Polarization telecentric lens and imaging detection system

Abstract

The present invention relates to a polarization telecentric lens and an imaging detection system. The polarization telecentric lens comprises: a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens and a seventh lens, which are arranged in sequence from the object side to the image side; the object side surface of the first lens is convex toward the object side, and the image side surface is convex toward the image side; the object side surface of the second lens is convex toward the image side, and the image side surface is convex toward the object side; the object side surface of the third lens is convex toward the object side, and the image side surface is convex toward the object side; the object side surface of the fourth lens is convex toward the object side, and the image side surface is convex toward the image side; both the object side surface and the image side surface of the fifth lens are convex toward the image side; both the object side surface and the image side surface of the sixth lens are convex toward the object side; the object side surface of the seventh lens is convex toward the image side, and the image side surface is convex toward the object side; the second lens and the third lens constitute a cemented lens, and the fourth lens and the fifth lens constitute a cemented lens.

Description

Technical Field

[0001] The present invention relates to the field of optics, and in particular to a polarization telecentric lens and an imaging detection system. Background Art

[0002] Polarization is a fundamental property of light fields. In-depth research on the characteristics and advantages of polarization detection imaging systems, combined with other advanced imaging sensing technologies to achieve higher-dimensional information acquisition and computation, has important applications in imaging scenarios at all scales and is crucial for expanding visual perception. Numerous researchers have conducted research on polarization image detection. Li Shiting, Ye Wenbin, and others from Shenzhen University proposed a DoF polarization image denoising method based on a dictionary learning algorithm (K-times Singular Value Decomposition, K-SVD). Using K-SVD and an orthogonal matching pursuit algorithm, they optimized a sparse combination of dictionary elements to represent the input DoF image. Results showed that this method eliminated Gaussian noise while preserving details and edges in the source image. Professor Shao Xiaopeng's team at Xidian University proposed a near-infrared monocular polarization 3D reconstruction method. By incorporating a reference gradient field into the global correction of the surface normal vector, they verified the two-point accuracy and robustness of the reconstruction scheme at various distances.

[0003] The numerous research results mentioned above demonstrate that polarization imaging can provide rich, detailed information in the field of visual inspection, playing a crucial role in detecting defects and maintaining inspection accuracy during additive manufacturing. Therefore, a polarization imaging device capable of providing excellent imaging results is urgently needed in the field of visual inspection. Summary of the Invention

[0004] The object of the present invention is to provide a polarization telecentric lens and an imaging detection system.

[0005] To achieve the above-mentioned object, the present invention provides a polarization telecentric lens, comprising: a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, and a seventh lens arranged in sequence from the object side to the image side;

[0006] The object-side surface of the first lens is convex toward the object side, and the image-side surface is convex toward the image side;

[0007] The object side surface of the second lens is convex toward the image side, and the image side surface is convex toward the object side;

[0008] The object-side surface of the third lens is convex toward the object, and the image-side surface is convex toward the object;

[0009] The object-side surface of the fourth lens element is convex toward the object side, and the image-side surface is convex toward the image side;

[0010] The object-side surface and the image-side surface of the fifth lens are both convex toward the image side;

[0011] The object-side surface and the image-side surface of the sixth lens are both convex toward the object side;

[0012] The object-side surface of the seventh lens element is convex toward the image side, and the image-side surface is convex toward the object side;

[0013] The second lens and the third lens form a cemented lens, and the fourth lens and the fifth lens form a cemented lens.

[0014] According to one aspect of the present invention, the invention further comprises: a stop;

[0015] The aperture stop is disposed between the third lens and the fourth lens.

[0016] According to one aspect of the present invention, the object-side surface of the second lens adopts a Q-type aspheric surface, and / or the image-side surface of the fourth lens and the object-side surface of the fifth lens adopt a Q-type aspheric surface.

[0017] According to one aspect of the present invention, the Q-type aspheric surface adopts a mild aspheric surface, and its expression is:

[0018]

[0019] h 2 =x 2 +y 2

[0020] r=hρ / ρh max =h / h max

[0021] Among them, Z() represents the height from the vertex of the surface to a certain point on the surface, ρ bsf represents the curvature of the aspheric reference quadratic surface, that is, the curvature of the best fitting sphere, h represents the aspheric surface sag, r represents the normalized aspheric surface sag, ρ represents the curvature at the aspheric surface vertex, h max Indicates the maximum value of aspheric sag height, f(h max ) represents the deviation between the aspheric surface and the best fitting spherical surface, m=0,1,2,…,M, M represents the highest number of aspheric surfaces, a m represents the coefficient of the aspheric term, represents a set of Jacobi polynomials whose first six terms are:

[0022]

[0023] According to one aspect of the present invention, the radius of curvature of the object-side surface of the first lens is 18.5 mm to 19.5 mm, and the radius of curvature of the image-side surface is -46.3 mm to -48.5 mm;

[0024] The object-side surface of the second lens has a curvature radius of -21.2 mm to -24.9 mm, and the image-side surface has a curvature radius of 7.8 mm to 9.6 mm;

[0025] The curvature radius of the image side surface of the third lens is 16.5 mm to 18.3 mm;

[0026] The curvature radius of the object side surface of the fourth lens is 33.4mm to 34.3mm, and the curvature radius of the image side surface is -418mm to -420.1mm.

