Finally, a corrected microscope lens for scanning applications

Abstract

A finally corrected microscope objective (2) for scanning applications is designed such that it has a numerical aperture (NA) of at least 0.9, a Strehl ratio of at least 0.8 over the entire field of view, and that a distance (d) OI ) between an object plane (O) and an intermediate image plane (I) conjugate to it is at most 250 mm.

Description

[0001] The invention relates to a finitely corrected microscope objective for scanning applications. The invention also relates to an optical assembly and a microscope with such an objective. Finally, the invention relates to the use of such an objective and a method for automated scanning of a sample.

[0002] Depending on the application, microscope lenses must meet different requirements.

[0003] High-resolution microscope lenses are well-known from the state of the art. Such lenses are often very large and require expert knowledge to use.

[0004] US 2019 / 0324246, US 9746658, and US 8350904 concern dry lenses with high light transmittance. US 8988780, JP 2011075982, and DE 102011109783 concern immersion lenses with high light transmittance. These lenses are infinity corrected. Finitely corrected lenses are known from US 9939622 and US 8350904. These are large and / or have a large number of lenses and / or their image quality drops sharply toward the edges.

[0005] One object of the invention is to improve a microscope objective. A particular object is to provide a finitely corrected microscope objective with a simplified, compact design and improved optical properties.

[0006] This object is achieved by a microscope objective according to the present invention.

[0007] The lens is finitely corrected. This means that it is designed for finite optics, i.e., for a defined tube length. The lens produces a real intermediate image, specifically at a defined, finite distance.

[0008] According to a first aspect, the lens can be designed such that a distance (d OI ) between an object plane (O) and an intermediate image plane (I) conjugated thereto is at most 250 mm. The distance (d OI ) may in particular not exceed 205 mm.

[0009] According to the invention, it was recognized that it is an advantage, particularly for scanning applications in which large, especially large-area, samples are examined, if the microscope objectives used for this purpose have a large field of view and at the same time offer a high resolution over the entire field of view.

[0010] The field of vision is also called the object field.

[0011] The Strehl ratio can be used to characterize the resolution. Despite their reduced complexity, the lenses according to the invention can have a Strehl ratio of at least 0.8, in particular at least 0.85, in particular at least 0.89.

[0012] The lenses can have such a high Strehl ratio in particular over at least 50%, in particular at least 70%, in particular at least 90%, in particular at least 95% of the field of view, in particular over the entire field of view.

[0013] In particular, they can cover a part of the field of view with an area of ​​at least 1 mm 2 have such a high Strehl ratio.

[0014] This ensures high resolution across large areas of the field of view, especially across the entire field of view. This makes it easier to combine multiple partially overlapping images into a mosaic image.

[0015] The reduced complexity leads in particular to cost savings and an increase in the robustness of the system.

[0016] In particular, the lenses may have a vignetting of less than 5%, in particular less than 3%, in particular less than 1%.

[0017] In particular, they can be apochromatically corrected over a spectral bandwidth of at least 200 nm, in particular in the range from 400 nm to 800 nm. They can be apochromatically corrected over a spectral bandwidth of at least 200 nm, in particular in the range from 400 nm to 700 nm. They can be apochromatically corrected in particular in the range from 460 nm to 660 nm.

[0018] Apochromatically corrected means that the maximum deviation of the focus position within the spectrum with respect to the reference wavelength lies within the depth of field.

[0019] The objectives may preferably have a numerical aperture of at least 0.9, in particular at least 0.95.

[0020] The lenses according to the invention are particularly cost-effective to manufacture. They nevertheless result in a high degree of robustness of the optical system.

[0021] Especially for scanning applications, it may be necessary to capture a large number of images and then combine them into a mosaic image. This is preferably done automatically.

[0022] In particular, the lenses can have an object field diameter (d obj = 2 hours obj ) of at least 1 mm, in particular at least 1.5 mm. The object field diameter is also referred to as the field of view size.

[0023] For high throughput, the time required to acquire individual images is a critical factor. It is always desirable to reduce the time required to acquire individual images. This leads to faster results and increased throughput. This generally leads to lower costs.

[0024] An important factor influencing the time required to acquire individual images is the field of view of the optical system. A larger field of view allows for larger areas to be captured in single images. This means fewer individual images are needed to image an extended sample. This leads to reduced scanning time and a reduction in the effort required to combine the images into a mosaic image.

