Device for imaging sample

Abstract

An apparatus for imaging a sample arranged in a first medium in an object plane. The apparatus includes an optical transmission system which images the sample in the object plane in an intermediate image in an intermediate image plane. The object plane and the intermediate image plane form an angle not equal to 90 with an optical axis of the transmission system. The apparatus further comprises an optical imaging system having an objective. The object plane may be imaged on a detector without distortion. The optical transmission system is symmetrical with respect to a pupil plane, the object plane, and the intermediate image plane to satisfy the Scheimpflug condition. The intermediate image lies in a second medium having a refractive index virtually identical to that of the first medium. A lens group of a subsystem arranged closest to the sample or intermediate image comprises at least one catadioptric assembly.

Claims

1. An apparatus for imaging a sample arranged in a first medium in an object plane, said apparatus comprising: an optical transmission system which comprises two subsystems constructed telecentrically, and which images the sample in the object plane in an intermediate image in an intermediate image plane, wherein each of the object plane and the intermediate image plane forms an angle not equal to 90 with an optical axis of the transmission system; an optical imaging system comprising an objective with an optical axis that is perpendicular to the intermediate image plane, the objective being focused on the intermediate image plane so as to image the intermediate image on a detector without distortion; and a coupler configured to couple an illumination light into a beam path of the transmission system for illuminating the sample with a light sheet, wherein the light sheet extends along a plane that lies substantially in the object plane at an angle to a detection direction that is not equal to zero; wherein the two subsystems of the optical transmission system comprise a plurality of lenses; wherein the optical transmission system is constructed symmetrically with respect to a symmetry plane from the two subsystems so that the imaging is carried out by the optical transmission system on a scale of 1:1; wherein the optical transmission system is also constructed symmetrically with respect to a pupil plane, the object plane, and the intermediate image plane to satisfy a Scheimpflug condition, whereby the symmetry plane corresponds to the pupil plane; wherein the intermediate image lies in a second medium which has a refractive index that is virtually identical to that of the first medium; wherein a lens group, of the plurality of lenses of the two subsystems, which is arranged closest to the sample or intermediate image comprises at least one catadioptric assembly; and wherein the coupler comprise a beamsplitter arranged in the pupil plane between the two subsystems.

2. The apparatus according to claim 1; wherein the coupler comprises an illumination device which couples the illumination light into a beam path via the second medium in the intermediate image plane, wherein the illumination of the intermediate image plane with the light sheet takes place in the intermediate image plane.

3. The apparatus according to claim 1; wherein the optical transmission system is configured to be in contact with the first medium and the second medium, wherein the first medium and second medium act as immersion media.

4. The apparatus according claim 1; wherein the first medium comprises water and the second medium, which has the refractive index that is virtually identical to that of the first medium, comprises an amorphous fluoropolymer.

5. The apparatus according to claim 1; wherein the catadioptric assembly comprises: a plano-convex lens or lens group with a convex surface and a flat surface which faces the object plane or intermediate image plane that is reflection-coated toward the inner side, wherein a region which encloses the optical axis is exempted from reflective coating so that light can pass through; and a mirror element arranged opposite the convex surface of the lens or lens group having a concave mirror surface that is reflection-coated which reflects light coming from the plano-convex lens or lens group, wherein a region which encloses the optical axis is exempted from reflective coating so that light can pass through.

6. The apparatus according to claim 5; wherein each of the subsystems has the following system data with lenses L1, L3, L4, L5, L6 and a mirror element S2, wherein surfaces 1 and 3 are reflection-coated, with refractive index n.sub.d and Abbe number .sub.d at a wavelength of .sub.d=578.56 nm: TABLE-US-00005 Thickness [mm]/ Lens Surface Radius [mm] Air Gap [mm] n.sub.d .sub.d L1 1 flat 17.56 1.52 64.17 2 59.77 7.22 S2 3 29.95 1.00 L3 4 784.92 3.35 1.59 64.27 5 21.53 2.56 L4 6 8.81 4.39 1.65 33.85 7 8.21 3.76 L5 8 189.42 3.50 1.52 64.17 9 15.81 0.50 L6 10 21.29 4.00 1.52 64.17 11 65.47.

