Systems, apparatus, and methods for discriminating optical signals
An analyte sensor incorporates one or more techniques for discriminating between different optical signals. In one embodiment, the sensor includes a photodetector that detects a narrow band optical signal. In another embodiment, the sensor includes a multilayer filter including an absorption filter, a reflection filter, and a transparent layer between the absorption and reflection filters. In another embodiment, the sensor employs an indicator that emits light for a period of time after an excitation source is turned off. In another embodiment, the sensor employs a first indicator that is excited by an excitation light source and a second indicator that is excited by light emitted by the first indicator. The second indicator emits light for a period after the excitation source is turned off. In another embodiment, excitation light is polarized by a first polarizer, and a second polarizer at a photodetector passes only light polarized by the first polarizer.
1. An analyte sensor comprising:
an excitation light source configured to emit light within an excitation wavelength range;
a first indicator configured to emit first light within a first indicator wavelength range when in the presence of an analyte of interest and when energized by light within the excitation wavelength range;
a second indicator configured to emit second light with a second indicator wavelength range when energized by the first light within the first indicator wavelength range; and
an indicator signal photodetector positioned to receive the second light emitted by the second indicator;
wherein the indicator signal photodetector is configured to make a second light reading during a period of time after the excitation light source stops emitting light.
2. The analyte sensor of claim 1 , wherein the period of time is 0.3 msec to 10 msec.
3. The analyte sensor of claim 1 , wherein the second indicator comprises a fluorophore.
4. An analyte sensor comprising:
an excitation light source configured to emit light within an excitation wavelength range;
a first indicator configured to emit light within a first indicator wavelength range when in the presence of an analyte of interest and when energized by light within the excitation wavelength range;
a second indicator positioned to receive light emitted by the first indicator and configured to emit light within a second indicator wavelength range when energized by light emitted by the first indicator; and
an indicator signal photodetector positioned to receive light emitted by the second indicator,
wherein the second indicator is configured to continue to emit light for a period of time after the excitation light source stops emitting light.
5. The analyte sensor of claim 4 , wherein the period of time is 0.3 msec to 10 msec.
6. The analyte sensor of claim 4 , wherein the first indicator and the second indicator each comprises a fluorophore.
7. The analyte sensor of claim 4 , wherein the first indicator wavelength range encompasses 435 nm.
8. The analyte sensor of claim 4 , wherein the excitation wavelength range is 10 nm to 400 nm.
9. The analyte sensor of claim 4 , wherein the second indicator wavelength range encompasses 600 nm.
10. A method comprising:
using an excitation light source of an analyte sensor to emit excitation light within an excitation wavelength range;
using a first indicator of the analyte sensor to emit first light within a first indicator wavelength range when in the presence of an analyte of interest and when energized by the excitation light within the excitation wavelength range;
using a second indicator of the analyte sensor to receive the first light emitted by the first indicator and to emit second light within a second indicator wavelength range when energized by the first light emitted by the first indicator;
using the excitation light source to stop emitting the excitation light, wherein the second indicator continues to emit the second light for a period of time after the excitation light source stops emitting the excitation light; and
during the period of time after the excitation light source stops emitting the excitation light, using an indicator signal photodetector of the analyte sensor to receive the second light emitted by the second indicator and make a second light reading.
11. The method of claim 10 , wherein the period of time is 0.3 msec to 10 msec.
12. The method of claim 10 , wherein the second indicator comprises a fluorophore.
13. The method of claim 10 , wherein the first indicator wavelength range encompasses 435 nm.
14. The method of claim 10 , wherein the excitation wavelength range is 10 nm to 400 nm.
15. The method of claim 10 , wherein the second indicator wavelength range encompasses 600 nm.