Apochromatic objective lens, optical system, and microscope

Abstract

An apochromatic microscope objective (2) having a large field of view, high resolution and particularly good chromatic aberration correction. The invention also provides an optical system and a microscope.

Description

[0001] The contents of German patent application DE 10 2024 210 979.7 are incorporated herein by reference. Summary of the Invention

[0002] This invention relates to apochromatic microscope objectives. It also relates to an optical system for a microscope. Finally, this invention relates to a microscope. Background Technology

[0003] A variety of different microscope objectives have been disclosed in the prior art. For specific requirements and / or applications, objectives with a large field of view, high resolution, and good chromatic aberration correction may be desired. Relevant objectives are known, for example, from WO 2023 / 120 104 A1, WO2023 / 095 723 A1, and US 2023 / 0185055 A1.

[0004] The objective lens needs further improvement, especially considering chromatic aberration correction. Summary of the Invention

[0005] This problem is solved by the microscope objective according to the present invention. Hereinafter, the microscope objective will also be referred to simply as the objective lens.

[0006] In particular, the objective lens according to the invention has high resolution over a wide field of view and excellent chromatic aberration correction, especially excellent lateral chromatic aberration correction.

[0007] Lateral chromatic aberration is also known as lateral color aberration or lateral color correction.

[0008] The field of view is also called the object field.

[0009] According to one aspect of the invention, the objective lens includes a diverging lens made of a material with an Abbe number (vd) of at least 75, particularly at least 80, at least 85, particularly at least 90, particularly at least 95. The diverging lens therefore has very low dispersion. It is also referred to as virtually dispersion-free.

[0010] In particular, the diverging lens can be made of a material with a low refractive index. In particular, the material of the diverging lens can have a refractive index of up to 1.5, especially up to 1.45, especially up to 1.434 nd.

[0011] It has been discovered that using this lens enables an objective design that results in an objective with particularly good chromatic aberration correction.

[0012] A diverging lens is a lens with negative refractive power. Therefore, it is also called a negative lens.

[0013] A diverging lens made of a material with a high Abbe number (vd) can be specifically used to form a third lens in the beam path of the objective lens.

[0014] In particular, objectives can be used in laser scanning microscopy and / or multiphoton microscopy and / or fluorescence microscopy. The advantages of objectives are particularly evident here.

[0015] Objective lenses can be either dry objectives or immersion objectives.

[0016] Specifically, it can be an infinity-corrected objective lens.

[0017] Typically, an objective lens consists of a first lens group with positive refractive power, a second lens group with negative refractive power, and a third lens group with positive refractive power.

[0018] In this case, the lens groups are arranged particularly in the direction from the object field to the image field. Specifically, the lens groups are arranged sequentially, especially directly in succession. In particular, the objective lens can consist of three lens groups. In this case, it has no other lenses.

[0019] The term "lens group" should be understood as referring to the arrangement of one or more lenses.

[0020] According to one aspect, the objective lens is apochromatic corrected within the conventional apochromatic spectral range.

[0021] In this article, the conventional apochromatic spectral range should be understood as representing the range from 435 nm to 656 nm.

[0022] Apochromatic correction should be understood as follows: axial chromatic aberration is at most equal to the depth of focus, particularly at most 0.8 times the depth of focus, particularly at most 0.6 times the depth of focus; and / or, in absolute terms, lateral chromatic aberration within the specified spectral range is at most equal to the Airy diameter d of the objective lens. Airy It is half the size of the e-line. In particular, the e-line (546.07 nm) is used as the reference wavelength in this case.

[0023] The depth of focus corresponds to only half of the Rayleigh length (0.5 RU).

[0024] Airy diameter d Airy For d Airy =1.22 λ ref / NA, that is, especially d Airy =666nm / NA.

[0025] In particular, the objective lens according to the present invention has not only excellent axial color correction, but also excellent lateral color correction.

[0026] In particular, the objective lens can have a flat field of view with a diameter of at least 8 mm, especially at least 10 mm.

[0027] In this context, flat field of view (fFOV) is understood to mean the maximum field size within which the focal deviation from the axial focal point is at most as large as the depth of focus, i.e., at most half the Rayleigh length.

