Manual and automatic probe calibration

• US 5,758,644 A
• Filed: 06/07/1995
• Issued: 06/02/1998
• Est. Priority Date: 06/07/1995
• Status: Expired due to Term

• Current Assignee: Masimo Corporation
• Original Assignee: Masimo Corporation
• Inventors: Kiani, Massi E., Diab, Mohamed Kheir, Lepper, James M. Jr., Ragsdale, Charles Robert
• Primary Examiner(s): Bahr, Jennifer
• Assistant Examiner(s): WINAKUR, ERIC FRANK
• Application Number:
  US08/478,493
• Time in Patent Office: 1,091 Days
• Field of Search: 128/633, 128/634, 128/664, 128/665, 356/39, 356/41, 315/151, 315/307, 315/310, 315/311, 250/552, 250/214 R
• US Class Current: 600/323
• CPC Class Codes: A61B 2562/08 Sensors provided with means for identification, e.g. barcodes or memory chips
• CPC Class Codes: A61B 5/0205 Simultaneously evaluating both cardiovascular conditions and different types of body conditions, e.g. heart and respiratory condition
• CPC Class Codes: A61B 5/02427 Details of sensor
• CPC Class Codes: A61B 5/14552 Details of sensors specially adapted therefor
• CPC Class Codes: A61B 5/1495 Calibrating or testing of in-vivo probes
• CPC Class Codes: A61B 5/6826 Finger
• CPC Class Codes: A61B 5/6838 Clamps or clips
• CPC Class Codes: G01J 2003/2866 Markers; Calibrating of scan
• CPC Class Codes: G01J 3/02 Details
• CPC Class Codes: G01J 3/0254 Spectrometers, other than colorimeters, making use of an integrating sphere
• CPC Class Codes: G01J 3/027 Control of working procedures of a spectrometer; Failure detection; Bandwidth calculation
• CPC Class Codes: G01J 3/0275 making use of sensor-related data, e.g. for identification of sensor parts or optical elements
• 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 2021/3144 for oxymetry
• CPC Class Codes: G01N 21/255 Details, e.g. use of specially adapted sources, lighting or optical systems
• CPC Class Codes: G01N 21/274 Calibration, base line adjustment, drift correction
• CPC Class Codes: G01N 21/31 Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry G01N21/72 takes precedence
• CPC Class Codes: G01N 21/3151 using two sources of radiation of different wavelengths G01N21/33 - G01N21/39 take precedence
• CPC Class Codes: G01N 21/39 using tunable lasers
• CPC Class Codes: G01N 2201/0627 : Use of several LED's for spectral resolution

Abstract

The method and apparatus of the present invention provides a system wherein light-emitting diodes (LEDs) can be tuned within a given range by selecting their operating drive current in order to obtain a precise wavelength. The present invention further provides a manner in which to calibrate and utilize an LED probe, such that the shift in wavelength for a known change in drive current is a known quantity. In general, the principle of wavelength shift for current drive changes for LEDs is utilized in order to allow better calibration and added flexibility in the use of LED sensors, particularly in applications when the precise wavelength is needed in order to obtain accurate measurements. The present invention also provides a system in which it is not necessary to know precise wavelengths of LEDs where precise wavelengths were needed in the past. Finally, the present invention provides a method and apparatus for determining the operating wavelength of a light emitting element such as a light emitting diode.

Claims

1. An oximeter sensor comprising:

a first light emitting device configured to generate light at a first known wavelength and which is active at or above a first voltage level and inactive below said first voltage level;

an information element electrically connected in parallel with said first light emitting device; and

a detector responsive to light which originated from said first light emitting device to generate an output signal.

2. The oximeter sensor of claim 1, wherein said information element operates at a voltage level below said first voltage level.

