Microscope objective optical system

Abstract

The present application relates to a kind of microscope objective optical systems, including front group, middle group and rear group in turn along optical axis, front group is used to correct system field curvature and lateral chromatic aberration;Middle group is used to bear optical power;Rear group is used to correct axial chromatic aberration and spherical aberration;Front group includes first lens, second lens, third lens and fourth lens in turn;Middle group includes fifth lens, sixth lens, seventh lens, eighth lens, ninth lens and tenth lens;Rear group includes concave mirror, meniscus lens and mangin mirror.The central part of concave mirror is provided with first circular hole, the back surface of mangin mirror is coated with reflective film, and the reflective film of the back surface of mangin mirror is provided with second circular hole;Rear group includes concave mirror, meniscus lens and mangin mirror.The present application has higher numerical aperture, wider waveband and larger field of view range, and has smaller center obscuration, can realize the large numerical aperture of NA reaches 0.9 and the field of view range of maximum 1mm.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of microscope objective design, in particular to a microscope objective optical system. BACKGROUND

[0002] Microscopes play a key role in many aspects of natural science research and industrial production, and are widely used in semiconductor manufacturing, biomedicine, industrial quality inspection, environmental science and other fields. According to the Dawes criterion, the resolution of a microscope is λ / (2NA), where λ is the wavelength and NA is the numerical aperture of the objective lens. As the demand for microscope resolution increases in various applications, the wavelength of the detection light source is shortened from visible light to ultraviolet light, which increases the difficulty of chromatic aberration correction. In addition to the shortening of the wavelength, increasing the numerical aperture can also improve the resolution of the objective lens, but it also increases the difficulty of correcting the spherical aberration of the optical system. Currently, it is difficult for a microscope to simultaneously achieve large field of view and high resolution performance. Low-power objective lenses (less than 20X) usually have a large field of view, such as the Olympus PLN 4X objective lens, which has a field of view of 5mm, but the numerical aperture is small (NA = 0.1) and the resolution is low. High-power objective lenses (greater than 50X) have a small field of view, such as the Olympus MXPLFLN50XBD objective lens, which has a field of view of less than 0.6mm, a large numerical aperture (NA = 0.8), and a high resolution. Due to the large Lagrange invariant of objective lenses with large numerical aperture and large field of view, the design and development are extremely difficult, and general commercial objective lenses do not have such performance. However, such objective lenses can significantly improve the detection efficiency while obtaining high-resolution microscopic images, which is urgently needed in various applications.

[0003] With the rapid development of semiconductor chips, gene sequencing, and life sciences, the demand for microscopic optical systems has increased significantly, and high numerical aperture, large field of view, and wide spectral range are required. The objective lens, as the core component of the microscopic optical system, directly affects the overall imaging performance. Currently, the imaging spectral range of the objective lens has gradually expanded from visible light to the deep ultraviolet (DUV) spectral range, and the numerical aperture has also been increasing. However, due to the limitations of ultraviolet band materials, it becomes more difficult to design a wide-band high-NA large-field-of-view microscope.

[0004] In 2015, Xue Jinlai et al. designed a flat-field apochromatic microscope objective lens with a numerical aperture of 0.75 and a field of view of 1.3mm, operating in the 400-760nm spectral range. The system uses a full-transmission structure, with a distortion of less than 2%, achieving apochromatic correction in the visible light band, but not suitable for the ultraviolet band. To solve the problem of chromatic aberration correction in a wide spectral range, a catadioptric structure can also be used. A U.S. patent uses this structure, the system uses immersion, the numerical aperture reaches 1.2, and the field of view is 0.15mm. Although it has a large numerical aperture, the field of view is small.

[0005] In 2018, Zhang Xin of Changchun Institute of Optics, Fine Mechanics and Physics designed a liquid immersion microscope, which adopts catadioptric structure, liquid medium is water or biological immersion liquid, has a high numerical aperture of 1.0 in the range of 320nm-800nm, the lens adopts spherical and aspherical design, although it can have a large field of view up to 2mm, but the aspherical surface is difficult to process, and the processing and adjustment tolerance is strict, the manufacturing cost is high.

[0006] In the field of gene sequencing, although the liquid immersion microscope can improve the numerical aperture and increase the detection throughput, the liquid medium may have some impact on the detection, which is a problem to be solved. Therefore, the development of non-liquid immersion high numerical aperture objective lens has become a technical problem to be solved by domestic and foreign researchers.

[0007] At present, the traditional non-liquid immersion high NA commercial microscope objective (such as Zeiss NA0.9 objective), its imaging spectral range is 400nm-700nm, the field of view is generally only about 0.1mm, but it can only be used in visible light band, and it is difficult to meet the demand of ultraviolet microscope with high resolution and large field of view.

[0008] Several patents of KLA-Tencor Technologies Company of the United States designed high NA wide band microscope objective with catadioptric structure, but its field of view is small, only 0.15mm. Another patent of the company designed a microscope objective with ultra-high NA, but it is only suitable for specific working wavelength, not suitable for wide band.

[0009] At present, the commercial reflective objective (such as Beck Optronics Solutions 5006) can be applied to ultraviolet to infrared band, but its NA and field of view are small, NA is 0.65, field of view is only 0.34mm, and the obstruction is relatively large.

