Microscope objective lens

Abstract

To provide an objective lens for microscopes that is usable under an influence of radiation, and aberration of which is suppressed.SOLUTION: There is provided an objective lens 100 for microscopes that has a first lens 102 that is located on the most observation object side and is composed of quartz. The first lens 102 has a first plane 3 that is a plane on the observation object side, and a second plane 4 that is a plane on a side opposite the first plane, the first plane 3 having a concave surface 102a, the second plane 4 having a convex surface. Assuming that n1 represents a refractive index of the quartz and r1 represents a radius of curvature (in mm) of the concave surface 102a, an expression 0.028<|(n1-1) / (r1×n1)|<0.063 is satisfied. In a use state, the concave surface 102a of the first lens 102 is exposed to an environment that is exposed to radiation.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a microscope objective lens that is expected to be used in radiation environments. [Background Art]

[0002] When a microscope is used in a radiation environment, a phenomenon occurs in which the glass lenses constituting the optical system are colored under the influence of radiation. This phenomenon is called radiation-induced browning. As a method for avoiding this phenomenon, a structure in which lenses exposed to the radiation environment are formed of quartz is conceivable. For example, Patent Document 1 and Patent Document 2 are known disclosures of microscopes having lenses formed of quartz. [Prior Art Documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent No. 6392947 [Patent Document 2] Japanese Patent No. 5385442 [Summary of the Invention] [Problem to be Solved by the Invention]

[0004] The lens most affected by radiation is the lens positioned closest to an observation object. On the other hand, in the case of a microscope, the lens (front lens) positioned closest to the observation object is required to have an optical function for obtaining a required NA. When a quartz lens is employed as the front lens, the following problems arise.

[0005] Quartz has a lower refractive index than glass. For example, the refractive index of quartz around 550 nm is 1.46, while the refractive index of glass for lenses ranges from 1.5 to 1.85 depending on the type of glass.

[0006] Therefore, in order to achieve the same power with a quartz lens as with a glass lens, the radius of curvature of the lens surface must be smaller compared to that of a glass lens. However, when the radius of curvature of the lens surface is reduced, the degree of lens curvature increases, and the problem of aberrations becomes apparent.

[0007] Against this backdrop, the present invention aims to provide a microscope objective lens that can be used under the influence of radiation (in a radiation-affected environment) and has suppressed aberrations. [Means for solving the problem]

[0008] The present invention relates to a microscope objective lens having a first lens made of quartz, located closest to the object to be observed, wherein the first lens has a first surface which is the surface facing the object to be observed and a second surface which is the surface opposite to the first surface, the first surface is concave and the second surface is convex, and where n1 is the refractive index of the quartz and r1 is the radius of curvature (in mm) of the concave surface, the following condition is met: 0.028 < |(n1-1) / (r1×n1)| < 0.063. The microscope objective lens of the present invention allows the first surface of the first lens to be exposed to an environment exposed to radiation when in use.

[0009] In the present invention, the second lens and the third lens are arranged on the side of the second surface of the first lens, away from the first lens, in order from the position closest to the first lens, the second lens has two concave surfaces, the second lens and the third lens have two concave surfaces, and the second lens and the third lens are arranged such that one concave surface of the second lens and one concave surface of the third lens face each other, and the refractive index of the second lens is n2, the refractive index of the third lens is n3, the radius of curvature of the one concave surface of the second lens (in mm) is r2, and the radius of curvature of the one concave surface of the third lens (in mm) is r3. 0.04 < |(n²-1) / (r²×n²)| < 0.07 0.02 < |(n3-1) / (r3×n3)| < 0.06 Examples of embodiments that satisfy this condition include:

[0010] In the present invention, a configuration in which the distance d between the one concave surface of the second lens and the one concave surface of the third lens on the optical axis is d = 2.5 mm to 5.0 mm is preferred. In the present invention, an optical aperture is arranged between the second lens and the third lens.