[0027] The curvature radius of the image side surface of the fifth lens is -33 mm to -34 mm;

[0028] The object-side surface of the sixth lens has a curvature radius of 27.1 mm to 29.02 mm, and the image-side surface has a curvature radius of 36.12 mm to 37.09 mm;

[0029] The object-side surface of the seventh lens has a curvature radius of -110.2 mm to -111.42 mm, and the image-side surface has a curvature radius of 106.121 mm to 110.093 mm;

[0030] The center thickness of the first lens is 5.345 mm to 7.124 mm, the center thickness of the second lens is 3 mm to 4.238 mm, the center thickness of the third lens is 5.045 mm to 7.34 mm, the center thickness of the fourth lens is 5.445 mm to 7.014 mm, the center thickness of the fifth lens is 6 mm to 7.604 mm, the center thickness of the sixth lens is 4.8 mm to 6.113 mm, and the center thickness of the seventh lens is 2.3 mm to 2.957 mm;

[0031] The center distance between the first lens and the second lens is 1.5mm to 1.8mm, the center distance between the third lens and the aperture is 0.65mm to 0.907mm, the center distance between the aperture and the fourth lens is 0.4mm to 0.6mm, the center distance between the fifth lens and the sixth lens is 1.982mm to 2.754mm, and the center distance between the sixth lens and the seventh lens is 32.124mm to 33.549mm.

[0032] According to one aspect of the present invention, the refractive index n of the first lens is 1.552670 to 1.7, and the Abbe number v is 63 to 64.42;

[0033] The refractive index n of the second lens is 1.654205 to 1.847204, and the Abbe number v is 26.30 to 28.15;

[0034] The refractive index n of the third lens is 1.656747 to 1.944315, and the Abbe number v is 22.12 to 24.93;

[0035] The refractive index n of the fourth lens is 1.535042 to 1.710025, and the Abbe number v is 59.57 to 62.63;

[0036] The refractive index n of the fifth lens is 1.696543 to 2.153315, and the Abbe number v is 38.23 to 40.5;

[0037] The refractive index n of the sixth lens is 1.749631 to 1.935211, and the Abbe number v is 45.97 to 47.55;

[0038] The refractive index n of the seventh lens is 1.694363 to 1.872518, and the Abbe number v is 36.23 to 38.5.

[0039] According to one aspect of the present invention, the radius of curvature of the object side surface of the first lens is 19.439 mm, and the radius of curvature of the image side surface is -47.337 mm;

[0040] The object-side surface of the second lens has a curvature radius of -22.925 mm, and the image-side surface has a curvature radius of 8.475 mm;

[0041] The curvature radius of the image side surface of the third lens is 16.618 mm;

[0042] The object-side surface of the fourth lens has a curvature radius of 34.063 mm, and the image-side surface has a curvature radius of -419.139 mm;

[0043] The curvature radius of the image side surface of the fifth lens is -33.117 mm;

[0044] The object-side surface of the sixth lens has a curvature radius of 28.659 mm, and the image-side surface has a curvature radius of 36.460 mm;

[0045] The object-side surface of the seventh lens has a curvature radius of -111.120 mm, and the image-side surface has a curvature radius of 108.481 mm;

[0046] The center thickness of the first lens is 6.545 mm, the center thickness of the second lens is 3.599 mm, the center thickness of the third lens is 6.591 mm, the center thickness of the fourth lens is 6.090 mm, the center thickness of the fifth lens is 6.918 mm, the center thickness of the sixth lens is 5.328 mm, and the center thickness of the seventh lens is 2.840 mm;

[0047] The center distance between the first lens and the second lens is 1.738 mm, the center distance between the third lens and the aperture is 0.777 mm, the center distance between the aperture and the fourth lens is 0.500 mm, the center distance between the fifth lens and the sixth lens is 2.315 mm, and the center distance between the sixth lens and the seventh lens is 33.249 mm;

[0048] The refractive index n of the first lens is 1.617998, and the Abbe number v is 63.41;

[0049] The refractive index n of the second lens is 1.755205, and the Abbe number v is 27.55;

[0050] The refractive index n of the third lens is 1.846670, and the Abbe number v is 23.79;

[0051] The refractive index n of the fourth lens is 1.620412, and the Abbe number v is 60.37;

[0052] The refractive index n of the fifth lens is 1.883001, and the Abbe number v is 39.23;

[0053] The refractive index n of the sixth lens is 1.802793, and the Abbe number v is 46.77;

[0054] The refractive index n of the seventh lens is 1.781796, and the Abbe number v is 37.09.

[0055] To achieve the above-mentioned object of the invention, the present invention provides an imaging detection system using the aforementioned polarization telecentric lens, comprising: an imaging device for imaging a target object, a uniform light source for illuminating the target object, and a host computer connected to the imaging device;

[0056] The imaging device includes: a polarizer, a polarization telecentric lens, a filter and a hub on the same optical path;

[0057] The polarization telecentric lens comprises: a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens and a seventh lens arranged in sequence from the object side to the image side;

[0058] The object-side surface of the first lens is convex toward the object side, and the image-side surface is convex toward the image side;

[0059] The object side surface of the second lens is convex toward the image side, and the image side surface is convex toward the object side;

[0060] The object-side surface of the third lens is convex toward the object side, and the image-side surface is convex toward the image side;

[0061] The object-side surface of the fourth lens element is convex toward the object side, and the image-side surface is convex toward the image side;

[0062] The object-side surface and the image-side surface of the fifth lens are both convex toward the image side;

[0063] The object-side surface and the image-side surface of the sixth lens are both convex toward the object side;

[0064] The object-side surface of the seventh lens element is convex toward the image side, and the image-side surface is convex toward the object side;

[0065] The second lens and the third lens form a cemented lens, and the fourth lens and the fifth lens form a cemented lens.

[0066] According to one aspect of the present invention, the uniform light source comprises: LED lamp beads, a microlens array and a mounting box;

[0067] The installation box is a regular structure with an open bottom end;

[0068] The microlens array is sealed and embedded in the opening end of the mounting box;

[0069] The LED lamp beads are mounted on the upper end of the mounting box opposite to the micro lens array and are located inside the mounting box;

[0070] The side walls of the installation box are attached with a light-absorbing layer, and the interior of the installation box is vacuumed;

[0071] The microlens array comprises: a plurality of microlenses arranged in an array;

[0072] The microlens is a free-form surface lens.

