Patent ID: 7016714

Claim:
An optical-based sensor for determining the presence or concentration of an analyte in a medium, said sensor comprising: a substrate, said substrate having a first side and a second side, the first and second sides having regions that are masked; a first radiation source mounted on the first side of said substrate; a second radiation source mounted on the second side of said substrate; a first detector for detecting radiation incident thereon and generating an electrical signal responsive thereto, said first detector mounted on the first side of said substrate; a second detector for detecting radiation incident thereon and generating an electrical signal responsive thereto, said second detector mounted on the second side of said substrate; a first indicator element having an optical characteristic that is affected by the presence or concentration of an analyte, said first indicator element being positioned to receive radiation from said first radiation source; a second indicator element having an optical characteristic that is affected by the presence or concentration of an analyte, said second indicator element being positioned to receive radiation from said second radiation source; and wherein said first detector generates an electrical signal responsive to radiation incident thereon emitted by said first indicator element and wherein said second detector generates an electrical signal responsive to radiation incident thereon emitted by said second indicator element.