A low distortion tube lens and microscope system

Abstract

The present disclosure discloses a low-distortion tube lens and a microscope system. The low-distortion tube lens includes: a first lens, a second lens, a third lens, a fourth lens and a fifth lens arranged in sequence along the optical axis, wherein the first lens is a biconvex lens and satisfies 0.89≤f1 / f≤1.09; the second lens is a biconvex lens and satisfies 0.40≤f2 / f≤0.49; the third lens is a biconcave lens and satisfies ‑0.45≤f3 / f≤‑0.37; the fourth lens is a biconvex lens and satisfies 0.36≤f4 / f≤0.44; the fifth lens is a biconcave lens, the fifth lens is glued with the fourth lens, and satisfies ‑0.33≤f5 / f≤‑0.27. Through the scheme of the embodiment of the present disclosure, the degree of distortion of the low-distortion tube lens during imaging can be reduced, and the chromatic aberration in the optical system can be effectively eliminated, thereby improving the imaging quality of the tube lens.

Description

Technical Field

[0001] The present disclosure generally relates to the field of optical lens technology. More specifically, the present disclosure relates to a low-distortion tube lens and a microscope system. Background Art

[0002] With the continuous development of technology in the semiconductor industry, the requirements for the detection accuracy of wafers and semiconductor chips are also increasing. Especially for wafer products after photolithography, the detection of surface defects is particularly critical. In modern semiconductor manufacturing technology, the etching process can achieve extremely high precision to meet the needs of high-density, high-performance integrated circuits.

[0003] Since the surface of the wafer product is etched to form a complex and fine chip pattern, any tiny defect may cause the failure of the final product. In addition, the dimensional accuracy of these patterns can reach the nanometer level. This leads to modern semiconductor processes placing higher requirements on the anti-distortion performance of the lens used for surface defect detection.

[0004] In view of this, there is an urgent need to provide a low-distortion tube lens solution to reduce the degree of distortion during imaging of the optical system, thereby meeting the requirements of modern semiconductor processes for surface defect detection imaging quality. Summary of the invention

[0005] In order to at least solve one or more of the technical problems mentioned above, the present disclosure proposes a low-distortion tube lens solution in multiple aspects.

[0006] In a first aspect, the present disclosure provides a low-distortion tube lens comprising: a first lens, a second lens, a third lens, a fourth lens and a fifth lens arranged in sequence along an optical axis, wherein the first lens is a biconvex lens and satisfies 0.89≤f1 / f≤1.09, f1 represents the focal length of the first lens, and f represents the total focal length of the low-distortion tube lens; the second lens is a biconvex lens and satisfies 0.40≤f2 / f≤0.49, f2 represents the focal length of the second lens; the third lens is a biconcave lens and satisfies -0.45≤f3 / f≤-0.37, f3 represents the focal length of the third lens; the fourth lens is a biconvex lens and satisfies 0.36≤f4 / f≤0.44, f4 represents the focal length of the fourth lens; the fifth lens is a biconcave lens, the fifth lens is glued to the fourth lens, and satisfies -0.33≤f5 / f≤-0.27, and f5 represents the focal length of the fifth lens.

[0007] In some embodiments, an absolute value of the optical power of any one of the first lens, the second lens, the third lens, the fourth lens, and the fifth lens is between 0.20 and 1.00.

[0008] In some embodiments, the low distortion tube lens satisfies the following conditions: 0.81D≤φ1≤1.00D; 0.41D≤φ2≤0.49D; -0.50D≤φ3≤-0.40D; 0.32D≤φ4≤0.48D; -0.35D≤φ5≤-0.25D; wherein φ1 represents the optical focal length of the first lens, φ2 represents the optical focal length of the second lens, φ3 represents the optical focal length of the third lens, φ4 represents the optical focal length of the fourth lens, and φ5 represents the optical focal length of the fifth lens.

[0009] In some embodiments, the low distortion tube lens satisfies at least one of the following conditions: 0.45≤BFL / f≤0.55; 0.40≤TTL / f≤0.48; 1.03≤BFL / TTL≤1.25; wherein BFL represents the optical back focal length of the low distortion tube lens, and TTL represents the total lens length of the low distortion tube lens.

[0010] In some embodiments, the low distortion tube lens satisfies the following conditions: the range of the radius of curvature of the object side surface of the first lens is [430.00mm, 545.00mm], and the range of the radius of curvature of the image side surface is [-360.00mm, -300.00mm]; the range of the radius of curvature of the object side surface of the second lens is [90.00mm, 125.00mm], and the range of the radius of curvature of the image side surface is [-260.00mm, -200.00mm]; the range of the radius of curvature of the object side surface of the third lens is [-250.00 The range of the radius of curvature of the object side of the fourth lens is [110.00mm, 190.00mm], and the range of the radius of curvature of the image side is [-180.00mm, -240.00mm]; the range of the radius of curvature of the object side of the fifth lens is [-180.00mm, -240.00mm], and the range of the radius of curvature of the image side is [65.00mm, 88.00mm].