[0010] In the above prior art, some shortcomings have been shown, that is, it is difficult for the current microscope objective to have high resolution and large field of view, wide band.

[0011] Generally, ultraviolet light above 200nm is divided into three categories: UV-A (320-400nm), UV-B (280-320nm), and UV-C (200-280nm). The so-called wide band ultraviolet objective refers to the ultraviolet objective whose working wavelength covers one or more of the above ultraviolet bands. In order to realize a wider working range, due to the limitation of ultraviolet band materials, the existing refractive ultraviolet objective generally has only a small numerical aperture under the condition of eliminating chromatic aberration, and still cannot realize high resolution, which is difficult to meet the working requirements of ultraviolet detection.

[0012] At present, catadioptric microscope objective can obtain larger numerical aperture under the condition of achromatism, but the processing and assembly tolerance is very strict, and the development is difficult.

[0013] In summary, it is difficult for the current microscope objective to meet the requirements of high resolution (corresponding to high numerical aperture) and large field of view, wide wavelength band. SUMMARY

[0014] To this end, the technical problem to be solved by the present application is to overcome the problem that the design of the microscope objective in the prior art generally cannot simultaneously obtain a large objective numerical aperture and a large field of view.

[0015] To solve the above technical problems, the present application provides a microscope objective optical system, comprising a front group, a middle group and a rear group arranged in sequence along an optical axis, wherein the front group is used to correct system curvature of field and lateral chromatic aberration; the middle group is used to bear optical power; and the rear group is used to correct axial chromatic aberration and spherical aberration.

[0016] The front group comprises a first lens, a second lens, a third lens and a fourth lens arranged in sequence.

[0017] The middle group comprises a fifth lens, a sixth lens, a seventh lens, an eighth lens, a ninth lens and a tenth lens.

[0018] The rear group comprises a concave mirror, a meniscus lens and a Mangin lens.

[0019] The concave mirror is provided with a first circular aperture in the center, and the Mangin lens is coated with a reflective film on the rear surface, and the reflective film on the rear surface of the Mangin lens is provided with a second circular aperture.

[0020] The focal length range of the front group is 40 < |f front / f | < 250, wherein f is the focal length of the entire microscope objective optical system, f front is the focal length of the front group;

[0021] The focal length range of the middle group is 1.5 < f middle / f < 4, wherein f middle is the focal length of the middle group;

[0022] The focal length range of the rear group is 2 < f back / f < 7, wherein f back is the focal length of the rear group;

[0023] The focal length range of the concave mirror is 0.5 < f mirror / f back < 1.5, wherein f mirror is the focal length of the concave mirror;

[0024] The aperture angle magnification β of the rear group ranges from 1.5 < β < 2.

[0025] In one embodiment of the present application, the first lens is a positive lens, the second lens is a negative lens, the third lens is a positive lens, and the fourth lens is a positive lens.

[0026] In one embodiment of the present application, the fifth lens is a positive lens, the sixth lens is a positive lens, the seventh lens is a negative lens, the eighth lens is a positive lens, the ninth lens is a positive lens, and the tenth lens is a positive lens.

[0027] In one embodiment of the present application, the meniscus lens is a negative lens, and the spherical centers of the front surface and the back surface of the meniscus lens are located on the same side of the meniscus lens, and the spherical center is located on the side close to the Mangin mirror.

[0028] In one embodiment of the present application, the meniscus lens and the concave mirror are in a separate assembly form, and the meniscus lens and the Mangin mirror are in a separate assembly form.

[0029] In one embodiment of the present application, the ratio of the first circular aperture of the concave mirror to the diameter of the concave mirror satisfies: 0.05 < D 1孔 / D 1镜 <0.2, wherein, D 1孔 is the diameter of the first circular aperture, and D 1镜 is the diameter of the concave mirror.

[0030] In one embodiment of the present application, the ratio of the second circular aperture of the reflective film on the back surface of the Mangin mirror to the diameter of the Mangin mirror satisfies: 0.05 < D 2孔 / D 2镜 <0.1, wherein, D 2孔 is the diameter of the second circular aperture of the reflective film on the back surface of the Mangin mirror, and D 2镜 is the diameter of the reflective film on the back surface of the Mangin mirror.

[0031] In one embodiment of the present application, a eleventh lens for correcting high-order aberrations is further included, the eleventh lens is a positive lens, the eleventh lens is arranged at any position between the intermediate image and the meniscus lens, and the intermediate image is formed between the concave mirror and the tenth lens.

[0032] In one embodiment of the present application, the materials of the first lens, the second lens, the third lens and the fourth lens, the fifth lens, the sixth lens, the seventh lens, the eighth lens, the ninth lens, the tenth lens, the concave mirror, the meniscus lens and the Mangin mirror are all silica;

[0033] or the materials of the eighth lens and the tenth lens are all calcium fluoride, and the materials of the first lens, the second lens, the third lens and the fourth lens, the fifth lens, the sixth lens, the seventh lens, the ninth lens, the concave mirror, the meniscus lens and the Mangin mirror are all silica.

[0034] In one embodiment of the present application, a diaphragm for eliminating stray light and limiting the imaging light beam is further included, and the diaphragm is arranged on the fifth lens or arranged between the fourth lens and the fifth lens.

