Tube lens and microscope system

Abstract

The present application discloses a microscope and microscope system. The microscope comprises: a first lens, a second lens, a third lens, a fourth lens, and a fifth lens, arranged in sequence along the optical axis from the object side to the image side; the first lens is a convex-concave lens; the second lens is a biconvex lens, the second lens being cemented to the first lens; the third lens is a biconcave lens; the fourth lens is a convex-concave lens; and the fifth lens is a biconvex lens. The microscope obtained by designing the above lenses ensures that the light incident on the object side first lens, after being coordinated and controlled by the lens group within the microscope, ultimately exits the fifth lens and remains parallel to the optical axis, eliminating the phenomenon of inconsistent size of each point in the image due to changes in object distance.

Description

Technical Field

[0001] The present invention relates generally to the field of optical lens technology and more specifically to a microscope system. Background Art

[0002] With the development of the semiconductor industry, the requirements for wafer and semiconductor chip inspection accuracy are becoming increasingly higher. Especially for wafer products after photolithography, surface defect detection is particularly important, because any defect may cause the final product to fail.

[0003] After etching, the wafer product will have the chip pattern on its surface, and the optical etching will produce height differences. Traditional optical lenses follow the principle of perspective projection (the closer the object is to the lens, the larger the image, and the farther the object is, the smaller the image). As a result, patterns on the same wafer plane will appear inconsistent in size due to different heights in the image, seriously affecting measurement precision and accuracy.

[0004] In view of this, there is an urgent need to provide a cylindrical lens and microscope system to reduce the perspective distortion caused by the height difference of the wafer surface, so that the patterns at different heights on the wafer surface maintain size consistency in imaging, thereby improving the measurement precision and accuracy of wafer products. Summary of the Invention

[0005] In order to at least solve one or more of the technical problems mentioned above, the present application proposes a cylindrical lens and a microscope system in multiple aspects to reduce the perspective distortion caused by the height difference of the wafer surface, so that the patterns at different heights on the wafer surface maintain size consistency in imaging, thereby improving the measurement precision and accuracy of the wafer product.

[0006] In a first aspect, the present application provides a tube lens, comprising: a first lens, a second lens, a third lens, a fourth lens, and a fifth lens, arranged in sequence from the object side to the image side along an optical axis; wherein the first lens is a convex-concave lens; the second lens is a biconvex lens, and the second lens is cemented to the first lens; the third lens is a biconcave lens; the fourth lens is a convex-concave lens; and the fifth lens is a biconvex lens; the tube lens satisfies at least one of the following conditions:

[0007] 0.385≤f1 / f≤0.500, where f1 represents the combined focal length of the first lens and the second lens, and f represents the total focal length of the tube lens; -0.425≤f2 / f≤-0.35, where f2 represents the focal length of the third lens; -0.6≤f3 / f≤-0.45, where f3 represents the focal length of the fourth lens; and 0.425-≤f4 / f≤0.475, where f4 represents the focal length of the fifth lens.

[0008] In some embodiments, the tube lens satisfies at least one of the following conditions: 0.010 mm -1 ≤φ1≤0.013mm -1 , φ1 represents the combined optical power of the first lens and the second lens; -0.118mm -1 ≤φ2≤-0.014mm -1 , φ2 represents the focal length of the third lens; -0.101mm -1 ≤φ3≤-0.005mm -1 , the φ3 represents the focal length of the fourth lens; 0.05mm -1 ≤φ4≤0.130mm -1 , the φ3 represents the optical power of the fifth lens.

[0009] In some embodiments, the tube lens satisfies at least one of the following conditions: 0.40≤BFL / f≤0.50; 0.70≤TTL / f≤0.75; 0.60≤BFL / TTL≤0.65; wherein the BFL represents the back focal length of the tube lens, and the TTL represents the total lens length of the tube lens.

[0010] In some embodiments, the tube lens satisfies at least one of the following conditions: the curvature radius range of the objective side of the first lens is [45, 57] mm, and the curvature radius range of the image side is [28, 36] mm; the curvature radius range of the objective side of the second lens is [28, 36] mm, and the curvature radius range of the image side is [-233, -170] mm; the curvature radius range of the objective side of the third lens is [-70, -55] mm, and the curvature radius range of the image side is [95, 130] mm; the curvature radius range of the objective side of the fourth lens is [150, 300] mm, and the curvature radius range of the image side is [43, 50] mm; the curvature radius range of the objective side of the fifth lens is [95, 113] mm, and the curvature radius range of the image side is [-139, -90] mm.

[0011] In some embodiments, the center thickness of the first lens, the second lens, the third lens, the fourth lens, and the fifth lens is in the range of [2, 11] mm, and the edge thickness is in the range of [1, 8] mm.

