Endoscopic system and procedure for examining a sample

Abstract

Endoscopic system for examining a sample (9) comprising a hybrid optical fiber (1) comprising a plurality of fiber cores (2), a first cladding (3) enclosing the plurality of fiber cores (2), and a second cladding (4) enclosing the first cladding (3), wherein the fiber cores (2) have a first refractive index n1, the first cladding (3) has a second refractive index n2, and the second cladding (4) has a third refractive index n3, and wherein n1 is greater than n2 and n2 is greater than n3, and an optical arrangement (21) comprising a coherent light source (13) configured to introduce light into a proximal end of the hybrid optical fiber (1), including the first cladding (3), so 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, with the light being totally reflected at an interface between the first cladding (3) and the second cladding (4), and a photodetector (20) comprising a plurality of pixels for detecting the light emerging from the individual fiber cores (2).

Description

Field of the invention

[0001] The invention relates to an endoscopic system for examining a sample and a method for examining a sample using an endoscopic system. background

[0002] Endoscopic procedures are used in a wide variety of forms and for examining a wide range of samples. One class of endoscopic procedures is based on the use of optical fibers as probes. Due to the typically small diameter of these optical fibers, these endoscopic procedures are only minimally invasive.

[0003] One example is endoscopy using fiber bundles or so-called multi-core optical fibers. In fiber bundles, a number of optical fibers, each with one or a few excitable light modes, are bundled together. In multi-core optical fibers, on the other hand, several fiber cores, each with one or a few excitable light modes, are combined within a single cladding. Each individual optical fiber or core serves as a single image pixel, so the achievable resolution depends on the distance between the individual optical fibers or cores.

[0004] Another example is holographic endoscopy, which uses an endoscopic system with a multimode optical fiber as a probe. This type of endoscopy allows for the acquisition of particularly high-resolution images of samples. A disadvantage of this method is that it is only applicable to stationary samples, as precise wavefront manipulation is essential and the wavefront is very sensitive to bending or deformation of the multimode optical fibers.

[0005] US patent application US 2010 / 0 046 897 A1 describes an endoscopic system with an image fiber having a plurality of cores. US patent application US 2019 / 0 270 667 A1 describes an image-guided fiber. US patent application US 2019 / 0 212 761 A1 describes an optical probe with a multimode optical waveguide. US patent application US 2020 / 0 174 181 A1 describes multicore fibers and endoscope configurations. US patent application US 2004 / 0 264 513 A1 describes a rare-earth doped fiber. US patent application US 5 566 196 A describes a fiber laser in which the optical fiber reinforcement medium has two or more non-concentric core regions. US patent application US 2020 / 0326472A1 describes multimode optical fibers. Summary

[0006] The object of the invention is therefore to propose an endoscopic system and a method for examining a sample that overcome the aforementioned disadvantages of the prior art, in particular providing a particularly high resolution and being applicable to moving samples. This object is achieved by the subject matter of the independent claims. Further developments of the invention are described in the dependent claims and the following description.

[0007] One example involves a hybrid optical fiber that comprises a plurality of fiber cores. The fiber cores are designed in such a way that, for the light to be used, particularly in the visible spectrum (i.e., with wavelengths in the range of approximately 380 nm to 750 nm), one or a few light modes can be excited.

[0008] Furthermore, the hybrid optical fiber comprises a first cladding that encloses the majority of the fiber cores. In a cross-section of the hybrid optical fiber, the first cladding is particularly circular, and the majority of the fiber cores are arranged within the first cladding.

[0009] Furthermore, the hybrid optical fiber comprises a second cladding that surrounds the first cladding. In a cross-section of the hybrid optical fiber, the second cladding is particularly ring-shaped, with the inner surface of the second cladding coinciding with the outer surface of the first cladding.

[0010] The first sheath, together with the majority of the fiber cores, can be used as a multimode optical fiber. Thus, with a suitable endoscopic system, a stationary sample in particular can be examined with high resolution.

[0011] However, individual fiber cores can also be used to examine the sample, with each fiber core then corresponding to an image pixel. In this case, it is also possible to examine a moving sample, since when the fiber cores are excited with one or a few light modes, they exhibit a high degree of insensitivity to bending or deformation.

[0012] Thus, the hybrid optical fiber offers both the possibility of examining a stationary sample with high resolution and the possibility of examining a moving sample, whereby the resolution is then limited to the distance between the fiber cores.