[0011] In some embodiments, the low distortion tube lens satisfies the following conditions: the center thickness of the first lens is in the range of [31.50mm, 38.50mm]; the distance from the image side surface of the first lens to the object side surface of the second lens is in the range of [6.20mm, 19.40mm]; the center thickness of the second lens is in the range of [23.00mm, 33.00mm]; the distance from the image side surface of the second lens to the object side surface of the third lens is in the range of [2.60mm, 3.70mm]; the center thickness of the third lens is in the range of [8.20mm, 15.00mm]; the distance from the image side surface of the third lens to the object side surface of the fourth lens is in the range of [18.50mm, 23.70mm]; the center thickness of the fourth lens is in the range of [18.00mm, 23.70mm]; the center thickness of the fifth lens is in the range of [7.20mm, 15.50mm].

[0012] In some embodiments, the low distortion tube lens satisfies the following conditions: 1.40<n1<1.80, 51.00<v1<66.00; 1.30<n2<1.80, 73.00<v2<87.00; 1.50<n3<2.10, 20.00<v3<29.00; 1.64<n4<3.28, 13.00<v4<21.00; 1.50<n5<2.10, 2 0.00<v5<29.00; wherein n1 represents the refractive index of the first lens, v1 represents the Abbe number of the first lens, n2 represents the refractive index of the second lens, v2 represents the Abbe number of the second lens, n3 represents the refractive index of the third lens, v3 represents the Abbe number of the third lens, n4 represents the refractive index of the fourth lens, v4 represents the Abbe number of the fourth lens, n5 represents the refractive index of the fifth lens, v5 represents the Abbe number of the fifth lens.

[0013] In some embodiments, the working distance of the low distortion tube lens ranges from [441 mm, 539 mm].

[0014] In some embodiments, the third lens and the fifth lens are made of the same or different materials.

[0015] In a second aspect, the present disclosure provides a microscope system comprising: a low-distortion tube lens as in any one of the first aspect; and a microscope objective lens, whose optical axis coincides with the optical axis of the low-distortion tube lens, and the distance between the microscope objective lens and the fifth lens is greater than the distance between the microscope objective lens and the first lens.

[0016] Through the low-distortion tube lens provided as above, the disclosed embodiment adopts a double convex lens design for the first lens, the second lens and the fourth lens, and combines the focal length distribution design of the first lens to the fifth lens to enhance the anti-distortion performance of the low-distortion tube lens. At the same time, gluing the fourth lens and the fifth lens is beneficial to eliminate chromatic aberration, and can reduce the difficulty of installation and debugging of the entire low-distortion tube lens, improve the adjustment accuracy, and further improve the optical performance of the low-distortion tube lens. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] By reading the detailed description below with reference to the accompanying drawings, the above and other objects, features and advantages of the exemplary embodiments of the present disclosure will become readily understood. In the accompanying drawings, several embodiments of the present disclosure are shown in an exemplary and non-limiting manner, and the same or corresponding reference numerals represent the same or corresponding parts, wherein:

[0018] Figure 1 An exemplary structural diagram of a low-distortion tube lens according to some embodiments of the present disclosure is shown;

[0019] Figure 2 shows a spot diagram of a low-distortion tube lens of some embodiments of the present disclosure;

[0020] Figure 3 shows a distortion diagram of a low-distortion tube lens of some embodiments of the present disclosure;

[0021] Figure 4 The distortion diagrams of low-distortion tube lenses of other embodiments of the present disclosure are shown;

[0022] Figure 5 A schematic diagram showing the MTF of a low-distortion tube lens according to some embodiments of the present disclosure is shown;

[0023] Figure 6 An exemplary structural diagram of a microscopy system according to some embodiments of the present disclosure is shown. DETAILED DESCRIPTION

[0024] The following will be combined with the drawings in the embodiments of the present disclosure to clearly and completely describe the technical solutions in the embodiments of the present disclosure. Obviously, the described embodiments are part of the embodiments of the present disclosure, not all of the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present disclosure.

[0025] It should be understood that the terms "include" and "comprising" used in the specification and claims of the present disclosure indicate the presence of described features, integers, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or collections thereof.

[0026] It should also be understood that the terms used in this disclosure are only for the purpose of describing specific embodiments and are not intended to limit the disclosure. As used in this disclosure and claims, the singular forms of "a", "an", and "the" are intended to include the plural forms unless the context clearly indicates otherwise. It should also be further understood that the term "and / or" used in this disclosure and claims refers to any combination of one or more of the associated listed items and all possible combinations, including these combinations.

[0027] As used in this specification and claims, the term "if" can be interpreted as "when" or "upon" or "in response to determining" or "in response to detecting," depending on the context. Similarly, the phrases "if it is determined" or "if [described condition or event] is detected" can be interpreted as meaning "upon determination" or "in response to determining" or "upon detection of [described condition or event]" or "in response to detecting [described condition or event]," depending on the context.

[0028] The specific implementation of the present disclosure is described in detail below with reference to the accompanying drawings.

