An ultraviolet long working distance flat-field microscope objective with NA = 0.7

Abstract

The present invention discloses an ultraviolet long working distance flat-field microscope objective with NA = 0.7, which is composed of a first lens, a lens unit and an optical observation window in sequence from the image side to the object side. The lens unit is composed of a second, a third, a fourth, a fifth and a sixth lens. The first lens has a negative optical power and is mainly used for correcting field curvature; the second, third, fourth, fifth and sixth lenses have positive optical powers and are mainly used for correcting spherical aberration and coma, and at the same time increasing the optical power. The working distance of the microscope objective of the present invention can reach 15 mm (including the optical observation window). The present invention can provide a microscope objective with a large working distance and high resolution in the 200-400 nm ultraviolet band, and at the same time can optimize and compensate for the aberration caused by vacuum glass windows with different thicknesses. The whole objective is composed of single-piece lenses processed from silica optical glass, and the system structure is simple, and it can be widely used for ultraviolet observation of micron-scale samples in extreme environments.

Description

Technical Field

[0001] The present invention relates to the technical field of microscopes, and particularly to an ultraviolet long working distance flat field microscope objective with NA = 0.7. Background Art

[0002] Ultraviolet long working distance flat field microscope objectives with large numerical apertures have extensive applications in the fields of ultraviolet spectrum detection and high-precision ultraviolet resolution. Especially in the ultraviolet observation of samples in extreme environments such as ultra-high vacuum and extremely low temperature, in order to obtain extreme environmental conditions, the samples to be observed are usually sealed in equipment with a glass observation window. The thickness of the glass observation window is usually about 5 mm, and the thick observation window introduces great spherical aberration and coma to the imaging objective system; in addition, the distance between the sample and the observation window can reach 10 mm, which requires the objective system to have a very large working distance. Existing products and technologies cannot meet the sample observation in such extreme environments. For example, the commercial ultraviolet long working distance microscope objectives produced by companies represented by Thorlabs in the United States cannot compensate for the aberration introduced by the thickness of the optical observation window, and their maximum numerical aperture is only NA = 0.42. Summary of the Invention

[0003] The purpose of the present invention is to provide an ultraviolet long working distance flat field microscope objective with a numerical aperture reaching 0.7, which can solve the problems of small numerical aperture of existing ultraviolet objectives and inability to compensate for the aberration introduced by thick observation window slices.

[0004] An ultraviolet long working distance flat field microscope objective with NA = 0.7 provided to achieve the purpose of the present invention includes a first lens, a lens group element, and an optical observation window sequentially arranged along the image side to the object side. The lens group element is composed of a second lens, a third lens, a fourth lens, a fifth lens, and a sixth lens. The first lens has a negative optical power and is mainly used for correcting field curvature; the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens have positive optical powers and are mainly used for correcting spherical aberration and coma, and at the same time increasing the optical power;

[0005] The first lens is a lens with a negative optical power, adopting a plano-concave structure, with the plane facing the image side and the concave surface facing the object side;

[0006] The second lens is a lens with a positive optical power, adopting a symmetric double convex structure;

[0007] The third lens is a plano-convex lens with a positive optical power, with the convex surface facing the image side and the plane facing the object side;

[0008] The fourth lens, the fifth lens, and the sixth lens all adopt a meniscus structure, with the convex surface facing the image side and the concave surface facing the object side;

[0009] The optical observation window is a glass plate with two parallel surfaces, placed perpendicular to the optical axis;

[0010] Let the focal length of the microscope objective be f and the focal length of the first lens be f1. Then, they satisfy the following condition:

[0011] Let the focal length of the microscope objective be f and the focal length of the lens element be f LG , then they satisfy the following condition:

[0012] Let the focal length of the second lens in the lens element be f2, the focal length of the third lens be f3, the focal length of the fourth lens be f4, the focal length of the fifth lens be f5, and the focal length of the sixth lens be f6. Then, they satisfy the conditional formula

[0013] The surface curvature radius, thickness of each lens, and the distance between the lenses are determined by the working wavelength of the microscope objective, the working distance, and the thickness of the optical observation window to be compensated. The thickness D of the optical observation window satisfies 3 mm ≤ D ≤ 10 mm.

