Microscopic imaging barrel lens and imaging system

Abstract

The invention discloses a microscopic imaging barrel lens and an imaging system. The microscopic imaging barrel lens specifically comprises a first balsaming lens and a second balsaming lens which are arranged along a main optical axis from an entrance pupil to an image plane; the first balsaming lens has positive focal power, and the second balsaming lens has negative focal power; the optical interval between the first balsaming lens and the second balsaming lens is 0.1 mm to 1 mm; the focal length of the first bonding lens is f1, the focal length of the second bonding lens is f2, and f2 / f1 is larger than or equal to 6 and smaller than or equal to 8. The two groups of bonding lenses are adopted, and the focal power types, the optical interval and the focal length proportion range of the two groups of bonding lenses are set, so that the Petzval sum of the whole barrel lens structure approaches to zero, the field curvature is reduced, the propagation path of light entering the barrel lens is effectively improved, and distortion is reduced. And meanwhile, only two groups of bonding lenses are arranged, so that the efficiency of the barrel lens is improved, and the processing and assembling difficulty of the barrel lens is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of tube lens imaging, and relates to a tube lens and an imaging system for microscopic imaging. Background Art

[0002] With the development of science and the continuous renewal and iteration of high-tech equipment, Automatic Optical Inspection (AOI) technology has gradually entered all walks of life. For example, in the field of semiconductor production, the quality control applied to advanced packaging is divided into two major links: inspection and metrology. With the continuous advancement of semiconductor manufacturing processes, the rapid and accurate detection of microstructures in the inspection and metrology links is the top priority. The automatic optical inspection technology uses an infinity-corrected objective lens to detect or re-inspect defects, and by combining with a suitable tube lens, it can achieve wide-spectrum illumination and autofocus functions.

[0003] However, traditional microscopic imaging tube lenses generally have problems such as small entrance pupil diameter, small detection range, large field curvature, and large distortion, and can no longer meet the requirements of high precision and large field of view in automatic optical inspection technology.

[0004] Therefore, some researchers have proposed a tube lens design method using multiple lens groups to meet the requirements of large field of view, small field curvature, and small distortion. For example, Patent CN115047611A discloses an optical system of a microscopic tube lens, which sequentially includes, from the object side to the image side: an entrance pupil, a first lens, a second lens, a third lens, a fourth lens component, and an image plane. Among them, the entrance pupil diameter of the optical system of the microscopic tube lens is greater than or equal to 18 mm and less than or equal to 20 mm, and the focal length of the optical system is greater than or equal to 100 mm and less than or equal to 140 mm. This solution solves the problems of small entrance pupil diameter, small detection range, and large field curvature in the optical system of the existing microscopic tube lens.

[0005] In addition, Patent CN111736303A discloses a tube lens and an automatic optical inspection device. Among them, the tube lens includes a first lens group with positive optical power, and the first lens group includes a first lens, a second lens, a third lens, a fourth lens, and a fifth lens sequentially arranged along the optical axis from the object plane to the image plane. The first lens has positive optical power, the second lens has negative optical power, the third lens has positive optical power, the fourth lens has positive optical power, and the fifth lens has negative optical power. The tube lens and the automatic optical inspection device provided by this solution achieve large-field imaging.

[0006] However, the current multi-group and multi-element tube lens design has also brought problems such as low tube lens efficiency, high difficulty in process assembly, and high cost; at the same time, the solution effects for problems such as large field curvature and large distortion are not ideal.

[0007] Therefore, how to design a reasonable barrel lens structure to reduce the field curvature and distortion while ensuring the efficiency of the barrel lens is an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0008] In view of the defects existing in the above-mentioned prior art, the present invention provides a barrel lens and an imaging system for microscopic imaging, specifically including: a first cemented lens and a second cemented lens arranged along the principal optical axis from the entrance pupil to the image plane; the first cemented lens has a positive optical power, and the second cemented lens has a negative optical power; the optical interval between the first cemented lens and the second cemented lens is 0.1 mm - 1 mm; the focal length of the first cemented lens is f 1 , and the focal length of the second cemented lens is f 2 , satisfying the following relationship: 6 ≤ |f 2 / f 1 | ≤ 8. The present invention adopts two groups of cemented lenses, and sets the optical power type, optical interval and focal length ratio range of the two groups of cemented lenses, so that the Petzval sum of the overall barrel lens structure approaches zero, reduces the field curvature, and effectively improves the propagation path of the light entering the barrel lens, reducing distortion. At the same time, only two groups of cemented lenses also improve the efficiency of the barrel lens as an optical system and reduce the processing and assembly difficulty of the barrel lens.

[0009] In a first aspect, the present invention provides a barrel lens for microscopic imaging, specifically including: a first cemented lens and a second cemented lens arranged along the principal optical axis from the entrance pupil to the image plane; The first cemented lens has a positive optical power, and the second cemented lens has a negative optical power; The optical interval between the first cemented lens and the second cemented lens is 0.1 mm - 1 mm; The focal length of the first cemented lens is f 1 , and the focal length of the second cemented lens is f 2 , satisfying the following relationship: 6 ≤ |f 2 / f 1 | ≤ 8.

[0010] Further, the optical interval between the first cemented lens and the second cemented lens is 0.1 mm - 0.5 mm.

[0011] Further, the focal length of the barrel lens is f, and 120 mm ≤ f ≤ 160 mm.

[0012] Further, the curvature radius of the object side surface of the first cemented lens is r 1 , and the curvature radius of the image side surface of the first cemented lens is r 1 ', satisfying the following relationship: 100 mm ≤ r 1 ≤ 150 mm, -150 mm ≤ r 1 ' ≤ -100 mm; The radius of curvature of the object side surface of the second cemented lens is r 2 , and the radius of curvature of the image side surface of the second cemented lens is r 2 ’, satisfying the following relationship: 20 mm ≤ r 2 ≤ 60 mm, 10 mm ≤ r 2 ’≤ 50 mm.