7. The apparatus according to claim 5; wherein each of the optical subsystems has the following system data with lenses L1, L2, L3, L5, L6, L7, L8, L9, L10 and a mirror element S4, wherein lenses L1, L2 and L3 are cemented together and lenses L8, L9 and L10 are cemented together to form lens groups, and wherein surfaces 1 and 5 are reflection-coated, with refractive index n.sub.d and Abbe number .sub.d at a wavelength of .sub.d=578.56 nm: TABLE-US-00006 Thickness [mm]/ Lens Surface Radius [mm] Air Gap [mm] n.sub.d .sub.d L1 1 flat 7.22 1.64 42.41 L2 2 122.40 8.53 1.46 67.87 L3 3 130.00 6.16 1.82 46.62 4 74.26 10.49 S4 5 38.74 0.10 L5 6 16.21 1.00 1.44 94.93 L6 7 6.19 3.28 1.64 42.21 8 85.87 10.80 L7 9 174.59 3.04 1.74 32.26 10 14.94 0.10 L8 11 42.60 3.40 1.61 56.65 L9 12 46.09 8.71 1.88 40.76 L10 13 17.72 7.67 1.82 46.62 14 37.45.

8. The apparatus according to claim 5; wherein the convex surface of the plano-convex lens or lens group is aspherically shaped.

9. The apparatus according to claim 8; wherein each of the optical subsystems has the following system data with lenses L1, L3, L4, L5, L6 and a mirror element S2, wherein lenses L5 and L6 form a lens group and are cemented together, with refractive index n.sub.d and Abbe number .sub.d at a wavelength of .sub.d=578.56 nm, wherein surface 2 is aspherically shaped: TABLE-US-00007 Thickness [mm]/ Lens Surface Radius [mm] Air Gap [mm] n.sub.d .sub.d L1 1 flat 16.60 1.52 64.17 2 51.89 6.85 S2 3 27.43 0.00 L3 4 95.19 1.00 1.52 64.17 5 13.07 1.00 L4 6 23.51 6.17 1.69 31.18 7 6.94 0.10 L5 8 26.32 5.00 1.69 31.18 L6 9 15.23 8.00 1.52 64.17 10 14.45.

10. The apparatus according to claim 8; wherein the mirror element is configured as a Mangin mirror.

11. The apparatus according to claim 5; wherein the mirror element is configured as a Mangin mirror.

12. The apparatus according to claim 11; wherein each of the optical subsystems has the following system data with lenses L1, L2, L3, L4, L5, L6, wherein lens L2 is the Mangin mirror, and wherein surfaces 1 and 4 are reflection-coated, with refractive index n.sub.d and Abbe number .sub.d at a wavelength of .sub.d=578.56 nm: TABLE-US-00008 Thickness [mm]/ Lens Surface Radius [mm] Air Gap [mm] n.sub.d .sub.d L1 1 flat 15.98 1.52 64.17 2 62.72 6.23 L2 3 32.45 3.50 1.52 64.17 4 31.64 0.53 L3 5 10.68 1.00 1.52 64.17 6 1.90 0.10 L4 7 3.44 7.31 1.69 31.18 8 19.46 0.54 L5 9 56.66 3.92 1.69 31.18 10 39.96 0.10 L6 11 24.67 4.00 1.52 64.17 12 14.04.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 the basic construction of an apparatus for imaging a sample with an optical transmission system and an optical imaging system;

(2) FIG. 2 an optical transmission system with another embodiment for coupling in illumination light;

(3) FIG. 3 a first specific embodiment of the optical transmission system;

(4) FIG. 4 a second specific embodiment of the optical transmission system;

(5) FIG. 5 a third specific embodiment of the optical transmission system;

(6) FIG. 6 a fourth specific embodiment of the optical transmission system.

DETAILED DESCRIPTION OF EMBODIMENTS

(7) It is to be understood that the figures and descriptions of the present invention have been simplified to illustrate elements that are relevant for a clear understanding of the present invention, while eliminating, for purposes of clarity, many other elements which are conventional in this art. Those of ordinary skill in the art will recognize that other elements are desirable for implementing the present invention. However, because such elements are well known in the art, and because they do not facilitate a better understanding of the present invention, a discussion of such elements is not provided herein.

(8) The present invention will now be described in detail on the basis of exemplary embodiments.

