Apparatus and methods for concentration determination using polarized light

An apparatus comprising:

• a first light source polarizer having a first light source polarization axis;
• a second light source polarizer having a second light source polarization axis generally perpendicular to the first light source polarization axis;
• a first light receiver polarizer having a first light receiver polarization axis;
• a first light receiver configured to measure an intensity of light transmitted from the first light receiver polarizer;
• a second light receiver polarizer having a second light receiver polarization axis substantially perpendicular to the first light receiver polarization axis;
• a second light receiver configured to measure an intensity of light transmitted from the second light receiver polarizer;
• and
• an optical merger, wherein the optical merger merges the light from the first polarized light source and the second polarized light source,
• wherein the first and second light receiver polarization axes are generally +/−45 degrees relative to the first and second light source polarization axes.