[0014] The beneficial effects of the present invention are as follows:

[0015] Compared with the prior art, a UV long working distance flat field microscope objective with a numerical aperture of 0.7 provided by the present invention has a working distance of up to 17 mm (including the observation window) and can optimize the aberration compensation for different UV wavelengths and different thicknesses of the observation window. Our design can meet the requirements of imaging, resolution, optical manipulation, and detection of samples in an extreme environment with a thick glass observation window in the case of UV monochromatic light through optimization. Attached Figure 2-6 Wave aberration, longitudinal spherical aberration, astigmatism, distortion, and modulation transfer function optical transfer function evaluation diagrams of the microscope objective of the present invention at wavelengths of 280.4, 334.1, and 248.3 nm and when the thickness of the optical observation window is D = 5 and 2 mm. It can be seen through comparison that the microscope objective designed according to the present invention can achieve diffraction-limited resolution within the range of the central field of view of φ < 0.2 mm for the monochromatic light field in the UV range. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The following further details the specific embodiments of the present invention in conjunction with the accompanying drawings, where:

[0017] Figure 1 is a schematic diagram of the optical system of the microscope objective of the present invention;

[0018] Figure 2 is the wave aberration, longitudinal spherical aberration, astigmatism, distortion, and modulation transfer function optical transfer function evaluation diagram of the microscope objective of the present invention when the working wavelength is 280.4 nm and the observation window thickness is 5 mm;

[0019] Figure 3 It is the evaluation diagram of wave aberration, longitudinal spherical aberration, astigmatism, distortion and modulation transfer function optical transfer function of the microscope objective lens of the present invention when the working wavelength is 280.4 nm and the thickness of the observation window is 2 mm;

[0020] Figure 4 It is the evaluation diagram of wave aberration, longitudinal spherical aberration, astigmatism, distortion and modulation transfer function optical transfer function of the microscope objective lens of the present invention when the working wavelength is 280.4 nm and the thickness of the observation window is 10 mm;

[0021] Figure 5 It is the evaluation diagram of wave aberration, longitudinal spherical aberration, astigmatism, distortion and modulation transfer function optical transfer function of the microscope objective lens of the present invention when the working wavelength is 334.1 nm and the thickness of the observation window is 5 mm;

[0022] Figure 6 It is the evaluation diagram of wave aberration, longitudinal spherical aberration, astigmatism, distortion and modulation transfer function optical transfer function of the microscope objective lens of the present invention when the working wavelength is 248.3 nm and the thickness of the observation window is 5 mm. Detailed implementation manners

[0023] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0024] Embodiment 1

[0025] As Figure 1 shown, a UV long working distance flat-field microscope objective lens with NA = 0.7 has a working wavelength of 280.4 nm, and the compensated optical observation window thickness is D = 5 mm. This microscope consists of a first lens 1, a lens group element 100, and an optical observation window 200 in sequence from the image side to the object side. The lens group element 100 consists of a second lens 2, a third lens 3, a fourth lens 4, a fifth lens 5, and a sixth lens 6. The first lens 1 has a negative optical power and is mainly used for correcting field curvature; the second lens 2, the third lens 3, the fourth lens 4, the fifth lens 5, and the sixth lens 6 have positive optical powers and are mainly used for correcting spherical aberration and coma, and at the same time increasing the optical power.

[0026] The first lens 1 is a lens with a negative optical power, adopting a plano-concave structure, with the plane facing the image side and the concave side facing the object side; the second lens 2 is a lens with a positive optical power, adopting a symmetric biconvex structure; the third lens 3 is a plano-convex lens with a positive optical power, with the convex side facing the image side and the plane facing the object side; the fourth lens 4, the fifth lens 5, and the sixth lens 6 all adopt a meniscus structure, with the convex side facing the image side and the concave side facing the object side; the optical observation window 200 is a glass plate with two parallel sides, placed perpendicular to the optical axis; all lenses and the optical observation window are made of fused silica material.

