microscope

Abstract

The application discloses a microscope, the microscope has an object side and an image side which are oppositely arranged along an optical axis, the microscope comprises a lens barrel and an optical system arranged in the lens barrel, the optical system comprises a first lens, a second lens, a third lens and a fourth lens which are sequentially and spacedly arranged along the optical axis, the first lens is a double-convex lens, the second lens is a meniscus lens, the concave surface of the second lens faces the object side, the third lens is a convex-concave lens, and the fourth lens is a double-concave lens; the optical powers of the first lens, the third lens and the fourth lens are positive, positive and negative respectively; the four lenses are spacedly arranged and single-piece glass lenses are adopted, thus avoiding the problem of interference fringes caused by traditional cemented lenses, optimizing the field curvature and making the image plane relatively flat; and through matching a suitable objective lens system, microstructures and defects can be conveniently observed and detected, so that the problems of interference fringes, field curvature and tolerance existing in the design of the sleeve lens are solved.

Description

Technical Field

[0001] This invention relates to the field of optical element technology, and more particularly to microscopes. Background Technology

[0002] Currently, in the field of semiconductor technology, with the continuous advancement of integrated circuit and chip manufacturing processes, high-resolution, high-precision microscope systems are needed to observe and detect minute structures and defects on chips. Sleeve lenses, as a crucial component in optical systems, help achieve superior optical performance and image quality.

[0003] Currently, most telescopic lenses in China employ a cemented lens design. However, when using a high-coherence light source, the cemented layer is prone to interference. After introducing other optical systems, interference fringes easily form on the image plane, interfering with the microscope system's detection results and affecting image quality. Meanwhile, designing cementless telescopic lenses also presents challenges, primarily in two key indicators: field curvature and tolerance yield. While pursuing the advantage of interference-free design, cementless lens designs often face significant reductions in field curvature and tolerance yield. This results in the performance of cementless telescopic lenses potentially being inferior to previous cemented telescopic lenses, and it is difficult to balance these two indicators in the design process, causing considerable difficulty. Summary of the Invention

[0004] The main objective of this invention is to propose a microscope that addresses the problems of interference fringes, field curvature, and tolerances in the design of sleeve lenses in current similar technologies.

[0005] To achieve the above objectives, the present invention provides a microscope having an object side and an image side arranged opposite to each other along the optical axis. The microscope includes a microscope tube and an optical system disposed within the microscope tube. The optical system includes a first lens, a second lens, a third lens, and a fourth lens arranged sequentially at intervals along the optical axis. The first lens is a biconvex lens, the second lens is a meniscus lens with its concave surface facing the object side, the third lens is a convex-concave lens, and the fourth lens is a biconcave lens. The optical power of the first lens is positive, the optical power of the third lens is positive, and the optical power of the fourth lens is negative.

[0006] Optionally, the first lens, the second lens, the third lens, and the fourth lens are all glass spherical lenses.

[0007] Optionally, the radius of the end face of the first lens facing the object side is R1, and the radius of the end face facing the image side is R2, where 35.9056mm≤R1≤45.9056mm and -133.8642mm≤R2≤-123.8642mm;

[0008] The radius of the end face of the second lens facing the object side is R3, and the radius of the end face facing the image side is R4, -71.7012mm≤R3≤-61.7012mm, -71.7012mm≤R4≤-61.7012mm;

[0009] The radius of the end face of the third lens facing the object side is R5, and the radius of the end face facing the image side is R6, where 57.3mm≤R5≤67.3mm and 453.9578mm≤R6≤463.9578mm.

[0010] The radius of the end face of the fourth lens facing the object side is R7, and the radius of the end face facing the image side is R8. -111.4437mm≤R7≤-101.4437mm, 27.2729mm≤R8≤37.2729mm.

[0011] Optionally, the center distance of the end face of the first lens facing the object side is d1, and the center distance of the end face facing the image side is d2, where 5.75mm≤d1≤7.75mm and 1.0mm≤d2≤2.0mm;

[0012] The center distance of the end face of the second lens facing the object side is d3, and the center distance of the end face facing the image side is d4, where 7.27mm≤d3≤9.27mm and 0.09mm≤d4≤0.11mm.