[0012] In some embodiments, the air spacing between the second lens and the third lens, between the third lens and the fourth lens, and between the fourth lens and the fifth lens is in the range of [0.2, 40] mm.

[0013] In some embodiments, the tube lens satisfies at least one of the following conditions: 1.10 < n1 < 1.70, 31.00 < v1 < 42.00, where n1 represents the refractive index of the first lens and v1 represents the Abbe number of the first lens; 1.51 < n2 < 1.60, 62.00 < v2 < 75.00, where n2 represents the refractive index of the second lens and v2 represents the Abbe number of the second lens; 1.50 < n3 < 1.55, 58.02 < v3 < 71.20, where n3 represents the refractive index of the third lens and v3 represents the Abbe number of the third lens; 1.57 < n4 < 1.62, 35.00 < v4 < 40.00, where n4 represents the refractive index of the fourth lens and v4 represents the Abbe number of the fourth lens; 1.51 < n5 < 1.70, v5 = 58.02, where n5 represents the refractive index of the fifth lens and v5 represents the Abbe number of the fifth lens.

[0014] In some embodiments, the object-side working distance range of the tube lens is [98, 102] mm, and the image-side working distance is greater than 85 mm.

[0015] In some embodiments, the total focal length f of the tube lens is 200 mm.

[0016] In a second aspect, the present application provides a microscopic system, including the tube lens according to any one of the above embodiments; a microscopic objective lens; and an image sensor; wherein, the optical axes of the microscopic objective lens and the image sensor coincide with the optical axis of the tube lens.

[0017] Through the tube lens provided as above, the tube lens obtained by the above design of each lens surface type and focal length distribution in the embodiments of the present application enables the light rays incident on the first lens on the object side to be finally parallel to the optical axis after being synergistically regulated by the lens group inside the tube lens, eliminating the phenomenon of inconsistent sizes at each point in imaging caused by the change of the object distance. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] By reading the following detailed description with reference to the accompanying drawings, the above and other objects, features and advantages of the exemplary embodiments of the present application will become easy to understand. In the drawings, several embodiments of the present application are shown in an exemplary rather than restrictive manner, and the same or corresponding reference numerals represent the same or corresponding parts, wherein:

[0019] Figure 1 An exemplary structural schematic diagram of the tube lens showing some embodiments of the present application;

[0020] Figure 2 An exemplary structural schematic diagram of the tube lens showing some embodiments of the present application;

[0021] Figure 3Shows a spot diagram of a tube lens according to some embodiments of the present application;

[0022] Figure 4 Schematic diagram showing the MTF of the tube lens of some embodiments of the present application;

[0023] Figure 5 A diagram showing the distortion of the tube lens of some embodiments of the present application;

[0024] Figure 6 A schematic diagram showing the telecentricity of a tube lens in some embodiments of the present application is shown;

[0025] Figure 7 An exemplary structural block diagram of a microscope system according to some embodiments of the present application is shown. DETAILED DESCRIPTION

[0026] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without making creative efforts are within the scope of protection of this application.

[0027] It should be understood that the terms "include" and "comprising" used in the description and claims of this application indicate the presence of described features, wholes, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or collections thereof.

[0028] It should also be understood that the terms used in this specification are for the purpose of describing specific embodiments only and are not intended to limit this application. As used in this specification and claims, the singular forms "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" as used in this specification and claims refers to any and all possible combinations of one or more of the associated listed items, including and including these combinations.

[0029] As used in this specification and claims, the term "if" can be interpreted as meaning "when . . . the present application" or "upon" or "in response to determining" or "in response to detecting," depending on the context. Similarly, the phrase "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.

[0030] The specific implementation of the present application will be described in detail below with reference to the accompanying drawings.

[0031] Example application scenarios

[0032] In semiconductor manufacturing, wafer surfaces often feature complex micro- and nanostructure patterns, with varying heights in different areas. When inspecting and measuring wafers with traditional optical imaging systems, variations in object distance can cause light angle shifts, leading to inconsistent sizes at each point in the image. This makes it difficult to accurately image patterns with varying heights on the wafer surface, severely impacting measurement precision and accuracy.

[0033] Exemplary application scenarios

[0034] In view of this, there is an urgent need to provide a tube lens, which, through the lens surface shape and focal length distribution design, can make the light incident on the first lens on the object side, after the coordinated control of the lens group inside the tube lens, finally the light emitted from the fifth lens remains parallel to the optical axis, thereby eliminating the inconsistent size of each point in the imaging caused by the height difference of the wafer surface (object distance change), and improving the measurement precision and accuracy.

