Method and apparatus for monitoring output signal instability in a light source

• US 20060114457A1
• Filed: 11/30/2004
• Published: 06/01/2006
• Est. Priority Date: 11/30/2004
• Status: Active Grant

• Current Assignee: Hutchinson Technology Incorporated (TDK Corporation)
• Original Assignee: Hutchinson Technology Incorporated (TDK Corporation)
• Inventors: Schmitz, Roger W., Scheele, Bryan J.
• Granted Patent: US 7,239,385 B2
• Time in Patent Office: Days
• US Class Current: 356/319
• CPC Class Codes: G01J 2003/2866 Markers; Calibrating of scan
• CPC Class Codes: G01J 3/02 Details
• CPC Class Codes: G01J 3/021 using plane or convex mirrors, parallel phase plates, or particular reflectors
• CPC Class Codes: G01J 3/0216 using light concentrators or collectors or condensers
• CPC Class Codes: G01J 3/0218 using optical fibers
• CPC Class Codes: G01J 3/024 using means for illuminating a slit efficiently (e.g. entrance slit of a spectrometer or entrance face of fiber)
• CPC Class Codes: G01J 3/0256 Compact construction
• CPC Class Codes: G01J 3/0291 Housings; Spectrometer accessories; Spatial arrangement of elements, e.g. folded path arrangements
• CPC Class Codes: G01J 3/10 Arrangements of light sources specially adapted for spectrometry or colorimetry
• CPC Class Codes: G01N 21/274 Calibration, base line adjustment, drift correction
• CPC Class Codes: G01N 21/474 Details of optical heads therefor, e.g. using optical fibres

Abstract

A spectrophotometric instrument is comprised of a processor, a probe having a tissue engaging surface with an aperture therethrough and a light source producing measurement light signals and optically coupled to the probe via a first optical path. A partially reflective first reflecting member is located in the probe and has a generally elliptical profile positioned to reflect a first portion of the measurement light signals to the tissue aperture and to transmit a second portion of the measurement light signals through the first reflecting member. A second reflecting member is located in the probe and has a generally elliptical profile positioned to reflect the measurement light signals transmitted through the first reflecting member. A second optical path has a distal end positioned to receive the measurement light signals reflected off of the second reflecting member and a proximal end coupled to the processor. A third optical path has a distal end positioned in the probe to receive light signals transmitted through the tissue sample and a proximal end coupled to the processor.

Claims

1. A probe for a spectrophotometric instrument, the probe comprising:

a probe housing having a tissue engaging surface with first and second apertures extending therethrough;

a first optical path having a proximal end optically coupleable to a light source and extending to a distal end optically coupled to the first aperture for delivering a beam of measurement light signals to a tissue sample;

a second optical path having a distal end optically coupled to the first optical path adjacent the first aperture for sampling a reference light signal portion of the measurement light signals of the first optical path and extending to a proximal end coupleable to a processor; and

a third optical path having a distal end optically coupled to the second aperture and extending to a proximal end coupleable to the processor.

2. The probe of claim 1 wherein the second optical path samples a discrete portion of the measurement light signals of the first optical path.

3. The probe of claim 1 wherein the second optical path samples an axis symmetric portion of the measurement light signals of the first optical path.

4. The probe of claim 1 wherein the second optical path samples from substantially the entire beam of the measurement light signals of the first optical path.

5. The probe of claim 1 wherein the first optical path further comprises:

a first optical fiber having a proximal end provided with a light input region and extending to a distal end provided with a light output region, said distal end extending into the probe housing parallel to the tissue engaging surface and positioned adjacent the first aperture;

a first reflective member having a reflective surface and formed with a first portion positioned adjacent the distal end of the first optical fiber and the first aperture; and

wherein the second optical path further includes a second optical fiber provided with a light input region at a distal end positioned within the probe housing and extending to a proximal end provided with a light output region.

6. The probe of claim 5, wherein the first portion of the first reflective member is positioned at an angle of about 45°

relative to the tissue engaging surface.

7. The probe of claim 5, wherein the first portion of the first reflective member is positioned to reflect light onto the tissue sample substantially perpendicular to the plane of the surface tissue.

8. The probe of claim 5, wherein the first portion of the first reflective member has a concave curved profile.

9. The probe of claim 5, wherein the first portion has a planar profile.

10. The probe of claim 5, wherein the second optical path further comprises a second portion formed in the first reflective member at an angle relative to the first portion and wherein the distal end of the second optical fiber is positioned adjacent the second portion.

11. The probe of claim 5 wherein the second optical path further comprises a second reflective member having a reflective surface positioned between the first reflective member and the first aperture and wherein the distal end of the second optical fiber is positioned adjacent the second reflective member.

12. The probe of claim 5 wherein the reflective surface of the first reflective member is partially reflective and partially transmissive and the second optical path further comprises a second reflective member having a reflective surface positioned on the opposite side of the first reflective member as the first optical fiber and wherein the distal end of the second optical fiber is positioned adjacent the second reflective member.

13. The probe of claim 12 wherein the reflective surface of the first reflective member is comprised of one of aluminum, gold, silver or a dielectric.

14. The probe of claim 12 wherein the reflective surface of the first reflective member has a reflection/transmission ratio of approximately 40:

1.