[0013] In some embodiments, the fiber cores in a cross-section of the hybrid optical fiber are arranged in an orthogonal or hexagonal point group. An orthogonal point group arrangement means that the fiber cores are located at the intersections of a rectangular grid. In particular, the fiber cores can be located at the intersections of a square grid. This results in a particularly simple arrangement of the fiber cores in an orthogonal coordinate system. Conversely, an orthogonal point group arrangement means that the fiber cores are located at the intersections of a hexagonal grid. This arrangement corresponds to the densest packing of the fiber cores in the hybrid optical fiber, allowing a maximum number of fiber cores of a given diameter to be arranged within a first cladding layer of a given diameter.It should be noted that the fiber cores in a cross-section of the hybrid optical fiber typically do not touch, so the light mode(s) excited in the fiber core do not couple to neighboring fiber cores. Thus, a predetermined minimum distance is maintained between two fiber cores in the cross-section. Furthermore, disordered and / or chaotic arrangements of the fiber cores are also conceivable.

[0014] In some embodiments, the fiber cores have a first refractive index n1, the first cladding a second refractive index n2, and the second cladding a third refractive index n3. Here, n1 is greater than n2 and n2 is greater than n3. Because n1 is greater than n2, total internal reflection is enabled within the individual fiber cores, allowing optical waveguides to occur within each core. Furthermore, because n2 is greater than n3, total internal reflection is enabled at the boundary between the first and second claddings, allowing the first cladding, together with the fiber cores, to function as a multimode optical fiber.

[0015] In some embodiments, the diameter of the fiber cores is between 5 µm and 20 µm, particularly between 8 µm and 13 µm. At these diameters, one to a few light modes can be excited in the fiber core and good resolutions, down to about 10 µm, can be achieved.

[0016] In some embodiments, the distance between two adjacent fiber cores is between 10 µm and 50 µm, particularly between 20 µm and 30 µm. This distance, together with a corresponding diameter of the fiber cores, ensures that no coupling of the light modes can occur from one fiber core to an adjacent fiber core, and that the individual fiber cores can thus function as individual image pixels.

[0017] In some embodiments, the number of fiber cores in the hybrid optical fiber is between 30 and 100, particularly between 50 and 70. With this number of fiber cores, a rough image of the sample can be obtained, especially when the sample is moving, while at the same time the diameter of the hybrid optical fiber remains relatively small, so that the sample is not damaged too much by the hybrid optical fiber.

[0018] In some embodiments, the hybrid optical fiber further comprises a protective coating and / or outer sheath surrounding the second cladding. This protects the second cladding from external influences and extends the lifespan of the hybrid optical fiber.

[0019] One aspect of the invention relates to an endoscopic system for examining a sample. The sample can be immobile or largely immobile at a first time point and mobile at a second time point. In particular, the sample is an animal, most specifically a human. With the aid of the endoscopic system, for example, neurons and / or the networking of neurons in the sample can be examined.

[0020] The endoscopic system includes a hybrid optical fiber as described above.

[0021] Furthermore, the endoscopic system includes an optical arrangement. This arrangement comprises a coherent light source for introducing light into the proximal end of the hybrid optical fiber. The coherent light source could, for example, be a laser, with a modifier used to modify the laser's emitted light wavefront. The light from the coherent light source can be introduced into the proximal end of the hybrid optical fiber in such a way that the fiber cores, together with the first cladding, function as a multimode optical fiber. The optical arrangement also includes a photodetector, comprising a plurality of pixels, for detecting the light emanating from the individual fiber cores. This light is emitted from the illuminated object point or area in front of the distal end of the hybrid optical fiber.This light response can occur, for example, through reflection, fluorescence, Raman scattering, stimulated Raman scattering, coherent anti-Stokes Raman scattering, autofluorescence, and / or frequency doubling. The light emitted from the illuminated object point or area is guided by the individual fiber cores and / or the first cladding to the proximal end of the hybrid optical fiber. To enable simultaneous illumination and detection, the coherent light source and the photodetector are integrated into the optical arrangement, for example, via a beam splitter, particularly a dichroic beam splitter.