[0025] However, when increasing the field of view, it is critically important that the lens delivers high resolution across all relevant wavelength ranges. This requirement for high resolution with a simultaneously large field of view corresponds to an increase, specifically a maximization, of the optical conductance (etendue). The etendue is proportional to the square of the linear dimension, specifically the diameter, of the field of view. It is also proportional to the square of the numerical aperture (NA).

[0026] At the same time, it may be desirable, especially for routine applications, to reduce the complexity of the microscope objective. This can lead to cost savings. Reduced complexity refers, in particular, to a reduction in the number of required optical elements, especially lenses. Preferably, the number of aspherical lenses is reduced. This has been shown to lead to significant cost savings.

[0027] According to one aspect, the lens has a maximum of 18 optical elements, in particular a maximum of 17 optical elements, in particular a maximum of 16 optical elements. Lenses can serve as optical elements, in particular.

[0028] The reduced number of optical elements, especially lenses, leads to significant cost savings.

[0029] The optical elements can be arranged in groups, in particular in nine groups. In this case, cemented elements are referred to as a group.

[0030] Lenses according to the invention exhibit significantly reduced complexity, in particular a smaller number of lenses for a given optical conductance. However, due to their high Strehl ratio, they still ensure high resolution across the entire field of view.

[0031] According to one aspect, the lens can be designed as a dry lens. This can be advantageous for simplifying the scanning process.

[0032] The lens can have a numerical aperture (NA) in the range of 0.9 to 1.0. This results in particularly high resolution.

[0033] The lens can have a chief ray angle (CRAI) on the image side of 5° or less. This ensures that the lens can be used with standardized digital image sensors. A small chief ray angle is particularly beneficial for the relative illumination and efficiency of the image sensor.

[0034] According to a further aspect, a distance (BFL, back focal length) between the rearmost optical surface and the intermediate image plane (I) can be at least 50 mm, in particular at least 58 mm. The large distance can facilitate the assembly of the optical system.

[0035] According to a further aspect, the lens can be designed entirely without aspherical lenses. This further reduces the complexity of the lens. This leads, in particular, to a reduction in costs.

[0036] The lenses of the objective can be made of at least 8, in particular at least 10, in particular at least 12 different types of glass.

[0037] It has been shown that particularly good optical properties of the lens can be achieved by a suitable selection of different types of glass.

[0038] The optical elements, in particular the lenses, of the objective can be arranged in three groups G1, G2, and G3. Each of these groups can have subgroups.

[0039] The first group, G1, can have a positive refractive power.

[0040] The second group, G2, can have a positive refractive power.

[0041] The third group, G3, can have a negative refractive power.

[0042] According to a further aspect, the third lens group G3 can have three subgroups (G31, G32, and G33). The first subgroup (G31) can have a positive refractive power. The second subgroup (G32) can have a negative refractive power. The third subgroup (G33) can have a negative refractive power.

[0043] Here and below, the order of the lens's optical elements is given in the direction from the object field to the image field. With respect to the lens, "front" refers to the side facing the object field, and "back" refers to the side facing away from the object field.

[0044] According to a further aspect, the first lens group G1 of the objective may comprise a cemented element, in particular a triple cemented element.

[0045] According to a further aspect, the second lens group G2 of the objective can have three cemented elements, in particular three double cemented elements.

[0046] According to a further aspect, the third lens group G3 of the objective can have two cemented elements, in particular two double cemented elements G31, G33.

[0047] Further possible details of the lens are described below.

[0048] The lens may have a relatively short working distance. In particular, this may apply: d:L<4.9×10−3, where d is the distance from the cover glass to the edge of the front lens surface of the objective and L is the total distance between the object field and the vertex of the rearmost lens surface of the objective in the direction of the beam.

[0049] The working distance of the lens can also meet the following conditions: d0:L<9×10−3, where d0 is the distance from the object field to the vertex of the front lens surface of the objective.

[0050] If one designates the greatest distance of light rays, which emanate from an object on the optical axis, to the optical axis in the three subgroups G31, G32 and G33 of the third lens group G3 with h1, h2 and h3, then these quantities can in particular satisfy the following inequalities: 1.1 < h1:h2 < 1.8 and / or 1.2 < h2:h3 < 1.6.

[0051] A further object of the invention is to improve a microscope, in particular for scan applications, in particular for optical mapping.