[0035] The above technical solution of the present application has the following advantages compared with the prior art:

[0036] The microscope objective optical system has a higher numerical aperture (NA) and a larger field of view range, and has a smaller central obstruction, can realize a large numerical aperture of NA reaching 0.9 and a field of view range of 1mm at most, and can be used in the fields of semiconductor wafer detection, gene sequencing, life science, industrial detection, etc.

[0037] The rear group structure of the present application adopts a concave mirror, a meniscus lens and a Mangin mirror structure, so that the rear group structure has a relatively loose tolerance and reduces the assembly difficulty;

[0038] The present application can use one of SiO2 or CaF2 single material to be achromatic in a wide waveband, and also can use both of the two materials to obtain better performance and lower processing and assembly difficulty;

[0039] All optical element surfaces of the present application are spherical surfaces, which reduces the processing difficulty and is convenient for practical application. BRIEF DESCRIPTION OF DRAWINGS

[0040] In order to make the content of the present application more easily understood, the present application will be further described in detail below according to the specific embodiments of the present application and in combination with the drawings.

[0041] Figure 1 is a schematic diagram of the microscope objective optical system structure in the first embodiment of the present application;

[0042] Figure 2 is a schematic diagram of the reflecting surface of the concave mirror and the Mangin mirror in the rear group in the embodiment of the present application;

[0043] Figure 3 is an axial chromatic aberration curve of the microscope objective in the first embodiment of the present application;

[0044] Figure 4 is a point spread diagram of the microscope objective in the first embodiment of the present application;

[0045] Figure 5 is an MTF curve of the microscope objective in the first embodiment of the present application;

[0046] Figure 6 is a schematic diagram of the microscope objective optical system structure in the second embodiment of the present application;

[0047] Figure 7is an axial chromatic aberration curve of the microscope objective in the second embodiment of the present application;

[0048] Figure 8 is a point spread diagram of the microscope objective in the second embodiment of the present application;

[0049] Figure 9 is an MTF curve of the microscope objective in the second embodiment of the present application;

[0050] Figure 10 is a schematic diagram of a microscope objective optical system structure in the third embodiment of the present application;

[0051] Figure 11 is an axial chromatic aberration curve of the microscope objective in the third embodiment of the present application;

[0052] Figure 12 is a point spread diagram of the microscope objective in the third embodiment of the present application;

[0053] Figure 13 is an MTF curve of the microscope objective in the third embodiment of the present application;

[0054] Figure 14 is a schematic diagram of a microscope objective optical system structure in the fourth embodiment of the present application;

[0055] Figure 15 is an axial chromatic aberration curve of the microscope objective in the fourth embodiment of the present application;

[0056] Figure 16 is a point spread diagram of the microscope objective in the fourth embodiment of the present application;

[0057] Figure 17 is an MTF curve of the microscope objective in the fourth embodiment of the present application. DETAILED DESCRIPTION

[0058] The present application will be further described below in conjunction with the drawings and specific embodiments, so that those skilled in the art can better understand the present application and implement it, but the embodiments are not limiting to the present application.

[0059] Referring to Figure 1 the present application relates to a microscope objective optical system, which adopts an axial catadioptric structure and sequentially includes a front group, a middle group and a rear group arranged in sequence along an optical axis from an image side to an object side, the front group is used for correcting system curvature of field and transverse chromatic aberration; the middle group is used for bearing optical power; the rear group is used for correcting axial chromatic aberration and spherical aberration;

[0060] The front group includes a first lens 1, a second lens 2, a third lens 3 and a fourth lens 4 arranged in sequence;

[0061] The middle group comprises a fifth lens 5, a sixth lens 6, a seventh lens 7, an eighth lens 8, a ninth lens 9 and a tenth lens 10;

[0062] The rear group comprises a concave mirror 11, a meniscus lens 12 and a Mangin mirror 13; wherein the meniscus lens 12 is mainly used for eliminating axial chromatic aberration; the Mangin mirror 13 is used for correcting chromatic aberration and spherical aberration, and also plays a role in reducing the aperture of the concave mirror 11; the concave mirror 11 is mainly used for providing optical power, and also performs secondary magnification on the numerical aperture;

[0063] The concave mirror 11 is centrally provided with a first circular aperture, and the Mangin mirror 13 is externally coated with a reflecting film on the rear surface, and the reflecting film on the rear surface of the Mangin mirror 13 is provided with a second circular aperture.

[0064] It should be noted that, Figure 1 The middle group further comprises an object plane 14, which is used for placing an observed object, such as a chip.

[0065] Working principle: the light of the observed object on the object plane 14 is transmitted through the second circular aperture of the Mangin mirror 13, and then reaches the concave mirror 11 through the meniscus lens 12; the light is reflected by the concave mirror 11, and then transmitted through the meniscus lens 12 again to reach the second circular aperture of the Mangin mirror 13; after the light converges with the observed object on the object plane 14, the converged light is transmitted through the meniscus lens 12, and then through the first circular aperture of the concave mirror 11; the light is then transmitted through the lenses of the middle group and the front group, and finally reaches the tube lens through the first lens 1, and is imaged on the CCD or CMOS detector through the tube lens to observe the image.

[0066] Further, the first lens 1 is a positive lens, the second lens 2 is a negative lens, the third lens 3 is a positive lens, and the fourth lens 4 is a positive lens.