[0011] In the present invention, between the first lens and the optical aperture, there are achromatic lenses 1, 2, and 3 formed by bonding a positive lens and a negative lens arranged in order from the side of the first lens. Achromatic lens 1 is composed of lens 1 and lens 2, achromatic lens 2 is composed of lens 3 and lens 4, and achromatic lens 3 is composed of lens 5 and lens 6. The refractive index of lens 1 on the g line is n01g, the refractive index on the F line is n01F, the refractive index on the C line is n01C, the Abbe number on the d line is νd1, the partial dispersion ratio θg.F.1 is θg.F.1=(n01g-n01F) / (n01F-n01C), the refractive index of lens 2 on the g line is n02g, the refractive index on the F line is n02F, the refractive index on the C line is n02C, the Abbe number on the d line is νd2, and the partial dispersion ratio θg.F.2 is θg.F.2=(n02g-n02F). / (n02F-n02C), the refractive index of lens 3 in the g line is n03g, the refractive index in the F line is n03F, the refractive index in the C line is n03C, the Abbe number in the d line is νd3, the partial dispersion ratio θg.F.3 is θg.F.3=(n03g-n03F) / (n03F-n03C), the refractive index of lens 4 in the g line is n04g, the refractive index in the F line is n04F, the refractive index in the C line is n04C, the Abbe number in the d line is νd4, the partial dispersion ratio θg.F.4 is θg.F.4=(n04g-n04F) / (n04F-n04C), the refractive index of lens 5 in the g line is n05g, the refractive index in the F line is n05F, the refractive index in the C line is n05C, the Abbe number in the d line is νd5, the partial dispersion ratio θg.F.5 is θg.F.5=(n05g-n05F) / (n05F-n05C), the refractive index of lens 6 in the g line is n06g, the refractive index in the F line is n06F, the refractive index in the C line is n06C, the Abbe number in the d line is νd6, the partial dispersion ratio θg.F.6 is θg.F.6=(n06g-n06F) One possible configuration is where / (n06F-n06C) satisfies -0.0015 < (θg.F.2-θg.F.1) / (νd2-νd1) < 0, -0.0015 < (θg.F.4-θg.F.3) / (νd4-νd3) < 0, and -0.0015 < (θg.F.6-θg.F.5) / (νd6-νd5) < 0. Here, lenses 2, 4, and 5 are anomalous dispersion glass. [Effects of the Invention]

[0012] According to the present invention, there is obtained an objective lens for a microscope that can be used under the influence of radiation and in which aberrations are suppressed. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] [Figure 1] It is a conceptual diagram of the objective lens of an embodiment. [Figure 2] It is a block diagram of the microscope of an embodiment. [Figure 3] It is a lens configuration diagram of Working Example 1. [Figure 4] It is a longitudinal aberration diagram of Working Example 1. [Figure 5] It is a lateral aberration diagram of Working Example 1. [Figure 6] It is a lens configuration diagram of Working Example 2. [Figure 7] It is a longitudinal aberration diagram of Working Example 2. [Figure 8] It is a lateral aberration diagram of Working Example 2. [Figure 9] It is a lens configuration diagram of Working Example 3. [Figure 10] It is a longitudinal aberration diagram of Working Example 3. [Figure 11] It is a lateral aberration diagram of Working Example 3. MODES FOR CARRYING OUT THE INVENTION

[0014] (Overview) FIG. 1 shows an objective lens 100 for a microscope, which has a first lens 102 made of quartz located closest to an observation object, the first lens 102 has a first surface 3 that is a surface on the observation object side and a second surface 4 that is a surface opposite to the first surface, the first surface 3 has a concave surface 102a, the second surface 4 has a convex surface, and where n1 is the refractive index of the quartz and r1 is the radius of curvature (unit: m) of the concave surface 102a, the objective lens satisfies 0.028<|(n1-1) / (r1×n1)|<0.062, and in a use state, the first surface 3 (concave surface 102a) of the first lens 102 is exposed to an environment exposed to radiation.

[0015] FIG. 1 shows the lens configuration of an objective lens 100 according to an embodiment. FIG. 2 shows an outline of a microscope 200 using the objective lens 100. In this example, an observation object (sample) 150 is observed using the microscope 200.

[0016] Observation of the observation object using the microscope 200 is performed through a quartz plate 101. In this example, the quartz plate 101 is a bottom plate portion of a petri dish that holds the observation object, and observation using the microscope 200 is performed through this bottom plate portion. The portion of the quartz plate 101 may also be a cover glass in some cases. In this example, the thickness of the quartz plate 101 is 0.3 mm.