[0028] The objective lens has high resolution. In particular, it can have a numerical aperture (NA) of at least 0.09, especially at least 0.1, especially at least 0.11, especially at least 0.12.

[0029] According to another aspect, the product of the numerical aperture (NA) of the objective lens and the diameter (Obj) of the flat field of view can be at least 1 mm, especially at least 1.1 mm, especially at least 1.2 mm.

[0030] In particular, the objective lens has a very small field curvature.

[0031] In particular, the objective lens has a very simple structure.

[0032] According to another aspect, the first lens group (G1) can take the form of a cemented member, particularly a cemented doublet lens. Specifically, the first lens group (G1) may include a biconcave first lens. Specifically, the first lens group (G1) may include a concave-convex second lens.

[0033] On the other hand, the second lens group (G2) can be in the form of a single lens.

[0034] In particular, the objective lens has a very simple structure.

[0035] In particular, the single lens of the second lens group (G2) can be the aforementioned diverging lens with low dispersion.

[0036] According to another aspect, the third lens group (G3) may include four or five lenses. In particular, it may include two cemented components, especially two cemented doublet lenses. Specifically, the third lens group may consist of two cemented doublet lenses and a single lens (especially a positive single lens).

[0037] Specifically, the third lens group (G3) may include a lens with positive refractive power. Specifically, this lens may be made of a high-dispersion material, particularly a material with an Abbe number of at most 40, and especially at most 35.31. Specifically, this may be the last lens in the beam path of the objective lens.

[0038] The last lens in the beam path of the objective lens can be made of flint glass, especially dense flint glass.

[0039] In particular, the objective lens can consist of up to 10, especially up to 9, especially up to 8 lenses.

[0040] In particular, the objective lens has a particularly simple structure. In particular, it can be manufactured in a cost-effective manner.

[0041] On the other hand, the objective lens has a magnification of up to 5x, particularly up to 4x, particularly up to 2.5x.

[0042] This can be the nominal magnification specified on the objective lens. In particular, magnification is achieved in conjunction with a specified lens barrel system.

[0043] According to another aspect, the diverging lens of the second lens group (G2) has a biconcave form.

[0044] On the other hand, the objective lens can be corrected for axial and / or lateral apochromatic aberration over an extended apochromatic spectral range.

[0045] In this article, the extended apochromatic spectral range should be understood as the range from 400 nm to 750 nm.

[0046] For information on maximum axial and / or lateral color difference, please refer to the descriptions given above.

[0047] On the other hand, the objective lens can have even better chromatic aberration correction over a smaller spectral range, particularly in the range of 510 nm to 750 nm. Within the spectral range of 510 nm to 750 nm, the axial chromatic aberration can be, in particular, up to a maximum length of 0.5 Rayleigh, in particular up to a maximum length of 0.3 Rayleigh, and in particular up to a maximum length of 0.2 Rayleigh.

[0048] According to another aspect, the following can be applied to the distance (t) between the first lens group and the second lens group. 12 The ratio of the length of the objective lens to the total length of the objective lens: t 12 : t a <0.2, especially t 12 : t a <0.18, especially t 12 : t a <0.16, especially t 12 : t a <0.15, especially t 12 : t a <0.12, especially t 12 : t a <0.1, especially t 12 : t a <0.088.

[0049] In this case, the total length t is measured from the object-side vertex of the first foremost lens surface to the image-side vertex of the last lens surface. a .

[0050] Distance t 12 This represents the air distance between the last lens of the first lens group and the first lens of the second lens group. In particular, this distance can be measured from the image-side vertex of the lowest lens surface of the first lens group to the object-side vertex of the highest lens surface of the second lens group.

[0051] The total length t of the objective lens a It can be at most 80mm, at most 60mm, at most 55mm, at most 52.75mm.

[0052] Spacing t 12 It can be up to 10mm, especially up to 7mm, especially up to 5mm, especially up to 4.44mm.

[0053] In particular, objectives can have a very compact structure.