[0013] Furthermore, the first cemented lens is composed of at least two lenses combined, and the second cemented lens is composed of at least two lenses combined.

[0014] Furthermore, each lens in the first cemented lens and the second cemented lens is made of glass material, and the surface type is a standard spherical lens.

[0015] Furthermore, the first cemented lens includes a first lens, a second lens and a third lens. The image side surface of the first lens is fixedly connected to the object side surface of the second lens, and the image side surface of the second lens is fixedly connected to the object side surface of the third lens.

[0016] Furthermore, the first lens and the second lens form a first cemented surface, and the radius of curvature of the first cemented surface is r 12 , the second lens and the third lens form a second cemented surface, and the radius of curvature of the second cemented surface is r 13 , satisfying the following relationship: -50 mm ≤ r 12 ≤ -20 mm, -50 mm ≤ r 13 ≤ -20 mm.

[0017] Furthermore, the refractive index of the first lens is n 1 , the radius of curvature of the object side surface of the first lens is r 11 , the refractive index of the second lens is n 2 , the refractive index of the third lens is n 3 , the radius of curvature of the image side surface of the third lens is r 14 ’, satisfying the following relationship: .

[0018] Furthermore, the first lens is a biconvex lens, the second lens is a concave-convex lens, and the third lens is a concave-convex lens; The refractive index of the first lens is n 1 , the refractive index of the second lens is n 2 , the refractive index of the third lens is n 3 , satisfying the following relationship: 1.4 ≤ n 1 ≤ 1.6, 1.8 ≤ n 2 ≤ 2, 1.5 ≤ n 3 ≤ 1.7.

[0019] Furthermore, the Abbe number of the first lens is v1 The Abbe number of the second lens is v 2 The Abbe number of the third lens is v 3 satisfying the following relationship: 50 ≤ v 1 ≤ 70, 15 ≤ v 2 ≤ 35, 35 ≤ v 3 ≤ 55.

[0020] Furthermore, the second cemented lens includes a fourth lens and a fifth lens, and the image side of the fourth lens is fixedly connected to the object side of the fifth lens; The fourth lens is a biconvex lens, the fifth lens is a biconcave lens, and the fourth lens and the fifth lens form a third cemented surface, and the radius of curvature of the third cemented surface is r 22 satisfying the following relationship: -650 mm ≤ r 22 ≤ -450 mm.

[0021] Furthermore, the refractive index of the fourth lens is n 4 and the refractive index of the fifth lens is n 5 satisfying the following relationship: 1.65 ≤ n 4 ≤ 1.85, 1.6 ≤ n 5 ≤ 1.8; Furthermore, the Abbe number of the fourth lens is v 4 and the Abbe number of the fifth lens is v 5 satisfying the following relationship: 40 ≤ v 5 ≤ 60, 25 ≤ v 5 ≤ 45.

[0022] The radius of curvature of the object side of the fourth lens is r 21 and the radius of curvature of the image side of the fifth lens is r 23 ', satisfying the following relationship: .

[0023] Furthermore, the working wavelength range of the barrel lens is between 486 nm and 660 nm.

[0024] In a second aspect, the present invention further provides an imaging system, specifically including: An entrance pupil; A barrel lens for microscopic imaging as described above; and an image plane; The entrance pupil, the barrel lens, and the image plane are arranged in sequence along the principal optical axis; The optical interval between the entrance pupil and the first cemented lens is 130 mm - 170 mm, and the optical interval between the second cemented lens and the image plane is 80 mm - 120 mm.

[0025] The barrel lens for microscopic imaging and the imaging system provided by the present invention have at least the following beneficial effects: The present invention uses two groups of cemented lenses, and sets the optical power type, optical interval, and focal length ratio range of the two groups of cemented lenses, so that the Petzval sum of the overall barrel lens structure approaches zero, reduces field curvature, and effectively improves the propagation path of the light entering the barrel lens, reducing distortion. At the same time, only two groups of cemented lenses also improve the efficiency of the barrel lens and reduce the processing and assembly difficulty of the barrel lens. Brief Description of the Drawings

[0026] Figure 1 Schematic diagram of a barrel lens structure for microscopic imaging provided by the present invention; Figure 2 Schematic diagram of the first cemented lens in the barrel lens for microscopic imaging according to the first embodiment provided by the present invention; Figure 3 Schematic diagram of the second cemented lens in the barrel lens for microscopic imaging according to the second embodiment provided by the present invention; Figure 4 Schematic diagram of the first cemented lens in the barrel lens for microscopic imaging according to the third embodiment provided by the present invention; Figure 5 Schematic diagram of the second cemented lens in the barrel lens for microscopic imaging according to the fourth embodiment provided by the present invention; Figure 6 Schematic diagram of a barrel lens structure for microscopic imaging according to the fifth embodiment provided by the present invention; Figure 7a Light fan diagrams of the barrel lens according to the fifth embodiment of the present invention at different wavelengths in the 0-degree field of view; Figure 7b Light fan diagrams of the barrel lens according to the fifth embodiment of the present invention at different wavelengths in the 1-degree field of view; Figure 7c Light fan diagrams of the barrel lens according to the fifth embodiment of the present invention at different wavelengths in the 2.45-degree field of view; Figure 7d Light fan diagrams of the barrel lens according to the fifth embodiment of the present invention at different wavelengths in the 3.5-degree field of view; Figure 8 Field curvature diagrams and distortion diagrams of the barrel lens according to the fifth embodiment of the present invention at different wavelengths; Figure 9 Modulation transfer function diagrams of the Fourier transform of the barrel lens according to the fifth embodiment of the present invention at different wavelengths; Figure 10 Image plane illuminance diagram of the barrel lens according to the fifth embodiment of the present invention when the working wavelength is 587.6 nm; Figure 11 Spot diagrams of the barrel lens according to the fifth embodiment of the present invention at different wavelengths; Figure 12 Schematic diagram of the structure of an imaging system provided by the present invention.