[0017] The microscope 200 is an example of a fluorescence microscope, and includes the objective lens 100, a light source 210 that emits illumination light for causing fluorescence in the observation object 150, a beam splitter 220 that separates illumination light from observation light, an imaging lens 230, and a detector 240 that performs imaging. As the beam splitter 220, one using a prism or a dichroic mirror is used. The objective lens 100 is an infinity-corrected objective lens, and the light beam emitted toward the detector 240 side becomes parallel light. The parallel light from the objective lens 100 is focused by the imaging lens 230, and an image of the observation object 150 is formed at the position of the detector 240. The detector 240 is a two-dimensional image sensor, and detects the formed image as image data. As the detector 240, for example, a CMOS image sensor or a CCD image sensor is used.

[0018] Illumination light from the light source 210 is irradiated onto the observation object 150 through the objective lens 100, the reflected light from the observation object 150 and the fluorescence generated in the observation object 150 are detected by the detector 240 through the objective lens 100, and image data of a microscope image is obtained.

[0019] (Structure of Objective Lens) As shown in Figure 1, the objective lens 100 has a structure in which lenses 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, and 113 are arranged from the side of the object to be observed.

[0020] The microscope 200 shown in Figure 2 is designed for use in a radiation environment. Therefore, the lens 102, which is closest to the object being observed 150 and exposed to the radiation environment, is made of quartz. The lens 102 is located at the very front of the objective lens 100 and is therefore called the front element.

[0021] In this example, since the thickness of lens 102 is sufficient and it is expected to adequately shield against radiation in a radioactive environment, the lens after lens 103 is made of optical glass for lenses. The required thickness of the quartz material to shield against radiation is estimated to be at least 2 mm, preferably around 3 mm. Although gamma rays are assumed as the radiation, it is also possible that the object being observed 150 is a radioactive material.

[0022] If lens 102 cannot shield against radiation and lens 103 also needs radiation resistance, then lens 103 is also made of quartz. The same applies to lenses 104 and beyond.

[0023] Furthermore, even if radiation resistance is required for lenses 103 and beyond, if the required performance is not very high, radiation-resistant glass can be used as the material for lenses 103 and beyond. However, since lens 102 is expected to be exposed to radiation for extended periods, it is essential that it be made of quartz.

[0024] The objective lens 100 is optically designed, including the quartz plate 101. The objective lens 100 is designed for the visible light band (F-line, d-line, C-line, g-line). The numerical aperture is set to NA = 0.56.

[0025] In this example, lens 102 is made of quartz, and lenses 103-106, 108, and 111-113 are made of optical glass for lenses. Lenses 107, 109, and 110 are made of anomalous dispersion glass for lenses.

[0026] Hereafter, the side of the object being observed 150 will be referred to as the front, front side, or front stage, and the side opposite the object being observed (the side of the detector 230) will be referred to as the rear, rear side, or rear stage. Furthermore, when focusing on a particular lens, the front lens surface will be referred to as the front surface, and the rear lens surface will be referred to as the rear surface.

[0027] Furthermore, each lens has a designation on its front and rear surfaces, and these designations are used to identify the lens surface. For example, the front surface of lens 102 is designated as surface 3 (surface with designation 3), and the rear surface of lens 102 is designated as surface 4 (surface with designation 4). Similarly, the front surface of lens 103 is designated as surface 5, and the rear surface of lens 103 is designated as surface 6.

[0028] Lens 102 has positive refractive power and is a meniscus lens with a concave front surface (3 surfaces) 102a and a convex rear surface (4 surfaces). Lens 103 is positioned behind lens 102.

[0029] Lens 103 has a positive refractive power. Lenses 104 and 105 are positioned behind lens 103. Lenses 104 and 105 form a cemented lens, and the lens as a whole has a positive refractive power.

[0030] Lenses 106 and 107 are positioned behind lenses 104 and 105. Lenses 106 and 107 form a cemented lens and have a positive refractive power as a whole.

[0031] Lenses 108 and 109 are positioned behind lenses 106 and 107. Lenses 108 and 109 form a cemented lens and have a positive refractive power as a whole.

[0032] Lenses 110 and 111 are positioned after lenses 108 and 109. Lenses 110 and 111 form a cemented lens and are meniscus lenses with their concave surfaces facing the detector.

