INTERFEROMETER FOR CARRYING OUT AN OPTICAL COHERENCE TOMOGRAPHY

Abstract

The invention relates to an interferometer for carrying out an optical coherence tomography. The interferometer has at least one first part (13) and a second part (14) which are arranged or can be arranged in a spatially separated manner, wherein the two parts (13, 14) are optically connected together by at least one optical fiber (8). The aim of the invention is to provide an interferometer comprising parts which are optically connected by at least one fiber and which can be moved relative to each other, said parts and fiber being as insusceptible as possible to polarization changes induced by movement and temperature changes. The invention is characterized in that the optical fiber (8) is designed as a polarizing fiber which prefers the propagation of a first light wave with a set first polarization state or polarization mode and impedes the propagation of second light waves with different polarization states or polarization modes than those of the first light wave.

Claims

1. An interferometer for carrying out optical coherence tomography, wherein the interferometer has at least one first part and one second part, which are arranged or arrangeable spatially separate from one another, and wherein the two parts are optically connected to one another by at least one light-conducting fiber, wherein the connecting light-conducting fiber is designed as a polarizing fiber, which favors the propagation of a specific polarization state or polarization mode and obstructs or suppresses the propagation of other polarization states or polarization modes.

2. The interferometer as claimed in claim 1, wherein the polarizing fiber is designed having a bowtie structure generating birefringence.

3. The interferometer as claimed in claim 1, wherein the polarizing fiber is designed having a tiger structure generating birefringence.

4. The interferometer as claimed in claim 1, wherein the polarizing fiber is designed having an elliptical structure generating birefringence.

5. The interferometer as claimed in claim 1, wherein the polarizing fiber is designed having a Panda structure generating birefringence.

6. The interferometer as claimed in claim 1 wherein a first beam splitter is provided, using which the light of a light source can be split into light of a reference arm and light of a sample arm.

7. The interferometer as claimed in claim 6, wherein at least one circulator is provided, by means of which the light of the sample arm can be guided in the direction of a sample and/or by means of which the light of the reference arm can be guided to a reference point and/or a second beam splitter.

8. The interferometer as claimed in claim 6, wherein two polarization setting units are provided, using each of which the light of the reference arm and the light of the sample arm is convertible or transferable into identically polarized light waves.

9. The interferometer as claimed in claim 8, wherein a second beam splitter is provided, in order to bring the light waves of the sample arm and the reference arm into interference.

10. The interferometer as claimed in claim 1, wherein a polarization setting unit is incorporated before the polarizing fiber and in the course of the single-mode fiber.

11. The interferometer as claimed in claim 1, wherein a polarization setting unit is incorporated before the polarizing fiber and in the course of the single-mode fiber, in particular the single-mode fiber of the sample arm.

12. The interferometer as claimed in claim 10, wherein the single-mode fiber opens at one end into the special polarizing fiber and at its other end into a first beam splitter.

13. The interferometer as claimed in claim 10, wherein the single-mode fiber opens at one end into the special polarizing fiber and at its other end into a circulator.

14. The interferometer as claimed in claim 1, wherein the fiber is accommodated in a flexible tube cable, which extends between the two parts.

Description

[0028] In the drawing

[0029] FIG. 1 shows a schematic representation of an interferometer having a reference arm and a sample arm, wherein the light of the sample arm is guided by a circulator to the special fiber,

[0030] FIG. 2 shows a schematic representation of an interferometer having a reference arm and a sample arm, wherein the light of the sample arm is guided by a beam splitter/fiber coupler to the special fiber,

[0031] FIG. 3 shows a schematic representation of an interferometer having a reference arm and a sample arm, wherein the light of the sample arm is guided by a circulator to the special fiber and wherein the light of the reference arm is guided by a circulator to a reference mirror,

[0032] FIG. 4 shows a schematic representation of an interferometer having a reference arm and a sample arm, wherein the light of the sample arm is guided by a beam splitter/fiber coupler to the special fiber, wherein the light of the reference arm is guided to a reference mirror by the same beam splitter/fiber coupler, and

[0033] FIG. 5 shows a schematic representation of an interferometer having a reference arm and a sample arm, wherein the light of the sample arm is guided by a beam splitter/fiber coupler to the special fiber onto a sample and is guided from the sample directly to a second beam splitter.

[0034] Interferometers for carrying out optical coherence tomography are schematically shown in the figures. When reference is made to single-mode fibers, this means typical single-mode fibers which are called single-mode fibers in the English language and are abbreviated by SMF.

[0035] Typical light-conducting single-mode fibers (abbreviated by SMF) only conduct components of light beams oriented transversely to the propagation direction.

[0036] Various exemplary embodiments of the interferometer configuration having a special fiber 8 in the sample arm 3 are described hereinafter. The principle using the special fiber 8 is explained on the basis of FIG. 1. However, the principle can also be transferred to the other exemplary embodiments according to FIGS. 2 to 5.

[0037] FIG. 1 schematically shows, restricted to the essential optical arrangement, an interferometer for carrying out optical coherence tomography, wherein the interferometer has at least one first part 13 and one second part 14, which are arranged spatially separated from one another.