[0027] Description of reference numerals: 10 - entrance pupil; 20 - first cemented lens; 201 - first lens; 201 - first lens; 202 - second lens; 203 - third lens; 30 - second cemented lens; 301 - fourth lens; 302 - fifth lens; 40 - image plane. Detailed implementation manners

[0028] In order to better understand the above technical solution, the above technical solution will be described in detail below in conjunction with the accompanying drawings of the specification and specific implementation manners. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0029] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. The singular forms "a", "the" and "said" used in the embodiments of the present invention and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise. "Plurality" generally includes at least two.

[0030] It should also be noted that the term "comprising", "including" or any other variant thereof is intended to cover a non-exclusive inclusion, so that a commodity or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such commodity or device. Without further limitation, the element defined by the statement "including one..." does not exclude the existence of another identical element in the commodity or device including the said element.

[0031] In the present invention, the surface of each lens close to the object side is the object side surface of the lens, and the surface of each lens close to the image side is called the image side surface of the lens. The positive and negative of the r value (r refers to the radius of curvature, usually the Radius value in the lens database (lensdata) of optical software) is used to judge the convexity and concavity. For the object side surface, when the r value is positive, it is judged as a convex surface, and when the r value is negative, it is judged as a concave surface; for the image side surface, when the r value is positive, it is judged as a concave surface, and when the r value is negative, it is judged as a convex surface.

[0032] The current design of the tube lens for microscopic imaging is mainly to overcome problems such as small entrance pupil diameter, small detection range, large field curvature, and large distortion. The multi-group and multi-piece method is generally adopted. This multi-group and multi-piece method can theoretically control the aberration of the tube lens to a very small degree, and can also achieve a large field of view, small field curvature, and small distortion of the tube lens imaging. However, the multi-group and multi-piece method will lead to a decrease in the efficiency of the tube lens, increase the difficulty of assembling and debugging the tube lens, and increase the manufacturing cost of the tube lens.

[0033] In order to improve the light processing efficiency of the barrel lens as an optical system, reduce costs, and the difficulty of process assembly, it is necessary to simplify the barrel lens design as much as possible, reduce the light absorption of the barrel lens, and improve the transmission efficiency of light passing through the barrel lens. Of course, while simplifying the barrel lens design, it is also necessary to design the lens parameters of the simplified barrel lens to simultaneously solve problems such as large field curvature and large distortion existing in conventional barrel lenses.

[0034] Thus, as Figure 1 shown, the present invention provides a barrel lens for microscopic imaging, specifically including: a first cemented lens 20 and a second cemented lens 30 arranged along the principal optical axis from the entrance pupil to the image plane; The first cemented lens 20 has a positive optical power, and the second cemented lens 30 has a negative optical power; The optical interval between the first cemented lens 20 and the second cemented lens 30 is 0.1 mm - 1 mm; The focal length of the first cemented lens 20 is f 1 , and the focal length of the second cemented lens 30 is f 2 , satisfying the following relationship: 6 ≤ |f 2 / f 1 | ≤ 8.

[0035] The focal length can determine the focal position where light converges after passing through a lens (or a lens group). The optical power is the reciprocal of the focal length of the lens, indicating the ability of the lens to converge or diverge light. A positive optical power indicates that the lens has a converging effect on light, and a negative optical power indicates that the lens has a diverging effect on light. The first cemented lens having a positive optical power means that the overall effect exhibited by the first cemented lens is to converge light. The second cemented lens having a negative optical power means that the overall effect exhibited by the second cemented lens is to diverge light. That is, the light entering the barrel lens is first converged by the first cemented lens, and then the converged light is moderately diverged by the second cemented lens, finally achieving imaging.

[0036] The first cemented lens is composed of at least two lenses combined. Similarly, the second cemented lens is also composed of at least two lenses combined. The convex and concave types of each lens in the first cemented lens and the second cemented lens can be reasonably set according to different application scenarios. Of course, for the setting of the convex and concave types of each lens, it is also necessary to consider parameter values such as the focal length, refractive index, and curvature radius of each lens set, thereby achieving the purpose of balancing factors such as the efficiency of the barrel lens and the field curvature and distortion of the barrel lens imaging.

[0037] Through the combined design of the first cemented lens and the second cemented lens, the Petzval sum is cancelled out, and the Petzval sum of the overall barrel lens can be made to approach zero, effectively reducing the field curvature.

[0038] The optical interval between the first cemented lens and the second cemented lens refers to the distance between the image-side focal point of the first cemented lens and the object-side focal point of the second cemented lens. Adjusting the optical interval between the first cemented lens and the second cemented lens to an appropriate range can effectively improve the propagation path of the light entering the barrel lens and reduce distortion.

[0039] For the barrel lens formed by the first cemented lens and the second cemented lens, it is necessary to satisfy that the converging effect of the positive optical power is greater than the diverging effect of the negative optical power in order to continue to maintain the positive optical power of the barrel lens and finally achieve the formation of a real image.

[0040] For Figure 1 the barrel lens structure, the optical interval between the first cemented lens 20 and the second cemented lens 30 is 0.1 mm - 1 mm, the focal length of the first cemented lens 20 is f 1 , and the focal length of the second cemented lens 30 is f 2 , satisfying the following relationship: 6 ≤ |f 2 / f 1 | ≤ 8. For the settings of the optical interval between the first cemented lens and the second cemented lens, as well as the focal lengths of the first cemented lens and the second cemented lens, there are the following effects: First, spherical aberration can be effectively corrected through spherical aberration compensation, making the imaging clearer; second, a wider field of view can be achieved to meet more application scenarios; third, macro imaging can be achieved to capture tiny details.