[0013] The center distance of the end face of the third lens facing the object side is d5, and the center distance of the end face facing the image side is d6, where 3.45mm≤d5≤5.45mm and 1.0mm≤d6≤2.0mm.

[0014] The center distance of the end face of the fourth lens facing the object side is d7, and the center distance of the end face facing the image side is d8, where 1.0mm≤d7≤2.0mm and 2.92mm≤d8≤4.92mm.

[0015] Optionally, the refractive index of the first lens is n1, where 1.4 ≤ n1 ≤ 1.5;

[0016] The refractive index of the second lens is n2, where 1.73 ≤ n2 ≤ 1.83;

[0017] The refractive index of the third lens is n3, where 1.54 ≤ n3 ≤ 1.64;

[0018] The refractive index of the second lens is n4, where 1.47 ≤ n4 ≤ 1.57.

[0019] Optionally, the distance from the entrance pupil to the image plane of the microscope is S, where 253mm ≤ S ≤ 353mm.

[0020] Optionally, the entrance pupil distance between the microscope and the end face of the first lens near the object side is S1, where 70mm≤S1≤170mm.

[0021] Optionally, the back focal length between the end face of the third lens near the image side and the image plane is BFL, where 140mm≤BFL≤170mm.

[0022] Optionally, the total optical length of the optical system is TTL, where 20mm ≤ TTL ≤ 30mm.

[0023] Optionally, the entrance pupil diameter of the optical system is set to D1, where 10mm ≤ D1 ≤ 30mm; and / or,

[0024] The image-side aperture of the optical system is set to NA, where 0.04 ≤ NA ≤ 0.06; and / or,

[0025] The image plane aperture of the optical system is set to D2, where 20mm ≤ D2 ≤ 25mm.

[0026] In the technical solution provided by the present invention, the microscope has a first lens, a second lens, a third lens, and a fourth lens arranged at intervals inside the microscope tube. The four lenses are single-piece glass lenses, which avoids the interference fringes that may be generated in traditional cemented lenses. Furthermore, the field curvature has been optimized, making the image plane relatively flat. By matching a suitable objective lens system, it is convenient to observe and detect small structures and defects, thereby solving the problems of interference fringes, field curvature, and tolerance in the design of sleeve lenses in current similar technologies. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0028] Figure 1 A schematic diagram of the optical system of the microscope provided by the present invention at an entrance pupil distance of 70 mm;

[0029] Figure 2 A schematic diagram of the optical system of the microscope provided by the present invention at an entrance pupil distance of 90 mm;

[0030] Figure 3 A schematic diagram of the optical system of the microscope provided by the present invention at an entrance pupil distance of 170 mm;

[0031] Figure 4 for Figure 1 The theoretical MTF curve of the optical system in the image;

[0032] Figure 5 for Figure 2 The theoretical MTF curve of the optical system in the image;

[0033] Figure 6 for Figure 3 The theoretical MTF curve of the optical system in the image;

[0034] Figure 7 for Figure 1 The theoretical defocus MTF curve of the optical system in the image;

[0035] Figure 8 for Figure 2 The theoretical defocus MTF curve of the optical system in the image;

[0036] Figure 9 for Figure 3 The theoretical defocus MTF curve of the optical system in the image.

[0037] Explanation of icon numbers:

[0038] 1 First lens 4 Fourth lens 2 Second lens 5 Entering the pupil 3 Third lens 6 Image

[0039] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0040] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0041] It should be noted that if the embodiments of the present invention involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicators will also change accordingly.

