ASSEMBLY FOR CARRYING OUT AN OPTICAL COHERENCE TOMOGRAPHY

Abstract

The invention relates to an assembly comprising a interferometer for carrying out an optical coherence tomography, wherein the interferometer is divided into two spatially spaced-apart interferometer parts (1, 2), wherein the two interferometer parts (1, 2) can be moved related to one another and are optically connected to one another via flexible light guides (3, 4, 5), which bridge the spatial distance, wherein according to the invention, an assembly having an interferometer is provided, which is as unsusceptible as possible to the effects brought about by bending a tube cable packet and allows for an optimum signal-to-noise ratio or an optimum image quality of an OCT image, characterised in that at least one first flexible light guide (3) is designed as a polarisation-maintaining light guide consisting of two connected polarisation-maintaining light-guiding fibres (3a, 3b).

Claims

1. An assembly comprising an interferometer for carrying out an optical coherence tomography, wherein the interferometer is divided into two interferometer parts (1, 2) at a spatial distance from each other, wherein the two interferometer parts (1, 2) are movable relative to each other and are optically connected to each other by flexible light guides (3, 4, 5) which bridge the spatial distance, characterized in that at least a first flexible light guide (3) is designed as a polarization-maintaining light guide which consists of two polarization-maintaining light-guiding fibers (3a, 3b) connected to each other.

2. The assembly as claimed in claim 1, characterized in that the first light guide (3) consists of two polarization-maintaining light-guiding fibers (3a, 3b) connected to each other, the respective crystal axes of which are arranged tilted by 90° relative to each other.

3. The assembly as claimed in claim 1, characterized in that the two polarization-maintaining light-guiding fibers (3a, 3b) are connected to each other by splicing and/or are of equal length.

4. The assembly as claimed in claim 1, characterized in that at least a second light guide (4) and/or third light guide (5) is or are designed as a single-mode fiber or as single-mode fibers.

5. The assembly as claimed in claim 1, characterized in that the light guides (3, 4, 5) are accommodated in a flexible hose cable (6) which extends between the two interferometer parts (1, 2).

6. The assembly as claimed in claim 1, characterized in that the first interferometer part (1) is assigned to a power supply unit (7).

7. The assembly as claimed in claim 1, characterized in that the second interferometer part (2) is assigned to a camera head (8) that is movable relative to the first interferometer part (1).

8. The assembly as claimed in claim 1, characterized in that the first interferometer part (1) is accommodated in a first housing (9) comprising electronic components and a power supply unit (7).

9. The assembly as claimed in claim 1, characterized in that the second interferometer part (2) is accommodated in a second housing (10) comprising the camera head (8).

10. The assembly as claimed in claim 7, characterized in that the sample arm (11) and the reference arm (12) are arranged in the second housing (10) or in the camera head (8).

Description

[0049] In the drawing:

[0050] FIG. 1 shows a schematic representation of an assembly with two interferometer parts spatially separated from each other,

[0051] FIG. 2 shows the assembly according to FIG. 1, with the interferometer parts and the hose cable package being depicted separately, and

[0052] FIG. 3 shows a schematic representation of the splicing of two polarization-maintaining light-guiding fibers of equal length, the crystal axes of which are tilted by 90° relative to each other at the splice point.

[0053] FIG. 1 shows an assembly comprising an interferometer for carrying out an optical coherence tomography, the interferometer being divided into two interferometer parts 1, 2 at a spatial distance from each other, the two interferometer parts 1, 2 being movable relative to each other and being optically connected to each other by flexible light guides 3, 4, 5 which bridge the spatial distance between the interferometer parts 1, 2.

[0054] At least a first flexible light guide 3 is designed as a polarization-maintaining light guide which consists of two polarization-maintaining light-guiding fibers 3a, 3b, so-called PMFs, which are connected to each other and have the same length.

[0055] The first light guide 3 consists of two polarization-maintaining light-guiding fibers 3a, 3b which are connected to each other and have the same length and the respective crystal axes 21, 22 of which are arranged tilted by 90° relative to each other at a splice point 20. This is shown schematically in FIG. 3.

[0056] The two polarization-maintaining light-guiding fibers 3a, 3b of equal length, which form the first light guide 3, are connected to each other by splicing at the splice point 20. The splice point 20 is in the middle of the light guide 3, which is formed by the two polarization-maintaining light-guiding fibers 3a, 3b arranged one behind the other and of equal length.

[0057] Furthermore, a second light guide 4 and a third light guide 5 are designed as single-mode fibers. All light guides 3, 4, 5 are accommodated in a flexible hose cable 6 which extends between the two interferometer parts 1, 2, and together with the hose cable 6 form a flexibly deformable hose cable package. The splice point 20 is positioned in the middle or approximately in the middle of the hose cable 6.

[0058] The first interferometer part 1 is assigned to a power supply unit 7. The second interferometer part 2 is assigned to a movable camera head 8.