15. The probe of claim 12 wherein the reflective surface of the first reflective member has a reflection/transmission ratio of approximately 50:

1.

16. The probe of claim 12 wherein the second reflective member has a concave curved profile.

17. The probe of claim 5 further comprising a light attenuator coupled to the distal end of the second optical fiber.

18. The probe of claim 17 wherein the attenuator is adapted to attenuate from about 97% to about 99% of the reference light signals.

19. The probe of claim 17 wherein the attenuator comprises a bulk scattering media.

20. The probe of claim 19 wherein the attenuator comprises:

a first surface having a convex curved profile;

a second surface optically coupled to the distal end of the second optical fiber; and

a tapering region extending between the first surface and the second surface.

21. The probe of claim 17 wherein the attenuator comprises:

a glass block;

a surface scattering media formed on the glass block; and

a light transmitting spacing member interposed between the glass block and the distal end of the second optical path.

22. The probe of claim 1 wherein the first aperture is spaced apart from the second aperture a minimum distance of from about 5 mm to about 35 mm.

23. The probe of claim 1 further comprising an optical connector coupled to the probe housing.

24. The probe of claim 23 wherein a distal end of the connector is detachably coupled to the probe housing.

25. The probe of claim 23 wherein a distal end of the connector is integrally formed with the probe housing.

26. The probe of claim 23 wherein a proximal end of the connector is optically coupleable to the light source and a distal end of the connector is optically coupled to the probe housing.

27. The probe of claim 23 wherein the connector further comprises at least one optical fiber.

28. The probe of claim 23 wherein a distal end of the connector is coupled to an interface mechanism coupled to the probe housing.

29. The probe of claim 1 wherein the light source emits light signals at about 800, 760, 720 and 680 nm.

30. The probe of claim 1 wherein the third optical path further comprises:

a reflective member having a reflective surface positioned adjacent the second aperture; and

an optical fiber having a distal end provided with a light input region positioned adjacent the reflective surface and a proximal end provided with a light output region.

31. The probe of claim 30 wherein the reflective surface has a concave curved profile.

32. A feedback system for monitoring output signal instability of a spectrophotometric instrument, the system comprising:

a probe having a tissue engaging surface with a first aperture extending therethrough;

a first optical path having a proximal end optically coupleable to a light source and extending to a distal end optically coupled to the first aperture for delivering a beam of measurement light signals to a tissue sample; and

a second optical path having a distal end optically coupled to the first optical path adjacent the first aperture for sampling a portion of the measurement light signals of the first optical path and extending to a proximal end coupleable to a processor.

33. A probe for use with a spectrophotometric instrument, the probe comprising:

a probe housing having a tissue engaging surface with first and second apertures extending therethrough;

a first optical path having a proximal end optically coupleable to a light source and extending to a distal end optically coupled to the first aperture for delivering a beam of measurement light signals to a tissue sample;

a feedback means for removing a portion of the measurement light signals from the first optical path adjacent the first aperture representative of the measurement light signals striking the tissue sample; and

a third optical path having a distal end optically coupled to the second aperture and extending to a proximal end coupleable to a processor.

34. The probe of claim 33 wherein the feedback means further comprises:

a first reflective member having a partially reflective surface positioned adjacent the first aperture for reflecting a portion of the measurement light signals of the first optical path through the first aperture and onto the tissue sample and for transmitting a portion of the measurement light signals;

a second reflective member having a reflective surface positioned to reflect the measurement light signals transmitted through the first reflective member; and

an optical fiber having a distal end adjacent the second reflective member for collecting light signals and extending to a proximal end coupleable to a processor.

35. The probe of claim 34 wherein the partially reflective surface has a reflection/transmission ratio of from about 40:

1 to about 50;

1.

36. The probe of claim 34 wherein the partially reflective surface has a substantially wavelength neutral reflection/transmission ratio.

37. A method for monitoring output signal instability in a spectrophotometric instrument, the method comprising:

providing a probe having a tissue engaging surface for delivering measurement light signals to a tissue sample and for receiving light emitted from the tissue sample;

providing a light source assembly for generating the measurement light signals, said light source assembly comprising;

a light source; and

at least one send optical fiber optically coupling the light source to the probe, said send optical fiber having a proximal end optically coupled to the light source and extending to a distal end protruding into the probe parallel to the tissue engaging surface;

delivering measurement light signals from the light source assembly to the probe through the send optical fiber;

reflecting the measurement light signals from the distal end of the send optical fiber onto the tissue sample; and

removing a reference sample of the measurement light signals representative of the measurement light signals reflected onto the tissue sample.

38. The method of claim 37 further comprising removing the reference sample from the measurement light signals adjacent the tissue engaging surface of the probe.

39. The method of claim 37 further comprising:

providing a first reflecting member having a partially reflective/partially transmissive surface adjacent the distal end of the send optical fiber for reflecting a first portion of the measurement light signals onto the tissue sample and transmitting a second portion of the measurement light signals through to the opposite side of the first reflecting member; and

providing a second reflecting member to reflect the second portion of the measurement light signals away from the tissue sample to form the reference sample.

40. The method of claim 37 further comprising attenuating the reference sample to an intensity level approximately equal to an intensity level of the light emitted from the tissue sample.