[0029] Exemplary application scenarios

[0030] Wafer surface defect detection is one of the key links in the semiconductor manufacturing process. Its purpose is to ensure the quality of the wafer surface, thereby improving the reliability and performance of the final product. With the continuous development of semiconductor technology, wafer surface defect detection technology is also constantly improving, especially for high-density, high-performance integrated circuits, because the surface of the wafer used is etched to form a complex and fine pattern, and the dimensional accuracy of the pattern can reach the nanometer level, which puts higher requirements on the optical performance of the detection lens during surface defect detection.

[0031] High-quality detection imaging can ensure that the defect information in the detection image is clearer and more accurate, which is convenient for subsequent image processing and analysis algorithms to identify and classify defects. If the imaging quality is poor, problems such as blur, distortion and noise may appear in the detection image. For high-precision etching patterns, these problems will interfere with the accuracy of defect detection. In the detection of etching patterns on the surface of the wafer, the position of the defect needs to be accurately located for subsequent repair or classification operations. Distortion will cause a deviation between the actual position of the defect and the detected position. Distortion will also change the shape of the detected pattern, making some originally clearly identifiable defects blurred or deformed, thereby affecting the accuracy of the detection results.

[0032] Exemplary Application Scenarios

[0033] In view of this, the disclosed embodiment provides a low-distortion tube lens solution, which can reduce the degree of distortion of the tube lens during imaging and effectively eliminate chromatic aberration in the optical system through reasonable lens surface design and focal length distribution design, thereby improving the imaging quality of the tube lens.

[0034] Figure 1 An exemplary structural diagram of a low-distortion tube lens according to some embodiments of the present disclosure is shown. Figure 1 As shown, the low-distortion tube lens in the disclosed embodiment includes the following five lenses: a first lens 11, a second lens 12, a third lens 13, a fourth lens 14 and a fifth lens 15. The first lens 11, the second lens 12, the third lens 13, the fourth lens 14 and the fifth lens 15 are arranged in sequence along the optical axis, and the first lens 11 is located on the light-entering side of the low-distortion tube lens, and the fifth lens 15 is located on the light-exiting side of the low-distortion tube lens. In other words, when the above-mentioned low-distortion tube lens is used for imaging, light enters the low-distortion tube lens through the first lens 11, passes through the second lens 12, the third lens 13 and the fourth lens 14 in sequence, and finally exits the low-distortion tube lens through the fifth lens 15.

[0035] Furthermore, in the low-distortion tube lens shown in the embodiment of the present disclosure, the first lens 11 is a biconvex lens, the second lens 12 is a biconvex lens, the third lens 13 is a biconcave lens, the fourth lens 14 is a biconvex lens, and the fifth lens 15 is a biconcave lens. Compared with the surface design using a meniscus lens, the first lens 11, the second lens 12 and the fourth lens 14 have more advantages in eliminating the distortion of the optical system by adopting the surface design of a biconvex lens, that is, they can achieve a better distortion elimination effect.

[0036] Furthermore, in the low-distortion tube lens shown in the embodiment of the present disclosure, the fourth lens 14 and the fifth lens 15 are glued together to form a glued lens. The design of the glued lens is conducive to achromatization, and reduces the difficulty of installation and debugging of the low-distortion tube lens, making it easy to improve the installation and adjustment accuracy and reduce the tolerance.

[0037] In addition to the above-mentioned surface design, the disclosed embodiment also designs the focal length distribution in the low-distortion tube lens to further improve the anti-distortion performance of the entire low-distortion tube lens and reduce the degree of distortion during imaging of the optical system.

[0038] Specifically, in the low-distortion tube lens shown in the embodiment of the present disclosure, the focal length of each lens satisfies the following conditions:

[0039] 0.89≤f1 / f≤1.09;

[0040] 0.40≤f2 / f≤0.49;

[0041] -0.45≤f3 / f≤-0.37;

[0042] 0.36≤f4 / f≤0.44;

[0043] -0.33≤f5 / f≤-0.27;

[0044] Among them, f1 represents the focal length of the first lens 11, f2 represents the focal length of the second lens 12, f3 represents the focal length of the third lens 13, f4 represents the focal length of the fourth lens 14, f5 represents the focal length of the fifth lens 15, and f represents the total focal length of the low-distortion tube lens.

[0045] Combined with the surface design and focal length distribution design shown in the above embodiments, the anti-distortion performance of the low-distortion tube lens can be effectively enhanced. In addition, the chromatic aberration of the low-distortion tube lens during imaging can be effectively eliminated through the setting of the cemented lens, and the difficulty of installation and debugging of the entire low-distortion tube lens can be reduced, the adjustment accuracy can be improved, and the optical performance of the low-distortion tube lens can be further improved.

[0046] Regarding the surface design of each lens in a low-distortion tube lens, some embodiments of the present disclosure also provide a range design of the curvature radius as shown below.