[0041] For the range of the optical interval between the first cemented lens and the second cemented lens, if the optical interval is too large (for example, exceeding 1 mm), the optical aberration of the barrel lens will increase significantly, and the modulation transfer function curve will drop significantly, which will not only affect the magnification and field of view of the imaging, but also reduce the light utilization rate, resulting in a decrease in the imaging quality. Moreover, if the optical interval is too large, the overall stability of the barrel lens will also be reduced; if the optical interval is too small (for example, close to the fitting state), it will cause interference when the light propagates between the first cemented lens and the second cemented lens, increasing the aberration, and the light will also be reflected multiple times during propagation, affecting the light utilization rate. Furthermore, if the optical interval is too small, the thermal expansion between the lenses may affect each other, thereby reducing the thermal stability of the barrel lens.

[0042] When the ratio f 2 / f 1 of the focal lengths of the second cemented lens and the first cemented lens does not satisfy the range of 6 - 8, it will also cause a significant increase in the optical aberration of the barrel lens, a significant drop in the modulation transfer function curve, and when the ratio f 2 / f 1 is too large, the diverging effect of the second cemented lens on the light is weak, and it cannot effectively compensate for the converging effect of the first cemented lens, resulting in inaccurate focusing of the light and blurred imaging; f 2 / f1 If the ratio is too small, the diverging effect of the second cemented lens on light will be too strong, which may cause the light to fail to focus and form a virtual image.

[0043] Preferably, the optical interval between the first cemented lens 20 and the second cemented lens 30 is 0.1 mm - 0.5 mm.

[0044] The present invention uses two groups of cemented lenses, and sets the optical power type, optical interval, and focal length ratio range of the two groups of cemented lenses, so that the Petzval sum of the overall barrel lens structure approaches zero, reduces field curvature, and effectively improves the propagation path of the light entering the barrel lens, reducing distortion. At the same time, only two groups of cemented lenses also improve the light processing efficiency of the barrel lens as an optical system and reduce the processing and assembly difficulty of the barrel lens.

[0045] Preferably, the focal length of the barrel lens is f, and 120 mm ≤ f ≤ 160 mm. The focal length of the barrel lens is inversely proportional to the field angle of view of the barrel lens, that is, the smaller the focal length of the barrel lens, the larger the field angle of view of the barrel lens; the larger the focal length of the barrel lens, the smaller the field angle of view of the barrel lens. The field angle of view of the barrel lens refers to the angle of the spatial range that the barrel lens can capture. Only by increasing the field angle of view of the barrel lens can the barrel lens capture a wider scene. Therefore, the focal length of the barrel lens given in the present invention is set within a smaller range, which can effectively increase the detection range of the barrel lens.

[0046] As Figure 2 shown, in the first embodiment, in the barrel lens formed by the combination of the first cemented lens 20 and the second cemented lens 30, the curvature radius of the object side surface of the first cemented lens 20 is r 1 , and the curvature radius of the image side surface of the first cemented lens 20 is r 1 ', and the following relationship is satisfied: 100 mm ≤ r 1 ≤ 150 mm, -150 mm ≤ r 1 ' ≤ -100 mm.

[0047] The curvature radius of the object side surface refers to the surface curvature radius of the lens close to the entrance pupil side, and the curvature radius of the image side surface refers to the surface curvature radius of the lens close to the image plane side.

[0048] Both the curvature radius of the object side surface of the first cemented lens and the curvature radius of the image side surface of the first cemented lens need to be set within a reasonable range. If they are too large or too small, it will affect the clarity of the final image and even cause distortion.

[0049] As Figure 3 shown, in the second embodiment, in the barrel lens formed by the combination of the first cemented lens 20 and the second cemented lens 30, the curvature radius of the object side surface of the second cemented lens 30 is r 2 , and the curvature radius of the image side surface of the second cemented lens 30 is r 2’ satisfies the following relationship: 20 mm ≤ r 2 ≤ 60 mm, 10 mm ≤ r 2 ’ ≤ 50 mm.

[0050] The curvature radius of the object side surface of the second cemented lens and the curvature radius of the image side surface of the second cemented lens both need to be set within a reasonable range. If they are too large or too small, it will affect the clarity of the final image and even cause distortion.

[0051] As Figure 4 shown, in the third embodiment, in the barrel lens formed by the combination of the first cemented lens 20 and the second cemented lens 30, the first cemented lens 20 includes a first lens 201, a second lens 202, and a third lens 203. The image side surface of the first lens 201 is fixedly connected to the object side surface of the second lens 202, and the image side surface of the second lens 202 is fixedly connected to the object side surface of the third lens 203.

[0052] The object side surface refers to the surface of the lens close to the entrance pupil, and the image side surface refers to the surface of the lens close to the image plane.

[0053] The first cemented lens formed by three lenses and two cemented surfaces can not only complement each other's spherical aberration, optimize the light propagation path, and improve the imaging clarity, but also ensure a compact structural design and improve the light utilization efficiency.

[0054] Preferably, the first lens 201 and the second lens 202 form a first cemented surface, and the curvature radius of the first cemented surface is r 12 , the second lens 202 and the third lens 203 form a second cemented surface, and the curvature radius of the second cemented surface is r 13 , satisfying the following relationship: -50 mm ≤ r 12 ≤ -20 mm, -50 mm ≤ r 13 ≤ -20 mm.

[0055] The cemented surface refers to the contact surface when adjacent lenses are bonded together with optical glue. The curvature radius of the cemented surface refers to the curvature radius of the contact surface. Here, the curvature radii of the first cemented surface and the second cemented surface are represented by the curvature radius of the object side surface of the latter lens.

[0056] Preferably, the curvature radii of the first cemented surface and the second cemented surface are the same.

[0057] Meanwhile, if the radius of curvature (absolute value) of the gluing surface is too large, it means that the gluing surface is relatively flat. An overly flat gluing surface has a poor diopter effect. When optimizing the aberration of the barrel lens system, more lens optical surfaces are required to undertake the optimization and distribution of aberration, which is not conducive to the simplification of the barrel lens system. If the radius of curvature of the gluing surface is too small (too concave or too convex), when light passes through these overly convex or concave surface shapes, it will increase the optical incident angle on each lens optical surface, which is not conducive to the smooth transition of light and aberration optimization. At the same time, overly convex or concave optical surfaces also increase the difficulty of processing, assembly and debugging.