[0022] In some embodiments, the endoscopic system is designed to operate in a first and a second operating mode. In the first operating mode, the coherent light source excites light modes in the hybrid optical fiber, which functions as a multimode optical fiber, such that individual object points in the sample are illuminated sequentially. The light response emitted by the individual object points is detected by the photodetector. In particular, the data is summed across all pixels of the photodetector. In the first operating mode, which is preferably used with a stationary sample, an examination of the sample with particularly high resolution can thus be achieved.

[0023] In the second operating mode, objects within the sample are illuminated using the coherent light source. The light response emitted by the objects is detected separately for each fiber core by the photodetector. For this purpose, each fiber core is assigned at least one pixel of the second photodetector. Moving samples can also be examined in this second operating mode, although the resolution is limited to the distance between two fiber cores.

[0024] In some embodiments, the optical arrangement includes an additional light source for introducing light into the fiber cores and / or the first cladding. This additional light source preferably comprises a plurality of partial light sources. These partial light sources can, in particular, be LEDs. The partial light sources are preferably arranged in an array such that they are assigned to the fiber cores of the hybrid optical fiber. Thus, light is introduced into each fiber core separately. It is possible to introduce light into all fiber cores simultaneously or sequentially. The additional light source is preferably used in the second operating mode of the endoscopic system to illuminate the objects within the sample.

[0025] In some embodiments, the optical arrangement includes a further photodetector for detecting the light emerging from the fiber cores and the first cladding. The coherent light source and the further photodetector are assigned to a first optical sub-arrangement, while the further light source and the photodetector are assigned to a second optical sub-arrangement. Preferably, the first operating mode is carried out using the first optical sub-arrangement and the second operating mode using the second optical sub-arrangement.

[0026] In some embodiments, the endoscopic system further comprises a switching device for changing between the first and second optical sub-assemblies. This switching device can be optical, for example, by means of an adjustable mirror, or mechanical, by moving the first and second optical sub-assemblies. Thus, the switching device allows switching between high-resolution examination of the stationary sample using the first optical sub-assembly and lower-resolution examination of the moving sample using the second optical sub-assembly.

[0027] In some embodiments, the first optical sub-assembly and / or the second optical sub-assembly can be used separately with the hybrid optical fiber. In these cases, the other optical sub-assembly can be separated from the rest of the endoscopic system. This is particularly advantageous when the first optical sub-assembly, which is typically very large compared to the second optical sub-assembly due to the coherent light source, is separated from the rest of the endoscopic system, leaving the hybrid optical fiber with the comparatively small second optical sub-assembly for examining the moving sample.

[0028] In some embodiments, the hybrid optical fiber consists of at least a first part and a second part. The first part and the second part are separably connected to each other via a connecting element. For this purpose, for example, ceramic end sleeves are applied to the first and second parts of the hybrid optical fiber, respectively, at the end of the first part facing the second part and at the end of the second part facing the first part. The two parts are then connected to each other via a connecting sleeve. Thus, the first part, which is inserted into the sample, can remain in the sample, and the rest of the endoscopic system can be connected to the first part via the second part for examination.

[0029] In some embodiments, the optical arrangement in the first operating mode and / or the first optical sub-arrangement has a first numerical aperture NA1, and the optical arrangement in the second operating mode and / or the second optical sub-arrangement has a second numerical aperture NA2, where NA1 is larger than NA2. NA1 is large enough that the light coupled into the fiber cores and the first cladding can pass from the fiber cores to the first cladding and back, so that the fiber cores and the first cladding together function as multimode optical fibers. NA2, on the other hand, is small enough that no light passes from the fiber cores to the cladding, so that the light remains in the individual fiber cores and each fiber core can function as an individual pixel.

[0030] Another aspect of the invention relates to a method for examining a sample. The sample can initially be immobile or largely immobile and later become mobile. In particular, the sample is an animal, especially a human. Using the endoscopic system, neurons and / or the network of neurons in the sample can be examined, for example.

[0031] The procedure is performed using an endoscopic system as described above. The hybrid optical fiber of the endoscopic system is inserted into the sample.

[0032] Initially, the sample is stationary, and the optical array and / or the first optical sub-array of the endoscopic system is connected to the hybrid optical fiber. Light is introduced into the fiber core and the first cladding of the hybrid optical fiber by means of the coherent light source, so that the hybrid optical fiber functions as a multimode fiber. A multitude of object points within the sample are sequentially illuminated by the hybrid optical fiber, and the light response emitted by these object points is detected by the hybrid optical fiber and by the photodetector or additional photodetectors. This examination of the stationary sample yields images with exceptionally high resolution.