[0047] In some embodiments, the low distortion tube lens satisfies the following conditions: the range of the radius of curvature of the object side surface of the first lens 11 is [430.00mm, 545.00mm], and the range of the radius of curvature of the image side surface is [-360.00mm, -300.00mm]; the range of the radius of curvature of the object side surface of the second lens 12 is [90.00mm, 125.00mm], and the range of the radius of curvature of the image side surface is [-260.00mm, -200.00mm]; the range of the radius of curvature of the object side surface of the third lens 13 is [-250.0 0mm, -200.00mm], and the range of the radius of curvature of the image side surface is [200.00mm, 270.00mm]; the range of the radius of curvature of the object side surface of the fourth lens 14 is [110.00mm, 190.00mm], and the range of the radius of curvature of the image side surface is [-180.00mm, -240.00mm]; the range of the radius of curvature of the object side surface of the fifth lens 15 is [-180.00mm, -240.00mm], and the range of the radius of curvature of the image side surface is [65.00mm, 88.00mm].

[0048] It should be noted that the object side of the lens refers to the side of the lens close to the object. In the above-mentioned low-distortion tube lens, the light is emitted from the inside of the lens from the object side of the lens and exits the lens through the image side of the lens. In other words, the image side of the lens is the side of the lens close to the imaging surface.

[0049] It should be noted that, in the above-mentioned low-distortion tube lens, since the fourth lens 14 and the fifth lens 15 are cemented together, the curvature radius of the image side surface of the fourth lens 14 and the object side surface of the fifth lens 15 are consistent.

[0050] On the basis of the low-distortion tube lens shown in any of the above embodiments, some embodiments of the present disclosure are also designed for the thickness of each lens in the low-distortion tube lens. Specifically, in some embodiments, the low-distortion tube lens meets the following conditions: the center thickness of the first lens 11 is in the range of [31.50mm, 38.50mm], the center thickness of the second lens 12 is in the range of [23.00mm, 33.00mm], the center thickness of the third lens 13 is in the range of [8.20mm, 15.00mm], the center thickness of the fourth lens 14 is in the range of [18.00mm, 23.70mm], and the center thickness of the fifth lens 15 is in the range of [7.20mm, 15.50mm].

[0051] It should be noted that the center thickness of a lens refers to the thickness at the optical center of the lens, that is, the distance between the two surfaces of the lens on the optical axis. Taking the first lens 11 as an example, the center thickness of the first lens 11 refers to the distance from the intersection of the object side surface of the first lens 11 and the optical axis to the intersection of the image side surface of the first lens 11 and the optical axis.

[0052] With respect to the focal length distribution design of the low-distortion tube lens shown in any of the above embodiments, the low-distortion tube lens of some embodiments of the present disclosure also meets the following lens spacing requirements, that is, the low-distortion tube lens of some embodiments of the present disclosure meets the following conditions: the range of the distance from the image side surface of the first lens 11 to the object side surface of the second lens 12 is [6.20mm, 19.40mm], the range of the distance from the image side surface of the second lens 12 to the object side surface of the third lens 13 is [2.60mm, 3.70mm], and the range of the distance from the image side surface of the third lens 13 to the object side surface of the fourth lens 14 is [18.50mm, 23.70mm].

[0053] It should be noted that the above distance refers to the distance on the optical axis. Taking the distance from the image side surface of the first lens 11 to the object side surface of the second lens 12 as an example, the distance refers to the distance from the intersection of the image side surface of the first lens 11 and the optical axis to the intersection of the object side surface of the second lens 12 and the optical axis.

[0054] It should be further explained that, in the above-mentioned low-distortion tube lens, since the fourth lens 14 and the fifth lens 15 are glued together, the distance from the image side surface of the fourth lens 14 to the object side surface of the fifth lens 15 is 0.

[0055] The other optical parameters of each lens in the low-distortion tube lens are further described below.

[0056] Taking the optical focal length as an example, in order to control the light deflection angle of each lens surface and avoid various aberration problems such as increased distortion caused by excessive deflection angle, in some embodiments, the absolute value of the optical focal length of any lens among the first lens 11, the second lens 12, the third lens 13, the fourth lens 14 and the fifth lens 15 is between 0.20 and 1.00.

[0057] Further, according to the above-mentioned optical power design, some embodiments of the present disclosure reasonably set the optical power of each lens in the low-distortion tube lens. In the low-distortion tube lens shown in this embodiment, the optical power of each lens satisfies the following conditions, including:

[0058] 0.81D≤φ1≤1.00D;

[0059] 0.41D≤φ2≤0.49D;

[0060] -0.50D≤φ3≤-0.40D;

[0061] 0.32D≤φ4≤0.48D;

[0062] -0.35D≤φ5≤-0.25D;

[0063] Among them, φ1 represents the focal power of the first lens 11, φ2 represents the focal power of the second lens 12, φ3 represents the focal power of the third lens 13, φ4 represents the focal power of the fourth lens 14, φ5 represents the focal power of the fifth lens 15, and D represents the unit of the focal power, which is diopter.

[0064] In a low-distortion tube lens, evenly distributing the optical power to each lens can ensure uniform and stable imaging quality of the entire optical system, avoid aberration problems such as blur or distortion, and thus prevent uneven imaging.

