Stabilized Multi-Wavelength Laser System for Non-Invasive Spectrophotometric Monitoring

• US 20080300473A1
• Filed: 12/14/2006
• Published: 12/04/2008
• Est. Priority Date: 12/16/2005
• Status: Abandoned Application

• Current Assignee: Cas Medical Systems Incorporated (Edwards Lifesciences Corporation)
• Original Assignee: Cas Medical Systems Incorporated (Edwards Lifesciences Corporation)
• Inventors: Benni, Paul
• Application Number:
  US12/097,438
• Publication Number:
  US 20080300473A1
• Time in Patent Office: Days
• US Class Current: 600/323
• CPC Class Codes: A61B 5/14553 specially adapted for cerebral tissue
• CPC Class Codes: G01N 2021/3144 for oxymetry
• CPC Class Codes: G01N 21/359 using near infrared light

Abstract

A spectroscopy system that may be used for spectrophotometric oxygenation monitoring of tissue includes a monitor portion and a sensor portion. The sensor portion generally includes a light source and one or more light detectors. The sensor portion may attach to a human to sense light signals from the light source that have traversed biological tissue, the light signals ultimately being used by the system to determine biological tissue blood hemoglobin oxygenation levels. The monitor portion generally includes a processor and a visual display. A laser beam combiner may couple a plurality of laser diode output light signals into one optical fiber. To stabilize the output of each of the laser diodes, an optical fiber light stabilizer is coupled to the combined laser diode output. The optical fiber light stabilizer redistributes the modes in the optical fiber such that the higher-order modes are filled until an equilibrium mode distribution is established. A light sensor may also provide feedback with respect to the laser diode output, which allows for compensation of any laser diode light output instability independently of optical fiber related instabilities.

Claims

1. A spectroscopic system that monitors oxygenation levels in biological tissue, comprising:

a light source having a light output;

a predetermined length of optical fiber coupled to the light output of the light source, where the light output of the light source propagates through the optical fiber;

an optical fiber light stabilizer provided within the optical fiber, where the light output of the light source propagates through the optical fiber light stabilizer, and where the light stabilizer redistributes modes of the light output from the light source until an equilibrium mode distribution is established in the light output propagating within the optical fiber; and

a sensor coupled at an output of the light stabilizer, where the sensor provides the light output with the equilibrium mode distribution at an output of the spectroscopic system.

2. The spectroscopic system of claim 1, where the light source comprises a laser diode.

3. The spectroscopic system of claim 1, where the light source provides the light output at one or more predetermined wavelengths.

4. The spectroscopic system of claim 1, where the light source provides the light output at one or more predetermined wavelengths of light.

5. The spectroscopic system of claim 1, where the light source comprises a plurality of laser diodes.

6. The spectroscopic system of claim 1, where the light source comprises a plurality of laser diodes, each of the laser diodes providing a laser beam output at a predetermined wavelength, and where the spectroscopic system further comprises a laser beam combiner that combines together the laser beam outputs and provides the combined laser beam output to the optical fiber.

7. The spectroscopic system of claim 1, where the light stabilizer comprises a spool and a predetermined length of the optical fiber wrapped around the spool.

8. The spectroscopic system of claim 1, where the light stabilizer comprises a spool and a predetermined length of the optical fiber wrapped around the spool, where the spool has a radius that is at least approximately equal to a long term bend radius of the optical fiber wrapped around the spool.

9. The spectroscopic system of claim 1, further comprising a light detector that detects the light output from the light source.

10. The spectroscopic system of claim 1, further comprising a light detector that detects the light output from the light source and provides a detected light signal indicative thereof, and a signal processor that is responsive to the detected light signal to compensate for instability relating to the light output from the light source.

11. The spectroscopic system of claim 1, further comprising a light detector that detects the light output from the light source and provides a reference input intensity used for quantitative measurement methods in spectrophotometric applications.

12. The spectroscopic system of claim 11, whereas said light detector is a component of the light source.

13. The spectroscopic system of claim 11, whereas said light detector is used to monitor light output of the light stabilizer.

14. The spectroscopic system of claim 1 wherein the light output has a numeral aperture which is increased after reaching modal equilibrium within the light stabilizer by use of one or more lenses or other optical light bending means.

15. The spectroscopic system of claim 1, further comprising a control for providing power to the light source.

16. The spectroscopic system of claim 1, where the light source comprises a plurality of laser diodes, and where the spectroscopic system further comprises a control for providing power to the plurality of laser diodes in a predetermined sequence.

17. A spectrophotometric system that determines oxygenation levels in biological tissue and provides an indication of the determined oxygenation levels, comprising:

a plurality of laser diodes each providing a laser output signal at a predetermined wavelengths of light;

a device that combines the plurality of laser output signals into a combined laser output signal;

a predetermined length of optical fiber coupled to the combined laser output signal, where the combined laser output signal propagates through the optical fiber;

an optical fiber light stabilizer connected with the optical fiber, where the combined laser output signal propagates through the light stabilizer, and where the light stabilizer redistributes modes of the combined laser output signal until an equilibrium mode distribution is established in the combined laser output signal propagating within the optical fiber; and

a sensor coupled to the light stabilizer, where the sensor provides the combined laser output signal with the equilibrium mode distribution at an output of the spectrophotometric system.