[0067] Further, the fifth lens 5 is a positive lens, the sixth lens 6 is a positive lens, the seventh lens 7 is a negative lens, the eighth lens 8 is a positive lens, the ninth lens 9 is a positive lens, and the tenth lens 10 is a positive lens.

[0068] Further, the meniscus lens 12 is a negative lens.

[0069] Further, the front group can reduce the incident angle, and is mainly used for correcting the field curvature and lateral chromatic aberration of the system, and also plays a balancing role in coma, astigmatism and spherical aberration; the focal length range of the front group is 40<|f front / f|<250, wherein f is the focal length of the entire microscopic objective optical system, f front is the focal length of the front group;

[0070] The middle element bears most of the optical power and forms a single image; the focal length range of the middle element is 1.5 < f. middle / f<4, where f middle The focal length of the middle group; at the same time, the seventh lens 7 also plays the role of correcting field curvature, while the tenth positive lens 10 undertakes a certain optical power and is used to correct the secondary spectrum;

[0071] The rear group works in conjunction with the first two groups to correct axial chromatic aberration and spherical aberration. The meniscus lens 12 is primarily used to eliminate axial chromatic aberration, while the Manningen lens 13 corrects chromatic aberration and spherical aberration, and also reduces the aperture of the concave mirror 11. The concave mirror 11 primarily provides optical power and simultaneously magnifies the numerical aperture. The focal length range of the rear group is 2 < f. back / f<7, where f back The focal length of the rear element;

[0072] The concave mirror 11 provides the main optical power for the rear group, and the focal length of the concave mirror 11 is in the range of 0.5 < f. mirror / f back <1.5, where f mirror The focal length of the concave mirror 11;

[0073] The magnification β range of the latter group is 1.5 < β < 2.

[0074] Furthermore, the meniscus lens 12 and the concave reflector 11 are assembled separately, and the meniscus lens 12 and the Manning lens 13 are also assembled separately. The meniscus lens 12 does not directly contact any other lens. The rear surface of the Manning lens 13 has an extremely small curvature, ranging from -1 / 800 mm. -1 <ρ<0.

[0075] Furthermore, the centers of spheres corresponding to the front and rear surfaces of the meniscus lens 12 are both located on the same side of the meniscus lens 12, and the centers of spheres are located on the side closer to the Manningen lens 13. In short, the meniscus lens 12 (including the front and rear surfaces) has a meniscus surface with the same radius of curvature direction as the concave mirror 11.

[0076] Furthermore, the ratio of the first circular opening of the concave reflector 11 to the diameter of the concave reflector 11 satisfies: D 1孔 / D 1镜 <0.2, where D 1孔 D is the diameter of the first circular opening. 1镜 The diameter of the concave mirror 11 is given.

[0077] Furthermore, the second circular opening of the reflective film on the rear surface of the Manning mirror 13 and the diameter of the Manning mirror 13 satisfy: 0.05 <D 2孔 / D 2镜<0.1, wherein D 2孔 D is the second circular aperture diameter of the reflective film of the back surface of the Mangin mirror 13. 2镜 D is the diameter of the reflective film of the back surface of the Mangin mirror 13.

[0078] Further, the embodiment further comprises an eleventh lens 16 for correcting high-order phase difference, the eleventh lens 16 being a positive lens, the eleventh lens 16 being arranged at any position between an intermediate image and the meniscus lens 12, the intermediate image being formed between the concave mirror 11 and the tenth lens 10.

[0079] Further, the materials of the first lens 1, the second lens 2, the third lens 3 and the fourth lens 4, the fifth lens 5, the sixth lens 6, the seventh lens 7, the eighth lens 8, the ninth lens 9, the tenth lens 10, the concave mirror 11, the meniscus lens 12 and the Mangin mirror 13 are all silica.

[0080] Or the materials of the eighth lens 8 and the tenth lens 10 are both calcium fluoride, and the materials of the first lens 1, the second lens 2, the third lens 3 and the fourth lens 4, the fifth lens 5, the sixth lens 6, the seventh lens 7, the ninth lens 9, the concave mirror 11, the meniscus lens 12 and the Mangin mirror 13 are all silica.

[0081] Further, the embodiment further comprises a diaphragm 15 for eliminating stray light and limiting an imaging light beam, the diaphragm 15 being arranged on the fifth lens 5, or the diaphragm 15 being arranged between the fourth lens 4 and the fifth lens 5.

[0082] Further, the microscopic objective optical system of the embodiment can work in a waveband of 360-550 nm.

[0083] The present application is described in detail below through four embodiments:

[0084] Embodiment One

[0085] Referring to Figure 1 Embodiment One is described, which provides a microscopic objective optical system, the optical system coaxially arranging a front group, a middle group and a rear group in sequence along an optical axis from left to right.

[0086] In actual application, as shown in Figure 1 from left to right along the optical axis, the front group of the objective is coaxially arranged by the first lens 1, the second lens 2, the third lens 3 and the fourth lens 4; the middle group of the objective is coaxially arranged by the fifth lens 5, the diaphragm 15 arranged on the fifth lens 5, the sixth lens 6, the seventh lens 7, the eighth lens 8 and the ninth lens 9; the rear group of the objective is coaxially arranged by the concave mirror 11, the meniscus lens 12 and the Mangin mirror 13, and all lens surfaces adopt standard spherical surfaces. Figure 2As shown, wherein A is the reflecting surface of the concave mirror 11 with a first circular aperture, and B is the reflecting surface of the Mangin mirror 13 with a second circular aperture.