[0035] Figure 1 An exemplary structural diagram of a tube mirror according to some embodiments of the present application is shown, Figure 1 As shown, the tube lens 10 is composed of five lenses. Specifically, they are a first lens 11, a second lens 12, a third lens 13, a fourth lens 14, and a fifth lens 15, arranged in order from the object side to the image side along the optical axis. In other words, when the tube lens 10 is used for imaging, light enters the tube lens 10 through the first lens 11, then passes through the second lens 12, the third lens 13, the fourth lens 14, and finally exits the tube lens 10 through the fifth lens 15. It should be understood that the object side refers to the side closest to the object, and the image side refers to the side closest to the imaging surface.

[0036] Furthermore, the surface geometry (surface shape) of each lens in the tube lens 10 is designed as follows: the first lens 11 is a convex-concave lens, the second lens 12 is a biconvex lens, and the second lens 12 is cemented to the first lens 11; the third lens 13 is a biconcave lens; the fourth lens 14 is a convex-concave lens; and the fifth lens 15 is a biconvex lens. Furthermore, the ratio of the focal length of each lens to the total focal length of the tube lens satisfies the following: 0.385 ≤ f1 / f ≤ 0.500, -0.425 ≤ f2 / f ≤ -0.35, -0.6 ≤ f3 / f ≤ -0.45, and 0.425 ≤ f4 / f ≤ 0.475. Here, f represents the total focal length of the tube lens 10, f1 represents the combined focal length of the first lens 11 and the second lens 12, f2 represents the focal length of the third lens 13, f3 represents the focal length of the fourth lens 14, and f4 represents the focal length of the fifth lens 15. It can be understood that the first lens 11 and the second lens 12 are cemented together, forming a cemented lens. In optical system design, cemented lenses cannot be designed separately. In other words, the optical parameters of the first lens 11 and the second lens 12, such as the focal length, cannot be designed separately. The core value of this method lies in the rigid combination, which utilizes the sign-complementary nature of the aberrations of the two lenses (e.g., one lens produces positive aberration and the other produces negative aberration), to achieve the cancellation or optimization of specific aberrations, ultimately approaching a "zero aberration" effect.

[0037] The cylindrical lens obtained by the above-mentioned surface design and focal length distribution of each lens can make the incident light on the object side, after being coordinated and controlled by the lens group in the cylindrical lens, the final outgoing light can remain parallel to the optical axis (such as Figure 2 The light propagation path shown in the figure is eliminated, thereby eliminating the inconsistency of the size of each point in the imaging caused by the height difference of the wafer surface pattern (object distance change), thereby improving the measurement precision and accuracy of the wafer product. In addition, the focal length distribution design of each lens in this embodiment can also control the light deflection angle of each surface of the lens to be smaller (such as Figure 2 The light propagation path is shown in the figure), avoiding various aberrations such as increased distortion caused by excessive deflection angles.

[0038] It can be understood that in an optical system, when the final ray emitted by the tube lens is parallel to the optical axis, the "near larger, far smaller" problem is effectively solved. According to the Gaussian imaging formula 1 / f = 1 / u + 1 / v, where f is the total focal length of the tube lens, u is the object distance, and v is the image distance. When the final ray emitted by the tube lens is parallel to the optical axis, the incident light is equivalent to coming from infinity. As the object distance u approaches infinity, 1 / u approaches 0, thus simplifying the formula to 1 / v = 1 / f, or the image distance v = f. Furthermore, the image size is determined solely by the total focal length f of the tube lens and the angular size of the object, and is independent of the object's actual distance. Therefore, regardless of the object's location, as long as its angular size remains constant, the light emitted from each object point will form an image with the same regular pattern after being processed by the tube lens. This eliminates magnification fluctuations caused by differences in object distance, ensures dimensional consistency across the entire imaging range, and avoids the "near larger, far smaller" phenomenon caused by variations in wafer surface pattern height (variable object distance). In addition, in this field, a tube lens whose outgoing light is parallel to the optical axis is called an image-side telecentric tube lens.

[0039] In some embodiments, the total focal length f of the tube lens 10 can be set to 200 mm. Furthermore, based on the set total focal length f of the tube lens 10 of 200 mm and the focal length distribution ratio of each lens described above, the focal length range of each lens can be determined as follows: 77 mm ≤ f1 ≤ 100 mm, -85 mm ≤ f2 ≤ -70 mm, -120 mm ≤ f3 ≤ -90 mm, and 85 mm ≤ f4 ≤ 95 mm. It will be understood that f1 represents the combined focal length of the first lens 11 and the second lens 12, f2 represents the focal length of the third lens 13, f3 represents the focal length of the fourth lens 14, and f4 represents the focal length of the fifth lens 15.

