Multi-channel low coherence interferometer

• US 20070278389A1
• Filed: 06/02/2006
• Published: 12/06/2007
• Est. Priority Date: 06/02/2006
• Status: Active Grant

• Current Assignee: Cardiolumen, Inc.
• Original Assignee: Abbott Cardiovascular Systems Incorporated (Abbott Laboratories Incorporated)
• Inventors: Ajgaonkar, Mahesh, Alphonse, Gerard
• Granted Patent: US 7,488,930 B2
• Time in Patent Office: Days
• US Class Current: 250/221
• CPC Class Codes: G01B 2290/70 Using polarization in the interferometer
• CPC Class Codes: G01B 9/02028 Two or more reference or object arms in one interferometer
• CPC Class Codes: G01B 9/0205 of probe head
• CPC Class Codes: G01B 9/0209 Low-coherence interferometers

Abstract

A multi-channel low coherence interferometer having sensing and reference arms, at least one of which has variable delay. The sensing arm includes an optical switch for connecting to two or more probe arms. The distal ends of the probe arms collect source light backscattered from a sample. The backscattered light collected by the distal end of a probe arm is combined with reference light and a low coherence interferometric signal is produced by a sweep of a variable delay of the device or a sweep of a variable frequency laser light source. The interference signal produced by the interaction of reference and sensing light at a detector measures backscattered light, which may be used to characterize the sample. The low coherence interferometric signals can provide information about the morphology, physical nature, composition, and properties of the sample. The device may be used to discriminate between finished surfaces and corroded surfaces, healthy and diseased tissue, and can sample the material or tissue in two or more areas. Versions of the invention include devices that are interferometers and or autocorrelators.

Claims

1. A system for determining a characteristic of a sample, the system comprising:

a light source for providing a light;

a splitter receptive to said light from said light source to produce a sensing light portion and a reference light portion;

a sensing light path comprising,

a light path configured to communicate said sensing light portion from said splitter and said sensing light portion reflected from the sample,

a plurality of probe light paths configured to direct said sensing light portion at the sample and to receive said sensing light portion reflected from the sample,

an optical switch selectable to define communication between said light path and a selected at least one of said probe light paths; and

means for increasing and decreasing the effective light path length of said sensing light path;

a reflecting device;

a reference light path configured to communicate said reference light portion from said splitter, said reference light path further configured to direct said reference light portion at said reflecting device and to receive said reference light portion reflected from said reflecting device;

means for increasing and decreasing the effective light path length of said reference light path;

wherein said means for increasing and decreasing the effective light path length of said sensing light path and said means for increasing and decreasing the effective light path length of said reference light path are configured such that when one of said means is increasing the other of said means is decreasing;

wherein said means for increasing and decreasing the effective light path length of said sensing light path and said means for increasing and decreasing the effective light path length of said reference light path are increased and decreased to obtain an effective light path length difference between the effective light path lengths of said sensing light path and said reference light path within about a coherence length of said light;

a detector receptive to said sensing light portion reflected from the sample and said reference light portion reflected from said reflecting device, said detector generating a signal indicative of an interference of said sensing light portion reflected from the sample and said reference light portion reflected from said reflecting device; and

processing means configured to determine a characteristic of the sample from said signal indicative of said interference of said sensing light portion reflected from the sample and said reference light portion reflected from said reflecting device.

2. The system of claim 1 wherein said means for increasing and decreasing the effective light path length of said sensing light path and said means for increasing and decreasing the effective light path length of said reference light path each comprise a piezoelectric modulator.

3. The system of claim 1 wherein said splitter has an asymmetrical ratio such that said sensing light portion is greater than said reference light portion.

4. The system of claim 1 wherein said detector comprises at least one photodetector.

5. The system of claim 1 further comprising means for maintaining polarization of said light.

6. The system of claim 1 wherein said broadband light source comprises a superluminescent diode.

7. The system of claim 1 wherein said optical switch is digitally selectable.

8. The system of claim 1 wherein the sample comprises a biological sample.

9. The system of claim 1 wherein said probe light paths are configured as a catheter.

10. A system for determining a characteristic of a sample, the system comprising:

a light source for providing a light;

a splitter receptive to said light from said light source to produce a sensing light portion and a reference light portion;

a sensing light path comprising,

a light path configured to communicate said sensing light portion from said splitter and said sensing light portion reflected from said sample,

a plurality of probe light paths configured to direct said sensing light portion at the sample and to receive said sensing light portion reflected from the sample, and

a plurality of switches arranged in a multi-level configuration, said optical switches selectable to define communication between said light path and a selected at least one of said probe light paths;