[0087] The front group is used to reduce the incident angle, eliminate a part of spherical aberration and field curvature, wherein the second lens 2 is used to correct the field curvature; the middle group is used to share the optical power of the whole system and reduce the pressure of the optical power of the remaining lens group, wherein the seventh lens 7 is used to correct the field curvature, and the tenth lens 10 is mainly used to correct the secondary spectrum; the rear group is used to eliminate the axial chromatic aberration introduced by the wide spectrum, wherein the concave mirror 11 provides the main optical power of the rear group, the meniscus lens 12 is mainly used to correct the axial chromatic aberration, and the Mangin mirror 13 is used to correct the chromatic aberration, spherical aberration and reduce the aperture of the objective lens, and the back surface curvature is ρ=-1 / 1038mm -1 The optical system of the embodiment has a large numerical aperture of 0.9 and an image field of view of 0.8mm, provides higher flux for microscopic measurement, and also increases the processability under the guarantee of the above technical indexes, so that the optical system of the embodiment not only can be designed, but also has processability.

[0088] The front group only has weak optical power, and the focal length f front satisfies: |f front / f| = 113.87.

[0089] The middle group bears most of the optical power of the objective lens, and the focal length f middle satisfies: f middle / f = 2.88.

[0090] The rear group bears part of the optical power of the objective lens, and the focal length f back satisfies: f back / f = 4.72; and simultaneously plays a role of amplifying the numerical aperture, and the amplification rate β = 1.88.

[0091] The concave mirror 11 bears the main optical power of the rear group, and the focal length f mirror satisfies: f mirror / f back = 0.94.

[0092] In a refractive optical system, according to the achromatic formula, two lenses are needed to correct chromatic aberration, and the Abbe number of the two lenses should be very different, and the optical power should be very small; if further correction of secondary spectrum is needed, the dispersion coefficients of the two lenses should be similar and the Abbe numbers should be different. For conventional optical materials, residual secondary spectrum cannot be completely eliminated, and special optical lenses or refractive-diffractive optical elements must be selected. For optical systems with a working wavelength below 400nm, the transmittance of optical materials in this wavelength band is mostly low, and the types that can be selected are even fewer, so it is difficult to achieve wide-band achromatic correction in the ultraviolet band with a refractive structure.

[0093] The microscope objective optical system provided in this embodiment employs an achromatic group consisting of a concave mirror 11, a meniscus lens 12 with negative optical power, and a Manning lens 13 with positive optical power. This group is used to eliminate axial chromatic aberration introduced into the optical system by the broadband spectrum. In other words, by combining the same material with an internal reflection lens structure, broadband intraspectral apochromatic aberration is achieved. This results in the optical system of the present invention having a broadband spectrum of 360nm to 550nm, and an RMS wavefront error of less than 0.0481λ at the dominant wavelength of 365nm, exhibiting excellent image quality.

[0094] The separate design of the meniscus lens 12 and the concave mirror 11 in the rear group allows for looser component tolerances.

[0095] The aperture 15 is mounted on the fifth lens 5 to eliminate stray light and limit the imaging beam.

[0096] The lens material used in Example 1 is SiO2.

[0097] like Figure 3 The optical system shown in this embodiment achieves apochromatic aberration.

[0098] like Figure 4 The RMS radius of the optical system dot plot shown in this embodiment is smaller than the radius of the Airy disk.

[0099] like Figure 5 The optical system shown in this embodiment has an MTF of over 0.1 at 3000 lp / mm, which is close to the diffraction limit, and the image quality is good.

[0100] The parameters of the first and middle groups in Example 1 are shown in Table 1, and the parameters of the last group in Example 1 are shown in Table 2.

[0101] Table 1. Parameters of the front and middle groups in Example 1

[0102]

[0103] Table 2 Parameters of the group after Example 1

[0104]

[0105] Example 2

[0106] See Figure 6 Example 2 describes a microscope objective optical system. The optical system has a front group, a middle group, and a rear group arranged coaxially from left to right along the optical axis. An eleventh lens 16 is added as a field lens after the first image in the middle group, which can give the system better image quality.

[0107] In practical applications, this implementation method, such as Figure 6As shown, from left to right along the optical axis, the front group is composed of the first lens 1, the second lens 2, the third lens 3, and the fourth lens 4; the middle group is composed of the fifth lens 5, the diaphragm 15 arranged on the fifth lens 5, the sixth lens 6, the seventh lens 7, the eighth lens 8, the ninth lens 9, the tenth lens 10, and the eleventh lens 16; and the rear group is composed of the concave mirror 11, the meniscus lens 12, and the Mangin lens 13.