[0058] Preferably, the refractive index of the first lens 201 is n 1 , the radius of curvature of the object side surface of the first lens 201 is r 11 , the refractive index of the second lens 202 is n 2 , the refractive index of the third lens 203 is n 3 , the radius of curvature of the image side surface of the third lens 203 is r 14 ’, and the following relationship is satisfied: .

[0059] The optical power of the first cemented lens is composed of the optical power Ф 1 of the first lens, the optical power Ф 2 of the second lens, and the optical power Ф 3 of the third lens. It needs to satisfy Ф 1 + Ф 2 + Ф 3 > 0. For the optical power of a lens, it is the reciprocal of the lens focal length and is also related to the lens refractive index and the curvature radius of each side surface of the lens. Therefore, for the first cemented lens composed of the first lens, the second lens, and the third lens, the lens refractive index and the curvature radius of each lens side surface of each lens should satisfy the following relationship: .

[0060] As a preferred solution of the third embodiment, the first lens can be set as a biconvex lens, the second lens can be set as a convex-concave lens, and the third lens can be set as a convex-concave lens, and the curvature radius, refractive index, etc. of each surface of the first lens, the second lens, and the third lens satisfy the above corresponding relationships. The first cemented lens is optimized by a combination of a biconvex lens, a convex-concave lens, and a convex-concave lens, which can well distribute the optical power and aberration to each lens, facilitating the design and processing of the lens.

[0061] In the preferred solution of the third embodiment, the value range of the refractive index of the first lens, the second lens, and the third lens can also be limited to cooperate with the curvature radius of each lens side surface to realize the function of the first cemented lens.

[0062] Among them, the refractive index of the first lens is n1 The refractive index of the second lens is n 2 The refractive index of the third lens is n 3 Satisfying the following relationship: 1.4 ≤ n 1 ≤ 1.6, 1.8 ≤ n 2 ≤ 2, 1.5 ≤ n 3 ≤ 1.7

[0063] The Abbe number of the first lens is v 1 The Abbe number of the second lens is v 2 The Abbe number of the third lens is v 3 Satisfying the following relationship: 50 ≤ v 1 ≤ 70, 15 ≤ v 2 ≤ 35, 35 ≤ v 3 ≤ 55

[0064] For example, when the refractive indices of the first lens, the second lens, and the third lens are too small, it will affect the converging effect of light passing through the barrel lens system, resulting in complete divergence, inability to focus on the image plane, and inability to perform imaging

[0065] However, when the refractive indices of the first lens, the second lens, and the third lens are too large, it will cause the light to be quickly focused, greatly reducing the back focal plane focusing force, which is not conducive to the integrated use of the barrel lens system

[0066] Lenses with too small Abbe numbers will cause obvious dispersion phenomena, with colored fringes appearing at the imaging edges, affecting visual clarity; lenses with high Abbe numbers perform better in imaging quality, but materials with high Abbe numbers usually have lower refractive indices, which means that when designing and manufacturing lenses, different materials need to be selected or the lens shape needs to be optimized to achieve the required optical performance. Therefore, setting the Abbe numbers and refractive indices of the three lenses in the first cemented lens within a reasonable range can not only meet the imaging quality requirements but also reduce the difficulty of processing, assembly, and debugging

[0067] As Figure 5 shown, in the fourth embodiment, in the barrel lens formed by combining the first cemented lens 20 and the second cemented lens 30, the second cemented lens 30 includes a fourth lens 301 and a fifth lens 302, and the image plane of the fourth lens 301 is fixedly connected to the object plane of the fifth lens 302

[0068] The second cemented lens formed by the two lenses can undertake partial optimization of aberrations. At the same time, the negative optical power makes the light have a certain diverging effect, which can make the light reach the image plane more smoothly. When the number of lens elements is too large, although it is beneficial to the optimization of aberrations, it will also increase the difficulty of design, processing, assembly, and debugging. If a single lens is used, there will be a problem of incomplete aberration optimization, reducing the imaging quality of the system

[0069] As a preferred solution of the fourth embodiment, the fourth lens 301 is a biconvex lens, the fifth lens 302 is a biconcave lens, and the fourth lens 301 and the fifth lens 302 form a third cemented surface, and the radius of curvature of the third cemented surface is r 22 , satisfying the following relationship: -650 mm ≤ r 22 ≤ -450 mm.

[0070] Similarly, here, the radius of curvature of the third cemented surface is represented by the radius of curvature of the object side surface of the latter lens. If the radius of curvature of the third cemented surface (in terms of absolute value) is too large, it means that the cemented surface is relatively flat. An overly flat cemented surface has a poor diopter effect. When optimizing the aberration of the barrel lens system, more lens optical surfaces are required to undertake the optimization and distribution of aberration, which is not conducive to the simplification of the barrel lens system. If the radius of curvature of the cemented surface is too small (too concave or too convex), when light passes through these overly convex or concave surface shapes, it will increase the optical incident angle on each lens optical surface, which is not conducive to the smooth transition of light and aberration optimization. At the same time, overly convex or concave optical surfaces also increase the difficulty of processing, assembly and debugging.

[0071] As a preferred solution of the fourth embodiment, the refractive index of the fourth lens 301 is n 4 , and the refractive index of the fifth lens 302 is n 5 , satisfying the following relationship: 1.65 ≤ n 4 ≤ 1.85, 1.6 ≤ n 5 ≤ 1.8.

[0072] The Abbe number of the fourth lens is v 4 , and the Abbe number of the fifth lens is v 5 , satisfying the following relationship: 40 ≤ v 5 ≤ 60, 25 ≤ v 5 ≤ 45.