[0033] At a later point, the sample moves, and the optical assembly and / or the second optical subassembly of the endoscopic system is connected to the hybrid optical fiber. Light is introduced into the fiber cores and / or the first cladding by means of the coherent light source or the additional light source. This illuminates objects at the distal ends of the fiber cores. The light response emitted by the objects is guided through the fiber cores to the photodetector and detected by pixels of the photodetector. Although this examination yields images with lower resolution, it is possible with a moving sample.

[0034] Since the high-resolution investigations on the stationary sample and the lower-resolution investigations on the moving sample are carried out using the same hybrid optical fiber, an accurate assignment of the pixels obtained by the fiber cores to areas in the high-resolution image is possible.

[0035] In some embodiments, the light transmission properties of the hybrid optical fiber used as a multimode optical fiber are measured before the sample is examined. The hybrid optical fiber is preferably held in the same shape, for example, straight or curved, as it will be positioned within the sample. Defined coherent light is introduced into the hybrid optical fiber at one end, and the result is measured at the other end. This allows the determination of which modifications of the coherent light are necessary to illuminate a single point on the object.

[0036] Alternatively or in addition to measuring the light transmission properties, the light transmission properties of the hybrid optical fiber can also be calculated by modeling based on wave propagation.

[0037] In some embodiments, when the second optical subassembly is connected to the hybrid optical fiber, the first optical subassembly is completely separated from the hybrid optical fiber. This separation can be achieved mechanically in various ways. Due to the separation of the first optical subassembly, which is much larger than the second, only the smaller second optical subassembly remains connected to the hybrid optical fiber and thus to the sample when examining a moving specimen. This facilitates easier examination of the specimen, for example, by attaching the second optical subassembly to the specimen.

[0038] In some embodiments, after an examination of the sample, the hybrid optical fiber is separated into a first part, which is inserted into the sample, and a second part. The first part of the hybrid optical fiber thus remains in the sample, but due to its small dimensions and low weight, it has little or no disruptive effect on the sample. At a later point, the first part and the second part are then reconnected for further examination of the sample. This eliminates the need to reinsert the hybrid optical fiber into the sample and ensures that the exact same area of ​​the sample is examined as in the first examination.

[0039] It is understood that a preferred embodiment can also be achieved from a combination of dependent claims with the respective independent claim.

[0040] For further clarification, the invention is described using embodiments illustrated in the figures. These embodiments are to be understood as examples only and not as limitations. Short description of the characters

[0041] It shows: Fig. 1 a perspective view of an embodiment of a hybrid optical fiber; Fig. 2 a cross-section through another embodiment of a hybrid optical fiber; Fig. 3 a cross-section through a further embodiment of a hybrid optical fiber; Fig. 4 a cross-section through a further embodiment of a hybrid optical fiber; Fig. 5 a longitudinal section through a joined first part and second part of a hybrid optical fiber; Fig. 6a a schematic view of an embodiment of an endoscopic system; Fig. 6b another schematic view of the embodiment of the endoscopic system Fig. 6a; and Fig. 7 a schematic view of another embodiment of an endoscopic system. Detailed description of embodiments

[0042] In the figures, identical reference symbols denote either identical elements or elements with equivalent functions. Elements that have already been described are not necessarily described again in subsequent figures.

[0043] Fig. Figure 1 shows a perspective view of an 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. The first refractive index n1 of the fiber cores 2 is greater than the second refractive index n2 of the first cladding 3, so that light traveling in the fiber cores 2 can undergo total internal reflection at the interface between the fiber core 2 and the first cladding 3. With a suitable angle of incidence of the light or a suitable numerical aperture of an optical arrangement connected to the hybrid optical fiber 1, the fiber cores 2 can therefore be treated as individual optical fibers.

[0044] A second cladding 4 is arranged around the first cladding 3. The second refractive index n2 of the first cladding 3 is greater than the third refractive index n3 of the second cladding 4, so that light traveling in the first cladding 3 can undergo total internal reflection at the interface between the first cladding 3 and the second cladding 4. Therefore, with a suitable angle of incidence of the light or a suitable numerical aperture of an optical arrangement connected to the hybrid optical fiber 1, the fiber cores 2 together with the first cladding 3 can function as a multimode optical fiber, with the light undergoing total internal reflection at the interface between the first cladding 3 and the second cladding 4.