[0033] Lenses 112 and 113 are positioned behind lenses 110 and 111. Lenses 112 and 113 form a cemented lens, a meniscus lens with its concave surface facing the object being observed. Together, these two meniscus lenses have a negative refractive power as a whole.

[0034] A space 114 is formed between the concave surface on the rear of lens 111 (reference numeral 18a) and the concave surface on the front of lens 112 (reference numeral 20a). An optical diaphragm 115 is positioned between lens 111 and lens 112. The optical diaphragm 115 has a flat plate shape with a round hole in the center.

[0035] (Details of Lens 102) Lens 102 uses quartz. Since quartz has a lower refractive index than glass, the radius of curvature of the lens surface must be smaller compared to the case of glass in order to obtain the same optical properties. In this case, the curvature of the lens must be smaller compared to the case of glass, and the problem of aberration becomes more apparent compared to the case of glass.

[0036] Therefore, in this embodiment, lens 102 allows for a certain degree of aberration while pursuing the necessary optical characteristics for the front element, and the aberration is corrected by the lens group in the rear stage (the side furthest from the object of observation 150 when viewed from lens 102).

[0037] To achieve the above objective, the front surface (3 surfaces) of lens 102 is designed under the following conditions. First, as described above, surface 3 is a concave surface 102a, and surface 4 is a convex surface. Here, if the refractive index of the quartz constituting lens 102 is n1, and the radius of curvature of the concave surface 102a (in mm) is r1, then the Petzval sum (n1-1) / (r1×n1) related to the concave surface 102a of lens 102 is designed to satisfy the following conditions. 0.028 < |(n1-1) / (r1×n1)| < 0.063

[0038] When |(n1-1) / (r1×n1)| ≤ 0.028, the radius of curvature r1 becomes larger, and the curvature of the lens surface becomes smaller (closer to a plane). As a result, the aberration correction required for the front element of the objective lens 100 (the lens 102 closest to the object being observed) becomes insufficient, making it difficult to obtain resolution in the peripheral field of view. In this case, aberration correction becomes difficult in subsequent stages.

[0039] On the other hand, if |(n1-1) / (r1×n1)|≧0.063, the radius of curvature r1 of the concave surface 102a becomes small, resulting in poor manufacturability. Also, as the radius of curvature of the concave surface 102a decreases, aberrations such as spherical aberration become more pronounced. In this case as well, correcting aberrations in subsequent stages becomes difficult.

[0040] For the reasons stated above, the lens 102, which is necessary to correct aberrations in the subsequent stage and to obtain the required resolution, must satisfy the above inequality.

[0041] (Conditions required for aberration correction) The following describes the mechanism for correcting aberrations that occur in the front element (lens 102) in subsequent stages. In this example, the above aberrations are corrected using lenses 111 and 112 shown in Figure 1. Here, the 18 surfaces of lens 111 and the 20 surfaces of lens 112 are designed to satisfy the following conditions.

[0042] Here, the refractive index of the glass constituting lens 111 is n17, the refractive index of the glass constituting lens 112 is n20, r18 is the radius of curvature of the 18th surface (concave surface of symbol 18a) (unit: mm), and r20 is the radius of curvature of the 20th surface (concave surface of part of symbol 20a) (unit: mm). The following conditions are satisfied with respect to the Petzval sum relating to the 18th and 20th surfaces.

[0043] 0.04<|(n17-1) / (r18×n17)|<0.07 0.02<|(n20-1) / (r20×n20)|<0.06

[0044] When |(n17-1) / (r18×n17)|≦0.04, r18 becomes large, and the function of correcting aberrations by the 18th surface is insufficient. That is, it becomes difficult to effectively correct aberrations.

[0045] When 0.07≦|(n17-1) / (r18×n17)|, r18 becomes small, which reduces the manufacturability of the lens 111, and also causes obvious occurrence of aberrations such as coma due to the concave structure of the 18th surface.

[0046] When |(n20-1) / (r20×n20)|≦0.02, r20 becomes large, and the function of correcting aberrations by the 20th surface is insufficient. That is, it becomes difficult to effectively correct aberrations.

[0047] When 0.06≦|(n20-1) / (r20×n20)|, r20 becomes small, which reduces the manufacturability of the lens 112, and also causes obvious occurrence of aberrations such as coma due to the concave structure of the 20th surface.

