A small ultraviolet wide-band high numerical aperture microscopic objective optical system

Abstract

The application discloses a small ultraviolet wide-band high numerical aperture microscopic objective optical system, and relates to the technical field of optical imaging. The system comprises a front group and a rear group coaxially arranged in sequence from an image side to an object side along an optical axis; the front group comprises first to fourth lenses, and the rear group comprises an aperture, a fifth lens, a sixth lens and a seventh lens; the fifth lens and the sixth lens form a cemented lens; the seventh lens is a Mangin mirror, a half-reflective and half-transmissive film is at least partially coated on the front surface of the seventh lens, a reflective film is coated on the rear surface of the seventh lens except a central circular area, and the central circular area is used for transmitting light. The application realizes ultraviolet wide-band (such as 260-450 nm) imaging by using only seven lenses, the numerical aperture is greater than or equal to 0.8, the field of view is greater than or equal to 0.6 mm, the system length is less than 30 mm, the structure is simple, the volume is small, and the system is easy to assemble and adjust, and can be used in the fields of semiconductor wafer detection, gene sequencing and life science.

Description

Technical Field

[0001] This invention relates to the field of optical imaging technology, and in particular to a small ultraviolet broadband high numerical aperture microscope objective optical system. Background Technology

[0002] Microscopes play an irreplaceable role in fields such as semiconductor manufacturing, biomedicine, and industrial inspection. According to the Dove criterion, the resolution of a microscope is... Decision, among which For the operating wavelength, This refers to the numerical aperture of the objective lens. To improve detection accuracy and efficiency, there is an urgent need for objectives to simultaneously possess short operating wavelengths, wide operating bands, and high numerical apertures to achieve higher imaging throughput. However, these three factors are mutually restrictive, significantly increasing the difficulty of correcting chromatic aberration and spherical aberration. To obtain higher throughput, existing objective lens structures tend to be more complex, often employing more than a dozen lens elements, which increases the system size and significantly enhances the design and manufacturing difficulty.

[0003] Currently, commercial microscopes struggle to simultaneously meet the requirements of a wide ultraviolet wavelength range, a large field of view, and high resolution. Low-magnification objectives (less than 20×) offer a large field of view but suffer from small numerical apertures and low resolution. High-magnification objectives (greater than 50×) have high numerical apertures, but their field of view is typically less than 0.6 mm, making them unsuitable for wide ultraviolet wavelength ranges. While catadioptric objectives can operate in the wide ultraviolet wavelength range, their size is usually large (over 100 mm) to achieve a large field of view, making their development challenging.

[0004] For high-NA objectives in the ultraviolet wideband, existing research has employed fully transmissive structures (such as the plan-field apochromatic objective designed by Xue Jinlai et al., with a numerical aperture of 0.75 and an operating wavelength of 400–760 nm), but these are not suitable for the ultraviolet band. Several patents from KLA-Tencor in the United States have achieved high-NA wideband imaging using a catadioptric structure, but the field of view is small (only 0.15 mm), or it is only applicable to specific wavelengths. The liquid-immersion catadioptric objective designed by the Changchun Institute of Optics, Fine Mechanics and Physics achieves NA 1.0 and a field of view of 2 mm in the 320–800 nm range, but the liquid medium may affect the sample being tested, limiting its application scenarios. The above solutions typically use more than 10 lenses, resulting in a system length exceeding 100 mm, and the tolerance requirements for the Manning mirror and the reflecting mirror are strict, making manufacturing and assembly difficult.

[0005] Therefore, there is an urgent need for a non-immersion ultraviolet wide-band high numerical aperture microscope objective that is simple in structure, small in size, and easy to assemble and adjust. Summary of the Invention

[0006] To address this, embodiments of the present invention provide a small-scale ultraviolet wide-band high numerical aperture microscope objective optical system, which solves the problem in the prior art of simultaneously achieving high numerical aperture, large field of view, simple structure, small size and easy assembly and adjustment in the ultraviolet wide-band.

[0007] To address the aforementioned technical problems, this invention provides a small ultraviolet broadband high numerical aperture microscope objective optical system, comprising a front group and a rear group coaxially arranged along the optical axis from the image side to the object side.

[0008] The front group includes a first lens, a second lens, a third lens, and a fourth lens;

[0009] The rear group includes an aperture stop, a fifth lens, a sixth lens, and a seventh lens;

[0010] The fifth lens and the sixth lens together form a cemented lens;

[0011] The seventh lens is a Manning lens, with at least a portion of its front surface coated with a semi-reflective and semi-transparent film, and its rear surface coated with a reflective film except for the central circular area, the central circular area being used to transmit light.