[0042] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the meaning of "and / or" throughout the text includes three parallel solutions; for example, "A and / or B" includes solution A, solution B, or a solution where both A and B are satisfied simultaneously. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0043] Currently, most telescopic lenses in China employ a cemented lens design. However, when using a high-coherence light source, the cemented layer is prone to interference. After introducing other optical systems, interference fringes easily form on the image plane, interfering with the microscope system's detection results and affecting image quality. Meanwhile, designing cementless telescopic lenses also presents challenges, primarily in two key indicators: field curvature and tolerance yield. While pursuing the advantage of interference-free design, cementless lens designs often face significant reductions in field curvature and tolerance yield. This results in the performance of cementless telescopic lenses potentially being inferior to previous cemented telescopic lenses, and it is difficult to balance these two indicators in the design process, causing considerable difficulty.

[0044] To address the above problems, the present invention provides a microscope. Figure 1 A schematic diagram of the optical system of the microscope provided by the present invention at an entrance pupil distance of 70 mm; Figure 2 A schematic diagram of the optical system of the microscope provided by the present invention at an entrance pupil distance of 90 mm; Figure 3 A schematic diagram of the optical system of the microscope provided by the present invention at an entrance pupil distance of 170 mm; Figure 4 for Figure 1 The theoretical MTF curve of the optical system in the image; Figure 5 for Figure 2 The theoretical MTF curve of the optical system in the image; Figure 6 for Figure 3 The theoretical MTF curve of the optical system in the image; Figure 7 for Figure 1 The theoretical defocus MTF curve of the optical system in the image; Figure 8 for Figure 2 The theoretical defocus MTF curve of the optical system in the image; Figure 9 for Figure 3 The theoretical defocus MTF curve of the optical system in the image.

[0045] Please see Figures 1 to 3 The microscope includes an object side and an image side arranged opposite each other along the optical axis. The microscope includes a microscope tube and an optical system disposed within the microscope tube. The optical system includes a first lens 1, a second lens 2, a third lens 3, and a fourth lens 4 arranged sequentially at intervals along the optical axis. The first lens 1 is a biconvex lens, the second lens 2 is a meniscus lens with its concave surface facing the object side, the third lens 3 is a convex-concave lens, and the fourth lens 4 is a biconcave lens. The optical power of the first lens 1 is positive, the optical power of the third lens 3 is positive, and the optical power of the fourth lens 4 is negative.

[0046] It should be noted that cemented lenses, due to their structure containing multiple lens elements with a transparent gap between them (which can be filled with air or transparent adhesive), cause light to refract and reflect when passing through this gap. This results in inconsistent optical path lengths because the refractive index of the medium within the gap differs from that of the lens elements. These inconsistent optical path lengths cause phase differences in the light waves. When two beams of light intersect again, they may be in different phases, thus producing an interference effect. At some locations, the two beams of light will overlap, enhancing the light intensity and forming bright interference fringes; at other locations, they will cancel each other out, forming dark interference fringes. Interference fringes are typically periodically occurring alternating bright and dark fringes, their position and shape depending on the angle of the incident light and the relative positions of the lenses. If the medium spacing between the lenses is small, the interference fringes will be denser and blurrier. If the medium spacing between the lenses is larger, the interference fringes will become sparser and sharper. In existing technology, to avoid interference fringes in cemented lenses, a material with a refractive index similar to that of the lenses can be filled between the lenses to eliminate the air gap. Furthermore, employing high-precision machining and assembly processes to ensure the accuracy of the position and angle between lenses can also reduce the generation of interference fringes. However, this will significantly increase the manufacturing cost of the product.

[0047] In the technical solution provided by the present invention, the microscope tube is provided with a first lens 1, a second lens 2, a third lens 3 and a fourth lens 4 at intervals. The four lenses are single-piece glass lenses, which avoids the interference fringes that may be generated in traditional cemented lenses. Furthermore, the field curvature is optimized, making the image plane 6 relatively flat. By matching a suitable objective lens system, it is convenient to observe and detect small structures and defects, thereby solving the problems of interference fringes, field curvature and tolerance in the design of sleeve lenses in current similar technologies.

[0048] It should be noted that field curvature refers to the fact that, during image formation, the image plane (6) is not a flat surface but exhibits a certain degree of curvature. This means that object points at different locations will lie on different radii of curvature during imaging, rather than all lying on the same plane. If the field curvature is large, it will affect the imaging effect.