[0073] According to one aspect of the present invention, the curve of the free-form surface of the microlens is expressed as:

[0074]

[0075] Among them, a1 and b1 represent the coordinates of the contact point between the incident light and the microlens, r1 represents the radius of the microlens, d represents the distance from the center of the microlens array to the light receiving plane, and n a Represents the outgoing vector of the light passing through the microlens.

[0076] According to one solution of the present invention, a Q-type aspheric surface is introduced into a polarized telecentric lens to achieve regulation of the mirror root mean square slope and optimization correction of high-order aberrations, which is conducive to simplifying the optical structure and effectively reducing the number of lenses while ensuring excellent imaging effects.

[0077] According to one solution of the present invention, the present invention introduces a Q-type aspheric surface to accurately control the root mean square slope of the mirror surface, which can not only regulate the propagation path of light, but also optimize and correct high-order aberrations, so as to be particularly outstanding in improving the performance of the optical system.

[0078] According to one solution of the present invention, the introduction of a Q-type aspheric surface allows for precise adjustment and control of how light passes during the lens design process, effectively reducing the scattering and aberrations produced by traditional spherical lenses when processing complex light. In particular, the introduction of the Q-type aspheric surface ensures that light is refracted in the most ideal manner through fine-tuning of the mirror's root mean square slope, thereby improving imaging quality.

[0079] According to one solution of the present invention, the introduction of a Q-type aspheric surface demonstrates unique advantages in optimizing higher-order aberrations. By employing this design, these complex aberrations can be effectively corrected, resulting in clearer and more accurate imaging without sacrificing image quality. This is of great significance for improving the performance of defect detection systems.

[0080] According to one solution of the present invention, the introduction of a Q-type aspheric surface also facilitates the simplification of optical structures. In many optical systems, achieving ideal imaging results often requires the use of a large number of lenses and other optical components. This not only increases system complexity and cost but can also introduce additional aberrations and light loss. However, the Q-type aspheric surface, with its superior optical performance, can effectively reduce the number of required lenses while ensuring excellent imaging results. This simplification not only reduces costs but also improves system stability and reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0081] Figure 1 is a perspective view schematically showing a polarization telecentric lens according to an embodiment of the present invention;

[0082] Figure 2 is a structural diagram schematically showing a polarization telecentric lens according to one embodiment of the present invention;

[0083] Figure 3 is a block diagram schematically showing a structure of an imaging detection system according to an embodiment of the present invention;

[0084] Figure 4 is a structural diagram schematically showing a uniform light source according to an embodiment of the present invention;

[0085] Figure 5 is a cross-sectional view schematically showing a microlens according to one embodiment of the present invention;

[0086] Figure 6Schematic diagrams showing image quality evaluation results of a polarized telecentric lens according to an embodiment of the present invention, wherein (a) shows an MTF curve of the polarized telecentric lens, (b) shows a field curvature diagram of the polarized telecentric lens, and (c) shows a distortion diagram of the polarized telecentric lens;

[0087] Figure 7 Schematic diagrams showing image quality evaluation results of a polarization telecentric lens according to an embodiment of the present invention, wherein (a) shows a point diagram of the polarization telecentric lens, (b) shows an energy bracketing diagram of the polarization telecentric lens,

[0088] Figure 8 Schematic diagrams showing image quality evaluation results of a polarization telecentric lens according to an embodiment of the present invention, wherein (a) represents a relative illumination diagram of the polarization telecentric lens, and (b) represents a wavefront diagram of the polarization telecentric lens. DETAILED DESCRIPTION

[0089] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be derived from these drawings without inventive effort.

[0090] When describing the embodiments of the present invention, the orientation or positional relationship expressed by the terms "longitudinal", "transverse", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" are based on the orientation or positional relationship shown in the relevant drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the above terms should not be understood as limiting the present invention.

[0091] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. The embodiments cannot be described one by one here, but the embodiments of the present invention are not limited to the following embodiments.

[0092] Combine Figure 1 and Figure 2As shown, according to one embodiment of the present invention, a polarization telecentric lens of the present invention includes: a first lens 1, a second lens 2, a third lens 3, a fourth lens 4, a fifth lens 5, a sixth lens 6 and a seventh lens 7 arranged in sequence from the object side to the image side; in this embodiment, the first lens 1, the second lens 2, the third lens 3, the fourth lens 4, the fifth lens 5, the sixth lens 6 and the seventh lens 7 are on the same optical path, thereby realizing the sequential transmission of light, wherein the object side surface of the first lens 1 is convex toward the object side, and the image side surface is convex toward the image side; the object side surface of the second lens 2 is convex toward the image side, and the image side surface is convex toward the object side; the object side surface of the third lens 3 is convex toward the object side, and the image side surface is convex toward the object side; the object side surface of the fourth lens 4 is convex toward the object side, and the image side surface is convex toward the image side; the object side surface and the image side surface of the fifth lens 5 are both convex toward the image side; the object side surface and the image side surface of the sixth lens 6 are both convex toward the object side; the object side surface of the seventh lens 7 is convex toward the image side, and the image side surface is convex toward the object side. In this embodiment, the second lens 2 and the third lens 3 constitute a cemented lens, whereby the image side surface of the second lens 2 is matched with the object side surface of the third lens 3; the fourth lens 4 and the fifth lens 5 constitute a cemented lens, whereby the image side surface of the fourth lens 4 is matched with the object side surface of the fifth lens 5.

[0093] Combine Figure 1 and Figure 2 As shown, according to one embodiment of the present invention, the polarization telecentric lens of the present invention further includes: an aperture 8; wherein the aperture 8 is arranged between the third lens 3 and the fourth lens 4. In this embodiment, the aperture 8 can be set as an adjustable aperture to control the amount of light passing.

