Tissue spectrometer with improved optical shutter

• US 20040236198A1
• Filed: 05/19/2003
• Published: 11/25/2004
• Est. Priority Date: 05/19/2003
• Status: Active Grant

• Current Assignee: Hutchinson Technology Incorporated (TDK Corporation)
• Original Assignee: Hutchinson Technology Incorporated (TDK Corporation)
• Inventors: Gritsenko, Sergey I.
• Granted Patent: US 7,239,901 B2
• Time in Patent Office: Days
• US Class Current: 600/323
• CPC Class Codes: A61B 5/1495 Calibrating or testing of in-vivo probes

Abstract

An improved system and method for calibrating spectrophotometric instruments for the effects of light source drift. An instrument includes both received light and reference light paths to a light sensor where light signals are converted to electrical signals to be used by a processor. A shutter is used to block or allow passage of one of the light signals to the sensor. When the selected light signal is blocked, the sensor produces an electrical signal representative only of the other signal. When the selected light signal is allowed to pass, the sensor produces an electrical signal representative of both light signals. By knowing the value of one of the signals by itself, the value of the other signal can be determined. The individual values are then processed to produce an output signal that is a function of both light signals. Further, because only one light path must be blocked, simpler structures for blocking the light may be used.

Claims

1. A spectrophotometric instrument;

comprising;

a source of measurement light signals having measurement light wavelengths;

a probe having;

a tissue-engaging surface;

a send fiber coupled to the measurement light signal source for transmitting the measurement light signals to the tissue-engaging surface; and

a receive fiber for receiving light including the measurement light signals after the measurement light has been transmitted through the tissue;

reference signal optics coupled to the measurement light signal between the measurement light signal source and the tissue-engaging surface, for transmitting a reference light signal portion of the measurement light signal;

a detector for generating electrical signals representative of the measurement light signals and the reference light signals;

an optical path for coupling the measurement light signal from the receive fibers and the reference light signal portion from the reference signal optics to the detector;

an optical path control for selectively allowing and preventing the reference light signal portion to the detector, whereby the detector can output a reference light sample value when the reference light signal portion is coupled to the detector, and the detector can output a measurement light sample value when the measurement light signal portion is coupled to the detector; and

a processor for determining corrected measurement sample signals at each measurement light wavelength as a function of a no light signal, a current measurement signal plus a no light signal and a no light signal plus a current measurement signal plus a current reference signal.

2. The instrument of claim 1, further comprising:

a processor for determining the values of a no light signal, a measurement light signal and a reference light signal.

3. The instrument of claim 1 wherein the optical paths include optics.

4. The instrument of claim 2 wherein the optics include an attenuator in the reference light signal path for reducing the portion of the reference light signal that is directed to the detector.

5. The instrument of claim 1 wherein the path control includes a shutter.

6. The instrument of claim 4 and further including an electric drive for driving the shutter.

7. The instrument of claim 1 wherein the measurement light signal source includes a plurality of sources of narrow-bandwidth light.

8. The instrument of claim 1 wherein the reference signal optics includes an optical fiber.

9. The instrument of claim 1 wherein the reference signal optics further includes a light mixer.

10. A spectrophotometric instrument, including

a measurement signal optical input for receiving a measurement light signal transmitted through tissue being analyzed;

a reference signal optical input for receiving a reference light signal which is a portion of the measurement light signal that has not been transmitted through the tissue being analyzed;

a detector for generating electrical signals representative of the measurement light signals and the reference light signals;

optical paths for coupling the measurement light signal from the measurement signal optical input and for coupling the reference light signal from the reference signal optical input to the detector; and

an optical path control for selectively allowing and preventing only the reference light signal to the detector, the detector outputting a reference light sample value as a function of a no light signal, a current measurement signal and a reference light signal.

11. The instrument of claim 10 and further including a processor/controller for calculating corrected measurement values as a function of a combined current measurement light signal and reference light signal.

12. An optical sensor, comprising:

a light source;

a first optical path for directing light to a first location;

a second optical path for collecting light from a second location;

a detector connected to the second optical path for generating electrical signals representative of the light collected in the second optical path;

a third optical path for direction of light from the light source to the detector; and

a shutter in the third optical path for selectively allowing and preventing light only in the third optical path from reaching the detector.

13. The optical sensor of claim 13, wherein the shutter comprises:

a) a flat coil having a coiled end and a free end with a vane mounted on the free end;

b) a power source operatively connected to the flat coil for energizing and de-energizing the flat coil

c) a magnet positioned near the free end of the flat coil whereby the flat coil is in a first position when energized and a second position when de-energized.

