HYBRID OPTICAL FIBER, ENDOSCOPIC SYSTEM, AND METHOD FOR EXAMINING A SAMPLE

Abstract

The invention relates to a hybrid optical fiber (1) which comprises a plurality of fiber cores (2), a first cladding (3) which encloses the plurality of fiber cores (2), and a second cladding (4) which surrounds the first cladding (3). In this case, the fiber cores (2) have a first refractive index ni, the first cladding (3) has a second refractive index nz and the second cladding (4) has a third refractive index n 3 , ni being greater than nz and nz being greater than n 3 . Furthermore, the invention relates to an endoscopic system (8) for examining a sample (9), comprising a hybrid optical fiber (1) and an optical arrangement (21). The optical arrangement (21) comprises a coherent light source (13) for introducing light into a proximal end of the hybrid optical fiber (1), such that the fiber cores (2) of the hybrid optical fiber (1) together with the first cladding (3) of the hybrid optical fiber (1) function as a multimode optical fiber. Furthermore, the optical arrangement (21) comprises a photodetector (20), comprising a plurality of pixels, for detecting the light exiting the individual fiber cores (2). The invention also relates to a method for examining a sample (9) by means of an endoscopic system (8).

Claims

1-18. (canceled)

19. A hybrid optical fiber, comprising: a plurality of fiber cores; a first cladding enclosing the plurality of fiber cores; and a second cladding enclosing the first cladding, wherein the plurality of fiber cores have a first refractive index, the first cladding has a second refractive index and the second cladding has a third refractive index, wherein the first refractive index is greater than second refractive index, and the second refractive index is greater than the third refractive index.

20. The hybrid optical fiber according to claim 19, wherein the plurality of fiber cores are arranged in an orthogonal point group or in a hexagonal point group in a cross section of the hybrid optical fiber.

21. The hybrid optical fiber according to claim 19, wherein a diameter of each one of the plurality of fiber cores is between 5 pm and 20 pm.

22. The hybrid optical fiber according to claim 21, wherein the diameter of each one of the plurality of fiber cores between 8 ?m and 13 ?m.

23. The hybrid optical fiber according to claim 19, wherein a distance between two adjacent ones of the plurality of fiber cores is between 10 ?m and 50 ?m.

24. The hybrid optical fiber according to claim 23, wherein the distance between the two adjacent ones of the plurality of fiber cores is between 20 ?m and 30 ?m.

25. The hybrid optical fiber according to claim 19, wherein a number of the plurality of fiber cores in the hybrid optical fiber is between 30 and 100.

26. The hybrid optical fiber according to claim 25, wherein the number of the plurality of fiber cores is between 50 and 70.

27. The hybrid optical fiber according to claim 19, further comprising a structure enclosing the second cladding, the structure being at least one of a protective coating or an outer sheath.

28. An endoscopic system for examining a sample, comprising a hybrid optical fiber comprising: a plurality of fiber cores, a first cladding enclosing the plurality of fiber cores, and a second cladding enclosing the first cladding, wherein the plurality of fiber cores have a first refractive index, the first cladding has a second refractive index and the second cladding has a third refractive index, wherein the first refractive index is greater than second refractive index, and the second refractive index is greater than the third refractive index; and an optical arrangement comprising: a coherent light source configured to introduce light into a proximal end of the hybrid optical fiber such that the plurality of fiber cores and the first cladding function as a multimode optical fiber, and a photodetector comprising a plurality of pixels configured to detect the light emerging from individual ones of the plurality of fiber cores.

29. The endoscopic system according to claim 28, wherein the endoscopic system is further adapted to operate in: a first operating mode in which the coherent light source is used to excite light modes in the hybrid optical fiber functioning as the multimode optical fiber in such a way that individual object points in the sample are illuminated one after another, and the light response emitted by the object points is detected by the photodetector, and a second operating mode in which the coherent light source is used to illuminate objects in the sample, and the light response emitted by the objects is detected separately for each of the plurality of fiber cores by the photodetector.

30. The endoscopic system according to claim 29, wherein the light response emitted by the object points is detected as a sum over all pixels.

31. The endoscopic system according to claim 28, wherein the optical arrangement comprises a further light source configured to introduce further light into at least one of the plurality of fiber cores or the first cladding.

32. The endoscopic system according to claim 31, wherein the further light source has a plurality of partial light sources, and wherein the partial light sources are arranged in an array and assigned to the plurality of fiber cores of the hybrid optical fiber, and wherein the objects in the sample are illuminated by the additional light source.

33. The endoscopic system according to claim 32, wherein the optical arrangement comprises a further photodetector configured to detect the light or the further light emerging from the plurality of fiber cores and the first cladding, wherein the coherent light source and the further photodetector are assigned to a first optical subassembly, wherein the further light source and the photodetector are assigned to a second optical subassei bly.