[0040] It should be noted that while the above description sets the total focal length f of the tube lens first, followed by the focal lengths of the individual lenses, this is merely an example and does not imply a fixed order for parameter design. In actual optical design, one can first determine the total focal length f based on overall system requirements, then derive the focal lengths of the individual lenses using the focal length allocation ratio. Alternatively, one can first select the focal lengths of the lenses and then reversely optimize the total focal length and other parameters. This embodiment does not impose any specific limitations on this.

[0041] Based on the above-mentioned surface requirements for each lens, the curvature radius of each lens is further designed. In some embodiments, the curvature radius range of each lens satisfies: the curvature radius range of the object side of the first lens 11 is [45, 57] mm, and the curvature radius range of the image side is [28, 36] mm. The curvature radius range of the object side of the second lens 12 is [28, 36] mm, and the curvature radius range of the image side is [-233, -170] mm. The curvature radius range of the object side of the third lens 13 is [-70, -55] mm, and the curvature radius range of the image side is [95, 130] mm. The curvature radius range of the object side of the fourth lens 14 is [150, 300] mm, and the curvature radius range of the image side is [43, 50] mm. The curvature radius range of the object side of the fifth lens 15 is [94, 113] mm, and the curvature radius range of the image side is [-139, -90] mm. It can be understood that the object-side surface of the lens refers to the side of the lens close to the object, and the image-side surface of the lens refers to the side of the lens close to the imaging surface.

[0042] In some embodiments, the center thickness of the first lens 11, the second lens 12, the third lens 13, the fourth lens 14, and the fifth lens 15 is in the range of [2, 11] mm. In some embodiments, the edge thickness of the first lens 11, the second lens 12, the third lens 13, the fourth lens 14, and the fifth lens 15 is in the range of [1, 8] mm.

[0043] In some embodiments, the center thickness range of the first lens 11 , the second lens 12 , the third lens 13 , the fourth lens 14 and the fifth lens 15 may be further limited to [2, 8] mm to further improve the imaging quality of the tube lens.

[0044] It should be noted that the tube mirror 10 can meet one or more of the above-mentioned center thickness range and edge thickness range. Those skilled in the art can select one or more combinations of these conditions to design the optical structure of the tube mirror 10 according to actual needs, and no excessive restrictions are imposed here.

[0045] Furthermore, the air gap between adjacent lenses is also designed. It is understood that in an optical system, the air gap refers to the distance between two adjacent optical elements (in this embodiment, two adjacent lenses) along the optical axis. For example, the distance between the image side of the first lens 11 and the object side of the second lens 12 is the air gap between them. In some embodiments, the air gap between the second lens 12 and the third lens 13, between the third lens 13 and the fourth lens 14, and between the fourth lens 14 and the fifth lens 15 is in the range of [0.2, 40] mm. Since the first lens 11 and the second lens 12 are glued together, the air gap between them is zero.

[0046] Through the above-mentioned optical structure design of the cylindrical lens 10, the cylindrical lens can have the function of image telecentricity, which solves the problem of "near larger and far smaller" imaging caused by the height difference of the wafer surface pattern (change in object distance), and the light deflection angle of each lens surface is small, avoiding various aberrations such as increased distortion due to excessive deflection angle.

[0047] In some embodiments, the incident light on the object side of the tube lens 10 can also be set to be parallel to the optical axis (e.g. Figure 2 (The light propagation path is shown in the figure). As a result, both the incident and outgoing light rays of the tube lens 10 are parallel to the optical axis, further improving the stability of the imaging magnification. Compared to tube lenses with only image-side telecentricity, the dual-side telecentric design ensures that the image size is virtually unaffected by changes in object distance at varying distances. This also reduces the angle of light deflection at the lens surface, effectively suppressing aberrations such as distortion and coma, ensuring consistent image proportions across all image regions, achieving higher-precision dimensional restoration and detail rendering, and further improving measurement precision and accuracy.

[0048] In some embodiments, the object-side working distance of the tube lens 10 satisfies a range of [98, 102] mm. It will be understood that the object-side working distance (WD) refers to the distance from the object side of the first lens 11 to the entrance pupil plane, which is approximately the distance from the object side of the first lens 11 to the mounting surface of the microscope objective. This working distance range allows for the addition of a coaxial illumination system and a coaxial autofocus system between the microscope objective and the tube lens, thereby achieving accurate and clear wafer pattern imaging. It also facilitates the addition of optical elements between the microscope objective and the tube lens without significantly affecting the final optical imaging.

[0049] In some embodiments, the image-side working distance of the tube lens 10 is greater than 85 mm, providing more space for image sensor installation and angle adjustment. The image-side working distance refers to the distance from the image side of the fifth lens 15 in the tube lens 10 to the photosensitive surface of the image sensor. For example, when the image sensor uses a CCD (Charge-Coupled Device), its photosensitive surface corresponds to the CCD's target surface.