[0054] According to another option, the objective lens may include a lens arrangement based on the following design data:

[0055] Surface No. r (mm) d (mm) nd vd 1 17.380 4.92 1.638 42.41 2 -9.257 2.05 1.717 29.62 3 -17.650 4.44 4 -12.888 1.05 1.434 95.22 5 8.432 22.67 6 -19.048 4.55 1.755 52.32 7 32.483 3.68 1.434 95.22 8 -15.552 0.30 9 145.275 3.59 1.529 76.98 10 -15.693 1.00 1.750 35.33 11 1917.685 0.36 12 156.186 4.14 1.593 35.31 13 -18.704

[0056] Another problem addressed by this invention is the improvement of optical systems made from microscope objectives and microscope tube lens units.

[0057] This problem is solved by an optical system having an objective lens and a barrel lens unit as described above.

[0058] The lens unit may include a lens assembly based on the following design data:

[0059] Surface No. r (mm) d (mm) nd vd 1 121.921 15.067 1.654 39.70 2 63.494 4.663 3 63.861 4.416 1.488 70.41 4 -202.192 0.154

[0060] The advantages are obvious from the advantages of the lens unit in the lens barrel.

[0061] Another problem addressed by this invention is the improvement of microscopes.

[0062] This problem is solved by using a microscope with objectives as described above.

[0063] The advantages are obvious from the advantages of the objective lens.

[0064] In particular, this objective lens allows for imaging of large object fields with high resolution and excellent axial chromatic aberration correction. This is especially advantageous for laser scanning microscopy, multiphoton microscopy, and fluorescence microscopy.

[0065] Specifically, the microscope can be a laser scanning microscope, a multiphoton microscope, or a fluorescence microscope. Attached Figure Description

[0066] Other advantages, details, and features of the invention will become apparent from the description of exemplary embodiments with reference to the accompanying drawings. In detail:

[0067] Figure 1 The structure of a microscope is shown schematically.

[0068] Figure 2 A schematic longitudinal section is shown through a lens assembly based on a modified microscope objective.

[0069] Figure 3 The diagram schematically illustrates the lateral chromatic aberration for different wavelengths, plotted relative to the field number.

[0070] Figure 4 The diagram schematically illustrates the axial focal position in Rayleigh units as a function of wavelength, and

[0071] Figure 5 A longitudinal section of the lens assembly passing through the lens barrel is schematically shown. Detailed Implementation

[0072] Figure 1 The basic structure of microscope 1 is illustrated schematically by way of example. This illustration should be understood as an example rather than a limitation.

[0073] Microscope 1 includes an infinity-corrected optics. This means that the beam path 3 downstream of objective lens 2 extends parallel. The area between objective lens 2 and the tube lens 5 of the tube lens unit 6 is also referred to as the infinity space 4. An intermediate image is generated in the intermediate image plane 7 by means of the tube lens unit 6. The intermediate image can be observed using eyepiece 8. It can also be directed to an image acquisition device, particularly in the form of a camera 9. Camera 9 can be, in particular, a digital camera.

[0074] Figure 1 An illumination device 10 is also shown as an example. The illumination device 10 includes a radiation source unit 11. In particular, a laser can be used as the radiation source unit 11.

[0075] The illumination device 10 may also have a beam splitter 12. With the aid of the beam splitter 12, the illumination radiation 3 can be guided through the objective lens 2 to the sample 13 to be observed. Figure 1 The beam path schematically shown is particularly suitable for epifluorescence systems. Illumination can be in the form of Köhler illumination. Critical illumination is also possible. Instead of beam splitter 12, prisms, especially cubic prisms, can also be used. Alternative variations for coupling illumination radiation are known from the prior art.

[0076] Figure 1 The scanning device 14 is also schematically shown. The scanning device 14 includes one or more displacement devices 15. By means of the displacement devices 15, the sample 13 can be displaced in the microscope 1 relative to the beam path 3, and in particular relative to the objective lens 2.

[0077] To illustrate the working distance of objective lens 2, Figure 1 The distance d from the cover plate 16 to the vertex 19 of the foremost lens surface 17 of the objective lens 2 is shown as an example.

[0078] The distance from the object plane 18 to the vertex 19 of the foremost lens surface 17 is plotted as d0.

[0079] Figure 2 A longitudinal section is shown of the arrangement of lenses L1 to L8 passing through objective lens 2.

[0080] Figure 2 The example illustrates the optical path of the central master ray HS, the peripheral ray RS, and another ray (unlabeled).