[0108] The front group is used to reduce the incident angle and eliminate a part of spherical aberration and field curvature, the second lens 2 is used to correct the field curvature, the middle group is used to share the optical power of the whole system and reduce the pressure of the optical power of the remaining lens groups, the seventh lens 7 is used to correct the field curvature, the tenth lens 10 and the eleventh lens 16 are used to correct the secondary spectrum, and the eleventh lens 16 is also used to correct a part of high-order aberration, and the rear group is used to eliminate the axial chromatic aberration introduced by a wide spectrum, the concave mirror 11 provides the main optical power of the rear group, the meniscus lens 12 is mainly used to correct the axial chromatic aberration, and the Mangin lens 13 is used to correct the chromatic aberration and spherical aberration and reduce the aperture of the objective lens, the curvature of the rear surface is ρ = -1 / 1953 mm -1 ; so that the optical system of the embodiment has a large numerical aperture of 0.9 and an image field of 0.8 mm, provides higher flux for microscopic measurement, and also increases the processability under the condition of ensuring the above technical indexes, so that the optical system of the embodiment not only can be designed, but also has processability.

[0109] The front group only has weak optical power, and the focal length f front of the front group satisfies: |f front / f| = 107.24.

[0110] The middle group bears most of the optical power of the objective lens, and the focal length f middle of the middle group satisfies: f middle / f = 3.

[0111] The rear group bears part of the optical power of the objective lens, and the focal length f back of the rear group satisfies: f back / f = 4.70; and simultaneously plays a role of amplifying the numerical aperture, and the amplification rate β = 1.88.

[0112] The concave mirror 11 bears the main optical power of the rear group, and the focal length f mirror of the concave mirror 11 satisfies: f mirror / f back = 0.95.

[0113] The embodiment adopts the achromatic group composed of the first concave mirror 11, the meniscus lens 12 with negative optical power and the meniscus mirror 13 with positive optical power, which is used to eliminate the axial chromatic aberration introduced by a wide spectral range to the optical system; that is, the achromaticity in a wide spectral range is realized by the combination of the same material and the internal reflection lens structure, so that the optical system has a wide spectral range of 360nm-550nm, and the RMS wavefront error at the main wavelength of 365nm is less than 0.0308lambda, and has excellent image quality.

[0114] The meniscus thick lens 12 in the rear group is separated from the concave mirror 11, so that the tolerance of the element is more relaxed.

[0115] The diaphragm 15 is arranged on the fifth lens 5, which is used to eliminate stray light and limit the imaging light beam.

[0116] The materials of the lenses in the second embodiment are all SiO2.

[0117] As shown in Figure 7 The optical system of the embodiment realizes complex achromaticity.

[0118] As shown in Figure 8 The point column diagram of the optical system of the embodiment is less than the Airy spot radius.

[0119] As shown in Figure 9 The MTF of the optical system of the embodiment is higher than 0.1 at 3000lp / mm, close to the diffraction limit, and the image quality is good.

[0120] The parameters of the front group and the middle group of the second embodiment are shown in Table 3, and the parameters of the rear group of the second embodiment are shown in Table 4.

[0121] Table 3 Parameters of the front group and the middle group of the second embodiment

[0122]

[0123] Table 4 Parameters of the rear group of the second embodiment

[0124]

[0125] Embodiment three

[0126] As shown in Figure 10 The embodiment three provides a microscopic objective optical system, which is coaxially arranged from left to right along the optical axis with a front group, a middle group and a rear group.

[0127] The optical system of the embodiment has a field of view of 1mm.

[0128] In actual application, as shown in Figure 10As shown, from left to right along the optical axis, the front group is sequentially coaxially placed by the first lens 1, the second lens 2, the third lens 3, and the fourth lens 4; the middle group is sequentially placed by the fifth lens 5, the diaphragm 15 arranged on the fifth lens 5, the sixth lens 6, the seventh lens 7, the eighth lens 8, the ninth lens 9, and the tenth lens 10; the rear group of the objective lens is composed of the concave mirror 11, the meniscus lens 12, and the Mangin mirror 13, and all lens surfaces are standard spherical surfaces.

[0129] The front group is used to reduce the incident angle and eliminate a part of spherical aberration and field curvature, the second lens 2 is used to correct the field curvature, the middle group is used to share the optical power of the whole system and reduce the pressure of the optical power of the remaining lens groups, the seventh lens 7 is used to correct the field curvature, and the tenth lens 10 is mainly used to correct the secondary spectrum; the rear group is used to eliminate the axial chromatic aberration introduced by the wide spectrum, the concave mirror 11 provides the main optical power of the rear group, the meniscus lens 12 is mainly used to correct the axial chromatic aberration, and the Mangin mirror 13 is used to correct the chromatic aberration, spherical aberration, and reduce the aperture of the objective lens, the curvature of the rear surface is ρ=-1 / 1174 mm -1 ; so that the optical system of the embodiment has a large numerical aperture of 0.9, a large image field of 1 mm, provides a larger field of view for microscopic measurement, and also increases the processability under the condition of ensuring the above technical indicators, so that the optical system of the embodiment not only can be designed, but also has processability.

[0130] The front group only has weak optical power, and the focal length f front of the front group satisfies: |f front / f| = 179.17.

[0131] The middle group bears most of the optical power of the objective lens, and the focal length f middle of the middle group satisfies: f middle / f = 2.96.

[0132] The rear group bears part of the optical power of the objective lens, and the focal length f back of the rear group satisfies: f back / f = 4.72; and simultaneously plays a role of amplifying the numerical aperture, and the amplification rate β = 1.90.

[0133] The concave mirror bears the main optical power of the rear group, and the focal length f mirror of the concave mirror satisfies: f mirror / f back = 0.94.