[0049] In this embodiment, the first lens 1, the second lens 2, the third lens 3, and the fourth lens 4 are all glass spherical lenses. Glass lenses have advantages such as high light transmittance, stable high-temperature performance, and high chemical stability. Therefore, the microscope is less affected by environmental factors and is more suitable for long-term use. Furthermore, the physical properties of glass lenses are relatively stable, and they are not easily deformed or shrunk, ensuring long-term image quality. Moreover, the manufacturing and processing precision of glass lenses is high, enabling higher optical performance and more precise dimensional control. Therefore, glass lenses can ensure higher assembly precision and lower errors during assembly, which is beneficial to improving the overall system performance.

[0050] In this embodiment, the radius of the end face of the first lens 1 facing the object side is R1, and the radius of the end face facing the image side is R2, where 35.9056mm ≤ R1 ≤ 45.9056mm and -133.8642mm ≤ R2 ≤ -123.8642mm; the radius of the end face of the second lens 2 facing the object side is R3, and the radius of the end face facing the image side is R4, where -71.7012mm ≤ R3 ≤ -61.7012mm and -71.7012mm ≤ R4 ≤ -61. The radius of the end face of the third lens 3 facing the object side is R5, and the radius of the end face facing the image side is R6, where 57.3mm≤R5≤67.3mm and 453.9578mm≤R6≤463.9578mm; the radius of the end face of the fourth lens 4 facing the object side is R7, and the radius of the end face facing the image side is R8, where -111.4437mm≤R7≤-101.4437mm and 27.2729mm≤R8≤37.2729mm. The end face radius of a lens usually refers to the radius of curvature of the front and rear surfaces of the lens. The radius of curvature is a physical quantity used to describe the degree of curvature of the lens surface. The larger the radius of curvature, the smaller the degree of curvature of the lens surface; the smaller the radius of curvature, the greater the degree of curvature of the lens surface. In the relationship between the focal length and the radius of curvature of a lens, determining the radii of curvature of the front and rear surfaces is crucial for calculating the focal length.

[0051] In one specific embodiment, preferably, in the first lens 1, R1 = 40.9056mm, R2 = -128.8642mm; in the second lens 2, R3 = -66.7012mm, R4 = -66.7012mm; in the third lens 3, R5 = 62.3mm, R6 = 458.9578mm; and in the fourth lens 4, R7 = -106.4437mm, R8 = 32.2729mm.

[0052] In this embodiment, the center distance of the end face of the first lens 1 facing the object side is d1, and the center distance of the end face facing the image side is d2, where 5.75mm≤d1≤7.75mm and 1.0mm≤d2≤2.0mm; the center distance of the end face of the second lens 2 facing the object side is d3, and the center distance of the end face facing the image side is d4, where 7.27mm≤d3≤9.27mm and 0.09mm≤d4≤0.11mm; the center distance of the end face of the third lens 3 facing the object side is d5, and the center distance of the end face facing the image side is d6, where 3.45mm≤d5≤5.45mm and 1.0mm≤d6≤2.0mm; the center distance of the end face of the fourth lens 4 facing the object side is d7, and the center distance of the end face facing the image side is d8, where 1.0mm≤d7≤2.0mm and 2.92mm≤d8≤4.92mm. It should be noted that the center distance of a lens refers to the distance from the top of the lens to the optical axis.

[0053] In one specific embodiment, preferably, in the first lens 1, d1 = 6.75mm, d2 = 1.29mm; in the second lens 2, d3 = 8.27mm, d4 = 0.1mm; in the third lens 3, d5 = 4.4298mm, d6 = 1.54mm; and in the fourth lens 4, d7 = 1.5mm, d8 = 3.92mm.

[0054] In this embodiment, the refractive index of the first lens 1 is n1, 1.4 ≤ n1 ≤ 1.5; the refractive index of the second lens 2 is n2, 1.73 ≤ n2 ≤ 1.83; the refractive index of the third lens 3 is n3, 1.54 ≤ n3 ≤ 1.64; and the refractive index of the second lens 2 is n4, 1.47 ≤ n4 ≤ 1.57. The refractive index of a lens is the ratio of the speed of light in a vacuum to the speed of light in the lens material.