a reflecting device;

a reference light path configured to communicate said reference light portion from said splitter, said reference light path further configured to direct said reference light portion at said reflecting device and to receive said reference light portion reflected from said reflecting device;

means for generating an interference condition between said sensing light portion reflected from the sample and said reference light portion reflected from said reflecting device;

a detector receptive to said sensing light portion reflected from the sample and said reference light portion reflected from said reflecting device, said detector generating a signal indicative of an interference of said sensing light portion reflected from the sample and said reference light portion reflected from said reflecting device; and

processing means configured to determine a characteristic of the sample from said signal indicative of said interference of said sensing light portion reflected from the sample and said reference light portion reflected from said reflecting device.

11. The system of claim 10 wherein said means for generating said interference condition comprises means for generating said interference condition in a time domain.

12. The system of claim 10 wherein said means for generating said interference condition comprises means for generating said interference condition in a frequency domain.

13. The system of claim 11 wherein said means for generating said interference condition in the time domain comprises:

means for varying an effective light path length of said at least one of said reference light path and said sensing light path to within about a coherence length of said light.

14. The system of claim 12 wherein said means for generating said interference condition in the frequency domain comprises:

means for varying a frequency of said light from said light source.

15. The system of claim 10 wherein said splitter has an asymmetrical ratio such that said sensing light portion is greater than said reference light portion.

16. The system of claim 10 wherein said optical switches are digitally selectable.

17. The system of claim 10 wherein the sample comprises a biological sample.

18. The system of claim 10 wherein said probe light paths are configured as a catheter.

19. A system for determining a characteristic of a sample, the system comprising:

a light source for providing a light;

a splitter receptive to said light from said light source to produce a sensing light portion and a reference light portion;

a sensing light path comprising,

a light path configured to communicate said sensing light portion from said splitter and said sensing light portion reflected from the sample,

a plurality of probe light paths configured to direct said sensing light portion at the sample and to receive said sensing light portion reflected from the sample, and

an optical switch selectable to define communication between said light path and a selected at least one of said probe light paths;

a reflecting device;

a reference light path configured to communicate said reference light portion from said splitter, said reference light path further configured to direct said reference light portion at said reflecting device and to receive said reference light portion reflected from said reflecting device;

means for generating an interference condition between said reference light portion reflected from said reflecting device and said sensing light portion reflected from the sample;

a detector receptive to said reference light portion reflected from said reflecting device and said sensing light portion reflected from the sample, said detector generating a signal indicative of an interference of said reference light portion reflected from said reflecting device and said sensing light portion reflected from the sample;

a first circulator disposed in said reference light path to transfer said reference light portion from said splitter to said reflecting device, and to transfer said reference light portion reflected from said reflecting device to said detector;

a second circulator disposed in said sensing light path to transfer said sensing light portion from said splitter to said optical switch, and to transfer said sensing light portion reflected from the sample to said detector;

a coupler receptive to said reference light portion reflected from said reflecting device and transferred by said first circulator, said coupler receptive also to said sensing light portion reflected from the sample and transferred by said second circulator, said coupler presenting said reference light portion reflected from said reflecting device and said sensing light portion reflected from the sample to said detector; and

processing means configured to determine a characteristic of the sample from said signal indicative of said interference of said reference light portion reflected from said reflecting device and said sensing light portion reflected from the sample.

20. The system of claim 19 wherein said means for generating said interference condition comprises means for generating said interference condition in a time domain.

21. The system of claim 19 wherein said means for generating said interference condition comprises means for generating said interference condition in a frequency domain.

22. The system of claim 20 wherein said means for generating said interference condition in the time domain comprises:

means for varying an effective light path length of said at least one of said reference light path and said sensing light path to within about a coherence length of said light.

23. The system of claim 21 wherein said means for generating said interference condition in the frequency domain comprises:

means for varying a frequency of said light from said light source.

24. The system of claim 19 wherein said splitter has an asymmetrical ratio such that said sensing light portion is greater than said reference light portion.