[0045] 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 possible: firstly, the fiber cores 2 together with the first cladding 3 can function as a multimode optical fiber, enabling particularly high resolution. However, since the propagation of the many light modes in the multimode optical fiber is sensitive to deformations and bends of the optical fiber, this operating mode is limited to predominantly stationary samples. In the second operating mode, the individual fiber cores 2 function as optical fibers, with only one or a few light modes being excited at a time. In this operating mode, the resolution is limited to the distance between the individual fiber cores 2, but investigations of moving samples can also be carried out.

[0046] As an example, consider the investigation of neurons and their connections in the brain of an animal or human. First, the hybrid optical fiber 1 is inserted into the brain of the sedated animal or human. While the animal or human is sedated, high-resolution images are then acquired using the hybrid optical fiber 1 as a multimode fiber. These images show, for example, individual neurons and the connections between them. In the next stage of the investigation, the animal or human is brought to a waking state. In this waking state, images are then acquired using the individual fiber cores 2 as optical fibers. While individual neurons can be observed in this state, the connections between them are no longer visible.Since the same hybrid optical fiber 1 is used for both recordings and its position is not changed between the recordings, it is possible to assign the neurons observed by means of the individual fiber cores 2 to the neurons from the high-resolution image.

[0047] Fig. Figure 2 shows a cross-section through another embodiment of a hybrid optical fiber 1. In this embodiment, a plurality 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.

[0048] Fig. Figure 3 shows a cross-section through a further embodiment of a hybrid optical fiber 1. In this embodiment, the fiber cores 2 are arranged in a hexagonal dot pattern. This allows the maximum number of fiber cores 2 to be arranged within the first cladding 3 for a given distance between adjacent fiber cores 2. Furthermore, the arrangement of the fiber cores 2 in the hexagonal dot pattern results in particularly good stability of the hybrid optical fiber 1.

[0049] Fig. Figure 4 shows a cross-section through a further embodiment of a hybrid optical fiber 1. In this embodiment, a protective coating 5 is arranged around the second cladding 4. This protective coating 5 protects the hybrid optical fiber 1 from external influences, for example, chemical or physical influences.

[0050] Fig. Figure 5 shows a section of a longitudinal section through another embodiment of a hybrid optical fiber 1. This hybrid optical fiber 1 consists of a first part 1.1 and a second part 1.2. To connect the first part 1.1 with the second part 1.2, ceramic end sleeves 6 are applied to the end of the first part 1.1 facing the second part 1.2 and to the end of the second part 1.2 facing the first part 1.1. The inner diameter of the ceramic end sleeves 6 corresponds exactly to the outer diameter of the second sheath 4. The first part 1.1 is connected to the second part 1.2 via a connecting sleeve 7 into which the two ceramic end sleeves are inserted. Such a connection makes it possible to leave the first part 1.1 of the hybrid optical fiber 1 in a sample while the second part 1.2 is separated from the sample together with the rest of the endoscopic system. Part 1.Part 1 does not affect the sample or only very slightly. For further testing, the first part 1.1 and the second part 1.2 are then rejoined.

[0051] Fig. Figure 6a shows a schematic view of an embodiment of an endoscopic system 8. A hybrid optical fiber 1 is inserted into a sample 9 in order to examine objects 10 in front of the hybrid optical fiber 1.

[0052] The endoscopic system 8 has an optical arrangement 21 comprising a first optical sub-arrangement 11 and a second optical sub-arrangement 12. Either the first optical sub-arrangement 11 or the second optical sub-arrangement 12 can be coupled to the hybrid optical fiber 1 via a mechanical system, which is not shown in detail here. Fig. In 6a, the first optical sub-assembly 11 is coupled to the hybrid optical fiber 1. Alternatively, the switch between the first optical sub-assembly 11 and the second optical sub-assembly 12 can be effected via optical elements, for example, an adjustable mirror. Furthermore, it is also possible that at any given time only the first optical sub-assembly 11 or the second optical sub-assembly 12 is connected to the hybrid optical fiber 1, while the other optical sub-assembly 12 or 11, respectively, is disconnected from the hybrid optical fiber 1.