34. The endoscopic system according to claim 29, wherein the optical arrangement comprises a further light source configured to introduce further light into at least one of the plurality of fiber cores or the first cladding, wherein the further light source has a plurality of partial light sources, and wherein the partial light sources are arranged in an array and assigned to the plurality of fiber cores of the hybrid optical fiber, and wherein the objects in the sample are illuminated by the additional light source, wherein the optical arrangement comprises a further photodetector configured to detect the light or the further light emerging from the plurality of fiber cores and the first cladding, wherein the coherent light source and the further photodetector are assigned to a first optical subassembly, wherein the further light source and the photodetector are assigned to a second optical subassembly, wherein the optical arrangement comprises a further photodetector configured to detect the light or the further light emerging from the plurality of fiber cores and the first cladding, wherein the coherent light source and the further photodetector are assigned to a first optical subassembly, wherein the further light source and the photodetector are assigned to a second optical subassembly, and wherein the first operating mode is performed using the first optical part arrangement, and the second operating mode is performed using the second optical subassembly.

35. The endoscopic system according to claim 33, further comprising a switching device configured to change between the first optical subassembly and the second optical subassembly.

36. The endoscopic system according to claim 33, wherein at least one of the first optical subassembly or the second optical subassembly is usable separately with the hybrid optical fiber.

37. The endoscopic system according to claim 28, wherein the hybrid optical fiber includes a first part and a second part, and wherein the first part and the second part are connected to one another in a detachable manner via a connecting element.

38. The endoscopic system according to claim 29, wherein at least one of (i) the optical arrangement in the first operating mode or (ii) a first optical subassembly has a first numerical aperture, and wherein at least one of (i) the optical arrangement in the second operating mode or (ii) a second optical subassembly has a second numerical aperture, and wherein the first numerical aperture is greater than the second numerical aperture.

39. A method for examining a sample using an endoscopic system which comprises a hybrid optical fiber comprising (i) a plurality of fiber cores, (ii) a first cladding enclosing the plurality of fiber cores, and (iii) a second cladding enclosing the first cladding, wherein the plurality of fiber cores have a first refractive index, the first cladding has a second refractive index and the second cladding has a third refractive index, wherein the first refractive index is greater than second refractive index, and the second refractive index is greater than the third refractive index, the endoscopic system further comprising an optical arrangement comprising (i) a coherent light source configured to introduce light into a proximal end of the hybrid optical fiber such that the plurality of fiber cores and the first cladding function as a multimode optical fiber, and (ii) a photodetector comprising a plurality of pixels configured to detect the light emerging from individual ones of the plurality of fiber cores, wherein the method comprising: inserting the hybrid optical fiber of the endoscopic system into the sample which is initially immovable, wherein at least one of the optical arrangement or the first optical subassembly of the endoscopic system is connected to the hybrid optical fiber; introducing light into the plurality of fiber cores and the first cladding of the hybrid optical fiber using the coherent light source, wherein the hybrid optical fiber functions as a multimode optical fiber, wherein a number of object points in the sample are illuminated one after another through the hybrid optical fiber; and detecting the light response emitted by the object points via the hybrid optical fiber using the photodetector; moving the sample, wherein the optical arrangement or the second optical subassembly of the endoscopic system is connected to the hybrid optical fiber; introducing light into at least one of the plurality of fiber cores or the first cladding using the coherent light source or a further light source so as to illuminate objects at the distal ends of the fiber cores; and detecting a light response emitted from the objects which is passed through the plurality of fiber cores by the pixels of the photodetector.

40. The method according to claim 39, further comprising measuring or calculating light transmission properties of the hybrid optical fiber used as a multimode optical fiber before examining the sample.

41. The method according to claim 39, wherein, when the second optical subassembly is connected to the hybrid optical fiber, the first optical subassembly is completely disconnected from the hybrid optical fiber.

42. The method according to claim 39, further comprising after examining the sample, separating the hybrid optical fiber into a first part inserted into the sample and a second part; and reconnecting the first part and the second part to one another thereafter for a further examination of the sample.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0040] In the figures:

[0041] FIG. 1 shows a perspective view of an exemplary embodiment of a hybrid optical fiber;

[0042] FIG. 2 shows a cross section through a further exemplary embodiment of a hybrid optical fiber;

[0043] FIG. 3 shows a cross section through yet a further exemplary embodiment of a hybrid optical fiber;

[0044] FIG. 4 shows a cross section through yet a further exemplary embodiment of a hybrid optical fiber;

[0045] FIG. 5 shows a longitudinal section through an assembled first part and second part of a hybrid optical fiber;

[0046] FIG. 6a shows a schematic view of an exemplary embodiment of an endoscopic system;

[0047] FIG. 6b shows a further schematic view of the exemplary embodiment of the endoscopic system from FIG. 6a; and

[0048] FIG. 7 shows a schematic view of a further exemplary embodiment of an endoscopic system.