[0048] Further, the separation distance d18 between the 18th surface and the 20th surface on the optical axis in the portion of the space 114 formed between the opposing concave surfaces between the 18th surface and the 20th surface is in the range of 2.5 mm < d18 < 5 mm. When 5 mm ≦ d18, it becomes difficult to correct field curvature. When d18 ≦ 2.5 mm, the lens 111 and the lens 112 contact each other, which cannot be physically implemented.

[0049] (Conditions for correcting chromatic aberration) In this embodiment, chromatic aberration is corrected in particular by the following configuration. Here, achromatic lens 1 is formed by a cemented lens of a negative lens 106 and a positive lens 107, achromatic lens 2 is formed by a cemented lens of a negative lens 108 and a positive lens 109, and achromatic lens 3 is formed by a cemented lens of a positive lens 110 and a negative lens 111. Lenses 107, 109, and 110 are made of anomalous dispersion glass. Chromatic aberration is corrected by satisfying the conditions described below. Here, (θg.F.2-θg.F.1) / (ν2-ν1) for each lens is limited as follows.

[0050] -0.0015<(θg.F.11-θg.F.10) / (ν11-ν10)<0 -0.0015<(θg.F.14-θg.F.13) / (ν14-ν13)<0 -0.0015<(θg.F.17-θg.F.16) / (ν17-ν16)<0

[0051] Here, θg.F = (ng - nF)(nF - nC), where ng is the refractive index at the g line (435.824 nm), nF is the refractive index at the F line (486.133 nm), and nC is the refractive index at the C line (656.273 nm).

[0052] In the above case, let n01g be the refractive index of lens 106 in the g line, n01F be the refractive index in the F line, and n01C be the refractive index in the C line, then θg.F.10 = (n01g - n01F)(n01F - n01C). Also, let ν10 be the Abbe number of lens 106. Note that the Abbe number is the value in the d line (wavelength 587.6560 nm). This is the same for other Abbe numbers.

[0053] Let n02g be the refractive index of lens 107 along the g line, n02F along the F line, and n02C along the C line. Then θg.F.11 = (n02g - n02F) / (n02F - n02C). Also, let ν11 be the Abbe number of lens 107.

[0054] Let n03g be the refractive index of lens 108 along the g line, n03F be the refractive index along the F line, and n03C be the refractive index along the C line. Then θg.F.13 = (n03g - n03F) / (n03F - n03C). Also, let ν13 be the Abbe number of lens 108.

[0055] Let n04g be the refractive index of lens 109 along the g line, n04F be the refractive index along the F line, and n04C be the refractive index along the C line. Then θg.F.14 = (n04g - n04F) / (n04F - n04C). Also, let ν14 be the Abbe number of lens 109.

[0056] Let n05g be the refractive index of lens 110 along the g line, n05F be the refractive index along the F line, and n05C be the refractive index along the C line, then θg.F.16 = (n05g - n05F) / (n05F - n05C). Also, let ν16 be the Abbe number of lens 110.

[0057] Let n06g be the refractive index of lens 111 in the g line, n06F be the refractive index in the F line, and n06C be the refractive index in the C line. Then θg.F.17 = (n06g - n06F) / (n06F - n06C). Also, let ν17 be the Abbe number of lens 111.

[0058] If (θg.F.2-θg.F.1) / (ν2-ν1) exceeds the above range, chromatic aberration correction will be excessive, leading to new chromatic aberration. Conversely, if (θg.F.2-θg.F.1) / (ν2-ν1) falls below the above range, chromatic aberration correction will be insufficient, leaving chromatic aberration.

[0059] The following describes specific examples of the objective lens mentioned above. Note that in the following examples, it is assumed that the imaging lens 230 is an ideal lens with a focal length of 112 mm.

[0060] (Specific example 1) The following are various data from Specific Example 1. The lens cross-section is shown in Figure 3. Magnification β=-11.2, numerical aperture NA=0.56, working distance D0=3mm, focal length f=10mm, d18=2.85mm |(n1-1) / (r1×n1)|=0.04833 |(n17-1) / (r18×n17)|=0.05498 |(n20-1) / (r20×n20)|=0.05231 (θg.F.11-θg.F.10) / (ν11-ν10)=-0.00106 (θg.F.14-θg.F.13) / (ν14-ν13) )=-0.00111 (θg.F.17-θg.F.16) / (ν17-ν16) )=-0.00106

[0061] Table 1 also shows the lens data for Specific Example 1. Here, R is the curvature, D is the thickness of the lens on the optical axis or the dimension of the gap behind the surface (unit: mm), nd is the refractive index of the glass constituting the lens, and νd is the Abbe number. The same applies to Tables 2 and 3.