[0050] Next, the focal length of the lens 10 is described. As can be understood, the focal length directly reflects the effect of the lens on light: a positive value indicates convergence of light, a negative value indicates divergence of light, and a larger value indicates a greater degree of light deflection.

[0051] In some embodiments, the distribution ratio of the optical power of each lens in the tube lens 10 to the total optical power of the tube lens 10 satisfies:

[0052] 2≤φ1 / φ≤2.6; -23.6≤φ2 / φ≤-2.8; -20.2≤φ3 / φ≤-1.00; 10≤φ4 / φ≤26. φ1 represents the combined focal power of the first lens 11 and the second lens 12, φ represents the total focal power of the tube lens, φ2 represents the focal power of the third lens 13, φ3 represents the focal power of the fourth lens 14, and φ4 represents the focal power of the fifth lens 15.

[0053] The cylindrical lens obtained by the above distribution of the focal length of each lens can make the incident light on the object side, after being coordinated and regulated by the lens group in the cylindrical lens, the final outgoing light can remain parallel to the optical axis (such as Figure 2 The light propagation path shown in the figure is eliminated, thereby eliminating the inconsistency of the size of each point in the imaging caused by the height difference of the wafer surface pattern (object distance change), thereby improving the measurement precision and accuracy of the wafer product. In addition, the above-mentioned lens focal length distribution ratio design of this embodiment can also control the light deflection angle of each lens surface to be smaller (such as Figure 2 The light propagation path is shown in the figure), avoiding various aberrations such as increased distortion caused by excessive deflection angles.

[0054] In some embodiments, the total optical power φ of the tube lens 10 can be set to 0.005 mm. -1 Furthermore, according to the set total optical power of the tube lens 10 φ = 0.005mm -1 , and the above lens focal power distribution ratio, the focal power range can be determined as:

[0055] ; ; ;0.05mm -1 ≤φ4≤0.130mm -1 .

[0056] It can be understood that φ1 represents the combined optical power of the first lens 11 and the second lens 12 , φ2 represents the optical power of the third lens 13 , φ3 represents the optical power of the fourth lens 14 , and φ4 represents the optical power of the fifth lens 15 .

[0057] Similarly, it should be noted that while the above description sets the total focal power φ of the tube lens first, followed by the focal powers of the individual lenses, this is merely an example and does not imply a fixed order for parameter design. In actual optical design, one can first determine the total focal power φ based on overall system requirements, and then derive the focal powers of the individual lenses using the focal power allocation ratio. Alternatively, one can first select the focal power range of the lenses and then reversely optimize the total focal power and other parameters. This embodiment does not impose any specific limitations on this.

[0058] Next, the barrel lens 10 will be further described in terms of refractive index and Abbe number. In some embodiments, the refractive index and Abbe number of each lens satisfy: 1.10 < n1 < 1.70, 31.00 < v1 < 42.00; 1.51 < n2 < 1.60, 62.00 < v2 < 75.00; 1.50 < n3 < 1.55, 58.02 < v3 < 71.20; 1.57 < n4 < 1.62, 35.00 < v4 < 40.00; 1.51 < n5 < 1.70, v5 = 58.02. Here, 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.

[0059] Through the above design of the refractive index and Abbe number of each lens, the barrel lens can have more precise beam collimation and focusing capabilities, and can correct chromatic aberration (axial chromatic aberration, magnification chromatic aberration), balance dispersion and other aberrations, and ensure wide-spectrum imaging quality.

[0060] Under the condition of meeting the above requirements for refractive index and Abbe number, in some embodiments, glass with a lower cost can be selected, for example, the glass of Chengduo Guangming can be selected.

[0061] Next, the barrel lens 10 will be further described in terms of optical back focal length (BFL) and total lens length (TTL).

[0062] In an optical system, the optical back focal length BFL refers to the distance from the image side of the last lens in the optical system (in this embodiment, the fifth lens 15 in the barrel lens 10) to the imaging plane.

[0063] In some embodiments, the ratio BFL / f of the optical back focal length BFL to the total focal length f has a certain influence on the distortion performance of the optical system. For example, different values of 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, and when the BFL / f ratio is too large, the risk of barrel distortion increases accordingly.

[0064] In some embodiments, the ratio of the optical back focal length BFL of the barrel lens 10 to the total focal length f satisfies: 0.40 ≤ BFL / f ≤ 0.50. This design of the BFL / f range can reduce distortion and improve imaging quality, thereby achieving the purpose of further optimizing the optical performance of the barrel lens.

[0065] In an optical system, TTL / f reflects the spatial compactness of the optical system. Different TTL / f values ​​can affect the system's aberrations, including spherical aberration, coma, astigmatism, field curvature, and chromatic aberration. A too small TTL / f value can make aberration correction more difficult, leading to reduced resolution and image quality, while a too large TTL / f value can increase system size and cost.