[0052] This object is achieved by a microscope with an objective according to the previous description. The advantages result from those described previously.

[0053] The microscope can be equipped with an automated scanning device. The scanning device can enable one-dimensional (linear) displacement of the sample, two-dimensional displacement of the sample, or three-dimensional displacement of the sample. In addition to linear displacements, the scanning device can also have one, two, or three rotational degrees of freedom. This allows for very flexible arrangement, especially for displacement, of the samples.

[0054] The scanning device may comprise an image capture device, in particular a digital image capture device, in particular a digital camera.

[0055] The scanning device may include an image processing device. This may, in particular, enable automated processing. This facilitates, in particular, the stitching of individual images into a mosaic image.

[0056] The microscope objectives described above are particularly advantageous for use in scanning applications, especially for optical mapping. They facilitate automated scanning of large, especially large-area, samples.

[0057] A further object of the invention is to improve a method for automated scanning of a sample. This object is achieved by a method comprising the following steps: - Providing a microscope according to the previous description, - Providing a sample to be examined, - Recording of at least two images of different sections of the sample, whereby the sections have an overlapping area and - Putting the pictures together to create a mosaic image.

[0058] The method can in particular be an optical mapping method.

[0059] Before the images are stitched together, they can be analyzed and / or processed using an image processing algorithm. This can simplify and / or improve the stitching process.

[0060] It is also possible to analyze and / or edit the composite mosaic image after the images have been combined using an image processing algorithm. This can further improve the quality.

[0061] To capture images of different sections of the sample, it can be moved linearly, two-dimensionally, or three-dimensionally. In particular, it can be moved stepwise.

[0062] The movement of the sample and the acquisition of successive images of different sections of the sample can be carried out in an automated manner.

[0063] Further details of the invention will become apparent from the description of exemplary embodiments with reference to the figures. They show: Fig. 1 schematically shows the structure of a microscope, Fig. 2 a schematic longitudinal section through the optical components of the microscope objective according to a first variant (E4), Fig. 3 schematically shows the Strehl ratio of the lens according to Fig. 2 about the field of view for light of different wavelengths and Fig. 4 schematically shows the course of an intensity of the incident light illumination over the field of view of the objective E4.

[0064] In the Fig. Figure 1 shows an exemplary and schematic representation of the basic structure of a microscope 1. This illustration is intended to be exemplary and not restrictive.

[0065] The microscope 1 has finite optics. This means that the beam path 3 passes through a real intermediate image plane 7 behind the objective lens 2 at a defined distance. The intermediate image can be viewed using an eyepiece 8. It can also be directed to an image capture device, in particular in the form of a camera 9. The camera 9 can, in particular, be a digital camera.

[0066] An example is shown in the Fig. 1 also includes an illumination device 10. The illumination device 10 has a radiation source unit 11. A laser can serve as the radiation source unit 11, in particular.

[0067] The illumination device 10 can also include a beam splitter 12. Using the beam splitter 12, the illumination radiation 3 can be guided through the objective lens 2 to a sample 13 to be viewed. The beam splitter 12 can be arranged in the convergence region between the objective lens 2 and the intermediate image plane 7.

[0068] The one in the Fig. The beam path schematically shown in Figure 1 is particularly suitable for epifluorescence (epi-fluorescence) systems. The illumination can be configured as a Köhler illumination. Critical illumination is also possible.

[0069] Instead of the beam splitter 12, a prism, in particular a cubic prism, can also be provided. Alternative variants for coupling the illumination radiation are known from the prior art.

[0070] Also shown schematically is the Fig. 1 a scanning device 14. The scanning device 14 has one or more displacement devices 15. Using the displacement devices 15, the sample 13 can be displaced relative to the beam path 3 in the microscope 1, in particular relative to the objective 2.

[0071] To clarify the working distance of lens 2, the Fig. 1 shows, as an example, the distance d from the cover glass 16 to the outer edge of the front lens surface 17 of the objective 2.

[0072] The distance from an object plane 18 to the vertex 19 of the front lens surface 17 is shown as d0.

[0073] L denotes the total distance between the object plane 18 and the vertex 19 of the rearmost lens surface of the objective 2 in the beam direction. The latter is in the Fig. 1 not explicitly shown.

[0074] The microscope 1 can have a footprint with a width b of at most 250 mm, in particular at most 205 mm.