[0062] [Table 1]

[0063] Figure 4 shows the longitudinal aberration data for Specific Example 1. Longitudinal aberration is an aberration in the direction of the optical axis. For example, a shift in the focal point in the direction of the optical axis is longitudinal aberration. Figure 4 shows spherical aberration and astigmatism, which are longitudinal aberrations, from left to right. The same applies to Figures 7 and 10. In all cases, if there are no aberrations, the graph will be a straight line coinciding with the vertical axis. Figure 5 shows the transverse aberration data. Transverse aberration is an aberration in the direction parallel to the image plane (parallel to the screen). The same applies to Figures 8 and 11. In all cases, if there are no aberrations, the graph will be a horizontal straight line coinciding with the horizontal axis.

[0064] (Specific example 2) The following are various data from Specific Example 2. The lens cross-section is shown in Figure 6. Magnification β=-11.2, numerical aperture NA=0.56, working distance D0=3mm, focal length f=10mm, d18=2.9mm |(n1-1) / (r1×n1)|=0.02856 |(n17-1) / (r18×n17)|=0.05933 |(n20-1) / (r20×n20)|=0.0536 (θg.F.11-θg.F.10) / (ν11-ν10)=-0.00103 (θg.F.14-θg.F.13) / (ν14-ν13) )=-0.00113 (θg.F.17-θg.F.16) / (ν17-ν16) )=-0.00101 Table 2 also shows the lens data for specific example 2.

[0065] [Table 2]

[0066] Figure 7 shows the longitudinal aberration data for Specific Example 2, and Figure 8 shows the transverse aberration data. These are aberration diagrams for the C line (wavelength 656.2725 nm), d line (wavelength 587.5618 nm), F line (wavelength 486.1327 nm), and g line (wavelength 435.8343 nm), respectively.

[0067] (Specific example 3) The following are various data from Specific Example 3. The lens cross-section is shown in Figure 9. Magnification β=-11.2, numerical aperture NA=0.56, working distance D0=3mm, focal length f=10mm, d18=2.5mm |(n1-1) / (r1×n1)|=0.06283 |(n17-1) / (r18×n17)|=0.0446 |(n20-1) / (r20×n20)|=0.03472 (θg.F.11-θg.F.10) / (ν11-ν10)=-0.00106 (θg.F.14-θg.F.13) / (ν14-ν13) )=-0.00113 (θg.F.17-θg.F.16) / (ν17-ν16) )=-0.00092 Table 3 shows the lens design data for specific example 3.

[0068] [Table 3]

[0069] Figure 10 shows the longitudinal aberration data for Specific Example 3, and Figure 11 shows the transverse aberration data. These are aberration diagrams for the C line (wavelength 656.2725 nm), d line (wavelength 587.5618 nm), F line (wavelength 486.1327 nm), and g line (wavelength 435.8343 nm), respectively.

[0070] (Regarding the design conditions for lens 102) The limitations regarding lens 102 in specific examples 1-3 are listed below. (Specific example 1) |(n1-1) / (r1×n1)|=0.04833 (Specific example 2) |(n1-1) / (r1×n1)|=0.02856 (Specific example 3) |(n1-1) / (r1×n1)|=0.06283

[0071] Here, the conditions in Specific Example 2 (0.02856) are close to the lower limit of the significant limiting range (0.028). Also, the conditions in Specific Example 3 (0.06283) are close to the upper limit of the significant limiting range (0.063). From each aberration diagram, it can be seen that various aberrations are well corrected across the wavelength range from the C line to the g line.

[0072] As described above, if the range satisfying 0.028 < |(n1-1) / (r1×n1)| < 0.063 is met, a microscope objective lens with suppressed aberrations can be obtained that is usable under the influence of radiation (in a radiation-affected environment).