DETAILED DESCRIPTION OF EMBODIMENTS

[0049] In the figures, identical reference signs denote either identical elements or elements with equivalent functions. Elements which have already been described are not necessarily described again in subsequent figures.

[0050] FIG. 1 shows a perspective view of an exemplary embodiment of a hybrid optical fiber 1. The hybrid optical fiber 1 comprises a plurality of fiber cores 2. These fiber cores 2 are enclosed by a common first cladding 3. In this case, a first refractive index ni of the fiber cores 2 is greater than a second refractive index nz of the first cladding 3, such that light running in the fiber cores 2 can undergo total reflection at the boundary surface between fiber core 2 and first cladding 3. In the case of a corresponding entrance angle of the light or in the case of a corresponding numerical aperture of an optical arrangement connected to the hybrid optical fiber 1, the fiber cores 2 can thus be referred to as individual optical fibers.

[0051] A second cladding 4 is also arranged so as to surround the first cladding 3. In this case, the second refractive index nz of the first cladding 3 is greater than a third refractive index n 3 of the second cladding 4, such that light running in the first cladding 3 can undergo total reflection at the boundary surface between first cladding 3 and second cladding 4. In the case of a corresponding entrance angle of the light or in the case of a corresponding numerical aperture of an optical arrangement connected to the hybrid optical fiber 1, the fiber cores 2 together with the first cladding 3 can thus function as a multimode optical fiber, the light undergoing total reflection at the boundary surface between first cladding 3 and second cladding 4.

[0052] Depending on the numerical aperture of the optical arrangement connected to the hybrid optical fiber 1, two different operating modes of the hybrid optical fiber 1 are thus possible: firstly, the fiber cores 2 together with the first cladding 3 can function as a multimode optical fiber, as a result of which a particularly high resolution is enabled. Since, however, the propagation of the many light modes in the multimode optical fiber is sensitive to deformations and bending of the optical fiber, this operating mode is limited to predominantly immobile samples. In the second operating mode, the individual fiber cores 2 function as optical fibers, only one or a few light modes being excited in each case. Although the resolution is limited to the spacing between the individual fiber cores 2 in this operating mode, it also allows examinations on moving samples to be performed.

[0053] Mention is made as an example here of the examination of neurons and of the networking of neurons in the brain of an animal or a human. First, the hybrid optical fiber 1 is introduced into the brain of the sedated animal or human. In the sedated state, high-resolution images are then also already taken with the hybrid optical fiber 1 as multimode optical fiber. These images show, by way of example, individual neurons and the networking between these neurons. During the further course of the examination, the animal or the human is brought into the awake state. In the awake state, images are then taken with the individual fiber cores 2 as optical fibers, it being possible here to observe for example the individual neurons, but no longer the networking between the neurons. Since the same hybrid optical fiber 1 is used for both images and its position is not changed between the images, it is possible for the neurons observed by means of the individual fiber cores 2 to be assigned to the neurons from the high- resolution image.

[0054] FIG. 2 shows a cross section through a further exemplary embodiment of a hybrid optical fiber 1. In this exemplary embodiment, a multiplicity of fiber cores 2 are arranged in an orthogonal point group. Imaging in an orthogonal coordinate system is particularly simple with this arrangement of the fiber cores 2.

[0055] FIG. 3 shows a cross section through yet a further exemplary embodiment of a hybrid optical fiber 1. In this exemplary embodiment, the fiber cores 2 are arranged in a hexagonal point group. It is thus possible, with a given spacing between adjacent fiber cores 2, to arrange the largest possible number of fiber cores 2 within the first cladding 3. Furthermore, the arrangement of the fiber cores 2 in the hexagonal point group provides a particularly good stability of the hybrid optical fiber 1.

[0056] FIG. 4 shows a cross section through yet a further exemplary embodiment of a hybrid optical fiber 1. In this exemplary embodiment, a protective coating 5 which surrounds the second cladding 4 is arranged around the second cladding 4. This protective coating 5 protects the hybrid optical fiber 1 against external influences, for example against chemical or physical influences.

[0057] FIG. 5 shows a detail of a longitudinal section through a further exemplary embodiment of a hybrid optical fiber 1. This hybrid optical fiber 1 is composed of a first part 1.1 and a second part 1.2. In order to connect the first part 1.1 to the second part 1.2, ceramic end sleeves 6 are fitted on that end of the first part 1.1 which faces the second part 1.2 and on that end of the second part 1.2 which faces the first part 1.1. An inner diameter of the ceramic end sleeves 6 corresponds in this case precisely to an outer diameter of the second cladding 4. The first part 1.1 is connected to the second part 1.2 by way of a connecting sleeve 7, into which the two ceramic end sleeves are plugged. Such a connection allows the first part 1.1 of the hybrid optical fiber 1 to be left in a sample while the second part 1.2 together with the rest of the endoscopic system is separated from the sample. The first part 1.1 has only a very minor adverse effect, if any, on the sample. For renewed examinations, the first part 1.1 and the second part 1.2 are then connected to one another again.