[0027] The focal length of the microscopic objective lens is f = 24.66 mm, and the focal length of the first lens 1 is f1 = -93.1 mm, satisfying the conditions of the following formula: The focal length of the lens unit 100 is f LG = 27.58 mm, satisfying the conditions of the following formula: In the lens unit 100, the focal length of the second lens 2 is f2 = 157.3 mm, the focal length of the third lens 3 is f3 = 139.7 mm, the focal length of the fourth lens 4 is f4 = 429 mm, the focal length of the fifth lens 5 is f5 = 90.2 mm, and the focal length of the sixth lens 6 is f6 = 74.7 mm. They satisfy the conditional formula:

[0028] The surface curvature radius, thickness of each lens, and the distance between lenses are shown in Table 1. It can be seen from Table 1 that the working distance when including the glass observation window is greater than 15 mm.

[0029] Table 1

[0030] Wavelength: 280.4 nm SFH(0): 1.000

[0031] Focal length: 24.66 mm SFH(0.1 mm): 0.847

[0032]

[0033] In Table 1, SFH represents the Strehl factor when the object-side field of view is 0 and 0.1 mm. e hl), Figure 2 It is the wave aberration, longitudinal spherical aberration, astigmatism, distortion, and modulation transfer function optical transfer function evaluation diagram of this embodiment. It can be seen that for the optical observation window with D = 5 mm in this embodiment, its spherical aberration, coma, and field curvature are all well corrected and tend to the diffraction limit within the field of view φ = 0.2 mm, indicating that within this field of view range, this microscopic objective lens can perform high-resolution imaging and observation on the observed sample in the 280.4 nm wavelength band.

[0034] Embodiment 2

[0035] The basic structure remains as Figure 1 shown. It is an ultraviolet long working distance flat field microscope objective with NA = 0.7, a working wavelength of 280.4 nm, and a compensated optical observation window thickness of D = 2 mm. The microscope consists of a first lens 1, a lens unit 100, and an optical observation window 200 from the image side to the object side. The lens unit 100 is composed of a second lens 2, a third lens 3, a fourth lens 4, a fifth lens 5, and a sixth lens 6. The first lens 1 has a negative optical power and is mainly used for correcting field curvature; the second lens 2, the third lens 3, the fourth lens 4, the fifth lens 5, and the sixth lens 6 have positive optical powers and are mainly used for correcting spherical aberration and coma, and at the same time increasing the optical power.

[0036] The first lens 1 is a lens with a negative optical power, adopting a plano-concave structure with the plane facing the image side and the concave side facing the object side; the second lens 2 is a lens with a positive optical power, adopting a symmetric biconvex structure; the third lens 3 is a plano-convex lens with a positive optical power, with the convex side facing the image side and the plane facing the object side; the fourth lens 4, the fifth lens 5, and the sixth lens 6 all adopt a meniscus structure, with the convex side facing the image side and the concave side facing the object side; the optical observation window 200 is a glass plate with parallel surfaces and is placed perpendicular to the optical axis; all lenses and the optical observation window are made of quartz glass material.

[0037] The focal length of the microscope objective is f = 25.52 mm, and the focal length of the first lens 1 is f1 = -93.1 mm, satisfying the conditions of the following formula: The focal length of the lens unit 100 is f LG = 27.74 mm, satisfying the conditions of the following formula: The focal length of the second lens 2 in the lens unit 100 is f2 = 157.7 mm, the focal length of the third lens 3 is f3 = 139.7 mm, the focal length of the fourth lens 4 is f4 = 279.8 mm, the focal length of the fifth lens 5 is f5 = 88.8 mm, and the focal length of the sixth lens 6 is f6 = 107.2 mm. They satisfy the conditional formulas:

[0038] The surface curvature radii, thicknesses of each lens, and the distances between the lenses are shown in Table 2. It can be seen from Table 2 that the working distance when including the glass observation window is greater than 14 mm.