[0073] For example, taking the case where the refractive indices of the fourth lens and the fifth lens are relatively small, it will make the focusing path of light longer after passing through the second cemented lens, increase the focal length ratio between the second cemented lens and the first cemented lens, increase the aberration of the barrel lens system, and the modulation transfer function curve cannot converge to the diffraction limit, greatly reducing the imaging quality.

[0074] Similar to the setting of the Abbe number and refractive index of the three lenses in the first cemented lens, setting the Abbe number and refractive index of the two lenses in the second cemented lens within a reasonable range can not only meet the imaging quality requirements but also reduce the difficulty of processing, assembly and debugging.

[0075] As a preferred solution of the fourth embodiment, the radius of curvature of the object side surface of the fourth lens 301 is r 21 , and the radius of curvature of the image side surface of the fifth lens 302 is r 23 ’, satisfying the following relationship: 。

[0076] The optical power of the second cemented lens is composed of the fourth lens Ф 4 and the fifth lens Ф 5 superimposed, and it is necessary to satisfy Ф 4 + Ф 5 < 0. For the optical power of a lens, it is the reciprocal of the focal length of the lens and is also related to the refractive index of the lens and the curvature radii of each side surface of the lens. Therefore, for the second cemented lens formed by cementing the fourth lens and the fifth lens, the refractive indices of the two lenses and the curvature radii of the side surfaces should satisfy the following relationship: 。

[0077] As Figure 6 shown, the fifth embodiment combines the solutions of the third embodiment and the fourth embodiment, that is, in the barrel lens formed by combining the first cemented lens 20 and the second cemented lens 30, the first cemented lens 20 includes the first lens 201, the second lens 202, and the third lens 203. The image surface of the first lens 201 is fixedly connected to the object surface of the second lens 202, and the image surface of the second lens 202 is fixedly connected to the object surface of the third lens 203. The second cemented lens 30 includes the fourth lens 301 and the fifth lens 302, and the image surface of the fourth lens 301 is fixedly connected to the object surface of the fifth lens 302.

[0078] As a preferred solution of the fifth embodiment, the curvature radius of the object side surface of the first cemented lens 20 is r 1 , and the curvature radius of the image side surface of the first cemented lens 20 is r 1 ', and they satisfy the following relationship: 100 mm ≤ r 1 ≤ 150 mm, -150 mm ≤ r 1 ' ≤ -100 mm.

[0079] The curvature radius of the object side surface of the second cemented lens 30 is r 2 , and the curvature radius of the image side surface of the second cemented lens 30 is r 2 ', and they satisfy the following relationship: 20 mm ≤ r 2 ≤ 60 mm, 10 mm ≤ r 2 ' ≤ 50 mm.

[0080] The first lens 201 and the second lens 202 form a first cemented surface, and the curvature radius of the first cemented surface is r 12 . The second lens 202 and the third lens 203 form a second cemented surface, and the curvature radius of the second cemented surface is r 13 , and they satisfy the following relationship: -50 mm ≤ r 12 ≤ -20 mm, -50 mm ≤ r 13 ≤ -20 mm.

[0081] Further, the refractive index of the first lens 201 is n 1 , the radius of curvature of the object side surface of the first lens 201 is r 11 , the refractive index of the second lens 202 is n 2 , the refractive index of the third lens 203 is n 3 , the radius of curvature of the image side surface of the third lens 203 is r 14 ’, and the following relationship is satisfied: .

[0082] Further, the first lens is set as a biconvex lens, the second lens is set as a concave-convex lens, the third lens is set as a concave-convex lens, and the radius of curvature, refractive index, etc. of each surface of the first lens, the second lens, and the third lens satisfy the above corresponding relationships.

[0083] Further, the refractive index of the first lens is n 1 , the refractive index of the second lens is n 2 , the refractive index of the third lens is n 3 , and the following relationship is satisfied: 1.4 ≤ n 1 ≤ 1.6, 1.8 ≤ n 2 ≤ 2, 1.5 ≤ n 3 ≤ 1.7.

[0084] The Abbe number of the first lens is v 1 , the Abbe number of the second lens is v 2 , the Abbe number of the third lens is v 3 , and the following relationship is satisfied: 50 ≤ v 1 ≤ 70, 15 ≤ v 2 ≤ 35, 35 ≤ v 3 ≤ 55.

[0085] As a preferred solution of the fifth embodiment, the fourth lens 301 is a biconvex lens, the fifth lens 302 is a biconcave lens, the fourth lens 301 and the fifth lens 302 form a third cemented surface, and the radius of curvature of the third cemented surface is r 22 , and the following relationship is satisfied: -650 mm ≤ r 22 ≤ -450 mm.

[0086] Further, the refractive index of the fourth lens 301 is n 4 , the refractive index of the fifth lens 302 is n 5 , and the following relationship is satisfied: 1.65 ≤ n 4 ≤ 1.85, 1.6 ≤ n 5 ≤ 1.8.

[0087] The Abbe number of the fourth lens is v 4, the Abbe number of the fifth lens is v 5 , satisfying the following relationship: 40 ≤ v 5 ≤ 60, 25 ≤ v 5 ≤ 45.

[0088] Furthermore, the object-side curvature radius of the fourth lens 301 is r 21 , and the image-side curvature radius of the fifth lens 302 is r 23 ’, satisfying the following relationship: .

[0089] In the fifth embodiment, the barrel lens is composed of a first cemented lens formed by stacking three lenses and a second cemented lens formed by stacking two lenses. By using two groups of cemented lens groups and a 3-piece lens for the first cemented lens, better aberration correction can be achieved. At the same time, when assembling and debugging, the first cemented lens is used as the reference lens, and the second cemented lens is used as the auxiliary lens to adapt to the first cemented lens for debugging, which also reduces the debugging difficulty of the entire barrel lens group.