[0038] The two parts 13, 14 are optically connected to one another by at least one light-conducting fiber 8. The light-conducting fiber 8 is designed as a special polarizing fiber 8, which favors the propagation of a first light wave having a set first polarization state or polarization mode and obstructs the propagation of second light waves having different polarization states or polarization modes in comparison to the first light wave. The special fiber 8 is formed uniformly and is not composed of two fibers.

[0039] A first beam splitter 1 is provided, using which the light of a light source 11 can be split into light of a reference arm 2 and light of a sample arm 3. At least one circulator 4 is provided, by means of which the light of the sample arm 3 can be guided in the direction of a sample 5.

[0040] The sample 5 itself is not part of the interferometer, but rather is a structure to be examined, for example the tissue of an eye, in particular a human eye.

[0041] Two polarization setting units 7, 10 are provided, using each of which the light of the reference arm 2 and the light of the sample arm 3 is convertible or transferable into identically polarized light waves. A second beam splitter 9 is provided, to bring the light waves of the sample arm 3 and the reference arm 2 into interference in order to obtain a signal at a detector 9.

[0042] A first polarization setting unit 7 is arranged between the special fiber 8 and a single-mode fiber 6. The single-mode fiber 6 opens at one end into the first polarization setting unit 7 and at its other end into a circulator 4.

[0043] The fiber 8 is accommodated in a flexible tube cable 15, which extends between the two parts 13, 14.

[0044] FIG. 1 specifically shows that the light of the light source 11 is divided via a first beam splitter 1 into a reference arm 2 and a sample arm 3. The light of the sample arm 3 is conducted with the aid of a circulator 4 in the direction of the sample 5. The light of the sample arm 3 initially passes through a part of the single-mode fiber 6 having the first polarization setting unit 7, in order to set the polarization of the light linearly on the light-guiding axis of the special fiber 8. Only linearly polarized light waves, which oscillate in a specific polarization plane, are thus passed on.

[0045] The special fiber 8 now conducts a linearly polarized light wave onto the sample 5 and can be subjected to movements and temperature changes due to its special properties.

[0046] This is schematically illustrated in that a first part 13 of the interferometer and a second part 14 of the interferometer are movable relative to one another, wherein the two parts 13, 14 are optically connected to one another, thus in a light-conducting manner, by the special fiber 8. In addition to an optical connection, still further connections can be provided, for example, data or electricity lines as connections.

[0047] A light wave takes the same path back from the examined sample 5 to the circulator 4 and is conducted thereby onto a second beam splitter 9, which unifies a light wave of the reference arm 2 and the sample arm 3 with one another and brings them into interference.

[0048] Therefore, a second polarization setting unit 10 is placed in the reference arm 2, using which the polarization of the light of the reference arm 2 is set so that a light wave of the reference arm 2 and a light wave of the sample arm 3 interfere with one another and can generate a signal at a detector 12. The two light waves interfering with one another are identically polarized, namely oscillate in the same polarization plane. The detector 12 is a so-called balanced detector.

[0049] FIG. 2 shows on the basis of a further embodiment that the light of the light source 11 is divided via a first beam splitter 1 into a reference arm 2 and a sample arm 3. The light of the sample arm 3 is conducted, without a circulator 4 according to FIG. 1, in the direction of the sample 5. The light of the sample arm 3 initially passes through a part of the single-mode fiber 6 having the first polarization setting unit 7, in order to set the polarization of the light linearly on the light-guiding axis of the special fiber 8.

[0050] The special fiber 8, which adjoins the first polarization setting unit 7, now conducts a specially linearly polarized light wave through the special fiber 8 onto the sample 5 and can be subjected to movements and temperature changes due to its special properties.

[0051] The light wave takes the same path back from the sample 5 to the first beam splitter 1 and is conducted thereby via a bypass line 3a, which is not identical to the special fiber 8, onto a second beam splitter 9, which unifies the light waves of the reference arm 2 and the sample arm 3 with one another and brings them into interference.

[0052] Therefore, a second polarization setting unit 10 is placed in the reference arm 2, using which the polarization of the light of the reference arm 2 is set so that a linearly polarized light wave of the reference arm 2 and a light wave of the sample arm 3 interfere with one another and can generate a signal at a detector 12. The two light waves interfering with one another are identically polarized, namely oscillate in the same polarization plane. The detector 12 is a so-called balanced detector.

[0053] FIG. 3 shows that the light of the light source 11 is divided via a first beam splitter 1 into a reference arm 2 and a sample arm 3. The light of the sample arm 3 is conducted with the aid of a circulator 4 in the direction of the sample 5. The light of the sample arm 3 initially passes through a part of the single-mode fiber 6 having the first polarization setting unit 7, in order to set the polarization of the light linearly on the light-guiding axis of the special fiber 8.

[0054] The special fiber 8, which adjoins the first polarization setting unit 7, now conducts a linearly polarized light wave onto the sample 5 and can be subjected to movements and temperature changes due to its special properties.

