Integrated optical filter system with low sensitivity to high angle of incidence light for an analyte sensor
Apparatuses and methods for improving the accuracy of an analyte sensor are disclosed. The sensor may include a photodetector and a low angle sensitive (LAS) optical filter. The photodetector may be configured to convert received light into current indicative of the intensity of the received light. The LAS optical filter may be configured to prevent light having a wavelength outside a band pass region from reaching the photodetector and to pass light having a wavelength within the band pass region to the photodetector. The percentage of light passing through the LAS optical filter may decrease as the angle of incidence of the light increases.
1. A sensor for measurement of an analyte in a medium within a living animal, the sensor comprising:
a first photodetector configured to convert received light into current indicative of the intensity of the received light;
a second photodetector configured to convert received light into current indicative of the intensity of the light received by the second photodetector;
an analyte indicator configured to emit emission light within a first band pass region;
a light source configured to irradiate excitation light within a second band pass region different than the first band pass region to the analyte indicator;
a first low angle sensitive (LAS) optical filter comprising layers of metal and oxides, wherein the layers of metal and oxides of the first LAS optical filter are configured to:
prevent light having a wavelength outside the first band pass region from reaching the first photodetector,
permit light reaching the first LAS optical filter at a first angle of incidence and having a wavelength within the first band pass region to pass to the first photodetector at a first transmission percentage, and
permit light reaching the first LAS optical filter at a second angle of incidence higher than the first angle of incidence and having a wavelength within the first band pass region to pass to the first photodetector at a second transmission percentage, wherein the second angle of incidence is greater than 25 degrees, the second transmission percentage is lower than the first transmission percentage and greater than zero, and the first LAS optical filter utilizes dichroic and absorptive filtering; and
a second LAS optical filter comprising layers of metal and oxides, wherein the layers of metal and oxides of the second LAS optical filter are configured to:
prevent light having a wavelength outside the second band pass region from reaching the second photodetector,
permit light reaching the second LAS optical filter at the first angle of incidence and having a wavelength within the second band pass region to pass to the second photodetector at a third transmission percentage, and
permit light reaching the second LAS optical filter at a second angle of incidence higher than the first angle of incidence and having a wavelength within the second band pass region to pass to the second photodetector at a fourth transmission percentage, wherein the fourth transmission percentage is lower than the third transmission percentage and greater than zero.
2. The sensor of claim 1 , wherein the first LAS optical filter is a plasmonic nanostructured filter.
3. The sensor of claim 1 , wherein the layers of metal and oxides of the first LAS optical filter have a thickness configured to pass light within the first band pass region.
4. The sensor of claim 1 , wherein the layers of metal and oxides of the first LAS optical filter are deposited on the first photodetector.
5. The sensor of claim 4 , wherein the layers of metal and oxides of the first LAS optical filter are deposited on the first photodetector by magnetron sputter coating.
6. The sensor of claim 1 , further comprising a glass slide positioned on the first photodetector, wherein the layers of metal and oxides of the first LAS optical filter are deposited on the glass slide.
7. The sensor of claim 6 , wherein the glass slide comprises an exit surface opposite a receiving surface, and the layers of metal and oxides of the first LAS optical filter are deposited on the exit surface of the glass slide.
8. The sensor of claim 1 , wherein the first bandpass region shifts by 20 nm or less as the angle of incidence of light received by the first LAS optical filter increases from 0 degrees to 89 degrees.
9. The sensor of claim 1 , wherein the first angle of incidence is less than or equal to 25 degrees.
10. The sensor of claim 1 , wherein the first angle of incidence is less than or equal to 20 degrees.
11. The sensor of claim 1 , wherein the first angle of incidence is less than or equal to 15 degrees.
12. The sensor of claim 1 , wherein the first angle of incidence is less than or equal to 10 degrees.
13. The sensor of claim 1 , wherein the first angle of incidence is less than or equal to 5 degrees.
14. A method of detecting an analyte using a sensor comprising a light source, an analyte indicator, a first low angle sensitive (LAS) optical filter comprising layers of metal and oxides, a second LAS optical filter comprising layers of metal and oxides, a first photodetector, and a second photodetector; the method comprising:
irradiating, by the light source, excitation light to the analyte indicator;
emitting, by the analyte indicator, emission light within a first band pass region, wherein the excitation light is within a second band pass region different than the first band pass region;
receiving, by the first LAS optical filter, first light comprising emission light emitted by the analyte indicator, wherein the first LAS optical filter utilizes dichroic and absorptive filtering;
preventing, by the layers of metal and oxides of the first LAS optical filter, light of the received first light having a wavelength outside the first band pass region from reaching the first photodetector;
permitting, by the layers of metal and oxides of the first LAS optical filter, light of the received first light having a first angle of incidence and a wavelength within the first band pass region to reach the first photodetector at a first transmission percentage;
permitting, by the layers of metal and oxides of the first LAS optical filter, light of the received first light having a second angle of incidence higher than the first angle of incidence and a wavelength within the first band pass region to reach the first photodetector at a second transmission percentage, wherein the second angle of incidence is greater than 25 degrees, and the second transmission percentage is lower than the first transmission percentage and greater than zero;
receiving, by the second LAS optical filter, second light comprising excitation light irradiated by the light source;
preventing, by the layers of metal and oxides of the second LAS optical filter, light of the received second light having a wavelength outside the second band pass region from reaching the second photodetector;
permitting, by the layers of metal and oxides of the second LAS optical filter, light of the received second light having the first angle of incidence and a wavelength within the second band pass region to reach the second photodetector at a third transmission percentage;
permitting, by the layers of metal and oxides of the second LAS optical filter, light of the received second light having the second angle of incidence and a wavelength within the second band pass region to reach the second photodetector at a fourth transmission percentage, wherein the fourth transmission percentage is lower than the third transmission percentage and greater than zero.