14. A light source drift compensation apparatus, comprising:

a reference light path connected to the light source and carrying a reference light signal;

a detector connected to the reference light path for creating a reference signal as a function of the reference light signal;

a shutter only in the reference light path between the light source and the detector, the shutter selectively blocking and allowing passage of the reference light signal;

a processor connected to the detector for comparing the reference light signal to a stored value and producing a correction signal as a function of the difference between the reference signal and the stored value.

15. A spectrophotometric instrument;

comprising;

a source of measurement light signals having measurement light wavelengths;

a probe having;

a tissue-engaging surface;

a send fiber coupled to the measurement light signal source for transmitting the measurement light signals to the tissue-engaging surface; and

a receive fiber for receiving light including the measurement light signals after the measurement light has been transmitted through the tissue;

reference signal optics coupled to the measurement light signal between the measurement light signal source and the tissue-engaging surface, for transmitting a reference light signal portion of the measurement light signal;

a detector for generating electrical signals representative of the measurement light signals and the reference light signals;

a first optical path for coupling the measurement light signal from the receive fiber to the detector;

a second optical path for coupling the measurement light signal from the reference light signal portion from the reference signal optics to the detector; and

an optical path control only in the second optical path for selectively allowing and preventing the reference light signal portion to the detector, whereby the detector can output a reference light sample value when the reference light signal portion is coupled to the detector, and the detector can output a measurement light sample value when the measurement light signal portion is coupled to the detector.

16. The instrument of claim 15, further comprising:

a processor for determining the values of a no light signal, a measurement light signal and a reference light signal.

17. The instrument of claim 15 wherein the optical paths include optics.

18. The instrument of claim 16 wherein the optics include an attenuator in the reference light signal path for reducing the portion of the reference light signal that is directed to the detector.

19. The instrument of claim 15 wherein the path control includes a shutter.

20. The instrument of claim 19 and further including an electric drive for driving the shutter.

21. The instrument of claim 15 wherein the measurement light signal source includes a plurality of sources of narrow-bandwidth light.

22. The instrument of claim 15 wherein the reference signal optics includes an optical fiber.

23. The instrument of claim 15 wherein the reference signal optics further includes a light mixer.

24. The instrument of claim 15 and further including a processor/controller for calculating corrected measurement sample signals at each measurement light wavelength as a function of a no light signal, a current measurement signal plus a no light signal and a no light signal plus a current measurement signal plus a current reference signal.

25. A method of adjusting an output signal for light source drift in a instrument that uses a light signal to measure an attribute of a target, comprising the steps of:

directing a light signal from the light source at the target;

redirecting a portion of the light signal as a reference light signal to a sensor input terminal;

collecting a portion of the light signal from the target to create a received light signal and directing the received light signal to the sensor input terminal;

blocking only one of the light signals selected from the group of the reference light signal and the received light signal at pre-selected times so that the sensor produces a first signal for the non-selected light signal that does not contain a component of the selected light signal and a second signal that contains components of both light signals;

making an output signal that is a function of the first and second signals.

26. The method of claim 25, wherein the blocking step further comprises the steps of:

selecting the reference light signal.

27. The method of claim 26, comprising the further steps of:

determining the first signal value as a function of the received light signal.

28. A shutter for switching optical signals between first and second optical components, comprising:

a flexible portion extending along a first axis and having first and second end regions, the first end region being held fixed with respect to the first and second optical components;

a light stop associated with the flexible portion;

a flat coil mounted on the flexible portion in the second end region;

a magnet positioned near the flat coil but stationary with respect thereto, the flat coil and the magnet cooperating to move the light stop between the first and second optical components when the flat coil is in a first energization state.

29. The shutter of claim 28 wherein:

the magnet and the flat coil cooperate to move the light stop out from between the optical components when the flat coil is in a second energization state.

30. An electrical actuator, comprising:

a fixed portion

a flexible portion extending along a first axis and having first and second end regions, the first end region being connected to the fixed portion;

a flat coil mounted on the flexible portion in the second end region;

a magnet positioned near the flat coil but stationary with respect thereto, the flat coil and the magnet cooperating to move the second end region to a first position when the flat coil is in a first energization state.

31. The actuator of claim 30, wherein:

the magnet and the flat coil cooperate to move the second end region to a second position when the flat coil is in a second energization state.

32. The actuator of claim 31, wherein:

the second end region is in a third position between the first and second positions when the flat coil is in a third energization state.