[0066] Based on this, in some embodiments, the ratio of the total length TTL of the lens of the tube lens 10 to the total focal length f satisfies: 0.70≤TTL / f≤0.75. The above TTL / f range design can balance the optical performance of the tube lens and the miniaturization design, further improving the optical performance of the tube lens.

[0067] In an optical system, the ratio of the optical back focal length (BFL) to the total lens length (TTL) (BFL / TTL) has a certain impact on image quality, distortion control, and system compactness. Through a reasonable BFL / TTL setting, a balance can be found between image quality, distortion control, and system compactness to meet the performance requirements of different application scenarios.

[0068] Based on this, in some embodiments, the ratio of the optical back focal length (BFL) of the tube lens 10 to the total lens length (TTL) satisfies the following: 0.60 ≤ BFL / TTL ≤ 0.65. By designing within this BFL / TTL range, the tube lens achieves a good balance between image quality, distortion control, and system compactness, further optimizing the optical performance of the tube lens.

[0069] It should be noted that the tubular lens 10 can meet one or more of the above conditions. In other words, the tubular lens 10 meets at least one of the following conditions: 0.40 ≤ BFL / f ≤ 0.50, 0.70 ≤ TTL / f ≤ 0.75, and 0.60 ≤ BFL / TTL ≤ 0.65. Those skilled in the art may select one or more combinations of these conditions to design the optical structure of the tubular lens 10 based on actual needs, and no excessive restrictions are imposed herein.

[0070] To facilitate those skilled in the art to understand the tubular mirrors disclosed herein, three exemplary tubular mirrors are provided below for reference. It should be noted that Table 1 is Example 1, Table 2 is Example 2, and Table 3 is Example 3.

[0071] Table 1. Example parameters of tube mirror

[0072]

[0073] It should be noted that the air gap column in Table 1 corresponds, from top to bottom, to the air gaps between first lens 11 and second lens 12, between second lens 12 and third lens 13, between third lens 13 and fourth lens 14, between fourth lens 14 and fifth lens 15, and between fifth lens 15 and the mirror surface closest to the object side of the image sensor. Similarly, the air gap columns in Tables 2 and 3 below follow this order and are not further detailed. The data in Table 2 indicate that they are all within the corresponding data ranges disclosed above.

[0074] Table 2. Example parameters of tube mirror

[0075]

[0076] According to the data in Table 2 above, they all meet the corresponding data range intervals disclosed above.

[0077] In some embodiments, to save costs, the first lens of Example 2 above may use glass of model KZFSN5, the second lens may use glass of model N-PSK58, the third lens may use glass of model ZKN7, the fourth lens may use glass of model F2HT, and the fifth lens may use glass of model N-SK15.

[0078] Table 3. Example parameters of tube mirror

[0079]

[0080] According to the data in Table 3 above, they all meet the corresponding data ranges disclosed above.

[0081] In some embodiments, to save costs, the first lens of Example 3 above may use glass of model F15, the second lens may use glass of model N-PSK58, the third lens may use glass of model N-ZK7A, the fourth lens may use glass of model F3, and the fifth lens may use glass of model N-SK15.

[0082] The other optical parameters of Examples 1, 2, and 3 above may adopt the specific parameters shown in Table 4. In addition, the object-side working distance of the cylindrical lens in each of the above examples is set to 100 mm.

[0083] Table 4. Example parameters of the tube mirror

[0084]

[0085] Furthermore, in order to facilitate those skilled in the art to understand the optical performance of the above-mentioned tube mirror, Figure 3 Shows the spot diagram of the tube lens of some embodiments of the present application. Figure 4A schematic diagram showing the MTF of the tube lens according to some embodiments of the present application. Figure 5 The distortion diagram of the tube lens of some embodiments of the present application is shown. Figure 6 Schematic diagram showing the telecentricity of the tube lens in some embodiments of the present application. Figures 3 to 6 The schematic diagram shown is a schematic diagram of the tube mirror of Example 1 above.

[0086] The spot diagram is an important tool for evaluating the imaging quality of an optical system. It visually illustrates the imaging performance of an optical system by showing the size and distribution of the spot formed on the image plane by light emitted from a point on an object. The spot size is usually expressed as its diameter, with smaller spots indicating better imaging quality and larger spots indicating poorer imaging quality. A uniformly distributed spot indicates relatively uniform aberrations, while an unevenly distributed spot indicates uneven aberrations.

[0087] MTF (Modulation Transfer Function) is a core indicator of imaging quality in optical systems. It describes the system's ability to transmit detail at different spatial frequencies. It reflects the degree to which contrast and resolution are maintained after an optical system images object details (such as brightness variations and line density).