[0094] Combine Figure 1 and Figure 2 As shown, according to one embodiment of the present invention, the object-side surface of the second lens 2 adopts a Q-type aspheric surface, and / or the image-side surface of the fourth lens 4 and the object-side surface of the fifth lens 5 adopt a Q-type aspheric surface.

[0095] Through the above-mentioned setting, the present invention introduces a Q-type aspheric surface into the polarization telecentric lens to achieve the regulation of the root mean square slope of the mirror surface and the optimization correction of high-order aberrations, which is conducive to the simplification of the optical structure, so as to effectively reduce the number of lenses while ensuring excellent imaging effects.

[0096] According to an embodiment of the present invention, the Q-type aspheric surface is divided into a mild aspheric surface Q bsf and strong aspheric Q con In this embodiment, a mild aspheric surface Q bsf To achieve the setting of the corresponding lens surface; among them, the mild aspheric surface Q bsfThe reference quadratic surface is the best fitting sphere, which uses the maximum value of the clear aperture to fit the surface vertex. The curvature of the best fitting sphere is:

[0097]

[0098] Where h max is the maximum value of the aspheric sag height. f(h max ) represents the deviation between the aspheric surface and the best fitting spherical surface, recorded as ΔZ, which can be expressed as:

[0099]

[0100] Where m = 0, 1, 2, ..., M, M represents the highest number of aspheric surfaces, a m The coefficient of the aspheric term, h 2 =x 2 +y 2 , h represents the aspheric surface sag, ρ represents the curvature at the aspheric vertex, r represents the normalized aspheric surface sag, and is expressed as: r = hρ / ρh max =h / h max , then the expression of aspheric surface is:

[0101]

[0102] Among them, Z() represents the height from the vertex of the surface (i.e. the origin of the surface or the intersection of the surface and the optical axis) to a certain point on the surface. represents a set of Jacobi polynomials whose first six terms are:

[0103]

[0104] Combine Figure 1 and Figure 2As shown, according to one embodiment of the present invention, the radius of curvature of the object side surface of the first lens 1 is 18.5mm to 19.5mm, and the radius of curvature of the image side surface is -46.3mm to -48.5mm; the radius of curvature of the object side surface of the second lens 2 is -21.2mm to -24.9mm, and the radius of curvature of the image side surface is 7.8mm to 9.6mm; the radius of curvature of the image side surface of the third lens 3 is 16.5mm to 18.3mm; the radius of curvature of the object side surface of the fourth lens 4 is 33.4mm to 34.6mm. .3mm, and the radius of curvature of the image side surface is -418mm to -420.1mm; the radius of curvature of the image side surface of the fifth lens element 5 is -33mm to -34mm; the radius of curvature of the object side surface of the sixth lens element 6 is 27.1mm to 29.02mm, and the radius of curvature of the image side surface is 36.12mm to 37.09mm; the radius of curvature of the object side surface of the seventh lens element 7 is -110.2mm to -111.42mm, and the radius of curvature of the image side surface is 106.121mm to 110.093mm.

[0105] Further preferably, the radius of curvature of the object side surface of the first lens element 1 is 19.439 mm, and the radius of curvature of the image side surface is -47.337 mm; the radius of curvature of the object side surface of the second lens element 2 is -22.925 mm, and the radius of curvature of the image side surface is 8.475 mm; the radius of curvature of the image side surface of the third lens element 3 is 16.618 mm; the radius of curvature of the object side surface of the fourth lens element 4 is 34.063 mm, and the radius of curvature of the image side surface is -419.139 mm; the radius of curvature of the image side surface of the fifth lens element 5 is -33.117 mm; the radius of curvature of the object side surface of the sixth lens element 6 is 28.659 mm, and the radius of curvature of the image side surface is 36.460 mm; and the radius of curvature of the object side surface of the seventh lens element 7 is -111.120 mm, and the radius of curvature of the image side surface is 108.481 mm.

[0106] Combine Figure 1 and Figure 2 As shown, according to one embodiment of the present invention, the center thickness of the first lens 1 is 5.345 mm to 7.124 mm, the center thickness of the second lens 2 is 3 mm to 4.238 mm, the center thickness of the third lens 3 is 5.045 mm to 7.34 mm, the center thickness of the fourth lens 4 is 5.445 mm to 7.014 mm, the center thickness of the fifth lens 5 is 6 mm to 7.604 mm, the center thickness of the sixth lens 6 is 4.8 mm to 6.113 mm, and the center thickness of the seventh lens 7 is 2.3 mm to 2.957 mm.

[0107] Further preferably, the center thickness of the first lens 1 is 6.545 mm, the center thickness of the second lens 2 is 3.599 mm, the center thickness of the third lens 3 is 6.591 mm, the center thickness of the fourth lens 4 is 6.090 mm, the center thickness of the fifth lens 5 is 6.918 mm, the center thickness of the sixth lens 6 is 5.328 mm, and the center thickness of the seventh lens 7 is 2.840 mm.

[0108] Combine Figure 1 and Figure 2 As shown, according to one embodiment of the present invention, the center interval between the first lens 1 and the second lens 2 is 1.5mm to 1.8mm, the center interval between the third lens 3 and the aperture 8 is 0.65mm to 0.907mm, the center interval between the aperture 8 and the fourth lens 4 is 0.4mm to 0.6mm, the center interval between the fifth lens 5 and the sixth lens 6 is 1.982mm to 2.754mm, and the center interval between the sixth lens 6 and the seventh lens 7 is 32.124mm to 33.549mm.

[0109] Further preferably, the center distance between the first lens 1 and the second lens 2 is 1.738 mm, the center distance between the third lens 3 and the aperture 8 is 0.777 mm, the center distance between the aperture 8 and the fourth lens 4 is 0.500 mm, the center distance between the fifth lens 5 and the sixth lens 6 is 2.315 mm, and the center distance between the sixth lens 6 and the seventh lens 7 is 33.249 mm.