(9) FIG. 1 shows first the basic construction of an apparatus for imaging a sample 1 arranged in an object plane 2 in a first medium 3. The first medium 3 can be water or an aqueous solution, for example. The apparatus includes an optical transmission system 4 which images the sample 1 in the object plane 2 in an intermediate image 5 in an intermediate image plane 6. The object plane 2 and the intermediate image plane 6, respectively, form an angle A not equal to 90 with an optical axis of the optical transmission system 4, the respective angles A preferably being identical. The optical transmission system 4 comprises two subsystems, i.e., an object-side subsystem 4a and an intermediate image-side subsystem 4b, each having a plurality of lenses, and is constructed symmetrically with respect to a symmetry plane 7 so that the imaging is carried out on a scale of 1:1. The object plane 2, intermediate image plane 6 and symmetry plane 7, which may also be called the objective plane, intersect in a straight line such that the Scheimpflug condition is satisfied. The construction of the optical transmission system is symmetrical with respect to a pupil plane, i.e., the symmetry plane 7 corresponds to a pupil plane. An optional, advantageously controllable pupil diaphragm 8 is arranged in this pupil plane in the construction shown in FIG. 1. In order to achieve a compact construction and minimize imaging aberrations, the lens group of the subsystems 4a and 4b which is arranged closest to the sample 1 or intermediate image has at least one catadioptric assembly in each instance. In order to ensure that the imaging is actually carried out on a scale of 1:1 and to extensively eliminate possible imaging aberrations, the transmission system 4 is constructed in such a way that the intermediate image 5 lies in a second medium 9 during imaging of the sample 1, and the second medium 9 has a refractive index that is virtually identical to that of the first medium 3. For example, if the first medium 3 is water and if the transmission system 4 is configured as an immersion system such that, for example, it is immersed directly in the sample chamber with water, then the second subsystem 4b is also configured as an immersion system and the intermediate image 5 then lies in the second medium 9 which has a refractive index virtually identical to that of water. Of course, the second medium 9 and the first medium 3 can also be identical. However, CYTOP can also be used as second medium instead of water, which facilitates construction, since it is not a fluid material. Other media which are more solid compared to water but which have virtually identical refractive indices can also be used. Certainly, it is also possible to place the sample 1 in an aqueous solution on a sample carrier 10 as is shown here for the sample-side subsystem 4a of the optical transmission system 4. Correspondingly, a sample carrier 10 or a corresponding optical, usually plane-parallel, element of the same material and of the same thickness as the sample carrier 10 is likewise arranged on the intermediate image side of the transmission system 4. Again, the transmission system 4 can be configured as an immersion system, and an immersion liquid is then located between the outer lens of the catadioptric system and the sample carrier 10. In this case, oil, for example, can also be used as immersion liquid, although this is not particularly suitable as first medium 3 because oil cannot be used to conserve living samples in particular.

(10) Facing the intermediate image plane 6 is an optical imaging system 11 with an objective 12 whose optical axis is perpendicular to the intermediate image plane 6 and an angle B, and which is focused on the intermediate image plane 6. In this way, the object plane 2 can be imaged overall on a detector 13 without distortion. The detector 13 can be, for example, the CCD chip or CMOS chip of a camera. Observation by means of an eyepiece or on a screen is, of course, also conceivable.

(11) The two subsystems 4a and 4b are telecentric systems, and the transmission system 4 as overall system is an afocal system so that the intermediate image is imaged without aberrations in a large area that is not focused. This is necessary because the object plane 2 is tilted relative to the optical axis such that a region of the volume is actually imaged on the detector 13.

(12) Beyond this, the use of catadioptric assemblies for the subsystems 4a, 4b offers the advantage that the pupil which forms the region between the two subsystems 4a and 4b is easily accessible. In this way, additional optical elements, like the pupil diaphragm 8 already mentioned, can be introduced into the beam path.

(13) The apparatus described above can be used particularly well in conjunction with the SPIM technique as it offers a number of options for coupling the illumination light into the beam path of the transmission system 4 for illuminating the sample 1 with a light sheet as is required in this method. The light sheet plane LS lies substantially in the object plane and at an angle not equal to zero relative to the detection direction. In principle, combining with a typical SPIM construction in which the illumination is effected through a separate illumination objective in the region of the sample or sample chamber is also possible.