[0055] In one specific embodiment, preferably, n1 = 1.45 in the first lens 1, n2 = 1.78 in the second lens 2, n3 = 1.59 in the third lens 3, and n4 = 1.52 in the fourth lens 4.

[0056] In this embodiment, the distance from the entrance pupil 5 to the image plane 6 of the microscope is S, where 253mm ≤ S ≤ 353mm, and the reference distance from the entrance pupil 5 to the image plane 6 is 273mm. The entrance pupil 5 is the effective aperture that restricts the incident light beam and is the virtual image formed by the front optical system with respect to the aperture stop. The position and size of the entrance pupil are closely related to the aperture stop. The entrance pupil determines the effective diameter of the light received by the system and affects the angle and incident conditions of the light. Generally, the larger the entrance pupil, the stronger the light receiving ability and the wider the angle range of the light.

[0057] The image plane 6 can be understood as the surface of the photosensitive chip facing the object, that is, the surface of a camera element such as a CCD or CMOS. It can be understood that the light carrying the information of the object being photographed can pass through the first lens 1, the second lens 2, the third lens 3, the fourth lens 4, and the filter in sequence and finally be imaged on the image plane 6.

[0058] In this embodiment, the entrance pupil 5 distance between the microscope and the end face of the first lens 1 near the object side is S1, 70mm≤S1≤170mm, and the reference distance of the entrance pupil 5 distance is 90mm.

[0059] In this embodiment, the back focal length between the end face of the third lens 3 near the image side and the image plane 6 is BFL, 140mm≤BFL≤170mm, preferably BFL=159mm. The working wavelength of the microscope is 430nm-680nm.

[0060] In this embodiment, the total optical length of the optical system is TTL, 20mm ≤ TTL ≤ 30mm, preferably TTL = 24mm. It should be noted that the total optical length is the distance from the center vertex of the object-side surface of the first lens 1 to the image plane 6.

[0061] In this embodiment, the entrance pupil 5 diameter of the optical system is set to D1, where 10mm ≤ D1 ≤ 30mm, preferably D1 = 20mm; the image-side aperture of the optical system is set to NA, where 0.04 ≤ NA ≤ 0.06, NA = 0.05; and the image plane 6 aperture of the optical system is set to D2, where 20mm ≤ D2 ≤ 25mm, preferably D2 = 22mm. The microscope's limiting resolution can reach 5μm, field curvature is less than 40μm, and relative distortion is controlled below 0.2%.

[0062] Specifically, in one embodiment, the refractive index, radius of curvature, and center distance of the lens material are shown in the table below:

[0063] surface 1 (stop) 90 2 40.9056 6.75 1.45 3 -128.8642 1.29 4 -66.7012 8.27 1.78 5 -66.7012 0.1 6 62.3 4.4298 1.59 7 458.9578 1.54 8 -106.4437 1.5 1.52 9 32.2729 3.92 10 155.14

[0064] Please see Figure 1The theoretical MTF curve of the optical system at an entrance pupil distance of 70 mm is as follows: Figure 4 As shown, the theoretical defocus MTF curve of the optical system is as follows: Figure 7 As shown.

[0065] Please see Figure 2 The theoretical MTF curve of the optical system at an entrance pupil distance of 90 mm is as follows: Figure 5 As shown, the theoretical defocus MTF curve of the optical system is as follows: Figure 8 As shown.

[0066] Please see Figure 3 The theoretical MTF curve of the optical system at an entrance pupil distance of 170 mm is as follows: Figure 6 As shown, the theoretical defocus MTF curve of the optical system is as follows: Figure 9 As shown.