[0110] Combine Figure 1 and Figure 2 As shown, according to one embodiment of the present invention, the refractive index n of the first lens 1 is 1.552670 to 1.7, and the Abbe number v is 63 to 64.42; the refractive index n of the second lens 2 is 1.654205 to 1.847204, and the Abbe number v is 26.30 to 28.15; the refractive index n of the third lens 3 is 1.656747 to 1.944315, and the Abbe number v is 22.12 to 24.93; the refractive index n of the fourth lens 4 is 1.53504 2 to 1.710025, and the Abbe number v is 59.57 to 62.63; the refractive index n of the fifth lens element 5 is 1.696543 to 2.153315, and the Abbe number v is 38.23 to 40.5; the refractive index n of the sixth lens element 6 is 1.749631 to 1.935211, and the Abbe number v is 45.97 to 47.55; the refractive index n of the seventh lens element 7 is 1.694363 to 1.872518, and the Abbe number v is 36.23 to 38.5.

[0111] Further preferably, the refractive index n of the first lens element 1 is 1.617998, and the Abbe number v is 63.41; the refractive index n of the second lens element 2 is 1.755205, and the Abbe number v is 27.55; the refractive index n of the third lens element 3 is 1.846670, and the Abbe number v is 23.79; the refractive index n of the fourth lens element 4 is 1.620412, and the Abbe number v is 60.37; the refractive index n of the fifth lens element 5 is 1.883001, and the Abbe number v is 39.23; the refractive index n of the sixth lens element 6 is 1.802793, and the Abbe number v is 46.77; and the refractive index n of the seventh lens element 7 is 1.781796, and the Abbe number v is 37.09.

[0112] Through the above-mentioned settings, the precise settings of the curvature radius, center thickness, mutual spacing, refractive index and Abbe number of each lens work together to improve the overall performance and imaging quality of the optical system. Specifically, the object side curvature radius of the first lens 1 is large, while the image side curvature radius is negative and has a large absolute value. This design helps to enhance its focusing ability while reducing spherical aberration, providing a better initial focused beam for subsequent lenses. The curvature configuration of the second lens 2 effectively corrects the chromatic aberration and field curvature produced by the first lens, further optimizing light transmission. The curvature radius settings of each of the third to seventh lenses are all designed to fine-tune the light path and reduce high-order aberrations. In particular, the extreme curvature configuration of the fourth lens 4 is specially optimized for aberrations in wide-field-of-view applications.

[0113] Furthermore, the decreasing center thickness from the first lens element 1 to the seventh lens element 7 helps reduce the overall weight of the optical system while ensuring a stable structure, achieving a balance between portability and stability. In particular, the larger center spacing between the sixth and seventh lenses not only facilitates heat dissipation within the lens assembly but also eases assembly and maintenance of the optical system.

[0114] Furthermore, by selecting glass materials with specific refractive indices and Abbe numbers, precise control of dispersion and refraction in the optical system is achieved. The use of high-refractive-index materials, such as those in the third and fifth lens elements 3 and 5, enhances the lens's focusing capability, while the appropriate Abbe number ensures color reproduction and clarity, particularly excelling in reducing chromatic aberration.

[0115] Furthermore, this invention effectively improves image clarity, contrast, and color reproduction while maintaining a compact optical system, making it particularly suitable for defect detection applications. Furthermore, this refined parameter adjustment provides greater design flexibility for the optical system, enabling it to adapt to diverse environments and usage requirements, enhancing the product's market competitiveness.

[0116] Combine Figure 1 、 Figure 2 and Figure 3 As shown, according to one embodiment of the present invention, an imaging detection system using the aforementioned polarization telecentric lens is provided, comprising: an imaging device a for imaging a target object, a uniform light source b for illuminating the target object, and a host computer c connected to the imaging device a. In this embodiment, the target object can be clamped on a support platform, wherein the imaging device a is disposed above the support platform and the uniform light source b is disposed below the support platform; thereby, image capture of the target object can be achieved. In this embodiment, the imaging device a comprises: a polarizer a1, a polarization telecentric lens a2, a filter a3, a sensor a4, and a hub a5, all located on the same optical path; wherein the polarization telecentric lens a2 comprises: a first lens 1, a second lens 2, a third lens 3, a fourth lens 4, a fifth lens 5, a sixth lens 6, and a seventh lens 7, arranged in sequence from the object side to the image side. In this embodiment, the object-side surface of the first lens 1 is convex toward the object side, and the image-side surface is convex toward the image side; the object-side surface of the second lens 2 is convex toward the image side, and the image-side surface is convex toward the object side; the object-side surface of the third lens 3 is convex toward the object side, and the image-side surface is convex toward the image side; the object-side surface of the fourth lens 4 is convex toward the object side, and the image-side surface is convex toward the image side; both the object-side surface and the image-side surface of the fifth lens 5 are convex toward the image side; both the object-side surface and the image-side surface of the sixth lens 6 are convex toward the object side; and the object-side surface of the seventh lens 7 is convex toward the image side, and the image-side surface is convex toward the object side. In this embodiment, the second lens 2 and the third lens 3 constitute a cemented lens, and the fourth lens 4 and the fifth lens 5 constitute a cemented lens; wherein the specific configuration of the polarization telecentric lens a2 is consistent with the above configuration and will not be repeated here.

[0117] In this embodiment, to facilitate the arrangement of the optical path in the imaging device a, a reflector a6 can be further provided in the imaging device a to achieve a turning of the optical path, thereby improving the flexibility of the arrangement. In this embodiment, the reflector a6 is provided between the polarizer a1 and the polarization telecentric lens a2.