[0088] In the distortion diagram, the distortion curve represents the degree of distortion in the form of a percentage. This value is the ratio of the difference between the actual image height and the ideal image height divided by the ideal image height, and the unit is %.

[0089] The telecentricity diagram intuitively displays the parallelism of the main light ray of the optical system with the optical axis and the symmetry of the edge light by drawing the light ray trajectories passing through the center and upper and lower edges of the entrance pupil. It can directly reflect the telecentricity of the tube lens of this embodiment, which is also the key means to verify whether the change of object distance causes fluctuation of imaging performance, and reflects the precision and accuracy of the tube lens of this application in measuring wafer products.

[0090] It should be noted that the above schematic diagrams are obtained based on experiments using an optical system consisting of a microscope objective lens, the tube lens 10 provided in the embodiment of the present application, and a CCD camera.

[0091] like Figure 3 In the point diagram shown, the horizontal and vertical axes are in μm (micrometers), and IMA is the imaging surface (the photosensitive surface of the image sensor). This embodiment uses a CCD as the image sensor. Among them, IMA: 3.6mm means the position 3.6mm away from the center on the CCD; IMA: 8.405mm means the position 8.405mm away from the center on the CCD; IMA: 12.518mm means the position 12.518mm away from the center on the CCD. Figure 3By observing the size and distribution of the light spot formed on the imaging plane, it can be seen that when the tube lens provided in this embodiment is used for imaging, the diameter of the light spot formed on the image plane by the light emitted from a point on the object is small and the distribution is relatively uniform. Figure 5 The distortion diagram shows that the maximum distortion is 0.14%, indicating that the tube lens of this embodiment has an extremely low distortion level. Semiconductor wafer inspection and precision parts size measurement require distortion less than 0.5%, which shows that the tube lens of this embodiment fully meets the requirements. Figure 6 The MTF performance of the tube lens has reached the diffraction limit, which shows that the tube lens has good imaging quality. Figure 7 As shown in the telecentricity diagram, the principal rays are almost parallel under different fields of view, indicating that the cylindrical lens of this embodiment has excellent telecentricity. This can eliminate the inconsistency in the size of each point in the image caused by the height difference of the pattern on the object wafer surface (variation in object distance), thereby improving the measurement precision and accuracy of the wafer product.

[0092] Some embodiments of the present application further provide a microscope system, comprising the tube lens 10, microscope objective lens 20, and image sensor 30 of any of the aforementioned embodiments. The optical axes of the microscope objective lens 20 and the image sensor 30 coincide with the optical axis of the tube lens 10. In the microscope system of this embodiment, light reflected from an object is converged by the microscope objective lens 20 and then emitted. It is then received by the tube lens 10 and further propagated before ultimately being projected onto the image sensor 30 to form an image.

[0093] It should be noted that the microscope system of this embodiment is suitable for detection scenarios requiring high measurement accuracy, such as wafer surface defect detection.

[0094] Based on the above description, it can be seen that the light emitted from the tube lens to the image sensor is parallel to the optical axis, thereby eliminating the inconsistency of the size of each point in the image sensor imaging caused by the height difference of the wafer surface pattern (object distance change), thereby improving the measurement precision and accuracy of the wafer product. In addition, the focal length distribution design of each lens of the tube lens in this embodiment can also control the light deflection angle of each lens surface to be smaller (such as Figure 2 The light propagation path is shown in the figure), avoiding various aberrations such as increased distortion caused by excessive deflection angles.

[0095] In some embodiments, the microscope objective lens adopts a parallel optical path. In other words, the outgoing light of the microscope objective lens is parallel to the optical axis. At this time, the outgoing light of the microscope objective lens directly serves as the incident light of the tube lens. The two are continuously transmitted along the same optical path, so the light received by the tube lens naturally remains parallel to the optical axis. As a result, the incident light and the outgoing light of the tube lens 10 are both parallel to the optical axis, thereby further improving the stability of the imaging magnification. Compared to a tube lens with only a telecentric image, the bilateral telecentric design makes the image size of the object at different distances almost unaffected by the change in object distance. At the same time, the deflection angle of the light on the lens surface is reduced, effectively suppressing aberrations such as distortion and coma, ensuring that the imaging ratio of each area of ​​the picture is consistent, achieving higher-precision size restoration and detail presentation, and further improving the precision and accuracy of the measurement.

[0096] In some embodiments, the image sensor uses a CCD camera. CCD has the characteristics of high imaging quality, low noise, and wide dynamic range, which can further improve the precision and accuracy of wafer surface measurement.

[0097] Although multiple embodiments of the present application 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 can conceive of many changes, modifications, and alternatives without departing from the thought and spirit of the present application. It should be understood that in the process of practicing the present application, various alternatives to the embodiments of the present application described herein can be adopted. The accompanying claims are intended to define the scope of protection of the present application and therefore cover equivalents or alternatives within the scope of these claims.