[0039] Table 2

[0040] Wavelength: 280.4 nm SFH(0): 0.994

[0041] Focal length: 25.52 mm SFH(0.1 mm): 0.803

[0042]

[0043] In Table 2, SFH represents the Strehl factor when the object space field of view is 0 and 0.1 mm. Figure 3 It is the evaluation diagram of wave aberration, longitudinal spherical aberration, astigmatism, distortion and modulation transfer function optical transfer function in this embodiment. It can be seen that for the optical observation window with D = 2 mm in this embodiment, its spherical aberration, coma and field curvature are all well corrected, and it tends to the diffraction limit within the field of view φ = 0.2 mm, indicating that within this field of view range, this microscope objective can perform high-resolution imaging and observation on the observed sample in the 280.4 nm band.

[0044] Example 3

[0045] The basic structure is still as Figure 1 shown. An ultraviolet long working distance flat field microscope objective with NA = 0.7, the working wavelength is 280.4 nm, and the compensated optical observation window thickness is D = 10 mm. This microscope consists of a first lens 1, a lens unit 100 and an optical observation window 200 from the image side to the object side in sequence. The lens unit 100 consists of a second lens 2, a third lens 3, a fourth lens 4, a fifth lens 5 and a sixth lens 6. The first lens 1 has a negative focal power and is mainly used for correcting field curvature; the second lens 2, the third lens 3, the fourth lens 4, the fifth lens 5 and the sixth lens 6 have positive focal powers and are mainly used for correcting spherical aberration and coma, and at the same time increasing the focal power.

[0046] The first lens 1 is a lens with a negative focal power, adopting a plano-concave structure with the plane facing the image side and the concave surface facing the object side; the second lens 2 is a lens with a positive focal power, adopting a symmetric double-convex structure; the third lens 3 is a plano-convex lens with a positive focal power, with the convex surface facing the image side and the plane facing the object side; the fourth lens 4, the fifth lens 5 and the sixth lens 6 all adopt a meniscus structure, with the convex surface facing the image side and the concave surface facing the object side; the optical observation window 200 is a glass plate with parallel surfaces, placed perpendicular to the optical axis; all lenses and optical observation window plates are made of quartz glass material.

[0047] The focal length of the microscope objective is f = 25.25 mm, and the focal length of the first lens 1 is f1 = -93.1 mm, satisfying the conditions of the following formula: The focal length of the lens unit 100 is f LG = 29.68 mm, satisfying the conditions of the following formula: The focal length of the second lens 2 in the lens unit 100 is f2 = 190.2 mm, the focal length of the third lens 3 is f3 = 139.7 mm, the focal length of the fourth lens 4 is f4 = 227.1 mm, the focal length of the fifth lens 5 is f5 = 147.9 mm, and the focal length of the sixth lens 6 is f6 = 68.5 mm. They satisfy the conditional formula:

[0048] The surface curvature radii, thicknesses of each lens, and the distances between the lenses are shown in Table 3. It can be seen from Table 3 that the working distance when it includes a glass observation window is greater than 20 mm.

[0049] Table 3

[0050] Wavelength: 280.4 nm, SFH(0): 0.999

[0051] Focal length: 25.25 mm, SFH(0.1 mm): 0.829

[0052]

[0053] In Table 3, SFH represents the Strehl factor when the object space field of view is 0 and 0.1 mm. Figure 4 It is the evaluation diagram of wavefront aberration, longitudinal spherical aberration, astigmatism, distortion, and modulation transfer function optical transfer function of this embodiment. It can be seen that for the optical observation window with D = 10 mm in this embodiment, its spherical aberration, coma, and field curvature are all well corrected and tend to the diffraction limit within the field of view φ = 0.2 mm, indicating that within this field of view range, this microscope objective can perform high-resolution imaging and observation on the observed sample in the 280.4 nm band.

[0054] Example 4

[0055] The basic structure is still as Figure 1 shown. An ultraviolet long working distance flat-field microscope objective with NA = 0.7, the working wavelength is 334.1 nm, and the compensated thickness of the optical observation window is D = 5 mm. This microscope consists of a first lens 1, a lens unit 100, and an optical observation window 200 from the image side to the object side in sequence. The lens unit 100 consists of a second lens 2, a third lens 3, a fourth lens 4, a fifth lens 5, and a sixth lens 6. The first lens 1 has a negative optical power and is mainly used for correcting field curvature; the second lens 2, the third lens 3, the fourth lens 4, the fifth lens 5, and the sixth lens 6 have positive optical powers and are mainly used for correcting spherical aberration and coma, and at the same time increasing the optical power.