(14) One of the possibilities for coupling illumination light 14 into the transmission system 4 is also shown in FIG. 1. However, this is only one of a number of possibilities. For example, combining with conventional separate illumination optics having their own illumination objective is also possible. The means for coupling in illumination light 14 shown in FIG. 1 include a beamsplitter 15 arranged in a pupil plane between the two subsystems 4a and 4b. The arrangement of the beamsplitter 15 in the pupil plane is easily possible because the beam path can be lengthened to a certain extent at this location between the two subsystems 4a and 4b so that the beamsplitter 15 can be arranged in the pupil plane without difficulty. In FIG. 1, the beamsplitter 15 is arranged in the symmetry plane 7. This is not absolutely necessary; it can also be associated directly with one of the two subsystems 4a or 4b. For this purpose, the beamsplitter 15 must be configured such that it passes light to be detected, which is not problematic for fluorescence microscopy applications because the wavelengths of illumination light 14 differ from those of light to be detected in that case. It can be seen in FIG. 1 that the left-hand portion of subsystem 4a is used for the illumination beam path, while the right-hand portion of subsystem 4a is used for detection. Because of this spatial separation of detection beam path and illumination beam path which is necessary for implementing SPIM observation with an individual optical system in the area of the sample, an element which is one half the size of the beamsplitter 15 and which leaves open the area on the right-hand side can be used instead of the beamsplitter 15 which takes up the entire pupil plane. In this way, slight light losses which can occur with the beamsplitter 15 can be prevented, which may be advantageous in case of weak fluorescence signals.

(15) A further possibility for coupling illumination light 14 into the beam path of the transmission system 4 is shown in FIG. 2, where, instead of showing the transmission system 4 in its entirety, only the intermediate image side subsystem 4b is shown schematically. The optical elements shown merely serve to illustrate the basic beam path. The illumination device 16 shown here is arranged on the side of the intermediate image 5 and is configured to introduce the illumination light 14 via the second medium 9 in the intermediate image plane 6 into the beam path. The illumination of the intermediate image plane 6 is already carried out with a light sheet in this plane. This light sheet is then correspondingly transmitted into the object plane 2, since the transmission system 4 functions in both directions.

(16) The intermediate image side subsystem 4b shown in FIG. 2 directly contacts the second medium 9 which accordingly acts as immersion medium. The first medium 3 directly contacts the corresponding optical element of the object-side subsystem 4a and acts as immersion medium. Accordingly, a special sample holder is omitted in this construction. If the first medium 3 is water, for example, the transmission system can be introduced into the corresponding sample chamber from above. Application from the side or from below is also possible via special connections at the sample chamber. For example, if water is used as first medium 3, water can also be used as second medium 9. However, instead of a liquid medium it is particularly advantageous to use a solid or amorphous medium, for example, an amorphous fluoropolymer such as that marketed by the firm BELLEX International Corporation under the tradename CYTOP. Owing to its consistency, this material need not be stored separately in a vessel, which is a great advantage for connecting the optical imaging system 11 and, as the case may be, the illumination device 16 shown in FIG. 2 because, otherwise, the optical imaging system 11 and the illumination device 16 would also have to be configured as immersion systems, which, of course, is also possible.

(17) Evidently, both the first medium 3 and the second medium 9 can also be replaced by a sample carrier 10 or coverslip or a corresponding element on the intermediate image side. In this case, the transmission system 4 need not necessarily be configured as an immersion system. However, configuration as immersion system is advantageous for achieving a high numerical aperture. In the apparatus shown in FIG. 2, the transmission system 4 can have, for example, a numerical aperture of 1.31, the optical imaging system 11 can have a numerical aperture of 1.0, and the illumination device 16 can have a numerical aperture of 0.5. Since it serves only for imaging and not for illumination, the optical imaging system 11 in this case no longer needs an extremely high numerical aperture, which facilitates the optical design with respect to the selection and assembly of components for a well-corrected imaging.

(18) The catadioptric assembly can be configured in different ways. The rest of the elements of the transmission system 4 are configured depending on the configuration of this assembly. In order to make the spatial length dimension of the transmission system 4 more compact along the optical axis, the catadioptric assembly comprises, for example, a plano-convex lens or lens group and a mirror element. The plano-convex lens or lens group has a flat surface which faces the object plane 2 or intermediate image plane 6 and is reflection-coated toward the inner side. A region which encloses the optical axis is exempted from the reflection-coating in order to pass light. The region must be large enough for sufficient light to enter the transmission system 4 along the detection direction through this uncoated region and, further, for illumination light at an angle of preferably 90 relative to the detection direction for optimal illumination with a light sheet. A convex surface is arranged opposite the flat surface, and the mirror element is in turn arranged opposite this convex surface of the lens or lens group. The mirror surface of this mirror element is concave and it reflects light coming from the plano-convex lens or lens group. There is likewise a region in this mirror element that encloses the optical axis and is exempted from the reflection-coating in order to pass light. The beam path is designed in such a way that light enters through the uncoated region at an angle in the region of the detection direction, initially passes through the plano-convex lens, exits at the convex surface and is reflected back at the mirror surface of the mirror element to the plano-convex lens. After passing anew through the convex surface of the plano-convex lens, the beam is reflected at the reflective flat surface in the direction of the region of the mirror element that is exempted from reflective coating in order to pass light. This region can be formed as an aperture, and a corresponding lens or lens group can also be inserted into this aperture.