[0053] The first optical sub-assembly 11 comprises a coherent light source 13, including a laser 14 and a modifier 15 that modifies the light wavefront emitted by the laser 14. The coherent light source 13 is optically connected to the hybrid optical fiber 1 via a first beam splitter 16, which is, for example, a dichroic beam splitter. The fiber cores 2, together with the first cladding 3, function as a multimode optical fiber. During an examination of the sample 9, the coherent light from the laser 14 is modified by the modifier 15 such that only one point of the object 10 is illuminated at a time. The necessary knowledge of the light transmission properties of the hybrid optical fiber 1 is measured and / or calculated prior to the examination.The light response emitted from the illuminated point of object 10, for example by reflection, fluorescence, Raman scattering, stimulated Raman scattering, coherent anti-Stokes Raman scattering, autofluorescence and / or frequency doubling, is guided from sample 9 by the hybrid optical fiber 1 and passes through the first beam splitter 16 to a further photodetector 17 of the first optical sub-assembly 11, where it is detected. By successively illuminating a large number of points of object 10, a high-resolution image can be created.

[0054] Fig. Figure 6b shows the endoscopic system 8 again. Fig. 6a, wherein the second optical sub-assembly 12 was coupled to the hybrid optical fiber 1 by means of the mechanical system. The second optical sub-assembly 12 comprises a further light source 18, which introduces light into the fiber cores 2 and / or the first cladding 3. The further light source 18 comprises, for example, an array of LEDs, with one LED assigned to each fiber core 2. The light from the additional 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 reaches a photodetector 20 of the second optical sub-arrangement 12 via the fiber cores 2 of the hybrid optical fiber 1 and the second beam splitter 19.The photodetector 20 comprises a plurality of pixels for detecting the light emerging from 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 distance between the fiber cores 2, but investigations on a moving sample 9 can also be carried out with this system.

[0055] Fig.Figure 7 shows a schematic view of another embodiment of an endoscopic system 8. The optical arrangement 21 of this endoscopic system 8 comprises only a coherent light source 13 and a photodetector 20. The coherent light source 13 introduces the light into the hybrid optical fiber 1 in both a first and a second operating mode of the endoscopic system 8. In the first operating mode, the light modes in the hybrid optical fiber 1, which functions as a multimode optical fiber, are excited such that individual object points in the sample 9 are illuminated successively. In the second operating mode, objects in the sample 9 are illuminated by means of the coherent light source 13. Likewise, the photodetector 20 detects the light response of the object points or objects in both the first and the second operating mode.In the first operating mode, the light response is summed over all pixels of the photodetector 20, while in the second operating mode, the light response for each fiber core 2 is detected separately.