[0056] The first lens 1 is a lens with a negative optical power, adopting a plano-concave structure with the plane facing the image side and the concave surface facing the object side; the second lens 2 is a lens with a positive optical power, adopting a symmetric biconvex structure; the third lens 3 is a plano-convex lens with a positive optical power, with the convex surface facing the image side and the plane facing the object side; the fourth lens 4, the fifth lens 5, and the sixth lens 6 all adopt a meniscus structure, with the convex surface facing the image side and the concave surface facing the object side; the optical observation window 200 is a glass plate with two parallel surfaces, placed perpendicular to the optical axis; all lenses and the optical observation window are made of quartz glass material.

[0057] The focal length of the microscope objective is f = 25.60 mm, and the focal length of the first lens 1 is f1 = -95.9 mm, satisfying the conditions of the following formula: The focal length of the lens unit 100 is f LG = 27.59 mm, satisfying the conditions of the following formula: In the lens unit 100, the focal length of the second lens 2 is f2 = 167.4 mm, the focal length of the third lens 3 is f3 = 143.8 mm, the focal length of the fourth lens 4 is f4 = 261.5 mm, the focal length of the fifth lens 5 is f5 = 96.1 mm, and the focal length of the sixth lens 6 is f6 = 76.3 mm. They satisfy the conditional formula:

[0058] The surface curvature radius, thickness of each lens, and the distance between the lenses are shown in Table 4. It can be seen from Table 4 that the working distance when including the glass observation window is greater than 15 mm.

[0059] Table 4

[0060] Wavelength: 334.1 nm SFH(0): 1.000

[0061] Focal length: 25.60 mm SFH(0.1 mm): 0.889

[0062]

[0063] In Table 4, SFH represents the Strehl factor when the object space field of view is 0 and 0.1 mm. Figure 5 It is the evaluation diagram of wave aberration, longitudinal spherical aberration, astigmatism, distortion, and modulation transfer function optical transfer function of this embodiment. It can be seen that for the optical observation window with D = 5 mm in this embodiment, its spherical aberration, coma, and field curvature are all well corrected and tend to the diffraction limit within the field of view φ = 0.2 mm, indicating that within this field of view range, this microscope objective can perform high-resolution imaging and observation on the observed sample in the 334.1 nm band.

[0064] Example 5

[0065] The basic structure is still as Figure 1As shown in the figure, an ultraviolet long working distance plan field microscope objective lens with NA = 0.7 has a working wavelength of 248.3 nm, and the thickness of the compensated optical observation window is D = 5 mm. The microscope consists of a first lens 1, a lens unit 100, and an optical observation window 200 from the image side to the object side. The lens unit 100 consists of a second lens 2, a third lens 3, a fourth lens 4, a fifth lens 5, and a sixth lens 6. The first lens 1 has a negative optical power and is mainly used for correcting field curvature. The second lens 2, the third lens 3, the fourth lens 4, the fifth lens 5, and the sixth lens 6 have positive optical powers and are mainly used for correcting spherical aberration and coma, and at the same time increasing the optical power.

[0066] The first lens 1 is a lens with a negative optical power, adopting a plano-concave structure with the plane facing the image side and the concave surface facing the object side. The second lens 2 is a lens with a positive optical power, adopting a symmetric double-convex structure. The third lens 3 is a plano-convex lens with a positive optical power, with the convex surface facing the image side and the plane facing the object side. The fourth lens 4, the fifth lens 5, and the sixth lens 6 all adopt a meniscus structure, with the convex surface facing the image side and the concave surface facing the object side. The optical observation window 200 is a glass plate with parallel surfaces and is placed perpendicular to the optical axis. All lenses and the optical observation window are made of quartz glass material.

