of these parameters and relationships is designed to ensure that the optical performance and imaging quality of the telecentric lens group meet specific requirements, and the stability and flexibility of the system are improved through the design of the cemented lens and the proportional control of the focal length of each lens. This design method can effectively optimize the imaging effect of the telecentric lens group while meeting the 1.5x magnification requirement and application needs.

[0103] Optionally, in a telecentric lens set with a magnification of 1.5x, the design parameters of the relevant optical elements are shown in Table 2 below:

[0104] Table 2:

[0105]

[0106]

[0107] Reference Figure 6 , Figure 6 This is the MTF diagram of the telecentric lens group with a magnification of 1.5x, indicating that the MTF of the full field of view is close to the diffraction limit, which is used to evaluate the imaging performance of the telecentric lens group, especially the spatial resolution. Here, the MTF diagram shows the imaging quality of the telecentric lens group in the full field of view, and the contrast transmission of the telecentric lens group at different spatial frequencies can be observed. It can be seen that the MTF curve of the telecentric lens group at different spatial frequencies is relatively close to 1 (that is, close to the diffraction limit), indicating that the telecentric lens group can effectively transmit high spatial frequency details and achieve good imaging performance.

[0108] In general, the MTF graph is close to the diffraction limit in the full field of view, which is a good performance, which means that the telecentric lens group has excellent imaging capabilities at a magnification of 1.5x, 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, and can improve the imaging performance and application value of the telecentric lens group.

[0109] Reference Figure 7 , Figure 7 : is an axial aberration diagram of a telecentric lens group with a magnification of 1.5x. It can be seen that when the pupil of the telecentric lens group provided in this embodiment is 0.7, the axial chromatic aberration is 0.07mm.

[0110] When the pupil is 0.7, the axial chromatic aberration of the telecentric lens group is 0.07mm, which means that under different wavelengths of light, the focus position offset of the telecentric lens group 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 image blur and color deviation problems caused by chromatic aberration and improve the overall imaging quality.

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

[0112] Reference Figure 8 , Figure 8 This is the distortion diagram of the telecentric lens group with a magnification of 1.5x. It can be seen 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 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. The maximum distortion of the telecentric lens group is 0.056%, indicating that the telecentric lens group performs well in image quality and can provide almost distortion-free imaging, helping to maintain the accuracy and reliability of the image.

[0114] In one embodiment, based on the above embodiment, referring to Figure 2 The magnification of the telecentric lens group is 1.2x; there is a certain distance between the eighth lens L8 and the ninth lens L9.

[0115] In this embodiment, the combined focal length of the front lens group is fA, the combined focal length of the rear lens group is fB, 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 relationship is satisfied:

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

[0117] 0.1<|fL6 / fB|<0.6 (a further preferred range may be 0.22<|fL6 / fB|<0.27);

[0118] 0.01<|fL7 / fB|<0.3 (a further preferred range may be 0.1<|fL7 / fB|<0.13);

[0119] 0.01<|fL8 / fB|<0.3 (a further preferred range may be 0.1<|fL8 / fB|<0.15);

[0120] 0.01<|fL9 / fB|<0.3 (a further preferred range may be 0.12<|fL9 / fB|<0.17).

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

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

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

[0124] The object-side numerical aperture is 0.07;

[0125] The aperture is 8.5;

[0126] The maximum telecentricity of the object space is 0.015°;

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

[0128] The object-space optical resolution is 4.75um;

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

[0130] The setting of these parameters and relationships is designed to ensure that the optical performance and imaging quality of the telecentric lens group meet specific requirements, and the stability and flexibility of the system are improved through the design of the cemented lens and the proportional control of the focal length of each lens. This design method can effectively optimize the imaging effect of the telecentric lens group while meeting the 1.2x magnification requirement and application needs.

[0131] Optionally, in a telecentric lens set with a magnification of 1.2x, the design parameters of the relevant optical elements are shown in Table 3 below:

[0132] Table 3:

[0133]

[0134]

[0135] Reference Fig. 9 , Fig. 9 This is the MTF diagram of the telecentric lens group with a magnification of 1.2x, indicating that the MTF of the full field of view is close to the diffraction limit, which is used to evaluate the imaging performance of the telecentric lens group, especially the spatial resolution. The MTF diagram of the full field of view close to the diffraction limit is a good performance, which means that the telecentric lens group has excellent imaging capabilities 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, and can improve the imaging performance and application value of the telecentric lens group.

[0136] Reference Fig.10 , Fig.10 This is the axial aberration diagram of the telecentric lens group with a magnification of 1.2x. It can be seen that when the pupil of the telecentric lens group provided in this embodiment is 0.7, the axial chromatic aberration is 0.07mm. When the pupil is 0.7, the axial chromatic aberration of the telecentric lens group is 0.07mm, which means that under different wavelengths of light, the focus position offset of the telecentric lens group 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 deviation problems caused by chromatic aberration and improve the overall imaging quality.

[0137] Reference Fig.11 , Fig.11This is the distortion diagram 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 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. The performance of the maximum distortion of the telecentric lens group is 0.051%, indicating that the telecentric lens group performs well in image quality, can provide almost distortion-free imaging, and helps maintain the accuracy and reliability of the image.