(19) The transmission system 4 can be implemented in various way using these two elements: the plano-convex lens or lens group and the mirror element.

(20) For example, each of the two subsystems 4a and 4b can have the system data indicated in the following Table 1.

(21) TABLE-US-00001 TABLE 1 Thickness [mm]/ Lens Surface Radius [mm] Air Gap [mm] n.sub.d .sub.d L1 1 flat 17.56 1.52 64.17 2 59.77 7.22 S2 3 29.95 1.00 L3 4 784.92 3.35 1.59 64.27 5 21.53 2.56 L4 6 8.81 4.39 1.65 33.85 7 8.21 3.76 L5 8 189.42 3.50 1.52 64.17 9 15.81 0.50 L6 10 21.29 4.00 1.52 64.17 11 65.47

(22) Each of the subsystems has lenses L1, L3, L4, L5 and L6 and a mirror element S2; surfaces 1 and 3 are reflection-coated. The refractive index n.sub.d and the Abbe number .sub.d relate to a wavelength of .sub.d=578.56 nm. A transmission system with these system data is shown by way of example in FIG. 3. Accordingly, in this case the catadioptric assembly has lens L1 and mirror element S2. The working distance is 0.5 mm in this case. A material which has a refractive index n.sub.d=1.33 and an Abbe number .sub.d=55.74, for example, water or a fluoropolymer such as CYTOP which has a refractive index of 1.34, is preferably used as first medium and second medium. The system described in Table 1 is also, and particularly, suitable for use in immersion environments.

(23) Another example for implementing the transmission system 4 is shown in FIG. 4. Each of the two subsystems 4a and 4b of the transmission system 4 shown in FIG. 4 has the following system data.

(24) TABLE-US-00002 TABLE 2 Thickness [mm]/ Lens Surface Radius [mm] Air Gap [mm] n.sub.d .sub.d L1 1 flat 7.22 1.64 42.41 L2 2 122.40 8.53 1.46 67.87 L3 3 130.00 6.16 1.82 46.62 4 74.26 10.49 S4 5 38.74 0.10 L5 6 16.21 1.00 1.44 94.93 L6 7 6.19 3.28 1.64 42.21 8 85.87 10.80 L7 9 174.59 3.04 1.74 32.26 10 14.94 0.10 L8 11 42.60 3.40 1.61 56.65 L9 12 46.09 8.71 1.88 40.76 L10 13 17.72 7.67 1.82 46.62 14 37.45

(25) In this case, each of the subsystems 4a and 4b has lenses L1, L2, L3, L5, L6, L7, L8, L9, L10 and a mirror element S4. Lenses L1, L2 and L3 are cemented together. Lenses L8, L9 and L10 are likewise cemented together. They form lens groups in each instance. In each of the subsystems, surfaces 1 and 5 are reflection-coated which is denoted in both FIG. 4 and FIG. 3 by the shading. This configuration can be used in particular with a coverslip having the refractive index n.sub.d=1.52 and an Abbe number .sub.d=59.48, in which case the coverslip preferably has a thickness of 0.17 mm. Water is again preferably used as first medium and second medium, and the working distance from the object planewithout the coverslipis 0.4 mm, i.e., the thickness of the water layer is 0.4 mm. A fluoropolymer can also be used, for example, instead of water, as second medium on the intermediate image side

(26) In a further configuration of the transmission system 4, the convex surface of the plano-convex lens or lens group is aspherically shaped. In case of a lens group, this means the surface located farthest from the object. An example of a transmission system 4 of this type is shown in FIG. 5. It has the following system data from Table 3:

(27) TABLE-US-00003 TABLE 3 Thickness [mm]/ Lens Surface Radius [mm] Air Gap [mm] n.sub.d .sub.d L1 1 flat 16.60 1.52 64.17 2 51.89 6.85 S2 3 27.43 0.00 L3 4 95.19 1.00 1.52 64.17 5 13.07 1.00 L4 6 23.51 6.17 1.69 31.18 7 6.94 0.10 L5 8 26.32 5.00 1.69 31.18 L6 9 15.23 8.00 1.52 64.17 10 14.45

