Patent ID: 7619725

Claim:
A critical wavelength refractometer comprising: a broadband light source; a sensor, wherein an entrance face of said sensor is optically coupled to said broadband light source, said sensor comprised of at least one sensing surface, wherein light emitted by said broadband light source and optically coupled to said sensor undergoes a plurality of internal reflections within said sensor, wherein a portion of said plurality of internal reflections are against said at least one sensing surface, wherein said portion is comprised of multiple reflections, and wherein for each of said multiple reflections a first fraction of said light is reflected from said sensing surface and a second fraction of said light passes through said sensing surface, wherein said first and second fractions of said light are a function of an index of refraction of a material in contact with said at least one sensing surface; a detector optically coupled to an exit face of said sensor, said detector measuring spectral intensity for said first fraction of said light passing through said sensor and exiting through said exit face of said sensor; and a microprocessor coupled to said detector, said microprocessor determining a critical wavelength for said material and said index of refraction for said material from said spectral intensity.