[0012] The focal length of the front group With the focal length of the entire objective lens satisfy: ;

[0013] The focal length of the rear group With the focal length of the entire objective lens satisfy: .

[0014] Preferably, the front surface of the seventh lens is coated with a semi-reflective and semi-transparent film over the entire area, or a semi-reflective and semi-transparent or internally reflective film is coated in the central inner reflection area and an anti-reflective film is coated in the remaining area.

[0015] Preferably, the front group consists of 3 to 6 lenses, and the rear group consists of 2 to 4 lenses.

[0016] Preferably, the total length of the microscope objective optical system is less than 30 mm, and the maximum aperture of the lens does not exceed 15 mm.

[0017] Preferably, the operating wavelength of the microscope objective optical system is 260nm~450nm or 365nm~600nm.

[0018] Preferably, at least one of the first to fourth lenses is an aspherical lens, used to further improve the image quality of the optical system or increase the field of view. Preferably, the front group is used to correct field curvature, lateral chromatic aberration, coma, astigmatism, and spherical aberration, and the rear group is used to handle the main optical power.

[0019] Preferably, the seventh lens is the only catadioptric element in the rear group.

[0020] Preferably, the numerical aperture of the microscope objective optical system is greater than or equal to 0.8, and the image-side field of view is greater than or equal to 0.6 mm.

[0021] Preferably, light enters from the object through the central circular area on the rear surface of the seventh lens, and is reflected sequentially by the front surface of the seventh lens, reflected by the reflective film on the rear surface, and transmitted through the area on the front surface coated with a semi-reflective or anti-reflective film. Then, it passes sequentially through the sixth lens, the fifth lens, the aperture stop, the fourth lens, the third lens, the second lens, and the first lens to form a parallel beam.

[0022] As can be seen from the above technical solutions, this invention application has the following beneficial effects:

[0023] First, the structure is simple and the size is small: the present invention uses only 7 lenses, the total length of the system is less than 30mm, and the maximum diameter of the lens does not exceed 15mm. Compared with the existing technology of microscope objectives with more than ten lenses and a length of more than 100mm, the structure is significantly simplified, the volume is reduced, and the material cost and manufacturing difficulty are reduced.

[0024] Second, it achieves both high resolution and a large field of view in the ultraviolet wide band: This invention can operate in the ultraviolet wide band of 260nm to 450nm (or 365nm to 600nm), with a numerical aperture of 0.8 or higher and an image-square field of view of 0.6mm or higher (1.0mm in some embodiments). It simultaneously achieves high resolution, a large field of view and wide spectrum imaging, overcoming the technical bottleneck of traditional objectives that are difficult to achieve both high NA and a large field of view in the ultraviolet band.

[0025] Third, it is easy to assemble and adjust and has low development difficulty: only one Manningen mirror is used as the catadioptric element in the rear group, avoiding the complex assembly tolerance of the double Manningen mirror structure; at the same time, the front surface of the Manningen mirror provides three coating methods (full area semi-reflective and semi-transparent film, or central semi-reflective and semi-transparent film, or central internal reflection film + peripheral anti-reflective film), which can be flexibly selected according to the blocking ratio requirements, reducing the assembly and adjustment accuracy requirements and manufacturing costs, and improving the system's manufacturability and engineering practicality. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly described below. Referring to the drawings will make the features and advantages of the present invention clearer. The drawings are illustrative and should not be construed as limiting the present invention in any way. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0027] Figure 1 This is a schematic diagram of the structure of the small ultraviolet broadband high numerical aperture microscope objective optical system provided in Embodiment 1 of the present invention;

[0028] Figure 2 This is a schematic diagram of the coating process for the entire front surface of the seventh lens (Mankin lens) in this invention, which involves coating a semi-reflective and semi-transparent film.

[0029] Figure 3 This is a schematic diagram of the coating process in this invention, in which a semi-reflective and semi-transparent film is coated in the central area of ​​the front surface of the seventh lens (Mankin lens), and an anti-reflective film is coated in the remaining areas.

