System and method of determining light source aging

• US 9,404,961 B2
• Filed: 12/09/2008
• Issued: 08/02/2016
• Est. Priority Date: 12/09/2008
• Status: Active Grant

• Current Assignee: Covidien LP (Medtronic Plc)
• Original Assignee: Covidien LP (Medtronic Plc)
• Inventors: Gonopolskiy, Oleg, Anderson, Arik, Barrett, Bruce J., Widman, Ronald A.
• Primary Examiner(s): Assouad, Patrick
• Assistant Examiner(s): Zhang, Haidong
• Application Number:
  US12/330,799
• Publication Number:
  US 20100145645A1
• Time in Patent Office: 2,793 Days
• Field of Search: 702/34, 702/57, 702/64, 700/175, 700/176, 700286-298, 250/200, 250/206
• US Class Current: 1/1
• CPC Class Codes: A61B 2560/0223 of calibration, e.g. protocols for calibrating sensors
• CPC Class Codes: A61B 5/14553 specially adapted for cerebral tissue
• CPC Class Codes: G01R 31/2635 Testing light-emitting diodes, laser diodes or photodiodes
• CPC Class Codes: H05B 47/20 Responsive to malfunctions or to light source life; for protection

Abstract

A physiological sensor includes a light source and an age detector circuit in communication with the light source. The age detector circuit is configured to determine an age of the light source based on current-voltage characteristics of said light source. In addition, a method includes measuring an initial I-V characteristic and an actual I-V characteristic of the light source, and comparing the initial I-V characteristic to the actual I-V characteristic since changes in the I-V characteristics indicate aging. Actual I-V characteristics can be compared between light sources when they age at different rates to determine light source aging. Moreover, the method may include updating the memory device with the actual I-V characteristic at predetermined times.

Claims

1. A monitoring system comprising:

a sensor having a light source; and

an age detector circuit in communication with said light source and configured to determine an age of said light source based on a current-voltage characteristic of said light source;

wherein said age detector circuit includes a memory device configured to store an initial current-voltage characteristic of said light source and wherein said age detector circuit is configured to update said memory device with an actual current-voltage characteristic of said light source that is measured after storing the initial current-voltage characteristic of said light source; and

an interference detection circuit in communication with said memory device and said age detector circuit and wherein the interference detection circuit is configured to measure interference caused by an external source of electromagnetic energy and allow said age detector circuit to communicate with said memory device only when no substantial interference from a source of electromagnetic energy is present.

2. A monitoring system as set forth in claim 1, wherein said age detector circuit is configured to compare the initial current-voltage characteristic of said light source to the actual current-voltage characteristic of said light source to determine the age of said light source.

3. A monitoring system as set forth in claim 1, wherein said interference detection circuit is configured to allow said age detector circuit to communicate with said memory device when substantially no light is emitted from said light source.

4. A monitoring system as set forth in claim 2, wherein said age detector circuit includes a voltage detector circuit in communication with said light source and wherein said voltage detector circuit is configured to measure the actual current-voltage characteristics of said light source.

5. A monitoring system as set forth in claim 4, wherein said voltage detector circuit is configured to detect a forward voltage of said light source.

6. A monitoring system as set forth in claim 1, wherein said initial current-voltage characteristic and said actual current-voltage characteristic each comprises a forward voltage of the light source.

7. A method comprising:

measuring an initial current-voltage characteristic of a light source of a physiological sensor;

storing the initial current-voltage characteristic in a memory device;

measuring an actual current-voltage characteristic of the light source;

measuring interference caused by an external source of electromagnetic energy;

updating the memory device with the actual current-voltage characteristic of said light source that is measured after to storing the initial current-voltage characteristic of said light source, wherein the updating of the memory is allowed to occur only while no substantial interference from a source of electromagnetic energy is present; and

comparing the initial current-voltage characteristic of the light source to the actual current-voltage characteristic of the light source to determine an age of the light source.

8. A method as set forth in claim 7, further comprising accessing the memory device to retrieve the initial current-voltage characteristic of the light source.

9. A method as set forth in claim 7, further comprising updating the memory device when substantially no light is emitted from said light source.

10. A method as set forth in claim 7, further comprising updating the memory device when no forward voltage passing through the light source is measured.

11. A method as set forth in claim 7, wherein measuring the initial current-voltage characteristic of the light source includes measuring an initial forward voltage of the light source.

12. A method as set forth in claim 11, wherein measuring the actual current-voltage characteristic of the light source includes measuring an actual forward voltage of the light source.

13. A method as set forth in claim 12, wherein comparing the initial current-voltage characteristic of the light source to the actual current-voltage characteristic of the light source includes comparing the initial forward voltage of the light source to the actual forward voltage of the light source to determine the age of the light source.

14. A monitoring system as set forth in claim 7, wherein said initial current-voltage characteristic and said actual current-voltage characteristic each comprises a forward voltage of the light source.

15. A monitoring system comprising:

a physiological sensor having a light source; and

an age detector circuit in communication with said light source and configured to determine an age of said light source based on a current-voltage characteristic of said light source;

wherein said age detector circuit includes a memory device configured to store an initial current-voltage characteristic of said light source and wherein said age detector circuit is configured to update said memory device with an actual current-voltage characteristic; and

an interference detection circuit in communication with said memory device and said age detector circuit and wherein the interference detection circuit is configured to measure interference caused by an external source of electromagnetic energy and allow said age detector circuit to communicate with said memory device only when no substantial interference from a source of electromagnetic energy is present;

wherein said age detector circuit is configured to adjust the initial current-voltage characteristic stored in the memory device to compensate for a current ambient temperature.

16. A monitoring system as set forth in claim 15, wherein the initial current-voltage characteristic stored in the memory device is an initial forward voltage of the light source.

17. A monitoring system as set forth in claim 15, wherein said initial current-voltage characteristic and said actual current-voltage characteristic each comprises a forward voltage of the light source.