[0118] Combine Figure 4 and Figure 5 As shown, according to one embodiment of the present invention, the uniform light source b includes: LED lamp beads b1, a microlens array b2 and a mounting box b3; in this embodiment, the mounting box b3 is a regular structure with an open bottom; specifically, the mounting box b3 can be set as a rectangular box supported by a transparent material, for example, the mounting box b3 can be set as a transparent box with a size of 50mm*50mm*25mm, and the wall thickness of the mounting box b3 can be set to 2mm; wherein, the thermal conductivity of the material used for the mounting box b3 can be as high as 1W / m·k, and its weight is 40%-50% lighter than that of aluminum material, and its density is only 2.05g / cm 3 The resistivity can reach above 1015, and its heat resistance temperature is relatively high and its flame retardancy can reach UL94V-0, among which the tensile strength is also well maintained and can reach 80MPa.

[0119] In this embodiment, the mounting box b3 is provided with connecting rails on both sides of the opposite sides of one end of the LED lamp bead b1 to achieve sliding connection with the mounting position, thereby making the uniform light source b of the present invention easy to disassemble and replace, and also facilitating subsequent maintenance and maintenance work.

[0120] Through the above arrangement, the mounting box b3 of the present invention has excellent mechanical properties, can effectively ensure the service life of the entire uniform light source b, and its failure rate and maintenance cost are low. In addition, the mounting box b3 of the present invention can also protect the internal structure, effectively reducing external damage and interference to the uniform lighting system.

[0121] In this embodiment, the microlens array b2 is sealed and embedded in the open end of the mounting box b3. The microlens array b2 and mounting box b3 can be secured using connectors or adhesive. Furthermore, the LED lamp bead b1 is mounted on the upper end of the mounting box b3, opposite the microlens array b2, and is located within the mounting box b3. This allows the LED lamp bead b1 to be positioned above the center of the microlens array b2. In this embodiment, the distance between the LED lamp bead b1 and the light-receiving plane of the microlens array b2 is between 100 mm and 600 mm. Preferably, the distance between the LED lamp bead b1 and the light-receiving plane of the microlens array b2 is 300 mm.

[0122] In this embodiment, a light-absorbing layer is attached to the surrounding side walls of the mounting box b3. The light-absorbing layer ensures that when the light emitted by the LED lamp bead b1 is irradiated around the mounting box b3, it will not generate reflection to affect the use of the receiving plane, so that it can be easily installed in optical instruments for use without affecting the function of the microlens array b2.

[0123] In this embodiment, after the microlens array b2 is installed in the mounting box b3, a vacuum pump is used to evacuate the interior to effectively ensure that the interior of the mounting box b3 is a vacuum environment. This can minimize the refraction of light by air, which is further beneficial to ensuring uniform illumination of the light source of the present invention.

[0124] like Figure 5 As shown, according to one embodiment of the present invention, a microlens array includes: a plurality of microlenses arranged in an array; wherein the microlenses are free-form surface lenses. In this embodiment, the curve of the free-form surface of the microlens (i.e., the curve of the entire cross-section of the microlens) is expressed as:

[0125]

[0126] Among them, a1 and b1 represent the coordinates of the contact point between the incident light and the microlens, r1 represents the radius of the microlens, d represents the distance from the center of the microlens array to the light receiving plane, and n a represents the exit vector of the light passing through the microlens and is expressed as n=(a2-a1, d-b1), where a2 and b2 represent the intersection points of the exit light and the receiving plane after refraction through the lens.

[0127] In this embodiment, in the microlens array, the radius of the microlens ranges from 0.5 mm to 3 mm; preferably, the radius of the microlens is 2 mm.

[0128] In this embodiment, in the microlens array, the microlenses may be arranged in an array of 11*11, 12*12, 13*13, 14*14, 15*15 or 16*16. Preferably, the array used is 13*13.

[0129] To further illustrate this solution, examples are given of the polarization telecentric lens and the uniform light source in this application.

[0130] Example 1

[0131] The Taguchi method was used to simulate the uniform light source in the present invention. The LED bead b1 was configured with a 1mm*0.2mm*1mm LED chip, a luminous efficiency of 90lm / W, a power of 1W, and an initial number of 10,000,000 light-emitting surfaces. The microlens array b2 was configured with three array configurations: 11*11, 13*13, and 15*15. The distance d between the light-receiving plane of microlens array b2 and LED bead b1 was set to 100mm, 300mm, and 500mm. The radius of the microlenses in microlens array b2 was set to 1mm, 2mm, and 3mm. Based on this, an experimental design was conducted, as shown in Table 1.

[0132]

[0133]

[0134] The above experimental design shows that when 13*13, radius 2mm, and d is 300mm, the highest luminous efficiency and uniformity can be achieved, which are 93.7% and 98.9% respectively. At this time, the highest uniform lighting effect in the simulation is achieved.

[0135] Example 2

[0136] Based on the above settings, the total optical system length of the polarized telecentric lens a2 in this embodiment is 163 mm, the back focus is 17.5 mm, the half image height is 5.3 mm, and the ratio of the total optical length to the focal length is 2.0. The image quality evaluation results of the imaging device a using the polarized telecentric lens a2 of the present invention at a working distance of 70 mm are as follows: Figure 6 、 Figure 7 and Figure 8 As shown, it includes MTF curve diagram, field curvature distortion diagram, point array diagram, energy bracket diagram, relative illumination diagram and wavefront diagram. Figure 6 In the MTF curve diagram (a), when the OTF value of each field reaches 100lp / mm, it is greater than 0.3, which meets the requirements; Figure 6 (b) and Figure 6 In the field curvature and distortion diagram (c), we can get Figure 6 (b) The maximum field curvature of the system is less than 0.2. The interval between field curvatures at each operating wavelength is very small, indicating that the astigmatism is very small and will not affect the image clarity of the image sensor. Figure 6 (c) It can be seen that the maximum value of the distortion is also less than 0.03%, which meets the design requirements. Figure 7 (a) The spot diagram of the optical imaging system. Different working wavelengths correspond to different colors. When the pixel size is known to be 3.45μm, the values ​​of the spot diagram under different fields of view vary relatively little. In the on-axis field of view, the mean square values ​​of the diffuse spots under 1.35, 3.15, and 5.3 fields of view are 1.475, 1.459, 1.65, and 1.939, respectively. The main energy is concentrated within the pixel size. Although it can be seen that the diffuse spots at the edge are not relatively concentrated, their root mean square is less than twice the pixel size, so it can meet the design requirements. The energy envelope distribution curves under various fields of view of the imaging system are shown in Figure 2. Figure 7 (b) and Figure 8 As shown in (a), it can be seen that the energy of all fields of view is within the range of the diffraction limit and is evenly distributed, with a high energy concentration, which can meet the requirements of imaging detection. Figure 8 (b) shows the wavefront diagram of the imaging system, with a PV value of 0.0808λ and an RMS value of 0.0215λ. Based on the above analysis, the imaging results meet the design parameter requirements in Table 2 and can meet the design requirements.