Claims

[1] Endoscopic system for examining a sample (9) comprising a hybrid optical fiber (1) having a plurality of fiber cores (2), a first cladding (3) enclosing the plurality of fiber cores (2), and a second cladding (4) surrounding the first cladding (3), wherein the fiber cores (2) have a first refractive index n1, the first cladding (3) has a second refractive index n2, and the second cladding (4) has a third refractive index n3, and wherein n1 is greater than n2 and n2 is greater than n3, and an optical arrangement (21) comprising a coherent light source (13) which is designed to introduce light into a proximal end of the hybrid optical fiber (1), also into the first cladding (3), so 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, the light being totally reflected at an interface between the first cladding (3) and the second cladding (4), and a photodetector (20) comprising a plurality of pixels for detecting the light emerging from the individual fiber cores (2). [2] The endoscopic system of claim 1, further configured to a first operating mode in which light modes in the hybrid optical fiber (1) acting as a multimode optical fiber are excited by means of the coherent light source (13) in such a way that individual object points in the sample (9) are illuminated one after the other and the light response emitted by the object points, in particular as a sum over all pixels, is detected by the photodetector (20), and a second operating mode in which objects (10) in the sample (9) are illuminated by means of the coherent light source (13) and the light response emitted by the objects (10) is detected separately for each fiber core (2) by the photodetector (20), to be operated. [3] Endoscopic system according to claim 1 or 2, wherein the optical arrangement (21) comprises a further light source (18) for introducing light into the fiber cores (2) and / or the first cladding (3), wherein the further light source (18) preferably has a plurality of partial light sources, in particular LEDs, and the partial light sources are preferably arranged in an array and assigned to the fiber cores (2) of the hybrid optical fiber (1), wherein preferably in the second operating mode the objects (10) in the sample (9) are illuminated by means of the further light source (18). [4] Endoscopic system according to claim 3, wherein the optical arrangement (21) comprises a further photodetector (17) for detecting the light emerging from the fiber cores (2) and the first cladding (3), and the coherent light source (13) and the further photodetector (17) are assigned to a first optical sub-arrangement (11), and the further light source (18) and the photodetector (20) are assigned to a second optical sub-arrangement (12), and preferably the first operating mode is carried out by means of the first optical sub-arrangement (11) and the second operating mode is carried out by means of the second optical sub-arrangement (12). [5] The endoscopic system according to claim 4, further comprising a switching device for switching between the first optical sub-array (11) and the second optical sub-array (12). [6] Endoscopic system according to claim 4 or 5, wherein the first optical sub-array (11) and / or the second optical sub-array (12) can be used separately with the hybrid optical fiber (1). [7] Endoscopic system according to one of claims 1 to 6, wherein the hybrid optical fiber (1) consists of at least a first part (1.1) and a second part (1.2), wherein the first part (1.1) and the second part (1.2) are separably connected to one another via a connecting element (6, 7). [8] Endoscopic system according to one of claims 2 to 7, wherein the optical arrangement (21) in the first operating mode and / or the first optical sub-arrangement (11) has a first numerical aperture NA1 and the optical arrangement (21) in the second operating mode and / or the second optical sub-arrangement (12) has a second numerical aperture NA2 and NA1 is greater than NA2. [9] Endoscopic system according to one of claims 1 to 8, wherein the fiber cores (2) are arranged in a cross section of the hybrid optical fiber (1) in an orthogonal point group or in a hexagonal point group. [10] Endoscopic system according to one of claims 1 to 9, wherein a diameter of the fiber cores (2) is between 5 µm and 20 µm, in particular between 8 µm and 13 µm. [11] Endoscopic system according to one of claims 1 to 10, wherein a distance between two adjacent fiber cores (2) is between 10 µm and 50 µm, in particular between 20 µm and 30 µm. [12] Endoscopic system according to one of claims 1 to 11, wherein the number of fiber cores (2) in the hybrid optical fiber (1) is between 30 and 100, in particular between 50 and 70. [13] Endoscopic system according to one of claims 1 to 12, wherein the hybrid optical fiber (1) further comprises a protective coating (5) and / or outer sheath enclosing the second cladding (4). [14] Method for examining a sample (9) by means of an endoscopic system (8) according to one of claims 1 to 13, wherein the hybrid optical fiber (1) of the endoscopic system (8) is introduced into the sample (9), the sample (9) is initially immobile, the optical arrangement (21) and / or the first optical sub-arrangement (11) of the endoscopic system (8) is connected to the hybrid optical fiber (1), light is introduced into the fiber cores (2) and the first cladding (3) of the hybrid optical fiber (1) by means of the coherent light source (13), so that the hybrid optical fiber (1) functions as a multimode optical fiber, a plurality of object points in the sample (9) are illuminated one after the other by the hybrid optical fiber (1), and the light response emitted by the object points is detected by the hybrid optical fiber (1) and by means of the photodetector (20) or another photodetector (17), the sample (9) then moves, the optical arrangement (21) and / or the second optical sub-arrangement (12) of the endoscopic system (8) is connected to the hybrid optical fiber (1), light is introduced into the fiber cores (2) and / or the first cladding (3) by means of the coherent light source (13) or the further light source (18), objects (10) at distal ends of the fiber cores (2) are illuminated and the light response emitted by the objects (10) is guided through the fiber cores (2) to the photodetector (20) and detected by the pixels of the photodetector (20). [15] A method for examining a sample (9) according to claim 14, wherein light transmission properties of the hybrid optical fiber (1) in use as a multimode optical fiber are measured and / or calculated before the examination of the sample (9). [16] A method for examining a sample (9) according to claim 14 or 15, wherein, when the second optical sub-assembly (12) is connected to the hybrid optical fiber (1), the first optical sub-assembly (11) is completely separated from the hybrid optical fiber (1). [17] Method for examining a sample (9) according to one of claims 14 to 16, wherein after an examination of the sample (9) the hybrid optical fiber (1) is separated into a first part (1.1) which is introduced into the sample (9) and a second part (1.2) and the first part (1.1) and the second part (1.2) are reconnected to one another at a later time for a further examination of the sample (9).

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