[0059] The first interferometer part 1 is accommodated in a first housing 9 which comprises electronic components and the power supply unit 7. The second interferometer part 2 is accommodated in a second housing 10 which comprises or forms the camera head 8. The sample arm 11 and the reference arm 12 are completely and only arranged in the second housing 10 or in the camera head 8.

[0060] FIG. 1 shows specifically that the assembly is divided into two interferometer parts 1, 2, which are essentially assigned to the power supply unit 7 and the camera head 8, respectively. The first interferometer part 1 contains all the essential electronic components which comprise the light source 13 or OCT light source, trigger circuits 14 and clocking circuits 15, DAQ electronics and detectors 16, 17. The first interferometer part 1 therefore contains all or almost all electronic components that are able to be reasonably assigned to the first interferometer part 1.

[0061] Specifically, the first interferometer part 1 contains the OCT light source, namely a laser light source known to a person skilled in the art as VCSEL swept source (“Vertical Cavity Surface Emitting Laser Swept Source”), which emits light with a wavelength of 1050 nm; the trigger circuit 14, which is designed as a scan trigger circuit; the clocking circuit 15, namely a so-called K-clock circuit; DAQ electronics; and a balanced detector 16 of the interferometer.

[0062] The second interferometer part 2 is integrated into the camera head 8 and contains essentially only passive fiber components of the entire interferometer.

[0063] Three light guides 3, 4, 5 run through the flexible hose cable 6 and together with it form the flexibly deformable hose cable package to optically connect the two interferometer parts 1, 2 to each other. The first light guide 3 guides light from the light source 13, namely the OCT light source, to the camera head 8 and is made of two polarization-maintaining light-guiding fibers 3a, 3b, namely PMFs, of equal length.

[0064] PMF means “Polarization-Maintaining Fiber” and is abbreviated PMF. The first light guide 3 is created by splicing two PMFs 3a, 3b of the same length.

[0065] The second light guide 4 and the third light guide 5 guide light from the imaging interferometer part 2 in the camera head 8 to the balanced detector 16 in the first interferometer part 1 or housing 1, in which the power supply unit 7 is arranged. The balanced detector 16 is insensitive to the polarization state of the received light, and PIN diodes detect only its intensity.

[0066] Conventional single-mode fibers, which are abbreviated SMFs, are therefore used to optically connect the balanced detector 16 in the first interferometer part 1 to the two outputs of the 50/50 coupler 18 of the second interferometer part 2 in the camera head 8, although the SMFs bring about unknown changes of polarization state when they are handled or bent.

[0067] It is therefore possible to handle the second and third light guides 4, 5 at will without fear of an effect on the quality of an optical coherence tomography image. The use of these two light guides 4, 5 in combination with the first light guide 3, which maintains polarization stability, is therefore particularly advantageous.

[0068] Since the three light guides 3, 4, 5 are either insensitive to changes in polarization state, or the detection of their signals is insensitive to changes in polarization, the hose cable package can contain all three light guides 3, 4, 5 and can be moved and handled at will without fear of an effect on the signal quality of the optical coherence tomography.

[0069] The interferometer configuration described here requires a one-time adjustment and is stable in further operation. It does not require periodic or real-time polarization optimization. In addition, the space used in the camera head 8 is minimized. This optimizes the configuration of both the power supply unit 7 and the camera head 8.

[0070] FIG. 2 shows schematically the two interferometer parts 1, 2 and the hose cable package 6 as well as the usual electronic, optical or optoelectronic components of an interferometer familiar to a person skilled in the art.

[0071] FIG. 3 schematically shows by means of the splice point 20 that, when splicing the two polarization-maintaining light-guiding fibers 3a, 3b of equal length, it is necessary to match the orientations of their crystal axes 21, 22 at the splice point 20. A deliberate offset of 90°, as shown in FIG. 3, is created at the splice point 20 to achieve the birefringence compensation effect described here.

[0072] A PM fiber fusion splicer, not shown, typically has a device for suitably rotating and aligning relative to each other polarization-maintaining light-guiding fibers to be connected.

LIST OF REFERENCE SIGNS

[0073] 1 First interferometer part [0074] 2 Second interferometer part [0075] 3 First light guide [0076] 3a, 3b Polarization-maintaining light-guiding fiber [0077] 4 Second light guide [0078] 5 Third light guide [0079] 6 Flexible hose cable [0080] 7 Power supply unit [0081] 8 Camera head [0082] 9 First housing [0083] 10 Second housing [0084] 11 Sample arm [0085] 12 Reference arm [0086] 13 Light source [0087] 14 Trigger circuit [0088] 15 Clocking circuit [0089] 16 Balanced detector 16 [0090] 17 Further detector [0091] 18 50/50 coupler [0092] 19 Scanning unit [0093] 20 Splice point [0094] 21 First crystal axis [0095] 22 Second crystal axis