[0137] Table 2

[0138] Design parameters Numerical Lens type Objects are far away Telecentricity <0.05° Operating wavelength (μm) 0.4-0.7 Image sensor type CMOS Number of pixels 2448×2048 Pixel size (μm) 3.45 F-number 10 Working distance WD(mm) Imaging within the range of 70mm±4% can meet the requirements distortion(%) <0.03 Relative illumination (%) ＞99.9 Object field diameter 10.6mm Image field diameter 10.6mm Magnification 1x Image-side MTF >0.3@100lp / mm

[0139] The above contents are merely examples of specific solutions of the present invention. For devices and structures not described in detail, it should be understood that they can be implemented by adopting general devices and methods available in the art.

[0140] The above description is merely one embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that the present invention is susceptible to various modifications and variations. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A polarization telecentric lens, characterized in that: include: A first lens (1), a second lens (2), a third lens (3), a fourth lens (4), a fifth lens (5), a sixth lens (6) and a seventh lens (7) are arranged in sequence from the object side to the image side; The object side surface of the first lens (1) is convex toward the object side, and the image side surface is convex toward the image side; The object side surface of the second lens (2) is convex toward the image side, and the image side surface is convex toward the object side; The object side surface of the third lens (3) is convex toward the object side, and the image side surface is convex toward the object side; The object side surface of the fourth lens (4) is convex toward the object side, and the image side surface is convex toward the image side; The object side surface and the image side surface of the fifth lens (5) are both convex toward the image side; The object side surface and the image side surface of the sixth lens (6) are both convex toward the object side; The object side surface of the seventh lens (7) is convex toward the image side, and the image side surface is convex toward the object side; The second lens (2) and the third lens (3) form a cemented lens, and the fourth lens (4) and the fifth lens (5) form a cemented lens.

2. The polarization telecentric lens according to claim 1, wherein: Also includes: Aperture (8); The aperture (8) is arranged between the third lens (3) and the fourth lens (4).

3. The polarization telecentric lens according to claim 2, wherein: The object side surface of the second lens (2) adopts a Q-type aspheric surface, and / or the image side surface of the fourth lens (4) and the object side surface of the fifth lens (5) adopt a Q-type aspheric surface.

4. The polarization telecentric lens according to claim 3, wherein: The Q-type aspheric surface adopts a mild aspheric surface, and its expression is: h 2 =x 2 +y 2 r=hρ / ρh max =h / h max Among them, Z(h) represents the height from the vertex of the surface to a certain point on the surface, ρ bsf represents the curvature of the aspheric reference quadratic surface, that is, the curvature of the best fitting sphere, h represents the aspheric surface sag, r represents the normalized aspheric surface sag, ρ represents the curvature at the aspheric surface vertex, h max Indicates the maximum value of aspheric sag height, f(h max ) represents the deviation between the aspheric surface and the best fitting spherical surface, m=0,1,2,…,M, M represents the highest number of aspheric surfaces, a m represents the coefficient of the aspheric term, represents a set of Jacobi polynomials whose first six terms are:

5. The polarization telecentric lens according to claim 4, characterized in that: The curvature radius of the object side surface of the first lens (1) is 18.5 mm to 19.5 mm, and the curvature radius of the image side surface is -46.3 mm to -48.5 mm; The curvature radius of the object side of the second lens (2) is -21.2 mm to -24.9 mm, and the curvature radius of the image side is 7.8 mm to 9.6 mm; The curvature radius of the image side surface of the third lens (3) is 16.5 mm to 18.3 mm; The curvature radius of the object side surface of the fourth lens (4) is 33.4 mm to 34.3 mm, and the curvature radius of the image side surface is -418 mm to -420.1 mm; The curvature radius of the image side surface of the fifth lens (5) is -33 mm to -34 mm; The curvature radius of the object side surface of the sixth lens (6) is 27.1 mm to 29.02 mm, and the curvature radius of the image side surface is 36.12 mm to 37.09 mm; The curvature radius of the object side surface of the seventh lens (7) is -110.2 mm to -111.42 mm, and the curvature radius of the image side surface is 106.121 mm to 110.093 mm; The center thickness of the first lens (1) is 5.345mm to 7.124mm, the center thickness of the second lens (2) is 3mm to 4.238mm, the center thickness of the third lens (3) is 5.045mm to 7.34mm, the center thickness of the fourth lens (4) is 5.445mm to 7.014mm, the center thickness of the fifth lens (5) is 6mm to 7.604mm, the center thickness of the sixth lens (6) is 4.8mm to 6.113mm, and the center thickness of the seventh lens (7) is 2.3mm to 2.957mm; The center distance between the first lens (1) and the second lens (2) is 1.5 mm to 1.8 mm, the center distance between the third lens (3) and the aperture (8) is 0.65 mm to 0.907 mm, the center distance between the aperture (8) and the fourth lens (4) is 0.4 mm to 0.6 mm, the center distance between the fifth lens (5) and the sixth lens (6) is 1.982 mm to 2.754 mm, and the center distance between the sixth lens (6) and the seventh lens (7) is 32.124 mm to 33.549 mm.