(28) In this case, the convex surface 2 of the plano-convex lens is aspherically shaped. The aspherically shaped surface, in this instance a rotationally symmetrical conic asphere, is described by the following relationship

(29) $f\left(h\right)=\frac{h^2}{1+\sqrt{1-\left(1+K\right).Math.{\left(h\right)}^2}}+\underset{i=2}{\overset{N}{.Math.}}{c}_{2i}{h}^{2i}$
K is the conic constant, i and N are natural numbers, and c.sub.2i is the coefficient of a polynomial in h. R denotes the radius of an imaginary conic surface at the vertex of this surface. i.e., the distance from the vertex to the closest focal point. Both the vertex and the focal points of the conic surface lie on the optical axis. The coefficients of conic constant K and radius R are determined by iteration. The radius of surface 2 in Table 3 denotes the spherical base radius in closest vicinity to the optical axis, i.e., for small h, and corresponds to .

(30) Further, in the example shown in FIG. 5, lenses L5 and L6 form a lens group and are cemented together. This configuration can also be used particularly with a coverslip having refractive index n.sub.d=1.52 and Abbe number .sub.d=59.48, the coverslip preferably having a thickness of 0.17 mm. Water is again preferably used as first medium and second medium, and the working distance, i.e., the thickness of the water layer, is 0.4 mm. When the selected conic constant is K=0 and with a conventional lens height of approximately 30 mm, the following coefficients of the polynomial in h to i=8 result for these parameters and the parameters indicated in Table 3: c.sub.4=8.9311.Math.10.sup.7, c.sub.6=1.4858.Math.10.sup.9, c.sub.8=2.1550.Math.10.sup.11, c.sub.10=1.1551.Math.10.sup.13, c.sub.12=3.6392.Math.10.sup.16, c.sub.14=5.7753.Math.10.sup.19 and c.sub.16=3.6408.Math.10.sup.22. Fluoropolymers can also be taken into consideration as coverslip and/or media.

(31) In a further configuration of the transmission system, the mirror element can also be configured as a Mangin mirror. An example for this is shown in FIG. 6. It has the following system data from Table 4:

(32) TABLE-US-00004 TABLE 4 Thickness [mm]/ Lens Surface Radius [mm] Air Gap [mm] n.sub.d .sub.d L1 1 flat 15.98 1.52 64.17 2 62.72 6.23 L2 3 32.45 3.50 1.52 64.17 4 31.64 0.53 L3 5 10.68 1.00 1.52 64.17 6 1.90 0.10 L4 7 3.44 7.31 1.69 31.18 8 19.46 0.54 L5 9 56.66 3.92 1.69 31.18 10 39.96 0.10 L6 11 24.67 4.00 1.52 64.17 12 14.04

(33) Each of the subsystems 4a, 4b has lenses L1, L2, L3, L4, L5 and L6. Lens L2 is configured as a Mangin mirror, i.e., one side of this lenswith the exception of the region around the optical axisis reflection-coated. This configuration can be used in particular with a coverslip having the refractive index n.sub.d=1.52 and an Abbe number .sub.d=59.48, in which case the coverslip preferably has a thickness of 0.17 mm. Again preferably water or a fluoropolymer is used as first medium and second medium, and the working distance, i.e., the thickness of the water layer, is 0.4 mm. The fluoropolymer can also be used instead of a coverslip.

(34) Owing to the use of catadioptric elements, the optical transmission systems described above make possible a sharp reduction in the length of the construction of an apparatus for imaging a sample, particularly in conjunction with SPIM applications. Since the intermediate image and the actual object are disposed in media with approximately identical refractive indices, the out-of-focus volume area is imaged virtually without optical aberrations so that even oblique object planes located in a large area outside of the focus can be imaged correctly.

(35) While this invention has been described in conjunction with the specific embodiments outlined above, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art. Accordingly, the preferred embodiments of the invention as set forth above are intended to be illustrative, not limiting. Various changes may be made without departing from the spirit and scope of the inventions as defined in the following claim.

LIST OF REFERENCE CHARACTERS

(36) 1 sample 2 object plane 3 first medium 4 optical transmission system 4a, 4b subsystem 5 intermediate image 6 intermediate image plane 7 symmetry plane 8 pupil diaphragm 9 second medium 10 sample carrier 11 optical imaging system 12 objective 13 detector 14 illumination light 15 beamsplitter 16 illumination device L1-L10 lenses S2, S4 mirror elements