[0067] The focal length of the microscope objective lens is f = 25.30 mm, and the focal length of the first lens 1 is f1 = -90.48 mm, satisfying the conditions of the following formula: The focal length of the lens unit 100 is f LG = 27.08 mm, satisfying the conditions of the following formula: The focal length of the second lens 2 in the lens unit 100 is f2 = 163.3 mm, the focal length of the third lens 3 is f3 = 135.7 mm, the focal length of the fourth lens 4 is f4 = 355.7 mm, the focal length of the fifth lens 5 is f5 = 91.4 mm, and the focal length of the sixth lens 6 is f6 = 72.9 mm. They satisfy the conditional formula:

[0068] The surface curvature radii, thicknesses of each lens, and the distances between the lenses are shown in Table 5. It can be seen from Table 5 that the working distance when including the glass observation window is greater than 15 mm.

[0069] Table 5

[0070] Wavelength: 248.3 nm SFH(0): 1.000

[0071] Focal length: 25.30 mm SFH(0.1 mm): 0.792

[0072]

[0073] In Table 5, SFH represents the Strehl factor when the object space field of view is 0 and 0.1 mm. Figure 6 It is the wavefront aberration, longitudinal spherical aberration, astigmatism, distortion, and modulation transfer function optical transfer function evaluation diagram of this embodiment. It can be seen that for the optical observation window with D = 5 mm in this embodiment, its spherical aberration, coma, and field curvature are well corrected and tend to the diffraction limit within the field of view φ = 0.2 mm, indicating that within this field of view range, this microscope objective can perform high-resolution imaging and observation on the observed sample in the 248.3 nm band.

[0074] For quartz glass observation windows with different thicknesses and different wavelengths, the present invention can correct various aberrations by optimizing the spherical curvature radius of the lens and the distance between the lenses while keeping the numerical aperture and the basic structure of the lens group unchanged.

[0075] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. For those skilled in the art, it is obvious that the present invention is not limited to the details of the above-described exemplary embodiments, and without departing from the spirit or basic characteristics of the present invention, the present invention can be implemented in other specific forms. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention. Any reference signs in the claims should not be regarded as limiting the claimed claim.

[0076] In addition, it should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative manner of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. An ultraviolet long working distance flat field microscope objective with NA = 0.7, characterized in that: It includes a first lens (1), a lens unit (100), and an optical observation window (200) arranged in sequence along the image space to object space direction. The lens unit (100) consists of a second lens (2), a third lens (3), a fourth lens (4), a fifth lens (5), and a sixth lens (6). The first lens (1) has a negative focal power and is mainly used for correcting field curvature. The second lens (2), third lens (3), fourth lens (4), fifth lens (5), and sixth lens (6) have positive focal powers and are mainly used for correcting spherical aberration and coma, while increasing the focal power. The first lens (1) is a lens with a negative focal power and adopts a plano-concave structure, with the plane facing the image space and the concave surface facing the object space. The second lens (2) is a lens with a positive focal power and adopts a symmetric biconvex structure. The third lens (3) is a plano-convex lens with a positive focal power, with the convex surface facing the image space and the plane facing the object space. The fourth lens (4), fifth lens (5), and sixth lens (6) all adopt a meniscus structure, with the convex surface facing the image space and the concave surface facing the object space. The optical observation window (200) is a glass plate with parallel surfaces and is placed perpendicular to the optical axis. Let the focal length of the microscope objective be \(f\) and the focal length of the first lens (1) be \(f_1\), then the following condition is satisfied between them: Let the focal length of the microscope objective be \(f\) and the focal length of the lens element (100) be \(f\). LG Then the condition between them satisfies the following formula: Let the focal length of the second lens (2) in the lens unit (100) be f2, the focal length of the third lens (3) be f3, the focal length of the fourth lens (4) be f4, the focal length of the fifth lens (5) be f5, and the focal length of the sixth lens (6) be f6. Then they satisfy the conditional formula The surface curvature radii, thicknesses of each lens, and the distances between the lenses are determined by the working wavelength of the microscope objective, the working distance, and the thickness of the optical observation window plate (200) to be compensated. The thickness D of the optical observation window plate (200) satisfies 3mm ≤ D ≤ 10mm.

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