[0030] Figure 4 This is an axial chromatic aberration curve of the microscope objective lens according to Embodiment 1 of the present invention;

[0031] Figure 5 This is the MTF curve of the microscope objective lens in Embodiment 1 of the present invention;

[0032] Figure 6 This is a schematic diagram of the structure of the microscope objective optical system provided in Embodiment 2 of the present invention;

[0033] Figure 7 This is an axial chromatic aberration curve of the microscope objective lens in Embodiment 2 of the present invention;

[0034] Figure 8 This is the MTF curve of the microscope objective lens in Embodiment 2 of the present invention;

[0035] Figure 9 This is a schematic diagram of the structure of the microscope objective optical system provided in Embodiment 3 of the present invention;

[0036] Figure 10 This is an axial chromatic aberration curve of the microscope objective lens in Embodiment 3 of the present invention;

[0037] Figure 11 This is the MTF curve of the microscope objective lens in Embodiment 3 of the present invention;

[0038] Figure 12 This is a schematic diagram of the structure of the microscope objective optical system provided in Embodiment 4 of the present invention;

[0039] Figure 13 This is an axial chromatic aberration curve of the microscope objective lens in Embodiment 4 of the present invention;

[0040] Figure 14 This is the MTF curve of the microscope objective in Embodiment 4 of the present invention.

[0041] Explanation of reference numerals in the accompanying drawings: 1. First lens; 2. Second lens; 3. Third lens; 4. Fourth lens; 5. Fifth lens; 6. Sixth lens; 7. Seventh lens; 8. Aperture stop; 9. Object plane. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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 some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0043] Example 1:

[0044] See Figure 1 Example 1 provides a small ultraviolet wide-band high numerical aperture microscope objective optical system. The optical system has a front group and a rear group arranged coaxially along the optical axis from left to right.

[0045] The objective lens adopts a coaxial catadioptric structure. From left to right, from image side to object side, the front group consists of lens 1, lens 2, lens 3, and lens 4; the rear group consists of aperture 8, lens 5, lens 6, and lens 7 (Manning lens). Among them, lens 5 and lens 6 form a cemented lens to eliminate chromatic aberration in the system.

[0046] The front surface of the seventh lens 7 (Mankin lens) can be coated in two ways: one is to coat the entire area with a semi-reflective and semi-transparent film, the other is to coat the central internal reflection area with an internal reflection film and the remaining areas with an anti-reflective film, and the third is to coat the central internal reflection area with a semi-reflective and semi-transparent film and the remaining areas with an anti-reflective film, in order to reduce the system's blocking ratio.

[0047] Specifically, such as Figure 2 and Figure 3 As shown:

[0048] Method 1 (e.g.) Figure 2 (As shown): The entire area is coated with a semi-reflective and semi-transparent film. Light is both reflected and transmitted on the front surface of the Manning lens, making it suitable for scenarios where the obstruction ratio is not critical.

[0049] Method 2 (e.g.) Figure 3 As shown): The central reflective area (i.e., the central circular area) is coated with a semi-reflective, semi-transparent film, while the remaining areas are coated with an anti-reflective film. This method can reduce the system's occlusion ratio and improve energy utilization, making it suitable for scenarios with higher requirements for imaging brightness and contrast.

[0050] Regardless of the method used, the rear surface of the seventh lens 7, except for the central circular area, is coated with a reflective film. The central circular area is not coated with a reflective film and is used to transmit light from the object side. This coating design allows the system to achieve a catadioptric optical path using only a single Manningen mirror, simplifying the structure and reducing assembly difficulty.

[0051] The rear surface of the seventh lens 7 is coated with a reflective film in the central circular area, which allows light reflected from the target object to pass through the seventh lens 7 and enter the system.

[0052] The front element is primarily used to correct spherical aberration, coma, field curvature, and astigmatism in the system, and also serves to correct chromatic aberration. The focal length of the front element... With the focal length of the entire objective lens satisfy: In this embodiment, the front group only has low light power, and the focal length of the front group is... satisfy: .

[0053] The rear element accounts for most of the system's optical power; the focal length of the rear element... With the focal length of the entire objective lens satisfy: In this embodiment, the rear focal length... satisfy: .

[0054] The rear group uses only one catadioptric element (i.e., the seventh lens 7), making the system easier to assemble and adjust. The system uses only 7 lenses, resulting in a simple structure and low cost. The maximum lens diameter does not exceed 10mm, and the total system length is 18.95mm, making the system very small in size.

[0055] The aperture 8 is positioned between the fourth lens 4 and the fifth lens 5 to eliminate stray light and limit the imaging beam.

[0056] The optical system described in this embodiment can be used in the 260-450nm band, has a large numerical aperture of 0.8 and an image-square field of view of 0.6mm, providing higher throughput for microscopic measurements. Furthermore, while ensuring the above technical specifications, it also increases the guarantee of manufacturability, so that the optical system described in this invention can not only be designed, but also has manufacturability.