[0055] The linearly polarized light wave takes the same path back from the sample 5 to the circulator 4 and is conducted thereby onto a second beam splitter 9, which unifies the identically linearly polarized light waves of the reference arm 2 and the sample arm 3 with one another.

[0056] A second polarization setting unit 10 is placed in the reference arm 2 for this purpose, using which the polarization of a light wave of the reference arm 2 is set so that the light waves of the reference arm 2 and the sample arm 3 interfere with one another and can generate a signal at a detector 12. The two light waves interfering with one another are identically polarized, namely oscillate in the same polarization plane. The detector 12 is a so-called balanced detector.

[0057] The light of the reference arm 2 is conducted by a second circulator 4b in the direction of the second polarization setting unit 10, from which a linearly polarized light wave reaches a reference point 2b.

[0058] From the reference point 2b, the light wave of the reference arm 2 runs back through the second polarization setting unit 10 and then through the second circulator 4b to the second beam splitter 9, where it can interfere with an identically polarized light wave of the sample arm 3 and generate a signal at the detector 12.

[0059] FIG. 4 shows that the light of the light source 11 is divided via a first beam splitter 1 into a reference arm 2 and a sample arm 3. The light of the sample arm 3 is conducted without a circulator 4 in the direction of the sample 5. The light of the sample arm 3 initially passes through a part 6 of the single-mode fiber having the first polarization setting unit 7, in order to set the polarization of the light linearly on the light-guiding axis of the special fiber 8.

[0060] The special fiber 8, which adjoins the first polarization setting unit 7, now conducts a specially linearly polarized light wave onto the sample 5 and can be subjected to movements and temperature changes due to its special properties.

[0061] The specially linearly polarized light wave takes the same path back from the sample 5 to the first beam splitter 1 and is conducted thereby onto a second beam splitter 9, which unifies the identically polarized light waves of the reference arm 2 and the sample arm 3 with one another.

[0062] A second polarization setting unit 10 is placed in the reference arm 2 for this purpose, using which the polarization of the light of the reference arm 2 is set so that the light waves of the reference arm 2 and the sample arm 3 interfere with one another and can generate a signal at a detector 12. The two light waves interfering with one another are identically polarized, namely oscillate in the same polarization plane. The detector 12 is a so-called balanced detector.

[0063] The light of the reference arm 2 is conducted for this purpose by the first beam splitter 1 in the direction of a second polarization setting unit 10, from which a linearly polarized light wave reaches a reference point 2b. From the reference point 2b, this light wave of the reference arm 2 runs back through the second polarization setting unit 10 and then through the first beam splitter 1 to the second beam splitter 9, where it can interfere with the linearly polarized light wave of the sample arm 3 and generate a signal at the detector 12. The detector 12 is arranged behind the second beam splitter 9.

[0064] FIG. 5 shows that the light of the light source 11 is divided via a first beam splitter 1 into a reference arm 2 and a sample arm 3. The light of the sample arm 3 is conducted without a circulator 4 in the direction of the sample 5.

[0065] The light of the sample arm 3 initially passes through a part of the single-mode fiber 6 having the first polarization setting unit 7, in order to set the polarization of the light linearly on the light-guiding axis of the special fiber 8.

[0066] The special fiber 8, which adjoins the first polarization setting unit 7, now conducts a specially linearly polarized light wave onto the sample 5 and can be subjected to movements and temperature changes due to its special properties.

[0067] The linearly specially polarized light wave takes a path from the sample 5 via a further line 3b, which is not identical to the special line 8, up to a second beam splitter 9, which unifies the linearly identically polarized light waves of the reference arm 2 and the sample arm 3 with one another.

[0068] A second polarization setting unit 10 is placed in the reference arm 2 for this purpose, using which the polarization of the light of the reference arm 2 is set so that the light waves of the reference arm 2 and the sample arm 3 interfere with one another and can generate a signal at a detector 12. The two light waves interfering with one another are identically polarized, namely oscillate in the same polarization plane. The detector 12 is a so-called balanced detector.

[0069] The light of the reference arm 2 is conducted for this purpose by the first beam splitter 1 in the direction of the second polarization setting unit 10. From the second polarization setting unit 10, a linearly specially polarized light wave of the reference arm 2 reaches the second beam splitter 9, where it can interfere with the light wave of the sample arm 3, which is identically linearly polarized thereto and is fed via the further line 3b, and can generate a signal at the detector 12. The detector 12 is arranged behind the second beam splitter 9.

LIST OF REFERENCE SIGNS

[0070] 1 first beam splitter [0071] 2 reference arm [0072] 2b reference mirror [0073] 3 sample arm [0074] 3a bypass line of 3 [0075] 3b further line of 3 [0076] 4 circulator [0077] 4b second circulator [0078] 5 sample [0079] 6 single-mode fiber [0080] 7 first polarization setting unit [0081] 8 special fiber [0082] 9 second beam splitter [0083] 10 second polarization setting unit [0084] 11 light source [0085] 12 detector [0086] 13 first part of an OCT interferometer [0087] 14 second part of an OCT interferometer [0088] 15 tube cable