25. The system of claim 19 wherein said detector comprises at least one photodetector.

26. The system of claim 19 further comprising means for maintaining polarization of said light.

27. The system of claim 19 wherein said broadband light source comprises a superluminescent diode.

28. The system of claim 19 wherein said optical switch is digitally selectable.

29. The system of claim 19 wherein the sample comprises a biological sample.

30. The system of claim 19 wherein said probe light paths are configured as a catheter.

31. A system for determining a characteristic of a sample, the system comprising:

a light source for providing a light;

a splitter receptive to said light from said light source to produce a sensing light portion and a reference light portion;

a sensing light path comprising,

a light path configured to communicate said sensing light portion from said splitter and said sensing light portion reflected from the sample,

a plurality of probe light paths configured to direct said sensing light portion at the sample and to receive said sensing light portion reflected from the sample, and

an optical switch selectable to define communication between said light path and a selected at least one of said probe light paths;

a reflecting device;

a reference light path configured to communicate said reference light portion from said splitter, said reference light path further configured to direct said reference light portion at said reflecting device and to receive said reference light portion reflected from said reflecting device;

means for generating an interference condition in a frequency domain between said sensing light portion reflected from the sample and said reference light portion reflected from said reflecting device;

a detector receptive to said sensing light portion reflected from the sample and said reference light portion reflected from said reflecting device, said detector generating a signal indicative of an interference of said sensing light portion reflected from the sample and said reference light portion reflected from said reflecting device; and

processing means configured to determine a characteristic of the sample from said signal indicative of said interference of said sensing light portion reflected from the sample and said reference light portion reflected from said reflecting device.

32. The system of claim 31 wherein said means for generating said interference condition in the frequency domain comprises:

means for varying a frequency of said light from said light source.

33. The system of claim 31 wherein said detector comprises at least one photodetector.

34. The system of claim 31 further comprising means for maintaining polarization of said light.

35. The system of claim 31 wherein said broadband light source comprises a superluminescent diode.

36. The system of claim 31 wherein said optical switch is digitally selectable.

37. The system of claim 31 wherein the sample comprises a biological sample.

38. The system of claim 31 wherein said probe light paths are configured as a catheter.

39. A system for determining a characteristic of a sample, the system comprising:

a light source for providing a light;

a splitter receptive to said light from said light source to produce a sensing light portion and a reference light portion, said splitter having an asymmetrical ratio such that said sensing light portion is greater than said reference light portion;

a sensing light path comprising,

a light path configured to communicate said sensing light portion from said splitter and said sensing light portion reflected from the sample,

a plurality of probe light paths configured to direct said sensing light portion at the sample and to receive said sensing light portion reflected from the sample, and

an optical switch selectable to define communication between said light path and a selected at least one of said probe light paths;

a reflecting device;

a reference light path configured to communicate said reference light portion from said splitter, said reference light path further configured to direct said reference light portion at said reflecting device and to receive said reference light portion reflected from said reflecting device;

means for generating an interference condition between said sensing light portion reflected from the sample and said reference light portion reflected from said reflecting device;

a detector receptive to said sensing light portion reflected from the sample and said reference light portion reflected from said reflecting device, said detector generating a signal indicative of an interference of said sensing light portion reflected from the sample and said reference light portion reflected from said reflecting device; and

processing means configured to determine a characteristic of the sample from said signal indicative of said interference of said sensing light portion reflected from the sample and said reference light portion reflected from said reflecting device.

40. The system of claim 39 wherein said asymmetrical ratio is about x:

100−

x, where 100−

x represents a relative amount of said sensing light portion and x represents a relative amount of said reference light portion in said asymmetrical ratio

41. The system of claim 39 wherein said means for generating said interference condition comprises means for generating said interference condition in a time domain.

42. The system of claim 39 wherein said means for generating said interference condition comprises means for generating said interference condition in a frequency domain.

43. The system of claim 41 wherein said means for generating said interference condition in the time domain comprises:

means for varying an effective light path length of said at least one of said reference light path and said sensing light path to within about a coherence length of said light.

44. The system of claim 42 wherein said means for generating said interference condition in the frequency domain comprises:

means for varying a frequency of said light from said light source.

45. The system of claim 39 wherein said optical switches are digitally selectable.

46. The system of claim 39 wherein the sample comprises a biological sample.

47. The system of claim 39 wherein said probe light paths are configured as a catheter.

48. A system for determining a characteristic of a sample, the system comprising:

a light source for providing a light;

a splitter receptive to said light from said light source to produce a sensing light portion and a reference light portion;

a sensing light path comprising,

a light path configured to communicate said sensing light portion from said splitter and said sensing light portion reflected from the sample,

a plurality of probe light paths configured to direct said sensing light portion at the sample and to receive said sensing light portion reflected from the sample, and

an optical switch selectable to define communication between said light path and a selected at least one of said probe light paths;

a reflecting device;

a reference light path configured to communicate said reference light portion from said splitter, said reference light path further configured to direct said reference light portion at said reflecting device and to receive said reference light portion reflected from said reflecting device;

a variable optical attenuator disposed in said reference light path to attenuate said reference light portion;

means for generating an interference condition between said sensing light portion reflected from the sample and said reference light portion reflected from said reflecting device;

a detector receptive to said sensing light portion reflected from the sample and said reference light portion reflected from said reflecting device, said detector generating a signal indicative of an interference of said sensing light portion reflected from the sample and said reference light portion reflected from said reflecting device; and

processing means configured to determine a characteristic of the sample from said signal indicative of said interference of said sensing light portion reflected from the sample and said reference light portion reflected from said reflecting device.