[0075] Fig. 2 shows a longitudinal section through the arrangement of the optical components of the lens 2.

[0076] The illustrated variant E4 of the objective is suitable for use with cover glasses 16 with a thickness of 0.188 mm, a refractive index of nd= 1.523 and the Abbe number vd=54.52 (related to a d-line of 587.562 nm).

[0077] In the Fig. 2 shows the course of a central main ray HS and two marginal rays RS 1, RS2 as an example.

[0078] For reasons of clarity, the Fig. 2 Mechanical components of lens 2 not shown.

[0079] Lens 2 is specifically an apochromatic lens 2.

[0080] In the Fig. The variant shown in figure 2 (E4) is in particular a dry lens.

[0081] The lens 2 according to Fig. 2 has 16 lenses L1 to L16. The lenses L1 to L16 are arranged in 3 groups with a total of 9 subgroups. The subgroups are each formed by individual lenses or cemented elements.

[0082] The optical design data of lens 2 according to Fig. 2 are summarized in Table 1. Table 1: optical design data of lens 2 according to Fig. 2 in the reverse direction, i.e. from the image side to the object side: Oberfläche Nr. r (mm) d (mm) nd vd Bild 59.610 1 -29.979 4.063 1.638 42.41 2 -26.122 5.351 1.488 70.41 3 -62.246 20.317 4 20.872 6.694 2.003 28.27 5 14.366 12.936 6 -18.113 1.625 1.613 44.50 7 35.512 10.746 1.569 71.34 8 -26.862 0.888 9 213.454 1.474 1.558 54.01 10 33.083 10.658 1.728 28.53 11 -222.471 0.557 12 142.402 14.900 1.659 71.34 13 -27.102 1.000 1.613 44.49 14 -53.143 0.433 15 107.303 12.568 1.497 81.55 16 -27.221 1.000 1.638 42.41 17 -112.216 0.962 18 23.244 10.344 1.659 71.34 19 -1231.237 1.000 1.855 24.80 20 19.168 5.698 1.659 71.34 21 74.601 0.206 22 12.168 7.337 1.755 52.32 23 10.368 2.766 24 8.315 5.582 1.883 40.76 25 11.242 1.096

[0083] The refractive index (nd) and Abbe number (vd) refer to the d-line (587.562 nm). The data are based on use with a cover glass 16 with a thickness of 0.188 mm.

[0084] Further data of lens 2: Magnification: 10x NA:0.95

[0085] Distance between object field and intermediate image (dOI): 200 mm L:140.39 mm h obj : 0.8 mm rear focus length: 59.61 mm image-side principal ray angle (CRAI): 4.65°

[0086] Lens 2 has three lens groups, G1, G2, and G3. The first lens group, G1, has positive refractive power. It includes lenses L1 to L5.

[0087] The lenses L3 to L5 form a triple cemented element.

[0088] The second lens group G2 has a positive refractive power. The second lens group G2 comprises lenses L6 to L11.

[0089] The lenses L6 and L7 form a double cemented element.

[0090] The lenses L8 and L9 form a double cemented element.

[0091] The lenses L10 and L11 form a double cemented element.

[0092] The third lens group G3 has a negative refractive power.

[0093] The third lens group G3 includes the lenses L12 to L16.

[0094] The lenses L12 and L13 form a double cemented element. They constitute the subgroup G31. The subgroup G31 has a positive refractive power.

[0095] The L14 lens forms the G32 subgroup. The G32 subgroup has a negative refractive power.

[0096] The L15 and L16 lenses form a double cemented element. They constitute the G33 subgroup. The G33 subgroup has a negative refractive power.

[0097] If the greatest distance of light rays emanating from an object on the optical axis to the optical axis in the three subgroups G31, G32 and G33 of the third lens group G3 is designated with h1, h2 and h3, then: h1=16.28mm,h2=9.78mm,h3=6.84mm, and thus h1:h2=1.665 and h2:h3=1.430.

[0098] In the Fig. 3 are the Strehl ratios of the lens 2 according to the Fig. 2 for light with a wavelength λ1 = 460 nm, λ2 = 546 nm and λ3 = 660 nm.

[0099] How to Fig. As can be seen from Figure 3, the Strehl ratio across the entire field of view is greater than 0.8. For individual wavelengths or a limited wavelength range, the Strehl ratio across the entire field of view is even greater, in particular greater than 0.83, and in particular greater than 0.89.