[0057] like Figure 4 As shown, the optical system in this embodiment achieves apochromatic aberration. Figure 5 As shown, the MTF of the optical system in this embodiment is higher than 0.15 at 3000 lp / mm, indicating good image quality.

[0058] The optical system parameters of this embodiment are shown in Table 1.

[0059] Table 1. Optical System Parameter Table for Example 1

[0060] It should be noted that in the table, S1 is the front surface of the first lens 1 (facing the image side), S2 is the rear surface of the first lens 1 (facing the object side), S3 is the front surface of the second lens 2, S4 is the rear surface of the second lens 2, S5 is the front surface of the third lens 3, S6 is the rear surface of the third lens 3, S7 is the front surface of the fourth lens 4, S8 is the rear surface of the fourth lens 4, and the aperture stop 8 (plane) is the plane where the aperture stop 8 is located between the fourth lens 4 and the fifth lens 5; S9 is the front surface of the fifth lens 5, S10 is the cemented surface between the rear surface of the fifth lens 5 and the front surface of the sixth lens 6, S11 is the rear surface of the sixth lens 6, S12 is the front surface of the seventh lens 7, i.e., the Manning lens, and S13 is the rear surface of the seventh lens 7, i.e., the Manning lens (coated with a reflective film, except for the central circular area).

[0061] Light enters from the object or specimen through the central optical aperture (central circular area) on the rear surface of the seventh lens 7, is reflected from the front surface of the seventh lens 7 to the reflective surface on its rear surface, is reflected again through the transmission area (or semi-reflective and semi-transparent film area) on the front surface of the seventh lens 7, and then the beam passes sequentially through the sixth lens 6, the fifth lens 5, the aperture 8, the fourth lens 4, the third lens 3, the second lens 2, and the first lens 1 to form a parallel beam, which is then imaged on the detector through the tube lens.

[0062] Example 2:

[0063] See Figure 6 Example 2 provides a compact ultraviolet wideband high numerical aperture microscope objective optical system. Compared with Example 1, the difference lies in the use of aspherical surfaces in the system, which gives the system a larger field of view and better image quality.

[0064] In practical applications, the objective lens of this embodiment adopts a coaxial catadioptric structure. From left to right, from image side to object side, the front group consists of a first lens 1, a second lens 2, a third lens 3, and a fourth lens 4 (aspherical); the rear group consists of an aperture stop 8, a fifth lens 5, a sixth lens 6, and a seventh lens 7 (Manningen lens). Among them, the fifth lens 5 and the sixth lens 6 form a cemented lens to eliminate chromatic aberration in the system.

[0065] The front surface of the seventh lens 7 (Mankin lens) can be coated in three ways: first, a semi-reflective coating is applied to the entire area; second, an internal reflection coating is applied to the central reflective area, while the remaining areas are partially coated with anti-reflective coatings; third, a semi-reflective coating is applied to the central reflective area, while the remaining areas are partially coated with anti-reflective coatings, in order to reduce the system's blocking ratio. The rear surface of the seventh lens 7 has a reflective coating in its central circular area, which allows light reflected from the target object to pass through the seventh lens 7 and enter the system.

[0066] The front group is mainly used to correct spherical aberration, coma, field curvature, and astigmatism in the system, and also corrects chromatic aberration. The focal length range of the front group is... In this embodiment, the front focal length... satisfy: .

[0067] The rear group handles most of the system's optical power, with a focal length range of [missing information]. In this embodiment, the rear focal length... satisfy: .

[0068] The rear group uses only one catadioptric element (seventh lens 7), making the system easier to assemble and adjust. The system uses only 7 lenses, resulting in a simple structure and low cost. The maximum lens diameter does not exceed 11mm, and the total system length does not exceed 19.12mm, making the system very small in size.

[0069] The aperture 8 is positioned between the fourth lens 4 and the fifth lens 5 to eliminate stray light and limit the imaging beam.

[0070] The optical system described in this embodiment can be used in the 260-450nm band, has a large numerical aperture of 0.8 and an image-side field of view of 1.0mm, and provides higher throughput for microscopic measurements.

[0071] like Figure 7 As shown, the optical system in this embodiment achieves apochromatic aberration. Figure 8 As shown, the MTF of the optical system in this embodiment is higher than 0.15 at 3100 lp / mm, indicating good image quality.