[0081] For clarity, the mechanical components of objective lens 2 are not shown in the figure.

[0082] Objective 2, particularly apochromatic objective 2. Specifically, objective 2 is chromatic aberration corrected, especially over a wide wavelength range. In particular, the objective is corrected over the conventional apochromatic range, and preferably over an extended apochromatic range.

[0083] according to Figure 2 Objective 2 includes eight lenses L1 to L8.

[0084] The lenses L1 to L8 of objective lens 2 are arranged into three groups: G1, G2 and G3.

[0085] The first lens group G1 has positive refractive power.

[0086] The second lens group G2 has negative refractive power.

[0087] The third lens group G3 has positive refractive power.

[0088] The first lens group G1 includes a first lens L1 and a second lens L2. Specifically, it can be composed of the first lens L1 and the second lens L2. Lenses L1 and L2 of the first lens group G1 can form a cemented doublet lens.

[0089] The second lens group G2 includes a second lens L2. In particular, it can be composed of the second lens L2.

[0090] In particular, the second lens L2 is a diverging lens, that is, a lens with negative refractive power.

[0091] Lens L2 has a biconcave shape.

[0092] Lens L2 is made of a material with very low dispersion characteristics. In particular, lens L2 is made of a material with an Abbe number vd of 95.22.

[0093] Lens L2 is made of a material with a low refractive index. In particular, lens L2 is made of a material with a refractive index nd = 1.434.

[0094] The third lens group G3 includes five lenses: L4, L5, L6, L7, and L8.

[0095] Specifically, the third lens group G3 includes cemented components, particularly cemented doublet lenses. Specifically, it may include two cemented components, particularly two cemented doublet lenses.

[0096] The last lens L8 of the third lens group G3 is made of a high-dispersion material. Specifically, it can be made of a material with an Abbe number vd = 35.31. More specifically, it can be made of flint glass.

[0097] The distance t between the first lens group G1 and the second lens group G2 12 In particular, the distance between the first lens L1 and the second lens L2 is 4.44 mm.

[0098] The distance t between the vertex 19 of the foremost lens surface 17 and the vertex 20 of the rearmost lens surface 21 in the beam path 3 of objective lens 2 a It is 52.75 mm.

[0099] Therefore, t 12 :t a =0.088 is applicable.

[0100] Table 1 summarizes the data based on... Figure 2 Optical design data for objective lens 2.

[0101] Table 1: According to Figure 2 Optical design data for objective lens 2:

[0102] Surface No. r (mm) d (mm) nd vd 1 17.380 4.92 1.638 42.41 2 -9.257 2.05 1.717 29.62 3 -17.650 4.44 4 -12.888 1.05 1.434 95.22 5 8.432 22.67 6 -19.048 4.55 1.755 52.32 7 32.483 3.68 1.434 95.22 8 -15.552 0.30 9 145.275 3.59 1.529 76.98 10 -15.693 1.00 1.750 35.33 11 1917.685 0.36 12 156.186 4.14 1.593 35.31 13 -18.704

[0103] The statements about the refractive index (nd) and Abbe number (vd) refer to the d-line (587.562 nm).

[0104] Objective 2 has a numerical aperture (NA) of 0.12.

[0105] The objective lens has a flat field of view diameter (Obj) of 10 mm. The product of the numerical aperture (NA) and the flat field of view diameter (Obj) is 1.2 mm, NA x Obj = 1.2 mm.

[0106] Objective lens 2 has a magnification of 2.5. This statement specifically relates to the use of the objective lens with the tube lens 5 described below. Table 2 specifies the parameters according to... Figure 4 Optical design data for lens 5 of the telescope barrel.

[0107] Table 2: According to Figure 4 Optical design data for lens 5 of the telescope barrel:

[0108] Surface No. r (mm) d (mm) nd vd 1 121.921 15.067 1.654 39.70 2 63.494 4.663 3 63.861 4.416 1.488 70.41 4 -202.192 0.154

[0109] Lens 5 is a 195mm lens.

[0110] Objective 2 is designed for use with coverslip 16, which has a thickness of 0.17 mm, a refractive index of nd=1.523, and an Abbe number of vd=54.52.

