Angle of incidence selective band pass filter for implantable chemical sensor

A method of detecting the concentration of an analyte using a sensor comprising a light source, indicator molecules, an angle of incidence filter element, a dichroic band pass filter, and a photodetector;

• the method comprising:
• irradiating, by the light source, excitation light to the indicator molecules;
• emitting, by the indicator molecules, emission light to the angle of incidence filter element;
• receiving, by a receiving surface of the angle of incidence filter element, light including the emission light;
• preventing, by the angle of incidence filter element, light of the received light having an angle of incidence greater than a threshold angle relative to an axis perpendicular to the receiving surface from reaching the dichroic band pass filter;
• propagating, by the angle of incidence filter element, light of the received light having an angle of incidence less than the threshold angle relative to the axis perpendicular to the receiving surface;
• preventing, by the dichroic band pass filter, light of the propagated light having a wavelength outside a band pass region of the dichroic band pass filter from reaching the photodetector;
• passing, by the dichroic band pass filter, light of the propagated light having a wavelength within the band pass region of the dichroic band pass filter to the photodetector;
• and
• receiving, by the photodetector, the passed light;
• wherein the angle of incidence filter element is a fiber optic bundle comprising a plurality of optical fibers.

An apparatus comprising:

• a dichroic band pass filter configured to prevent light having a wavelength outside a band pass region from passing through the dichroic band pass filter and to pass light having a wavelength within the band pass region;
• and
• an angle of incidence filter element comprising a receiving surface and configured to prevent light having an angle of incidence relative to an axis perpendicular to the receiving surface greater than a threshold angle from reaching the dichroic band pass filter and to propagate light having an angle of incidence relative to the axis perpendicular to the receiving surface less than the threshold angle to the dichroic band pass filter;
• wherein the angle of incidence filter element is a fiber optic bundle comprising a plurality of optical fibers.

A method of filtering light using an apparatus comprising an angle of incidence filter element and a dichroic band pass filter, the method comprising:

• receiving, by a receiving surface of the angle of incidence filter element, light;
• preventing, by the angle of incidence filter element, light of the received light having an angle of incidence greater than a threshold angle relative to an axis perpendicular to the receiving surface from reaching the dichroic band pass filter;
• propagating, by the angle of incidence filter element, light of the received light having an angle of incidence less than the threshold angle relative to the axis perpendicular to the receiving surface;
• preventing, by the dichroic band pass filter, light of the propagated light having a wavelength outside a band pass region of the dichroic band pass filter from passing through the dichroic band pass filter;
• and
• passing, by the dichroic band pass filter, light of the propagated light having a wavelength within the band pass region of the dichroic band pass filter;
• wherein the angle of incidence filter element is a fiber optic bundle comprising a plurality of optical fibers.