[0100] In the Fig. To illustrate the marginal light falloff, the relative illumination intensity at a wavelength of 546.074 nm is shown across the field of view.

[0101] How to Fig. As can be seen from Figure 4, the lens 2 provides homogeneous illumination of the field of view with slight vignetting when illuminated by incident light. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] US 2019 / 0324246

[0004] US 9746658

[0004] US 8350904

[0004] US 8988780

[0004] JP 2011075982

[0004] DE 102011109783

[0004] US 9939622

[0004]

Claims

[1] Finitely corrected microscope objective (2) for scanning applications having 1.

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

2. a second lens group (G2) with positive refractive power and 1.

3. a third lens group (G3) with negative refractive power, 1.

4. where the microscope objective (2) 1.4.

1. has a numerical aperture (NA) of at least 0.9, 1.4.

2. has an object field diameter (dobj = 2 hobj) of at least 1 mm, 1.4.

3. has less than 5% vignetting and 1.4.4 is apochromatically corrected over a spectral bandwidth of at least 200 nm, 1.4.

5. wherein the microscope objective (2) is designed such that a distance (dOI) between an object plane (O) and an intermediate image plane (I) conjugated thereto is at most 250 mm. [2] Microscope objective (2) according to claim 1, characterized bythat the object field diameter (d obj ) is at least 1.5 mm. [3] Microscope objective (2) according to one of the preceding claims, characterized by that it has a Strehl ratio of at least 0.8 over at least 70% of the field of view. [4] Microscope objective (2) according to one of the preceding claims, characterized by that it has a maximum of 18 optical elements (Li; 1 ≤ i ≤ 18). [5] Microscope objective (2) according to one of the preceding claims, characterized by that it is designed as a dry lens. [6] Microscope objective (2) according to one of the preceding claims, characterized by that the image-side chief ray angle (CRAI) is no more than 5°. [7] Microscope objective (2) according to one of the preceding claims, characterized by that a distance (BFL) between the rearmost optical surface and the intermediate image plane (I) is at least 50 mm. [8] Microscope objective (2) according to one of the preceding claims, characterized by that it is apochromatically corrected over a bandwidth of at least 200 nm in a wavelength range between 400 nm and 800 nm. [9] Microscope objective (2) according to one of the preceding claims, characterized by that the third lens group (G3) has three subgroups (G31, G32 and G33), wherein the first subgroup (G31) has a positive refractive power, the second subgroup (G32) has a negative refractive power and the third subgroup (G33) has a negative refractive power. [10] Microscope objective (2) according to one of the preceding claims, characterized by that it does not have aspherical lenses. [11] Microscope objective (2) according to one of the preceding claims characterized by following optical design data (in reverse order): Surface No. r (mm) d (mm) and vd Picture 59.610 1 -29.979 4.063 1.638 42.41 2 -26.122 5.351 1.488 70.41 3 -62.246 20.317 4 20.872 6.694 2.003 28.27 5 14.366 12.936 6 -18.113 1.625 1.613 44.50 7 35.512 10.746 1.569 71.34 8 -26.862 0.888 9 213.454 1.474 1.558 54.01 10 33.083 10.658 1.728 28.53 11 -222.471 0.557 12 142.402 14.900 1.659 71.34 13 -27.102 1.000 1.613 44.49 14 -53.143 0.433 15 107.303 12.568 1.497 81.55 16 -27.221 1.000 1.638 42.41 17 -112.216 0.962 18 23.244 10.344 1.659 71.34 19 -1231.237 1.000 1.855 24.80 20 19.168 5.698 1.659 71.34 21 74.601 0.206 22 12.168 7.337 1.755 52.32 23 10.368 2.766 24 8.315 5.582 1.883 40.76 25 11.242 1.096 [12] Microscope (1) with a microscope objective (2) according to one of claims 1 to 11. [13] Microscope (1) according to claim 12, characterized by that it has a footprint of no more than 250 mm x 200 mm. [14] Microscope (1) according to one of claims 12 to 13 characterized by an automated scanning device (14). [15] A method for automated scanning of a sample comprising the following steps: 15.

1. Providing a microscope according to one of claims 12 to 14, 15.

2. Providing a sample to be examined, 15.

3. Taking at least two images of different sections of the sample, with the sections having an overlapping area, 15.

4. Assemble the images into a mosaic.

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