[0111] Objective 2 exhibits excellent lateral apochromatic correction in the conventional apochromatic range 22 from 435 nm to 656 nm. Figure 3 The lateral chromatic aberration from any wavelength within this range is particularly small compared to the Airy diameter (d) of objective 2. Airy This statement also applies in particular to the extended apochromatic range of 400 nm to 750 nm.23 These statements refer to the e-line (546.07 nm) as a reference wavelength.

[0112] from Figure 4 It can be seen that objective lens 2 has excellent axial apochromatic correction within the conventional apochromatic range 22 from 435nm to 656nm.

[0113] Objective 2 exhibits good apochromatic correction in the extended apochromatic range 23 from 400 nm to 750 nm.

[0114] Objective 2 has near-perfect apochromatic correction in the range of 510 nm to 750 nm. Within this range, the maximum axial deviation of the focal position from the focal position at the e-line (546.07 nm) is at most 0.2 Rayleigh units (RU), and at most 0.1 Rayleigh units.

[0115] In particular, objective lens 2 can have such good axial apochromatic correction in a wavelength range of at least 100 nm, especially at least 200 nm, especially at least 250 nm, from 300 nm to 1200 nm, especially from 400 nm to 750 nm, especially from up to 700 nm, such that the maximum axial variation of the focal position in this range is at most 0.2 Rayleigh units (RU), especially at most 0.1 Rayleigh units.

Claims

1. An apochromatic microscope objective (2), comprising: 1.

1. The first lens group (G1) with positive refractive power. 1.

2. The second lens group (G2) with negative refractive power, and 1.

3. The third lens group (G3) with positive refractive power. 1.

4. The microscope objective (2) is apochromatic corrected within the conventional apochromatic spectral range, and the lateral chromatic aberration is at most equal to the Airy diameter (d) of the microscope objective (2). Airy It is the same size as half of ) 1.

5. The microscope objective (2) therein has a flat field of view (fFOV) and a numerical aperture (NA), wherein the flat field of view (fFOV) has a diameter (Obj), wherein the following applies: NA*Obj>1mm.

2. The apochromatic microscope objective (2) according to claim 1, wherein, The second lens group (G2) includes a diverging lens (L2) made of a material with an Abbe number (vd) of at least 75.

3. The apochromatic microscope objective (2) according to claim 1 or 2, characterized in that, The third lens group (G3) includes a positive lens (L8) made of a material with an Abbe number (vd) of up to 40.

4. The apochromatic microscope objective (2) according to any one of the preceding claims, characterized in that, The numerical aperture (NA) is at least 0.

09.

5. The apochromatic microscope objective (2) according to any one of claims 1 to 3, wherein, The microscope objective (2) has a flat field of view (fFOV) with a diameter (Obj) of at least 8 mm.

6. The apochromatic microscope objective (2) according to any one of the preceding claims, characterized in that, The first lens group (G1) is in the form of a cemented doublet lens (L1, L2).

7. The apochromatic microscope objective (2) according to any one of the preceding claims, characterized in that, The second lens group (G2) is in the form of a single lens (L2).

8. The apochromatic microscope objective (2) according to any one of the preceding claims, characterized in that, The third lens group (G3) includes two cemented elements.

9. The apochromatic microscope objective (2) according to any one of the preceding claims, characterized in that... A maximum magnification of 5 times.

10. The apochromatic microscope objective (2) according to any one of the preceding claims, characterized in that, The diverging lens (L2) has a biconcave shape.

11. The apochromatic microscope objective (2) according to any one of the preceding claims, characterized in that, The apochromatic microscope objective is axially apochromatic corrected within the conventional apochromatic spectral range, and the axial chromatic aberration is at most the same as the depth of focus of the microscope objective (2).

12. The apochromatic microscope objective (2) according to any one of the preceding claims, characterized in that, The following applies to the distance (t) between the first lens group (G1) and the second lens group (G2). 12 ) and the total length (t) of the microscope objective (2) a The ratio of t: 12 :t a <0.

2.

13. The apochromatic microscope objective (2) according to any one of the preceding claims, characterized in that... The following optical design data:

14. An optical system, include: 14.

1. The microscope objective (2) according to any one of the preceding claims, and 14.

2. Lens tube unit (6).

15. A microscope (1) having a microscope objective (2) according to any one of claims 1 to 13.

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