[0072] The optical system parameters of this embodiment are shown in Table 2 and the aspheric coefficients in Table 2-1.

[0073] Table 2 Optical System Parameter Table for Example 2

[0074] Table 2-1 Aspherical Coefficients Table for Example 2

[0075] The light path is the same as in Example 1, and will not be described again here.

[0076] Example 3:

[0077] See Figure 9 Example 3 provides a small ultraviolet broadband high numerical aperture microscope objective optical system. Compared with Examples 1 and 2, the difference is that an aspherical mirror is used, giving the system a field of view of 0.85NA and 0.6mm.

[0078] In practical applications, the objective lens of this embodiment adopts a coaxial catadioptric structure. From left to right, from image side to object side, the front group consists of a first lens 1, a second lens 2 (aspheric), a third lens 3, and a fourth lens 4 (aspheric); the rear group consists of an aperture stop 8, a fifth lens 5, a sixth lens 6, and a seventh lens 7 (Manningen lens). Among them, the fifth lens 5 and the sixth lens 6 form a cemented lens to eliminate chromatic aberration in the system.

[0079] The front surface of the seventh lens 7 (Mankin lens) can be coated in three ways: first, a semi-reflective coating is applied to the entire area; second, an internal reflection coating is applied to the central reflective area, while the remaining areas are partially coated with anti-reflective coatings; third, a semi-reflective coating is applied to the central reflective area, while the remaining areas are partially coated with anti-reflective coatings, in order to reduce the system's blocking ratio. The rear surface of the seventh lens 7 has a reflective coating in its central circular area, which allows light reflected from the target object to pass through the seventh lens 7 and enter the system.

[0080] The front group is mainly used to correct spherical aberration, coma, field curvature, and astigmatism in the system, and also corrects chromatic aberration. The focal length range of the front group is... In this embodiment, the front focal length... satisfy: .

[0081] The rear group handles most of the system's optical power, with a focal length range of [missing information]. In this embodiment, the rear focal length... satisfy: .

[0082] The rear group uses only one catadioptric element (seventh lens 7), making the system easier to assemble and adjust. The system uses only 7 lenses, resulting in a simple structure and low cost. The maximum lens diameter does not exceed 11mm, and the total system length does not exceed 21.69mm, making the system very small in size.

[0083] The aperture 8 is positioned between the fourth lens 4 and the fifth lens 5 to eliminate stray light and limit the imaging beam.

[0084] The optical system described in this embodiment can be used in the 260-450nm band, has a large numerical aperture of 0.85 and an image-side field of view of 0.6mm, providing higher throughput for microscopic measurements.

[0085] like Figure 10 As shown, the optical system in this embodiment achieves apochromatic aberration. Figure 11 As shown, the MTF of the optical system in this embodiment is higher than 0.15 at 3300 lp / mm, indicating good image quality.

[0086] The optical system parameters of this embodiment are shown in Table 3 and the aspherical coefficients in Table 3-1.

[0087] Table 3 Optical System Parameter Table for Example 3

[0088] Table 3-1 Aspherical Coefficients Table for Example 3

[0089] The light path is the same as in Example 1, and will not be described again here.

[0090] Example 4:

[0091] See Figure 12 Example 4 provides a small ultraviolet wideband high numerical aperture microscope objective optical system. Compared with the previous examples, the difference lies in the use of aspherical mirrors, which gives the system a field of view of 0.9 NA and 0.6 mm.

[0092] In practical applications, the objective lens of this embodiment adopts a coaxial catadioptric structure. From left to right, from image side to object side, the front group consists of a first lens 1, a second lens 2 (aspheric), a third lens 3, and a fourth lens 4 (aspheric); the rear group consists of an aperture stop 8, a fifth lens 5, a sixth lens 6, and a seventh lens 7 (Manningen lens). Among them, the fifth lens 5 and the sixth lens 6 form a cemented lens to eliminate chromatic aberration in the system.

[0093] The front surface of the seventh lens 7 (Mankin lens) can be coated in three ways: first, a semi-reflective coating is applied to the entire area; second, an internal reflection coating is applied to the central reflective area, while the remaining areas are partially coated with anti-reflective coatings; third, a semi-reflective coating is applied to the central reflective area, while the remaining areas are partially coated with anti-reflective coatings, in order to reduce the system's blocking ratio. The rear surface of the seventh lens 7 has a reflective coating in its central circular area, which allows light reflected from the target object to pass through the seventh lens 7 and enter the system.