[0065] Next, let's take the optical back focal length and the total length of the lens as an example. In an optical system, the optical back focal length refers to the distance from the surface of the last lens in the optical system to the image plane, and the total focal length is the distance from the optical center of the optical system to the focal plane (also called the imaging plane). The optical center refers to the point in the optical system where light will not be deflected when passing through it. For an optical system composed of a single lens, the total focal length is the focal length of the lens. For an optical system composed of multiple lenses, the total focal length is the equivalent focal length of the entire optical system. The ratio of the optical back focal length to the total focal length, BFL / f, has a certain influence on the distortion performance of the optical system. For example, the difference in BFL / f will affect the type and degree of distortion. When the BFL / f ratio is too small, the optical system is prone to pincushion distortion. When the BFL / f ratio is too large, the risk of barrel distortion increases accordingly.

[0066] The effect of BFL / f on distortion will indirectly affect the image clarity. For example, poor distortion correction will lead to blurred image edges and severe distortion, thereby reducing the image quality. In order to further improve the optical performance of the low-distortion tube lens, especially the anti-distortion performance, in some embodiments, the low-distortion tube lens meets the following conditions: 0.45≤BFL / f≤0.55, where BFL represents the optical back focal length of the low-distortion tube lens.

[0067] In an optical system, the ratio of the total lens length to the total focal length TTL / f reflects the spatial compactness of the optical system. Differences in TTL / f will affect the aberrations of the optical system, including spherical aberration, coma, astigmatism, field curvature, and chromatic aberration. Too small TTL / f may increase the difficulty of correcting aberrations, resulting in reduced resolution and imaging quality, while too large TTL / f will increase the size and cost of the system. In order to balance the optical performance and miniaturization design of the low-distortion tube lens, in some embodiments, the low-distortion tube lens satisfies the following conditions: 0.40≤TTL / f≤0.48, where TTL represents the total lens length of the low-distortion tube lens.

[0068] In an optical system, BFL / TTL has a certain influence on image quality, distortion control and system compactness. Through reasonable BFL / TTL settings, a balance can be found between image quality, distortion control and system compactness to meet the performance requirements of different application scenarios. Based on this, in some embodiments, the low distortion tube lens meets the following conditions: 1.03≤BFL / TTL≤1.25.

[0069] It should be noted that the low-distortion tube lens can meet one or more of the above conditions. In other words, the low-distortion tube lens meets at least one of the following conditions: 0.45≤BFL / f≤0.55, 0.40≤TTL / f≤0.48 and 1.03≤BFL / TTL≤1.25. One or more of these conditions can be selected according to actual needs to design the optical structure of the low-distortion tube lens, and no excessive restrictions are made here.

[0070] Next, the materials of each lens in the low-distortion tube mirror are exemplarily described. Different lens materials will affect the refractive index and dispersion characteristics of the lens. In some embodiments, the low-distortion tube mirror meets the following conditions:

[0071] 1.40<n1<1.80, 51.00<v1<66.00;

[0072] 1.30<n2<1.80, 73.00<v2<87.00;

[0073] 1.50<n3<2.10, 20.00<v3<29.00;

[0074] 1.64<n4<3.28, 13.00<v4<21.00;

[0075] 1.50<n5<2.10, 20.00<v5<29.00;

[0076] Among them, n1 represents the refractive index of the first lens 11, v1 represents the Abbe number of the first lens 11, n2 represents the refractive index of the second lens 12, v2 represents the Abbe number of the second lens 12, n3 represents the refractive index of the third lens 13, v3 represents the Abbe number of the third lens 13, n4 represents the refractive index of the fourth lens 14, v4 represents the Abbe number of the fourth lens 14, n5 represents the refractive index of the fifth lens 15, and v5 represents the Abbe number of the fifth lens 15.

[0077] By designing the refractive index and Abbe number of each lens in the low-distortion tube mirror, the requirements of the modulation transfer function (MTF) and distortion rate for high-precision detection scenarios can be effectively met. The modulation transfer function measures the ability of the optical system to transfer image contrast at different spatial frequencies. The imaging quality of the optical system is evaluated by quantifying this transfer ability. The value range of MTF is [0, 1], where a value of 1 indicates complete transfer, that is, the contrast of the input signal is completely retained in the output, and 0 indicates no transfer, that is, the contrast of the input signal is completely lost in the output. The closer the MTF value is to 1, the higher the imaging quality of the optical system. The distortion rate is a parameter used to describe the degree of distortion caused by the shape, size or position of the lens imaging. It is usually expressed as a percentage and reflects the deviation between the actual imaging and the ideal imaging.

[0078] On the basis of satisfying the above refractive index and Abbe number conditions, one or more of the first lens 11, the second lens 12, the third lens 13, the fourth lens 14 and the fifth lens 15 can be made of suitable glass materials, for example, optical glass of model H-ZK9A, optical glass of model H-FK61 and / or optical glass of model H-ZF7LA, etc., so as to reduce the lens cost as a whole.

[0079] In order to facilitate those skilled in the art to understand the low-distortion tube lens disclosed herein, two exemplary low-distortion tube lenses are provided below for reference.

[0080] Table 1 shows the optical parameters of the first exemplary low-distortion tube lens provided by the present disclosure.