[0138] Optionally, the preferred values ​​of the telecentric lens group parameters for magnifications of 2.0x, 1.5x, and 1.2x are shown in Table 4 below:

[0139] Table 4:

[0140] Relationships 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 / fB| 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 under the corresponding magnification.

[0142] The present application further proposes a measuring device, which includes a camera module and a computing module, and the camera module is communicatively connected to the computing module; wherein a telecentric lens group is provided in the camera module, and the specific structure of the telecentric lens group refers to the above-mentioned embodiment. Since the present measuring device adopts all the technical solutions of all the above-mentioned embodiments, it has at least all the technical effects brought by the technical solutions of the above-mentioned embodiments, which will not be described one by one here.

[0143] It should be noted that, in this article, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, device, article or method including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, device, article or method. In the absence of further restrictions, an element defined by the sentence "includes a ..." does not exclude the presence of other identical elements in the process, device, article or method including the element.

[0144] The above description is only a preferred embodiment of the present application, and does not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly used in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A telecentric lens assembly, characterized in that: The invention comprises a front lens group and a rear lens group, and a diaphragm arranged between the front lens group and the rear lens group; in the front lens group, a first lens, a second lens, a third lens, a fourth lens, a fifth lens and a beam splitter prism are arranged in sequence from the object side to the image side; in the rear lens group, a sixth lens, a seventh lens, an eighth lens and a ninth lens are arranged in sequence from the object side to the image side; Among them, the first lens, the third lens, the fourth lens, the sixth lens, and the eighth lens have positive optical power; the second lens, the fifth lens, the seventh lens, and the ninth lens have negative optical power; 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 group is fixed, and the rear lens group with different combined focal lengths is matched to form a telecentric lens group with different magnifications.

2. The telecentric lens assembly according to claim 1, characterized in that: The relevant parameters of the telecentric lens group include at least one of the following: The object working distance is 111-113mm; The maximum image size is φ19.2mm.

3. The telecentric lens assembly according to claim 1 or 2, characterized in that: The magnification of the telecentric lens group is 2.0x or 1.5x; the eighth lens and the ninth lens are combined into a cemented lens.

4. The telecentric lens assembly according to claim 3, characterized in that: The magnification of the telecentric lens set is 2.0x; The combined focal length of the front lens group is fA, the combined focal length of the rear lens group is fB, 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, the focal length of the ninth lens is fL9, and the focal length of the cemented lens formed by the eighth lens and the ninth lens is fL89, and the following relationship is satisfied: 0.1<|fA / fB|<0.2; 0.1<|fL6 / fB|<0.3; 0<|fL7 / fB|<0.1; 0<|fL8 / fB|<0.2; 0<|fL9 / fB|<0.2; 0.02<|fL89 / fB|<0.

2.

5. The telecentric lens assembly according to claim 4, characterized in that: The relevant parameters of the telecentric lens group include at least one of the following: The maximum object field of view is φ9.6mm; The object-side numerical aperture is 0.112; The aperture is 9; The maximum telecentricity of the object space is 0.06°; The object-image distance is 350mm; The object-space optical resolution is 3um.

6. The telecentric lens assembly according to claim 3, characterized in that: The magnification of the telecentric lens set is 1.5x; The combined focal length of the front lens group is fA, the combined focal length of the rear lens group is fB, 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, the focal length of the ninth lens is fL9, and the focal length of the cemented lens formed by the eighth lens and the ninth lens is fL89, and the following relationship is satisfied: 0.1<|fA / fB|<0.3; 0.1<|fL6 / fB|<0.5; 0<|fL7 / fB|<0.2; 0<|fL8 / fB|<0.2; 0<|fL9 / fB|<0.3; 0.02<|fL89 / fB|<0.

3.

7. The telecentric lens assembly according to claim 6, characterized in that: The relevant parameters of the telecentric lens group include at least one of the following: The maximum object field of view is φ12.8mm; The object-side numerical aperture is 0.088; The aperture is 8.5; The maximum telecentricity of the object space is 0.008°; The object-image distance is 330mm; The object-space optical resolution is 3.8um.

8. The telecentric lens assembly according to claim 1 or 2, characterized in that: The magnification of the telecentric lens group is 1.2x; The combined focal length of the front lens group is fA, the combined focal length of the rear lens group is fB, 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, and the following relationship is satisfied: 0.1<|fA / fB|<0.5; 0.1<|fL6 / fB|<0.6; 0.01<|fL7 / fB|<0.3; 0.01<|fL8 / fB|<0.3; 0.01<|fL9 / fB|<0.

3.

9. The telecentric lens assembly according to claim 8, characterized in that: The relevant parameters of the telecentric lens group include at least one of the following: The maximum object field of view is φ16mm; The object-side numerical aperture is 0.07; The aperture is 8.5; The maximum telecentricity of the object space is 0.015°; The object-image distance is 322mm; The object-space optical resolution is 4.75um.

10. A measuring device, characterized in that: The measuring device comprises a camera module and a computing module, and the camera module is communicatively connected with the computing module; the camera module is provided with a telecentric lens group as described in any one of claims 1-9.

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