49. The system of claim 48 further comprising:

a digital voltage controller configured to control said variable optical attenuator.

50. The system of claim 48 wherein said means for generating said interference condition comprises means for generating said interference condition in a time domain.

51. The system of claim 48 wherein said means for generating said interference condition comprises means for generating said interference condition in a frequency domain.

52. The system of claim 50 wherein said means for generating said interference condition in the time domain comprises:

means for varying an effective light path length of said at least one of said reference light path and said sensing light path to within about a coherence length of said light.

53. The system of claim 51 wherein said means for generating said interference condition in the frequency domain comprises:

means for varying a frequency of said light from said light source.

54. The system of claim 48 wherein said optical switches are digitally selectable.

55. The system of claim 48 wherein the sample comprises a biological sample.

56. The system of claim 48 wherein said probe light paths are configured as a catheter.

57. A method for determining a characteristic of a sample, the method comprising:

asymmetrically splitting a light from a light source into a sensing light portion and a reference light portion, said sensing light portion being greater than said reference light portion;

selecting a probe light path from a plurality of probe light paths, said probe light paths forming a portion of a sensing light path;

directing said sensing light portion by means of said sensing light path, including the selected at least one of said probe light paths, at the sample;

receiving said sensing light portion reflected from the sample by means of said sensing light path, including the selected at least one of said probe light paths;

directing said reference light portion by means of a reference light path at a reflecting device;

receiving said reference light portion reflected from said reflecting device by means of said reference light path;

generating an interference condition between said sensing light portion reflected from the sample and said reference light portion reflected from said reflecting device;

detecting said sensing light portion reflected from the sample and said reference light portion reflected from said reflecting device, to generate a signal indicative of an interference of said sensing light portion reflected from the sample and said reference light portion reflected from said reflecting device; and

determining a characteristic of the sample from said signal indicative of said interference of said sensing light portion reflected from the sample and said reference light portion reflected from said reflecting device.

58. The method of claim 57 wherein said generating said interference condition comprises generating said interference condition in a time domain.

59. The method of claim 57 wherein said generating said interference condition comprises generating said interference condition in a frequency domain.

60. The method of claim 58 wherein said generating said interference condition in the time domain comprises:

varying an effective light path length of said at least one of said reference light path and said sensing light path to within about a coherence length of said light.

61. The method of claim 59 wherein said generating said interference condition in the frequency domain comprises:

varying a frequency of said light from said light source.

62. The method of claim 57 further comprising maintaining polarization of said light.

63. The method of claim 57 wherein said light comprises a broadband light.

64. The method of claim 57 wherein said light comprises laser lights.

65. The method of claim 57 wherein the sample comprises a biological sample.

66. A method for determining a characteristic of a sample, the method comprising:

splitting a light from a light source into a sensing light portion and a reference light portion;

selecting a probe light path from a plurality of probe light paths, said probe light paths forming a portion of a sensing light path;

directing said sensing light portion by means of said sensing light path, including the selected at least one of said probe light paths, at the sample;

receiving said sensing light portion reflected from the sample by means of said sensing light path, including the selected at least one of said probe light paths;

directing said reference light portion by means of a reference light path at a reflecting device;

receiving said reference light portion reflected from said reflecting device by means of said reference light path;

generating an interference condition in a frequency domain between said sensing light portion reflected from the sample and said reference light portion reflected from said reflecting device;

detecting said sensing light portion reflected from the sample and said reference light portion reflected from said reflecting device, to generate a signal indicative of an interference of said sensing light portion reflected from the sample and said reference light portion reflected from said reflecting device; and

determining a characteristic of the sample from said signal indicative of said interference of said sensing light portion reflected from the sample and said reference light portion reflected from said reflecting device.

67. The method of claim 66 wherein said generating said interference condition in the frequency domain comprises:

varying a frequency of said light from said light source.

68. The method of claim 66 further comprising maintaining polarization of said light.

69. The method of claim 66 wherein said light comprises a broadband light.

70. The method of claim 66 wherein said light comprises laser lights.

71. The method of claim 66 wherein the sample comprises a biological sample.