[0090] Based on the analysis of the above embodiments, the barrel lens designed by the present invention is mainly for visible light. The following is the performance test of the barrel lens in the visible light band with a working wavelength range between 486nm - 660nm.

[0091] As Figure 7a , Figure 7b , Figure 7c , Figure 7d , Figure 8 , Figure 9 , Figure 10 , Figure 11 For the performance test of the barrel lens of the fifth embodiment as shown in Figure 6 . The performance test includes aberration, field curvature, distortion, resolution, illuminance, etc.

[0092] As Figure 7a , Figure 7b , Figure 7c , Figure 7dAs shown, the fan diagrams of light at different wavelengths (486nm, 588nm, 656nm) and different field regions under the tube lens structure of the fifth embodiment. In the fan diagram, the light ray profile of the meridian plane is the beam profile passing through the Y-axis of the pupil. The horizontal axis of the meridian plane represents the normalized pupil Y-axis coordinate (Py), and the vertical axis represents the Y-axis coordinate deviation (Ey) on the image plane; the sagittal plane is a plane perpendicular to the meridian plane, that is, the beam profile passing through the X-axis of the pupil. The horizontal axis of the sagittal plane represents the normalized pupil X-axis coordinate (Px), and the vertical axis represents the X-axis coordinate deviation (Ex) on the image plane. It can be found from the fan diagram that when the field of view is not greater than 1 degree, the aberration conditions at different wavelengths are not very different. However, when the field of view exceeds 1 degree, it has a certain impact on the light with a wavelength of 486nm, especially in the meridian plane.

[0093] Regarding the situation presented by the fan surface, further tests such as field curvature diagrams, distortion diagrams, and spot diagrams are carried out to analyze different wavelengths (486nm, 588nm, 656nm), different field regions, etc. It should be noted that since the tube lens structures given in the present invention are all rotationally symmetric, therefore, the field curvature, distortion, image plane illuminance, and spot diagrams are all studied by means of analyzing the performance of the semi-field of view.

[0094] As Figure 8 shown, on the left is the field curvature diagram for different wavelengths (486nm, 588nm, 656nm) under the tube lens structure of the fifth embodiment. Among them, the abscissa is the deviation, with the unit of μm, and the ordinate is the semi-field of view interval of the tube lens (the maximum field of view is 3.5 degrees). The solid lines from left to right are the meridional planes of 588nm, 486nm, and 656nm respectively, and the dashed lines from left to right are the sagittal planes of 588nm, 486nm, and 656nm respectively. The maximum deviation between the sagittal field curvature and the meridional field curvature is 7.4 μm, which is much smaller than the depth of focus of the tube lens structure. The field curvature under this deviation can be ignored. Among them, the depth of focus is the distance within which the image still remains within the allowable clarity range when the object moves along the optical axis within a certain range in the tube lens; the depth of focus is an important parameter for measuring the tolerance of the tube lens to changes in the object position.

[0095] The depth of focus is related to parameters such as the wavelength of light, the focal length of the tube lens, and the diameter of the entrance pupil. In the working wavelength bands of 588nm, 486nm, and 656nm, adopting the tube lens structure of the fifth embodiment of the present invention, the depth of focus is approximately several millimeters, which is much larger than the maximum deviation between the sagittal field curvature and the meridional field curvature. Therefore, for the above working wavelength bands, the tube lens structure given in the present invention can significantly reduce the field curvature.

[0096] In addition, from Figure 8It can also be seen that on the right side is the distortion diagram of the cylindrical lens structure in the fifth embodiment for different wavelengths (588nm, 486nm, 656nm). Among them, the abscissa is the percentage of distortion, and the ordinate is the half field of view interval of the cylindrical lens (the maximum field of view is 3.5 degrees). The 3 curves respectively represent the distortion diagrams of the cylindrical lens for the working wavelengths of 588nm, 486nm, and 656nm. The maximum distortion of the cylindrical lens appears at the edge position, and the maximum distortion percentage at this time is 0.0923%, which is less than 1%, meeting the requirements for designing the cylindrical lens and being applicable to high-precision measurements. Therefore, for the above working wavelengths, the cylindrical lens structure given by the present invention can significantly reduce distortion.

[0097] As Figure 9 shown, it is the modulation transfer function diagram of the Fourier transform of the cylindrical lens structure in the fifth embodiment for different wavelengths (588nm, 486nm, 656nm). Among them, the abscissa is the spatial frequency, and the ordinate is the optical transfer function coefficient. It can be seen from the figure that whether it is the curve representing the meridional plane or the curve representing the sagittal plane, the modulation transfer functions at the three wavelengths all show a convergent state and reach the diffraction limit. That is to say, for the light in the working wavelength band that shows convergence and reaches the diffraction limit, a higher resolution can be achieved under this cylindrical lens structure.

[0098] As Figure 10 shown, it is the image plane illuminance diagram of the cylindrical lens structure in the fifth embodiment for the working wavelength of 587.6nm. Among them, the abscissa is the half field of view interval of the cylindrical lens (the maximum field of view is 3.5 degrees), and the ordinate is the relative illuminance. It can be seen from the figure that the relative illuminance at the edge position can also reach more than 98.9% of the central image plane illuminance. The relative illuminance of the cylindrical lens mainly reflects the distribution of light illumination in different field of view regions of the image plane after the light passes through the cylindrical lens for imaging, and reflects the attenuation degree of the illuminance under different fields of view. From Figure 10 the change of the relative illuminance in different fields of view, it can be shown that with the change of the field of view, there are also slight changes in the uniformity of the relative illuminance, but the changes are not significant, meeting the requirements for the imaging uniformity and quality of the large field of view.