[0134] The embodiment provides a microscope objective optical system, which adopts a concave mirror 11, a meniscus lens 12 with negative optical power and a meniscus mirror 13 with positive optical power to form an achromatic group for eliminating axial chromatic aberration of an optical system caused by a wide spectrum; that is, by combining the same material and an internal reverse lens structure, wide spectrum chromatic aberration is eliminated, so that the optical system has a wide spectrum of 360nm-550nm, and the RMS wavefront error is less than 0.0569lambda at a main wavelength of 365nm, and has excellent image quality.

[0135] The meniscus thick lens 12 in the rear group is separated from the concave mirror 11, so that the tolerance of the element is looser.

[0136] The diaphragm 15 is arranged on the fifth lens 5 and is used for eliminating stray light and limiting an imaging light beam.

[0137] In the embodiment three, the materials of the lenses are all SiO2.

[0138] As shown in the figure, the optical system in the embodiment realizes complex chromatic aberration. Figure 11

[0139] As shown in the figure, the point array diagram of the optical system in the embodiment is smaller than the Airy disk radius. Figure 12

[0140] As shown in the figure, the MTF of the optical system in the embodiment is higher than 0.1 at 3000lp / mm, approaches the diffraction limit, and has good image quality. Figure 13

[0141] The parameters of the front group and the middle group in the embodiment three are shown in Table 5, and the parameters of the rear group in the embodiment three are shown in Table 6.

[0142] Table 5 Parameters of the front group and the middle group in the embodiment three

[0143]

[0144] Table 6 Parameters of the rear group in the embodiment three

[0145]

[0146] Embodiment four

[0147] As shown in the figure, the optical system in the embodiment four realizes complex chromatic aberration. Figure 14 The embodiment four provides a microscope objective optical system, which is coaxially arranged from left to right along an optical axis and sequentially has a front group, a middle group and a rear group.

[0148] The embodiment four uses CaF2 and SiO2, so that the system has better imaging quality and looser tolerance.

[0149] In actual application, as shown in the figure, the embodiment is used for imaging. Figure 14 ​​​As shown, from left to right along the optical axis, the front group is sequentially coaxially placed by the first lens 1, the second lens 2, the third lens 3, and the fourth lens 4; the middle group is sequentially placed by the fifth lens 5, the diaphragm 15 arranged between the fourth lens and the fifth lens 5, the sixth lens 6, the seventh lens 7, the eighth lens 8, the ninth lens 9, and the tenth lens 10; the rear group of the objective lens is composed of the concave mirror 11, the meniscus lens 12, and the Mangin mirror 13, and all the lens surfaces are standard spherical surfaces. The eighth lens 8 and the tenth lens 10 are made of CaF2, and the rest of the lenses are made of SiO2.

[0150] The front group is used to reduce the incident angle and eliminate a part of spherical aberration and field curvature, and the second lens 2 is used to correct the field curvature.

[0151] In particular, the eighth lens 8 and the tenth lens 10 not only provide the optical power, but also correct the secondary spectrum.

[0152] The rear group is used to eliminate the axial chromatic aberration introduced by the wide spectrum, the concave mirror 11 provides the main optical power of the rear group, the meniscus lens 12 is mainly used to correct the axial chromatic aberration, and the Mangin mirror 13 is used to correct the chromatic aberration, spherical aberration, and reduce the aperture of the objective lens, and the curvature of the rear surface is ρ=-1 / 1052mm -1 ; so that the optical system of the embodiment has a large numerical aperture of 0.9 and an image field of 0.8mm, provides higher flux for microscopic measurement, and also increases the processability under the condition of ensuring the above technical indicators, so that the optical system of the embodiment not only can be designed, but also has processability.

[0153] The front group only has weak optical power, and the focal length f front of the front group satisfies: |f front / f|=47.15.

[0154] The middle group bears most of the optical power of the objective lens, and the focal length f middle of the middle group satisfies: f middle / f=2.91.

[0155] The rear group bears part of the optical power of the objective lens, and the focal length f back of the rear group satisfies: f back / f=4.66; and also plays a role in amplifying the numerical aperture, and the amplification rate β=1.88.

[0156] The concave mirror 11 bears the main optical power of the rear group, and the focal length f mirror of the concave mirror 11 satisfies f mirror / f back =0.94.

[0157] The embodiment provides a microscope objective optical system, which adopts a concave mirror 11, a meniscus lens 12 with negative optical power and a Mangin mirror 13 with positive optical power to form an achromatic group, so as to eliminate the axial chromatic aberration introduced by a wide spectral range to the optical system.

[0158] The meniscus lens 12 in the rear group is separated from the concave mirror 11, so that the tolerance of the element is looser.

[0159] The diaphragm 15 is arranged between the fourth lens 4 and the fifth lens 5, so as to eliminate stray light and limit the imaging light beam.

[0160] As shown in the point spread function of the optical system in the embodiment, the optical system is implemented to be apochromatic. Figure 15 As shown in the point spread function of the optical system in the embodiment, the point spread function RMS radius of the optical system is less than the Airy disc radius.

[0161] Figure 16 As shown in the point spread function of the optical system in the embodiment, the point spread function RMS radius of the optical system is less than the Airy disc radius.