[0067] according to Figures 4 to 9 It is known that the optical system can guarantee a contrast ratio of nearly 0.3 (100 lp / mm) at entrance pupil distances of 70mm / 90mm / 170mm, and the theoretical MTF tolerance yield of the lens is above 80%. When the lens has field curvature, the intersection of the entire beam does not coincide with the ideal image point. Although a clear image point can be obtained at each specific point, the entire image plane is a curved surface. This makes it impossible to see the entire image plane clearly during microscopic examination, causing difficulties for observation and photography. The optical system optimizes the field curvature, resulting in a flatter image plane, and solves the interference fringes, field curvature, and tolerance problems existing in the design of sleeve lenses in current similar technologies.

[0068] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention's specification and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A microscope, characterized in that, The microscope has an object side and an image side arranged opposite each other along the optical axis. The microscope includes a microscope tube and an optical system disposed within the microscope tube. The optical system consists of a first lens, a second lens, a third lens, and a fourth lens arranged sequentially at intervals along the optical axis. The first lens is a biconvex lens, the second lens is a meniscus lens with its concave surface facing the object side, the third lens is a convex-concave lens, and the fourth lens is a biconcave lens. The optical power of the first lens is positive, the optical power of the third lens is positive, and the optical power of the fourth lens is negative. The radius of the end face of the first lens facing the object side is R1, and the radius of the end face facing the image side is R2, where 35.9056mm≤R1≤45.9056mm and -133.8642mm≤R2≤-123.8642mm; The radius of the end face of the second lens facing the object side is R3, and the radius of the end face facing the image side is R4, -71.7012mm≤R3≤-61.7012mm, -71.7012mm≤R4≤-61.7012mm; The radius of the end face of the third lens facing the object side is R5, and the radius of the end face facing the image side is R6, where 57.3mm≤R5≤67.3mm and 453.9578mm≤R6≤463.9578mm. The radius of the end face of the fourth lens facing the object side is R7, and the radius of the end face facing the image side is R8, -111.4437mm≤R7≤-101.4437mm, 27.2729mm≤R8≤37.2729mm; The center distance of the end face of the first lens facing the object side is d1, and the center distance of the end face facing the image side is d2, where 5.75mm≤d1≤7.75mm and 1.0mm≤d2≤2.0mm; The center distance of the end face of the second lens facing the object side is d3, and the center distance of the end face facing the image side is d4, where 7.27mm≤d3≤9.27mm and 0.09mm≤d4≤0.11mm. The center distance of the end face of the third lens facing the object side is d5, and the center distance of the end face facing the image side is d6, where 3.45mm≤d5≤5.45mm and 1.0mm≤d6≤2.0mm. The center distance of the end face of the fourth lens facing the object side is d7, and the center distance of the end face facing the image side is d8, where 1.0mm≤d7≤2.0mm and 2.92mm≤d8≤4.92mm. The refractive index of the first lens is n1, where 1.4 ≤ n1 ≤ 1.5; The refractive index of the second lens is n2, where 1.73 ≤ n2 ≤ 1.83; The refractive index of the third lens is n3, where 1.54 ≤ n3 ≤ 1.64; The refractive index of the second lens is n4, where 1.47 ≤ n4 ≤ 1.

57.

2. The microscope as described in claim 1, characterized in that, The first lens, the second lens, the third lens, and the fourth lens are all glass spherical lenses.

3. The microscope as described in claim 1, characterized in that, The distance from the entrance pupil to the image plane of the microscope is S, where 253mm ≤ S ≤ 353mm.

4. The microscope as described in claim 1, characterized in that, The entrance pupil distance between the microscope and the end face of the first lens near the object side is S1, where 70mm≤S1≤170mm.

5. The microscope as described in claim 1, characterized in that, The back focal length between the end face of the third lens near the image side and the image plane is BFL, 140mm≤BFL≤170mm.

6. The microscope as described in claim 1, characterized in that, The total optical length of the optical system is TTL, 20mm≤TTL≤30mm.

7. The microscope as described in claim 1, characterized in that, The entrance pupil diameter of the optical system is set to D1, where 10mm ≤ D1 ≤ 30mm; and / or, The image-side aperture of the optical system is set to NA, where 0.04 ≤ NA ≤ 0.06; and / or, The image plane aperture of the optical system is set to D2, where 20mm ≤ D2 ≤ 25mm.

Images