[0094] The front group is mainly used to correct spherical aberration, coma, field curvature, and astigmatism in the system, and also corrects chromatic aberration. The focal length range of the front group is... In this embodiment, the front focal length... satisfy: .

[0095] The rear group handles most of the system's optical power, with a focal length range of [missing information]. In this embodiment, the rear focal length... satisfy: .

[0096] The rear group uses only one catadioptric element (seventh lens 7), making the system easier to assemble and adjust. The system uses only 7 lenses, resulting in a simple structure and low cost. The maximum lens diameter does not exceed 11mm, and the total system length does not exceed 24.81mm, making the system very small in size.

[0097] The aperture 8 is positioned between the fourth lens 4 and the fifth lens 5 to eliminate stray light and limit the imaging beam.

[0098] The optical system described in this embodiment can be used in the 260-450nm band, has a large numerical aperture of 0.9 and an image-side field of view of 0.6mm, and provides higher throughput for microscopic measurements.

[0099] like Figure 13 As shown, the optical system in this embodiment achieves apochromatic aberration. Figure 14 As shown, the MTF of the optical system in this embodiment is higher than 0.12 at 3500 lp / mm, indicating good image quality.

[0100] The optical system parameters of this embodiment are shown in Table 4 and the aspherical coefficients are shown in Table 4-1.

[0101] Table 4 Optical System Parameter Table for Example 4

[0102] Table 4-1 Aspherical Coefficients Table for Example 4

[0103] The light path is the same as in Example 1, and will not be described again here.

[0104] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A small ultraviolet broadband high numerical aperture microscope objective optical system, characterized in that, This includes a front group and a rear group arranged coaxially from the image side to the object side along the optical axis; The front group includes a first lens, a second lens, a third lens, and a fourth lens; The rear group includes an aperture stop, a fifth lens, a sixth lens, and a seventh lens; The fifth lens and the sixth lens together form a cemented lens; The seventh lens is a Manning lens, with at least a portion of its front surface coated with a semi-reflective and semi-transparent film, and its rear surface coated with a reflective film except for the central circular area, the central circular area being used to transmit light. The focal length of the front group With the focal length of the entire objective lens satisfy: ; The focal length of the rear group With the focal length of the entire objective lens satisfy: .

2. The compact ultraviolet broadband high numerical aperture microscope objective optical system according to claim 1, characterized in that, The front surface of the seventh lens is coated with a semi-reflective and semi-transparent film over the entire area, or with a semi-reflective and semi-transparent or internally reflective film coated in the central inner reflection area and an anti-reflective film coated in the remaining area.

3. The compact ultraviolet broadband high numerical aperture microscope objective optical system according to claim 1, characterized in that, The front group consists of 3 to 6 lenses, and the rear group consists of 2 to 4 lenses.

4. The compact ultraviolet broadband high numerical aperture microscope objective optical system according to claim 1, characterized in that, The total length of the microscope objective optical system is less than 30 mm, and the maximum aperture of the lens does not exceed 15 mm.

5. The compact ultraviolet broadband high numerical aperture microscope objective optical system according to claim 1, characterized in that, The operating wavelength range of the microscope objective optical system is 260nm~450nm or 365nm~600nm.

6. The compact ultraviolet broadband high numerical aperture microscope objective optical system according to claim 1, characterized in that, At least one of the first to fourth lenses is an aspherical lens, used to further improve the image quality of the optical system or increase the field of view.

7. The compact ultraviolet broadband high numerical aperture microscope objective optical system according to claim 1, characterized in that, The front group is used to correct field curvature, lateral chromatic aberration, coma, astigmatism, and spherical aberration, while the rear group is used to handle the main optical power.

8. The compact ultraviolet broadband high numerical aperture microscope objective optical system according to claim 1, characterized in that, The seventh lens is the only catadioptric element in the rear group.

9. The compact ultraviolet broadband high numerical aperture microscope objective optical system according to claim 1, characterized in that, The numerical aperture of the microscope objective optical system is greater than or equal to 0.8, and the image-side field of view is greater than or equal to 0.6 mm.

10. The optical system for a small ultraviolet broadband high numerical aperture microscope objective according to claim 1, characterized in that, Light enters from the object through the central circular area on the rear surface of the seventh lens, and is reflected sequentially by the front surface of the seventh lens, the reflective film on the rear surface, and the area on the front surface coated with a semi-reflective or anti-reflective film. Then, it passes sequentially through the sixth lens, the fifth lens, the aperture, the fourth lens, the third lens, the second lens, and the first lens to form a parallel beam.

Images