[0162] As shown in the point spread function of the optical system in the embodiment, the point spread function RMS radius of the optical system is less than the Airy disc radius. Figure 17 As shown in the MTF of the optical system in the embodiment, the MTF of the optical system is higher than 0.1 at 3100 l p / mm, close to the diffraction limit, and the image quality is good.

[0163] The parameters of the front group and the middle group of the embodiment four are shown in Table 7, and the parameters of the rear group of the embodiment four are shown in Table 8.

[0164]

[0165]

[0166]

[0167] The parameters of the rear group of the embodiment four are shown in Table 8.

[0168]

[0169] Although the preferred embodiments of the present application have been described, those skilled in the art who understand the basic inventive concept can make additional changes and modifications to the embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present application.

[0170] ​​Obviously, the above embodiments are merely example for clearly illustrating, and are not limitation to the embodiments. For ordinary skilled in the art, other different forms of changes or variations can be made on the basis of the above description. Here, all the embodiments need not and can not be exhausted. The obvious changes or variations derived therefrom are still within the scope of the present invention.

Claims

1. A microscope objective optical system, characterized in that: From image to object, the system comprises a front group, a middle group, and a rear group arranged sequentially along the optical axis. The front group is used to correct system field curvature and lateral chromatic aberration; the middle group is used to handle optical power; and the rear group is used to correct axial chromatic aberration and spherical aberration. The front group includes a first lens (1), a second lens (2), a third lens (3) and a fourth lens (4) arranged in sequence; the first lens (1) is a positive lens, the second lens (2) is a negative lens, the third lens (3) is a positive lens, and the fourth lens (4) is a positive lens; The middle group includes a fifth lens (5), a sixth lens (6), a seventh lens (7), an eighth lens (8), a ninth lens (9), and a tenth lens (10); the fifth lens (5) is a positive lens, the sixth lens (6) is a positive lens, the seventh lens (7) is a negative lens, the eighth lens (8) is a positive lens, the ninth lens (9) is a positive lens, and the tenth lens (10) is a positive lens; The rear group includes a concave mirror (11), a meniscus lens (12), and a Manning lens (13); the meniscus lens (12) is a negative lens, and the centers of the spheres corresponding to the front and rear surfaces of the meniscus lens (12) are located on the same side of the meniscus lens (12), and the centers of the spheres are located on the side closer to the Manning lens (13). The concave mirror (11) has a first circular opening in the center, and the rear surface of the Manning mirror (13) is coated with a reflective film and the reflective film on the rear surface of the Manning mirror (13) has a second circular opening. The focal length range of the front group is 40 < |f front / f|<250, where f is the focal length of the entire microscope objective optical system, f front The focal length of the front group; The focal length range of the middle group is 1.5 < f middle / f<4, where f middle The focal length of the middle group; The focal length range of the rear group is 2 < f back / f<7, where f back The focal length of the rear element; The focal length range of the concave mirror (11) is 0.5 < f. mirror / f back <1.5, where f mirror The focal length of the concave mirror (11); The aperture angular magnification β of the rear group is in the range of 1.5 < β < 2.

2. The microscope objective optical system according to claim 1, characterized in that: The meniscus lens (12) and the concave reflector (11) are assembled separately, and the meniscus lens (12) and the Manningen mirror (13) are assembled separately.

3. The microscope objective optical system according to claim 1, characterized in that: The ratio of the first circular opening of the concave mirror (11) to the diameter of the concave mirror (11) satisfies: D 1孔 / D 1镜 <0.2, where D 1孔 D is the diameter of the first circular opening. 1镜 The diameter of the concave mirror (11) is given.

4. The microscope objective optical system according to claim 1, characterized in that: The second circular opening of the reflective film on the rear surface of the Manning mirror (13) and the diameter of the Manning mirror (13) satisfy: 0.05 <D 2孔 / D 2镜 <0.1, where D 2孔 D is the diameter of the second circular opening in the reflective film on the rear surface of the Manning mirror (13). 2镜 The diameter of the reflective film on the back surface of the Mankind mirror (13) is given.

5. The microscope objective optical system according to claim 1, characterized in that: It also includes an eleventh lens (16) for correcting higher-order phase aberrations. The eleventh lens (16) is a positive lens and is positioned at any position between the intermediate image and the meniscus lens (12). The intermediate image is formed between the concave mirror (11) and the tenth lens (10).

6. The microscope objective optical system according to claim 1, characterized in that: The first lens (1), the second lens (2), the third lens (3), the fourth lens (4), the fifth lens (5), the sixth lens (6), the seventh lens (7), the eighth lens (8), the ninth lens (9), the tenth lens (10), the concave mirror (11), the meniscus lens (12), and the Manningen mirror (13) are all made of silicon dioxide. Alternatively, the eighth lens (8) and the tenth lens (10) are both made of calcium fluoride, and the first lens (1), the second lens (2), the third lens (3), the fourth lens (4), the fifth lens (5), the sixth lens (6), the seventh lens (7), the ninth lens (9), the concave mirror (11), the meniscus lens (12), and the Manningen mirror (13) are all made of silicon dioxide.

7. The microscope objective optical system according to claim 1, characterized in that: It also includes an aperture (15) for eliminating stray light and limiting the imaging beam, the aperture (15) being disposed on the fifth lens (5), or the aperture (15) being disposed between the fourth lens (4) and the fifth lens (5).

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