[0073] (others) Figures 1, 3, 6, and 9 show examples of objective lenses 100 using 12 lenses, but the number of lenses is not limited to those shown. Configurations using more lenses are also possible. It is also possible to use fewer lenses, but achieving a balance between numerical aperture (NA) and aberrations will be a challenging design. Microscope objective lenses 100 can also be used in environments free from radiation. [Explanation of symbols]

[0074] 100...Objective lens, 101...Quartz plate, 102-113...Lenses, 114...Space between two concave surfaces, 115...Optical diaphragm, 150...Sample to be observed, 200...Microscope, 210...Light source, 220...Beam splitter, 230...Imaging lens, 240...Detector for imaging.

Claims

1. It is located closest to the object being observed and has a first lens made of quartz, The first lens has a first surface which is the side of the object being observed and a second surface which is the side opposite to the first surface. The first surface has a concave surface, The second surface has a convex surface, The refractive index of the quartz is n1, Let r1 be the radius of curvature (in mm) of the concave surface. 0.028<|(n1-1) / (r1×n1)|<0.063 Satisfying the conditions, On the side of the second surface of the first lens, and at a position away from the first lens, the second lens and the third lens are arranged in order from the position closest to the first lens. The second lens has two concave surfaces, The third lens has two concave surfaces, The second lens and the third lens are arranged such that one concave surface of the second lens and one concave surface of the third lens face each other. Let the refractive index of the second lens be n2. The refractive index of the third lens is n3, Let the radius of curvature (in mm) of one concave surface of the second lens be r2. The radius of curvature (in mm) of one concave surface of the third lens is r3. as, 0.04<|(n2-1) / (r2×n2)|<0.07 0.02<|(n3-1) / (r3×n3)|<0.06 A microscope objective lens that meets the following requirements.

2. The microscope objective lens according to claim 1, wherein the distance d on the optical axis between the one concave surface of the second lens and the one concave surface of the third lens is d = 2.5 mm to 5.0 mm.

3. The microscope objective lens according to claim 2, wherein an optical aperture is arranged between the second lens and the third lens.

4. Between the first lens and the optical aperture, It has achromatic lenses 1, 2, and 3 formed by bonding a positive lens and a negative lens, Achromatic lens 1 consists of lens 1 and lens 2. Achromatic lens 2 is lens 3 and lens 4. The achromatic lens 3 is composed of lens 5 and lens 6. Lenses 2, 4, and 5 are made of anomalous dispersion glass. The refractive index of lens 1 in the g-line is n01g, the refractive index in the F-line is n01F, the refractive index in the C-line is n01C, the Abbe number in the d-line is νd1, and the partial dispersion ratio θg.F.1 is θg.F.1 = (n01g - n01F) / (n01F - n01C). The refractive index of lens 2 in the g-line is n02g, the refractive index in the F-line is n02F, the refractive index in the C-line is n02C, the Abbe number in the d-line is νd2, and the partial dispersion ratio θg.F.2 is θg.F.2 = (n02g - n02F) / (n02F - n02C). The refractive index of lens 3 in the g line is n03g, the refractive index in the F line is n03F, the refractive index in the C line is n03C, the Abbe number in the d line is νd3, and the partial dispersion ratio θg.F.3 is θg.F.3 = (n03g - n03F) / (n03F - n03C). The refractive index of lens 4 in the g line is n04g, the refractive index in the F line is n04F, the refractive index in the C line is n04C, the Abbe number in the d line is νd4, and the partial dispersion ratio θg.F.4 is θg.F.4 = (n04g - n04F) / (n04F - n04C). The refractive index of lens 5 in the g line is n05g, the refractive index in the F line is n05F, the refractive index in the C line is n05C, the Abbe number in the d line is νd5, and the partial dispersion ratio θg.F.5 is θg.F.5 = (n05g - n05F) / (n05F - n05C). Let n06g be the refractive index of lens 6 in the g line, n06F be the refractive index of lens 6 in the F line, n06C be the refractive index of lens 6 in the C line, νd6 be the Abbe number in the d line, and θg.F.6 be the partial dispersion ratio θg.F.6 = (n06g - n06F) / (n06F - n06C). -0.0015<(θg.F.2-θg.F.1) / (νd2-νd1)<0 -0.0015<(θg.F.4-θg.F.3) / (νd4-νd3)<0 -0.0015<(θg.F.6-θg.F.5) / (νd6-νd5)<0 The microscope objective lens according to claim 3.

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