Patent ID: 8152365

Claim:
A method for determining at least one optical characteristic of a substrate comprising: emitting light onto a first surface of a substrate, the substrate including the first surface and a second and opposite surface separated from the first surface by a thickness; directing the light through an optical pathway that includes at least one optical device separate from the substrate that separates the light reflected from the first surface from light reflected from the second surface; wherein the optical device comprises a focusing device having a focal length sufficient to at least partially separate the path of the light reflected from the second surface from the path of the light reflected from the first surface; detecting the amount of light reflected from the first surface; and based on the amount of detected light reflected from the first surface, determining at least one optical characteristic of the substrate, the characteristic comprising a reflectivity, an emissivity, absorptivity, or a transmissivity of the first surface, or a reflectance, an emittance, an absorptance, or a transmittance of the substrate, or mixtures of any of the above.