[0081]

[0082] Table 1

[0083] In Table 1, in the column of thickness or spacing, the upper data indicates the lens thickness, and the lower data indicates the spacing between the lenses. Taking the first lens as an example, according to the data shown in Table 1, the center thickness of the first lens is 35.00mm, and the distance from the image side of the first lens to the object side of the second lens is 17.74mm, and so on. The focal length of the low-distortion tube lens is the total focal length. According to the data shown in Table 1, the total focal length of the low-distortion tube lens is 334mm.

[0084] According to the data shown in Table 1, in the first exemplary low-distortion tube lens, the focal length distribution is as follows: f1 / f=330 / 334 = 0.988, f2 / f= 150 / 334 = 0.449, f3 / f= -138 / 334 = -0.413, f4 / f= 134 / 334 = 0.4, f5 / f= -98 / 334 = -0.3.

[0085] Further, in the first exemplary low-distortion tube lens, the first lens 11 can be made of optical glass of model H-ZK9A, the second lens 12 can be made of optical glass of model H-FK61, the third lens 13 can be made of optical glass of model H-ZF7LA, the fourth lens 14 can be made of optical glass of model H-ZF88, and the fifth lens 15 can be made of optical glass of model ZF7L. In the above-mentioned low-distortion tube lens, the refractive index and Abbe number of the third lens 13 and the fifth lens 15 are consistent, the dispersion coefficient of the third lens 13 is 0.0098, and the dispersion coefficient of the fifth lens 15 is 0.0074. The dispersion coefficient is a parameter that describes the change in the refractive index of an optical material to light of different wavelengths, and is used to quantify the dispersion characteristics of the material, that is, the difference in the refractive index of the material to light of different wavelengths. Since the low-distortion tube lens disclosed in the present invention does not have strict requirements for the dispersion characteristics, in some embodiments, the third lens 13 and the fifth lens 15 can be made of the same material to reduce the types of materials used.

[0086] It can be understood that, in the low-distortion tube lens shown in this embodiment, the third lens 13 and the fifth lens 15 can be made of the same or different materials.

[0087] Table 2 shows the optical parameters of the second exemplary low-distortion tube lens provided by the present disclosure.

[0088]

[0089] Table 2

[0090] According to the data shown in Table 2, the focal length distribution of the second exemplary low-distortion tube lens is consistent with the focal length distribution of the first exemplary low-distortion tube lens.

[0091] Further, in the second exemplary low-distortion tube lens, the first lens 11 can adopt an optical glass of model H-ZK9A, the second lens 12 can adopt an optical glass of model H-FK61, the third lens 13 can adopt an optical glass of model H-ZF7LA, the fourth lens 14 can adopt an optical glass of model H-ZF88, and the fifth lens 15 can adopt an optical glass of model ZF51.

[0092] In addition, other optical parameters of the first exemplary low-distortion tube lens and the second exemplary low-distortion tube lens are consistent. Specifically, other optical parameters of the first exemplary low-distortion tube lens and the second exemplary low-distortion tube lens are shown in Table 3.

[0093]

[0094] Table 3

[0095] In order to facilitate those skilled in the art to understand the optical performance of the above-mentioned low-distortion tube lens, Figure 2 shows a spot diagram of a low-distortion tube lens of some embodiments of the present disclosure, Figure 3 1 shows the distortion diagram of the low distortion tube lens of some embodiments of the present disclosure, Figure 4 The distortion diagrams of low-distortion tube lenses of other embodiments of the present disclosure are shown. Figure 5 The MTF schematic diagram of the low distortion tube lens of some embodiments of the present disclosure is shown. Among them, the spot diagram is an important tool for evaluating the imaging quality of the optical system. It intuitively represents the imaging performance of the optical system by showing the size and distribution of the spot formed by the light emitted from a point on the object on the image plane. The size of the spot is usually expressed by the diameter of the spot. A smaller spot indicates better imaging quality, and a larger spot indicates poor imaging quality. Evenly distributed spots indicate more uniform aberrations, and unevenly distributed spots indicate uneven aberrations. The distortion curve represents the distortion size value in percentage form. The distortion size value is the ratio of the difference between the actual image height and the ideal image height divided by the ideal image height, and its unit is %.

[0096] It should be noted that the spot diagram and MTF of the first exemplary low-distortion tube lens and the second exemplary low-distortion tube lens shown in the above embodiment are consistent, that is, Figure 2 The spot diagrams shown are spot diagrams of a first exemplary low-distortion tube lens and a second exemplary low-distortion tube lens. Figure 5 The MTF diagrams shown are MTF diagrams of a first exemplary low-distortion tube lens and a second exemplary low-distortion tube lens. Figure 3 The distortion diagram shown is a distortion diagram of a first exemplary low-distortion tube lens. Figure 4 The distortion diagram shown is that of a second exemplary low-distortion tube lens.

[0097] according to Figure 2-Figure 5 It can be seen that when the low-distortion tube lens provided in this embodiment is used for imaging, the diameter of the light spot formed by the light emitted from a point on the object on the image plane is small and the distribution is relatively uniform, and the distortion value of the low-distortion tube lens is small, all less than 0.5%. Combined with the MTF performance of the low-distortion tube lens, it can be seen that the low-distortion tube lens has good imaging quality.