[0099] As Figure 11 shown, it is the spot diagram of the cylindrical lens structure in the fifth embodiment for different wavelengths (588nm, 486nm, 656nm), that is, the diffusion situation of the light of different wavelengths passing through the entrance pupil of different field of view regions and converging to the image plane by the cylindrical lens. From Figure 11It can be seen that within the working wavelength range, the RMS radii of the central field spot and the marginal field spot can both reach within 1.92 μm. In the spot diagram, the RMS radius of the spot can be obtained by calculating the sum of the squares of the coordinates of each point in the spot relative to the reference center point, dividing by the number of points, and finally taking the square root. The RMS radius of the spot is used to evaluate the imaging quality. The smaller the RMS radius, the smaller the aberration of the tube lens and the closer the imaging is to the ideal state.

[0100] As Figure 12 shown, the present invention also provides an imaging system, specifically including: An entrance pupil; A tube lens for the above-mentioned microscopic imaging; And, an image plane; The entrance pupil, the tube lens and the image plane are sequentially arranged along the principal optical axis from the object side to the image side; The optical interval between the entrance pupil and the first cemented lens is 130 mm - 170 mm, and the optical interval between the second cemented lens and the image plane is 80 mm - 120 mm.

[0101] Among them, the tube lens for the above-mentioned microscopic imaging can be Figures 1 - 6 Any type of tube lens for microscopic imaging, not limited to Figure 11 the lens combination of this shape given.

[0102] A tube lens for microscopic imaging and an imaging system provided by the present invention have at least the following beneficial effects: The present invention adopts two groups of cemented lenses, and sets the optical power types, optical intervals and focal length ratio ranges of the two groups of cemented lenses, so that the Petzval sum of the overall tube lens structure approaches zero, reduces the field curvature, and effectively improves the propagation path of the light entering the tube lens, reducing the distortion. At the same time, only two groups of cemented lenses also improve the light processing efficiency of the tube lens as an optical system and reduce the processing and assembly difficulty of the tube lens.

[0103] Although the preferred embodiments of the present invention have been described, those skilled in the art can make additional changes and modifications to these embodiments once they know the basic creative concept. Therefore, the appended claims are intended to be construed to include the preferred embodiments and all changes and modifications falling within the scope of the present invention. Obviously, those skilled in the art can make various changes and variations to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention is also intended to include these modifications and variations.

Claims

1. A microscope for microscopic imaging, characterized in that: Specifically include: A first cemented lens and a second cemented lens arranged along the principal optical axis from the entrance pupil to the image plane; The first cemented lens has positive power, and the second cemented lens has negative power; The optical interval between the first cemented lens and the second cemented lens is 0.1mm-1mm; The focal length of the first cemented lens is f1, and the focal length of the second cemented lens is f2, satisfying the following relationship: 6≤|f2 / f1|≤8.

2. The microscope tube lens for microscopic imaging as claimed in claim 1, characterized in that: The focal length of the tube lens is f, 120mm≤f≤160mm.

3. The microscope tube lens for microscopic imaging as claimed in claim 1, characterized in that: The object side curvature radius of the first cemented lens is r1, and the image side curvature radius of the first cemented lens is r1', which satisfy the following relationship: 100mm≤r1≤150mm, -150mm≤r1'≤-100mm; The object side surface of the second cemented lens has a curvature radius of r2, and the image side surface of the second cemented lens has a curvature radius of r2', which satisfy the following relationship: 20mm≤r2≤60mm, 10mm≤r2'≤50mm.

4. The microscope tube according to any one of claims 1 to 3, characterized in that: The first cemented lens includes a first lens, a second lens and a third lens. The image side surface of the first lens is fixedly connected to the object side surface of the second lens, and the image side surface of the second lens is fixedly connected to the object side surface of the third lens.

5. The microscope tube lens for microscopic imaging as claimed in claim 4, characterized in that: The first lens and the second lens form a first bonding surface, and the curvature radius of the first bonding surface is r 12 , the second lens and the third lens form a second cemented surface, and the curvature radius of the second cemented surface is r 13 , satisfying the following relationship: -50mm≤r 12 ≤-20mm, -50mm≤r 13 ≤-20mm.

6. The microscope tube lens for microscopic imaging as claimed in claim 5, characterized in that: The refractive index of the first lens is n1, and the radius of curvature of the object side of the first lens is r 11 , the refractive index of the second lens is n2, the refractive index of the third lens is n3, and the radius of curvature of the image side of the third lens is r 14 ', satisfying the following relationship: 。 7. The microscope tube lens for microscopic imaging as claimed in claim 4, characterized in that: The first lens is a biconvex lens, the second lens is a concave-convex lens, and the third lens is a concave-convex lens; The refractive index of the first lens is n1, the refractive index of the second lens is n2, and the refractive index of the third lens is n3, satisfying the following relationship: 1.4≤n1≤1.6, 1.8≤n2≤2, 1.5≤n3≤1.

7.

8. The microscope tube lens according to any one of claims 1 to 3, characterized in that: The second cemented lens includes a fourth lens and a fifth lens, wherein the image side surface of the fourth lens is fixedly connected to the object side surface of the fifth lens; The fourth lens is a biconvex lens, the fifth lens is a biconcave lens, the fourth lens and the fifth lens form a third cemented surface, and the curvature radius of the third cemented surface is r 22 , satisfying the following relationship: -650mm≤r 22 ≤-450mm.

9. The microscope tube lens for microscopic imaging as claimed in claim 8, characterized in that: The refractive index of the fourth lens is n4, and the refractive index of the fifth lens is n5, satisfying the following relationship: 1.65≤n4≤1.85, 1.6≤n5≤1.8; The radius of curvature of the object side of the fourth lens is r 21 , the image side curvature radius of the fifth lens is r 23 ', satisfying the following relationship: 。 10. An imaging system, characterized in that it specifically comprises: Enter the pupil; A microscope tube for microscopic imaging as claimed in any one of claims 1 to 9; and, image surface; The entrance pupil, the tube lens and the image plane are arranged in sequence along the principal optical axis; The optical distance between the entrance pupil and the first cemented lens is 130mm-170mm, and the optical distance between the second cemented lens and the image plane is 80mm-120mm.

Images