[0058] FIG. 6a shows a schematic view of an exemplary embodiment of an endoscopic system 8. A hybrid optical fiber 1 is introduced into a sample 9 in order to examine objects 10 in front of the hybrid optical fiber 1.

[0059] The endoscopic system 8 comprises an optical arrangement 21 which comprises a first optical partial arrangement 11 and a second optical partial arrangement 12. A mechanical system, which is not illustrated in any more detail here, can be used to couple either the first optical partial arrangement 11 or the second optical partial arrangement 12 to the hybrid optical fiber 1. In this case, the first optical partial arrangement 11 is coupled to the hybrid optical fiber 1 in FIG. 6a. As an alternative thereto, it is possible to perform the change between the first optical partial arrangement 11 and the second optical partial arrangement 12 by way of optical elements, for example an adjustable mirror. Furthermore, it is also possible for only the first optical partial arrangement 11 or the second optical partial arrangement 12 to be connected to the hybrid optical fiber 1 at a given point in time, while the respectively other optical partial arrangement 12 or 11 is separated from the hybrid optical fiber 1.

[0060] The first optical partial arrangement 11 comprises a coherent light source 13 comprising a laser 14 and a modifier 15 which modifies the light wavefront emitted by the laser 14. A first beam splitter 16, which is for example a dichroic beam splitter, is used to optically connect the coherent light source 13 to the hybrid optical fiber 1, the fiber cores 2 together with the first cladding 3 functioning as a multimode optical fiber. In the case of an examination of the sample 9, the coherent light of the laser 14 is modified by means of the modifier 15 in such a way that in each case only one point of the object 10 is illuminated. The necessary knowledge of the light transmission properties of the hybrid optical fiber 1 are, to this end, measured and/or calculated prior to the examination. The light response emitted by the illuminated point of the object 10 for example by reflection, fluorescence, Raman scattering, stimulated Raman scattering, coherent anti-Stokes Raman scattering, autofluorescence and/or frequency doubling is conducted by the hybrid optical fiber 1 out of the sample 9 and passes via the first beam splitter 16 to a further photodetector 17 of the first optical partial arrangement 11, where said light response is detected. By virtue of a multiplicity of points of the object 10 being successively illuminated, a high-resolution image can be created.

[0061] FIG. 6b shows the endoscopic system 8 from FIG. 6a again, the second optical partial arrangement 12 having been coupled to the hybrid optical fiber 1 by means of the mechanical system. The second optical partial arrangement 12 comprises a further light source 18 which introduces light into the fiber cores 2 and/or into the first cladding 3. In this case, the further light source 18 comprises, for example, an array of LEDs, each fiber core 2 being assigned an LED. The light from the further light source 18 illuminates the object 10 via a second beam splitter 19, which is for example a dichroic beam splitter, and the hybrid optical fiber 1. A light response emitted by the object 10 for example by reflection, fluorescence, Raman scattering, stimulated Raman scattering, coherent anti-Stokes Raman scattering, autofluorescence and/or frequency doubling then passes via the fiber cores 2 of the hybrid optical fiber 1 and the second beam splitter 19 to a photodetector 20 of the second optical partial arrangement 12. The photodetector 20 in this case comprises a plurality of pixels for detecting the light exiting the individual fiber cores 2. The resolution of the combination of the hybrid optical fiber 1 with the second optical arrangement 12 is limited to the spacing between the fiber cores 2, however examinations on a moving sample 9 can also be performed with this combination.

[0062] FIG. 7 shows a schematic view of a further exemplary embodiment of an endoscopic system 8. The optical arrangement 21 of this endoscopic system 8 comprises merely a coherent light source 13 and a photodetector 20. In this case, the coherent light source 13 introduces the light into the hybrid optical fiber 1 both in a first operating mode and in a second operating mode of the endoscopic system 8. In the first operating mode, the light modes in the hybrid optical fiber 1 functioning as a multimode optical fiber are excited in such a way that individual object points in the sample 9 are successively illuminated. In the second operating mode, objects in the sample 9 are illuminated by means of the coherent light source 13. Equally, the light response of the object points or objects is detected by the photodetector 20 both in the first and in the second operating mode. In this case, summing is performed over all pixels of the photodetector 20 in the first operating mode, while the light response is detected separately for each fiber core 2 in the second operating mode.