[0098] Based on the low-distortion tube lens shown in any of the above embodiments, combined with a microscope objective lens and / or other optical elements, a microscope system with good optical performance can be formed.

[0099] In order to ensure that the length of the microscope system can meet the requirements of adding multiple optical elements between the microscope objective lens and the low-distortion tube lens to achieve different optical functions, in some embodiments, the working distance of the low-distortion tube lens is in the range of [441mm, 539mm]. For example, the working distance of the low-distortion tube lens can be set to 490mm, thereby realizing a low-distortion tube lens with a long working distance. At the same time, since the back focus of the microscope objective lens is a parallel optical path, adding optical elements between the microscope objective lens and the low-distortion tube lens will not have a significant impact on the final optical imaging.

[0100] It should be noted that the working distance refers to the distance from the lens end face of the low-distortion tube lens to the entrance pupil plane, which is similar to the distance from the low-distortion tube lens to the mounting surface of the microscope objective lens.

[0101] Figure 6 An exemplary structural diagram of a microscopic system according to some embodiments of the present disclosure is shown. Figure 6 As shown, the microscope system shown in some embodiments of the present disclosure may include: a low-distortion tube lens 10 and a microscope objective lens 20, the optical axis of the microscope objective lens 20 coincides with the optical axis of the low-distortion tube lens 10, that is, the low-distortion tube lens 10 and the microscope objective lens 20 have the same optical axis.

[0102] Furthermore, the distance between the microscope objective lens 20 and the fifth lens 15 is greater than the distance between the microscope objective lens 20 and the first lens 11. In other words, when the microscope system is used for imaging, the light reflected by the object to be measured enters the microscope objective lens 20, is emitted through the microscope objective lens 20 and enters the first lens 11 in the low-distortion tube lens 10, passes through the second lens 12, the third lens 13 and the fourth lens 14 in sequence, and finally exits the low-distortion tube lens through the fifth lens 15 and enters the imaging device to form an image. In practical applications, the imaging device can be a device such as a CCD sensor.

[0103] In addition to the above-mentioned low-distortion tube lens 10 and microscope objective lens 20, other optical elements may also be included in the microscope system, such as an objective lens switching nose wheel module, a DIC prism, an autofocus sensor and an illumination beam splitter prism, etc. These optical elements can be arranged between the low-distortion tube lens 10 and the microscope objective lens 20 to meet the optical function requirements in different application scenarios.

[0104] In summary, the disclosed embodiment provides a low-distortion tube lens, which enhances the anti-distortion performance of the low-distortion tube lens by adopting a double convex lens design for the first lens, the second lens and the fourth lens, and combines the focal length distribution design of the first lens to the fifth lens to eliminate chromatic aberration by gluing the fourth lens and the fifth lens, thereby reducing the difficulty of installation and debugging of the entire low-distortion tube lens, improving the adjustment accuracy, and further improving the optical performance of the low-distortion tube lens.

[0105] Furthermore, some embodiments of the present disclosure also provide a microscope system, which uses a low-distortion tube lens that can combine the surface design and focal length distribution design of each optical lens to effectively enhance the anti-distortion performance of the low-distortion tube lens, and can effectively eliminate the chromatic aberration of the low-distortion tube lens during imaging through the setting of the cemented lens. In addition, through the design of a long working distance, the demand for the combined use of a low-distortion tube lens and a microscope objective lens is met, thereby forming a microscope system with good imaging quality and suitable for a variety of detection scenarios.

[0106] Although multiple embodiments of the present disclosure have been shown and described herein, it will be apparent to those skilled in the art that such embodiments are provided by way of example only. Those skilled in the art may think of many changes, modifications, and alternatives without departing from the thought and spirit of the present disclosure. It should be understood that in the process of practicing the present disclosure, various alternatives to the embodiments of the present disclosure described herein may be adopted. The attached claims are intended to define the scope of protection of the present disclosure, and therefore cover equivalents or alternatives within the scope of these claims.

[0107] The collection and acquisition of various data in this disclosure complies with relevant laws and regulations and is authorized by the data provider. Any organization or individual that needs to obtain external data must obtain authorization in accordance with the law and ensure data security. It is prohibited to illegally collect, use, process, or transmit unauthorized or unprotected data, or to illegally buy, sell, provide, or disclose unauthorized or unprotected data.

Claims

1. A low distortion tube lens, characterized in that: It is composed of five lenses, including: a first lens (11), a second lens (12), a third lens (13), a fourth lens (14) and a fifth lens (15) arranged in sequence along the optical axis, wherein: The first lens (11) is a biconvex lens and satisfies 0.89≤f1 / f≤1.09, f1 represents the focal length of the first lens, and f represents the total focal length of the low-distortion tube lens; The second lens (12) is a biconvex lens and satisfies 0.40≤f2 / f≤0.49, where f2 represents the focal length of the second lens; The third lens (13) is a biconcave lens and satisfies -0.45≤f3 / f≤-0.37, where f3 represents the focal length of the third lens; The fourth lens (14) is a biconvex lens and satisfies 0.36≤f4 / f≤0.44, where f4 represents the focal length of the fourth lens; The fifth lens (15) is a biconcave lens, the fifth lens (15) is glued to the fourth lens (14), and -0.33≤f5 / f≤-0.27 is satisfied, and f5 represents the focal length of the fifth lens.