Claims

1. A tube lens, characterized in that: The tube lens 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 from the object side to the image side along the optical axis; wherein, The first lens (11) is a convex-concave lens; The second lens (12) is a biconvex lens, and the second lens (12) is glued to the first lens (11); The third lens (13) is a biconcave lens; The fourth lens (14) is a convex-concave lens; The fifth lens (15) is a biconvex lens; The tube mirror satisfies: 0.385≤f1 / f≤0.500, f1 represents the combined focal length of the first lens (11) and the second lens (12), and f represents the total focal length of the tube lens; -0.6≤f3 / f≤-0.45, wherein f3 represents the focal length of the fourth lens (14); The tube lens also satisfies at least one of the following conditions: -0.425≤f2 / f≤-0.35, wherein f2 represents the focal length of the third lens (13); 0.425≤f4 / f≤0.475, where f4 represents the focal length of the fifth lens (15).

2. The tube lens according to claim 1, characterized in that The tube lens satisfies at least one of the following conditions: 0.010mm -1 ≤φ1≤0.013mm -1 , the φ1 represents the combined optical power of the first lens (11) and the second lens (12); -0.118mm -1 ≤φ2≤-0.014mm -1 , the φ2 represents the focal length of the third lens (13); -0.101mm -1 ≤φ3≤-0.005mm -1 , the φ3 represents the optical power of the fourth lens (14); 0.05mm -1 ≤φ4≤0.130mm -1 , the φ4 represents the optical focal length of the fifth lens (15).

3. The tube lens according to claim 1, characterized in that The tube lens satisfies at least one of the following conditions: 0.40≤BFL / f≤0.50; 0.70≤TTL / f≤0.75; 0.60≤BFL / TTL≤0.65; Wherein, the BFL represents the back focal length of the tube lens, and the TTL represents the total length of the lens of the tube lens.

4. The tube lens according to claim 1, characterized in that The tube lens satisfies at least one of the following conditions: The curvature radius of the object side of the first lens (11) is in the range of [45, 57] mm, and the curvature radius of the image side is in the range of [28, 36] mm; The curvature radius of the object side of the second lens (12) ranges from [28, 36] mm, and the curvature radius of the image side ranges from [-233, -170] mm; The curvature radius of the object side of the third lens (13) is in the range of [-70, -55] mm, and the curvature radius of the image side is in the range of [95, 130] mm; The curvature radius of the object side of the fourth lens (14) is in the range of [150, 300] mm, and the curvature radius of the image side is in the range of [43, 50] mm; The curvature radius of the object side of the fifth lens (15) is in the range of [94, 113] mm, and the curvature radius of the image side is in the range of [-139, -90] mm.

5. The tube lens according to claim 1, characterized in that The center thickness range of the first lens (11), the second lens (12), the third lens (13), the fourth lens (14) and the fifth lens (15) is [2, 11] mm, and the edge thickness range is [1, 8] mm.

6. The tube lens according to claim 1, characterized in that The air spacing range between the second lens (12) and the third lens (13), between the third lens (13) and the fourth lens (14), and between the fourth lens (14) and the fifth lens (15) is [0.2, 40] mm.

7. The tube lens according to claim 1, characterized in that The tube lens satisfies at least one of the following conditions: 1.10 < n1 < 1.70, 31.00 < v1 < 42.00, where n1 represents the refractive index of the first lens (11), and v1 represents the Abbe number of the first lens (11); 1.51 < n2 < 1.60, 62.00 < v2 < 75.00, where n2 represents the refractive index of the second lens (12), and v2 represents the Abbe number of the second lens (12); 1.50 < n3 < 1.55, 58.02 < v3 < 71.20, where n3 represents the refractive index of the third lens (13), and v3 represents the Abbe number of the third lens (13); 1.57 < n4 < 1.62, 35.00 < v4 < 40.00, where n4 represents the refractive index of the fourth lens (14), and v4 represents the Abbe number of the fourth lens (14); 1.51 < n5 < 1.70, v5 = 58.02, where n5 represents the refractive index of the fifth lens (15), and v5 represents the Abbe number of the fifth lens (15).

8. The tube lens according to claim 1, characterized in that The object - side working distance range of the tube lens is [98, 102] mm, and the image - side working distance is greater than 85 mm.

9. The tube lens according to claim 1, characterized in that: The total focal length f of the tube lens is 200 mm.

10. A microscope system, characterized in that: Comprising the tube lens according to any one of claims 1 to 9; A microscopic objective lens; and An image sensor; wherein, The optical axes of the microscopic objective lens and the image sensor coincide with the optical axis of the tube lens.

Images