3. The oximeter sensor of claim 1, where said information element comprises a resistor.

4. The oximeter sensor of claim 1, wherein said information element comprises an impedance network.

5. The oximeter sensor of claim 1, wherein said information element comprises a memory device.

6. The oximeter sensor of claim 1, wherein the light emitting device comprises a light emitting diode.

7. The oximeter sensor of claim 1, wherein said information element comprises an encoding resistor, the resistance value of said encoding resistor indicative of the first known wavelength value, and the resistance value sufficiently high such that the encoding resistor draws effectively insignificant current during active operation of said first light emitting device.

8. The oximeter sensor of claim 1, wherein said information element comprises a security element, the security element indicative that the oximeter sensor is of a predetermined type.

9. The oximeter sensor of claim 8, wherein said security element comprises a resistor with a resistance value that is sufficiently high such that the resistor draws effectively insignificant current during active operation of said first light emitting device.

10. A sensor system comprising:

at least one light emitting element;

at least one photosensing element;

an information element electrically coupled in parallel with said at least one light emitting element;

a controller connected to said at least one light emitting element and said information element coupled in parallel, said controller addressing said information element below a first voltage and said at least one light emitting element at or above said first voltage.

11. The sensor system of claim 10, wherein said at least one light emitting element is a light emitting diode and said information element is a resistor.

12. The sensor system of claim 11, wherein the resistance of said resistor is sufficiently high that current flowing through said resistor is insignificant when said light emitting diode is addressed at or above said first voltage.

13. The sensor system of claim 11, wherein said resistor has a resistance value indicative of a first known wavelength value for said at least one light emitting element.

14. An oximeter sensor system comprising:

a first light emitting device configured to generate light at a first known wavelength when active said first light emitting device active at and above a first voltage and inactive below said first voltage;

an information element electrically connected in parallel with said first light emitting device;

a photodetector responsive to light which originated from said first light emitting device to generate an output signal; and

a controller coupled to said light emitting device and said information element, said controller addressing said information element at a voltage below said first voltage and addressing said first light emitting device at a voltage at or above said first voltage to activate said first light emitting device.

15. The oximeter sensor system of claim 14, wherein said information element comprises an encoding resistor, the resistance value of said encoding resistor indicative of the first known wavelength value.

16. The oximeter sensor system of claim 15, wherein the resistance value of said resistor is sufficiently high such that most of the current flows through the first light emitting device when a voltage at or above the first voltage is applied across said first light emitting device and resistor.

17. The oximeter system of claim 14, wherein said information element comprises a memory device.

18. The oximeter sensor system of claim 14, wherein at a voltage level below said first voltage level, said light emitting device draws substantially insignificant current.

19. The oximeter sensor system of claim 14, further comprising a second light emitting device configured to generate light at a second known wavelength, said second light emitting device connected in a back-to-back configuration with said first light emitting device.

20. The oximeter sensor system of claim 14, wherein said controller is configured to cyclicly activate said first light emitting device at or above said first voltage and cyclicly read said information element at a voltage below said first voltage.

21. A sensor system comprising:

at least one light emitting element;

at least one photosensing element;

an information element electrically coupled in parallel with said at least one photosensing element;

a controller connected to said at least one photosensing element and said information element in parallel, said controller addressing said information element at a predetermined voltage wherein said at least one photosensing element is inactive at said predetermined voltage.

22. A physiological sensor comprising:

a first light emitting device configured to generate light and which is active at or above a predetermined non-zero voltage, and inactive below said predetermined voltage;

an information element electrically connected in parallel with said first light emitting device, said information element readable at a voltage below said predetermined non-zero voltage; and

a detector responsive to light which originated from said first light emitting device to generate an output signal.

23. The physiological sensor of claim 22, wherein said first light emitting device is a light emitting diode which draws insignificant current at a non-zero voltage below said predetermined voltage.

24. The physiological sensor of claim 23, wherein said information element is a resistor.

25. The physiological sensor of claim 24, further comprising a second light emitting device electrically connected in parallel and opposite polarity with said first light emitting device.

26. The physiological sensor of claim 24, wherein said predetermined non-zero voltage is approximately 1.5 volts.