2. The low-distortion tube lens according to claim 1, characterized in that: The absolute value of the optical focal length of any one of the first lens (11), the second lens (12), the third lens (13), the fourth lens (14) and the fifth lens (15) is between 0.20 and 1.

00.

3. The low distortion tube lens according to claim 2, characterized in that: The low distortion tube lens meets the following conditions: 0.81D≤φ1≤1.00D; 0.41D≤φ2≤0.49D; -0.50D≤φ3≤-0.40D; 0.32D≤φ4≤0.48D; -0.35D≤φ5≤-0.25D; Among them, φ1 represents the optical power of the first lens, φ2 represents the optical power of the second lens, φ3 represents the optical power of the third lens, φ4 represents the optical power of the fourth lens, and φ5 represents the optical power of the fifth lens.

4. The low-distortion tube lens according to any one of claims 1 to 3, characterized in that: The low distortion tube lens satisfies at least one of the following conditions: 0.45≤BFL / f≤0.55; 0.40≤TTL / f≤0.48; 1.03≤BFL / TTL≤1.25; Wherein, BFL represents the optical back focal length of the low-distortion tube lens, and TTL represents the total lens length of the low-distortion tube lens.

5. The low-distortion tube lens according to any one of claims 1 to 3, characterized in that: The low distortion tube lens meets the following conditions: The range of the radius of curvature of the object side surface of the first lens (11) is [430.00 mm, 545.00 mm], and the range of the radius of curvature of the image side surface is [-360.00 mm, -300.00 mm]; The range of the radius of curvature of the object side surface of the second lens (12) is [90.00 mm, 125.00 mm], and the range of the radius of curvature of the image side surface is [-260.00 mm, -200.00 mm]; The range of the radius of curvature of the object side surface of the third lens (13) is [-250.00 mm, -200.00 mm], and the range of the radius of curvature of the image side surface is [200.00 mm, 270.00 mm]; The range of the radius of curvature of the object side surface of the fourth lens (14) is [110.00 mm, 190.00 mm], and the range of the radius of curvature of the image side surface is [-180.00 mm, -240.00 mm]; The range of the radius of curvature of the object side surface of the fifth lens (15) is [-180.00 mm, -240.00 mm], and the range of the radius of curvature of the image side surface is [65.00 mm, 88.00 mm].

6. The low-distortion tube lens according to any one of claims 1 to 3, characterized in that: The low distortion tube lens meets the following conditions: The center thickness of the first lens (11) is in the range of [31.50 mm, 38.50 mm]; The distance between the image side surface of the first lens (11) and the object side surface of the second lens (12) is in the range of [6.20 mm, 19.40 mm]; The central thickness of the second lens (12) is in the range of [23.00 mm, 33.00 mm]; The distance between the image side surface of the second lens (12) and the object side surface of the third lens (13) is in the range of [2.60 mm, 3.70 mm]; The central thickness of the third lens (13) is in the range of [8.20 mm, 15.00 mm]; The distance between the image side surface of the third lens (13) and the object side surface of the fourth lens (14) is in the range of [18.50 mm, 23.70 mm]; The center thickness of the fourth lens (14) is in the range of [18.00 mm, 23.70 mm]; The central thickness of the fifth lens (15) is in the range of [7.20 mm, 15.50 mm].

7. The low-distortion tube lens according to any one of claims 1 to 3, characterized in that: The low distortion tube lens meets the following conditions: 1.40<n1<1.80, 51.00<v1<66.00; 1.30<n2<1.80, 73.00<v2<87.00; 1.50<n3<2.10, 20.00<v3<29.00; 1.64<n4<3.28, 13.00<v4<21.00; 1.50<n5<2.10, 20.00<v5<29.00; Among them, n1 represents the refractive index of the first lens, v1 represents the Abbe number of the first lens, n2 represents the refractive index of the second lens, v2 represents the Abbe number of the second lens, n3 represents the refractive index of the third lens, v3 represents the Abbe number of the third lens, n4 represents the refractive index of the fourth lens, v4 represents the Abbe number of the fourth lens, n5 represents the refractive index of the fifth lens, and v5 represents the Abbe number of the fifth lens.

8. The low-distortion tube lens according to claim 1, characterized in that: The working distance range of the low distortion tube lens is [441mm, 539mm].

9. The low distortion tube lens according to claim 1, characterized in that: The third lens (13) and the fifth lens (15) are made of the same or different materials.

10. A microscopic system, characterized in that: include: The low-distortion tube lens (10) as claimed in any one of claims 1 to 9; and The microscope objective lens (20) has an optical axis that coincides with the optical axis of the low-distortion tube lens (10), and the distance between the microscope objective lens (20) and the fifth lens (15) is greater than the distance between the microscope objective lens (20) and the first lens (11).

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