6. The polarization telecentric lens according to claim 5, characterized in that: The refractive index n of the first lens (1) is 1.552670 to 1.7, and the Abbe number v is 63 to 64.42; The refractive index n of the second lens (2) is 1.654205 to 1.847204, and the Abbe number v is 26.30 to 28.15; The refractive index n of the third lens (3) is 1.656747 to 1.944315, and the Abbe number v is 22.12 to 24.93; The refractive index n of the fourth lens (4) is 1.535042 to 1.710025, and the Abbe number v is 59.57 to 62.63; The refractive index n of the fifth lens (5) is 1.696543 to 2.153315, and the Abbe number v is 38.23 to 40.5; The refractive index n of the sixth lens (6) is 1.749631 to 1.935211, and the Abbe number v is 45.97 to 47.55; The refractive index n of the seventh lens (7) is 1.694363 to 1.872518, and the Abbe number v is 36.23 to 38.

5.

7. The polarization telecentric lens according to claim 6, wherein: The curvature radius of the object side of the first lens (1) is 19.439 mm, and the curvature radius of the image side is -47.337 mm; The curvature radius of the object side of the second lens (2) is -22.925 mm, and the curvature radius of the image side is 8.475 mm; The curvature radius of the image side surface of the third lens (3) is 16.618 mm; The curvature radius of the object side surface of the fourth lens (4) is 34.063 mm, and the curvature radius of the image side surface is -419.139 mm; The curvature radius of the image side surface of the fifth lens (5) is -33.117 mm; The curvature radius of the object side surface of the sixth lens (6) is 28.659 mm, and the curvature radius of the image side surface is 36.460 mm; The curvature radius of the object side surface of the seventh lens (7) is -111.120 mm, and the curvature radius of the image side surface is 108.481 mm; The center thickness of the first lens (1) is 6.545 mm, the center thickness of the second lens (2) is 3.599 mm, the center thickness of the third lens (3) is 6.591 mm, the center thickness of the fourth lens (4) is 6.090 mm, the center thickness of the fifth lens (5) is 6.918 mm, the center thickness of the sixth lens (6) is 5.328 mm, and the center thickness of the seventh lens (7) is 2.840 mm; The center distance between the first lens (1) and the second lens (2) is 1.738 mm, the center distance between the third lens (3) and the aperture (8) is 0.777 mm, the center distance between the aperture (8) and the fourth lens (4) is 0.500 mm, the center distance between the fifth lens (5) and the sixth lens (6) is 2.315 mm, and the center distance between the sixth lens (6) and the seventh lens (7) is 33.249 mm; The refractive index n of the first lens (1) is 1.617998, and the Abbe number v is 63.41; The refractive index n of the second lens (2) is 1.755205, and the Abbe number v is 27.55; The refractive index n of the third lens (3) is 1.846670, and the Abbe number v is 23.79; The refractive index n of the fourth lens (4) is 1.620412, and the Abbe number v is 60.37; The refractive index n of the fifth lens (5) is 1.883001, and the Abbe number v is 39.23; The refractive index n of the sixth lens (6) is 1.802793, and the Abbe number v is 46.77; The refractive index n of the seventh lens (7) is 1.781796, and the Abbe number v is 37.

09.

8. An imaging detection system using the polarization telecentric lens according to any one of claims 1 to 7, characterized in that: include: An imaging device (a) for imaging a target object, a uniform light source (b) for illuminating the target object, and a host computer (c) connected to the imaging device (a); The imaging device (a) comprises: a polarizing plate (a1), a polarizing telecentric lens (a2), a filter (a3), a sensor (a4) and a hub (a5) on the same optical path; The polarization telecentric lens (a2) comprises: a first lens (1), a second lens (2), a third lens (3), a fourth lens (4), a fifth lens (5), a sixth lens (6) and a seventh lens (7) arranged in sequence from the object side to the image side; The object side surface of the first lens (1) is convex toward the object side, and the image side surface is convex toward the image side; The object side surface of the second lens (2) is convex toward the image side, and the image side surface is convex toward the object side; The object side surface of the third lens (3) is convex toward the object side, and the image side surface is convex toward the image side; The object side surface of the fourth lens (4) is convex toward the object side, and the image side surface is convex toward the image side; The object side surface and the image side surface of the fifth lens (5) are both convex toward the image side; The object side surface and the image side surface of the sixth lens (6) are both convex toward the object side; The object side surface of the seventh lens (7) is convex toward the image side, and the image side surface is convex toward the object side; The second lens (2) and the third lens (3) form a cemented lens, and the fourth lens (4) and the fifth lens (5) form a cemented lens.

9. The imaging detection system according to claim 8, characterized in that: The uniform light source (b) comprises: LED lamp beads (b1), a microlens array (b2) and a mounting box (b3); The installation box (b3) is a regular structure with an open bottom end; The microlens array (b2) is sealed and embedded in the opening end of the mounting box (b3); The LED lamp bead (b1) is mounted on the upper end of the mounting box (b3) opposite to the micro lens array (b2), and is located inside the mounting box (b3); The side walls of the installation box (b3) are attached with a light-absorbing layer, and the interior of the installation box (b3) is vacuumed; The microlens array comprises: a plurality of microlenses arranged in an array; The microlens is a free-form surface lens.

10. The imaging detection system according to claim 9, characterized in that: The curve of the free-form surface of the microlens is expressed as: Among them, a1 and b1 represent the coordinates of the contact point between the incident light and the microlens, r1 represents the radius of the microlens, d represents the distance from the center of the microlens array to the light receiving plane, and n a Represents the outgoing vector of the light passing through the microlens.

Images