18. The spectrophotometric system of claim 17, further comprising a light detector that detects the combined laser output signal and provides a detected light signal indicative thereof, and a signal processor that is responsive to the detected light signal to compensate for any instability relating to the combined laser output signal.

19. The spectroscopic system of claim 17, further comprising a light detector that detects the light output from the light source and provides a reference input intensity used for quantitative measurement methods in spectrophotometric applications.

20. The spectroscopic system of claim 19, whereas said light detector is a component of the light source.

21. The spectroscopic system of claim 19, whereas said light detector is used to monitor light output of the light stabilizer.

22. The spectroscopic system of claim 17 wherein the light output has a numeral aperture which is increased after reaching modal equilibrium within the light stabilizer by use of one or more lenses or other optical light bending means.

23. The spectrophotometric system of claim 17, where the light stabilizer comprises a spool and a predetermined length of the optical fiber wrapped around the spool

24. The spectrophotometric system of claim 17, where the light stabilizer comprises a spool and a predetermined length of the optical fiber wrapped around the spool, where the spool has a radius that is at least approximately equal to a long term bend radius of the optical fiber wrapped around the spool.

25. A spectrophotometric system that monitors biological tissue, comprising:

at least one laser diode that provides a laser output signal at a predetermined wavelength;

a predetermined length of optical fiber coupled to the laser output signal, where the laser output signal propagates through the optical fiber;

an optical fiber light stabilizer connected with the optical fiber, where the laser output signal propagates through the light stabilizer, and where the light stabilizer redistributes modes of the laser output signal until an equilibrium mode distribution is established in the laser output signal propagating within the optical fiber; and

a sensor coupled to the light stabilizer, where the sensor provides the laser output signal with the equilibrium mode distribution at an output of the spectrophotometric system.

26. The spectrophotometric system of claim 25, further comprising a plurality of laser diodes each providing a laser output signal at predetermined wavelengths of light, and a device that combines the plurality of laser output signals into a combined laser output signal, the predetermined length of optical fiber being coupled to the combined laser output signal.

27. The spectrophotometric system of claim 25, where the light stabilizer comprises a spool and a predetermined length of the optical fiber wrapped around the spool

28. The spectroscopic system of claim 25, further comprising a light detector that detects the light output from the light source and provides a reference input intensity used for quantitative measurement methods in spectrophotometric applications.

29. The spectroscopic system of claim 28, whereas said light detector is a component of the light source.

30. The spectroscopic system of claim 28, whereas said light detector is used to monitor light output of the light stabilizer.

31. The spectroscopic system of claim 25 wherein the light output has a numeral aperture which is increased after reaching modal equilibrium within the light stabilizer by use of one or more lenses or other optical light bending means.

32. The spectrophotometric system of claim 25, where the light stabilizer comprises a spool and a predetermined length of the optical fiber wrapped around the spool, where the spool has a radius that is at least approximately equal to the long term bend radius of the optical fiber wrapped around the spool.

33. The spectrophotometric system of claim 25, where the laser output signal at the output of the spectrophotometric system is provided to a human subject under test to monitor the oxygenation level in certain biological tissue of the human under test.

34. A method for spectrophotometrically determining oxygenation levels in biological tissue of a human subject under test, comprising the steps of:

providing a plurality of laser output signals each at a predetermined wavelength of light;

combining the plurality of laser output signals into a combined laser output signal;

providing the combined laser output signal to an optical fiber, where the combined laser output signal propagates through the optical fiber;

stabilizing the combined laser output signal within the optical fiber by redistributing modes of the combined laser output signal until an equilibrium mode distribution is established in the combined laser output signal propagating within the optical fiber;

emitting the combined laser output signal with established equilibrium mode distribution into the biological tissue of the human subject under test;

sensing the combined laser output signal after it has passed through the biological tissue of the human subject under test; and

determining the oxygenation levels in the biological tissue of the human subject under test from the sensed combined laser output signal.

35. A device for spectrophotometrically examining a subject'"'"'s tissue, comprising:

a transmitter operable to transmit at least one light signal along at least three independent wavelengths;

at least one light signal detector operable to detect the light signal after passage through tissue being examined, and produce at least one detected signal corresponding to the light signal;

a secondary light signal detector to monitor the light signal prior to passage through the subject'"'"'s tissue; and

a processor having an algorithm for examining the subject'"'"'s tissue, which algorithm is adapted to process the detected signal along at least three wavelengths.

36. The device of claim 35, wherein the secondary light detector is operable to provide an output to the algorithm regarding the light signal transmitted by the transmitter.

37. The device of claim 36, wherein the secondary signal detector is operably disposed to receive at least a portion of the light signal.

38. The device of claim 37, wherein the secondary light detector includes a beam splitter.