Patent ID: 7233396

Claim:
A sensor for determining the optical properties of a sample material, the sensor comprising: a light source for generating a first light beam having first and second lightwaves, the first lightwave having a first linear polarization and the second lightwave having a second linear polarization, the first and second linear polarizations being substantially orthogonal to each other, the first and second lightwaves being in phase relative to each other; an optical retarder for providing a substantially 90 degree phase shift between the first and second lightwaves by imposing a relative delay between the first and the second lightwaves; an optical interface for reflecting the first light beam from the sample material under total internal reflection conditions; a polarizing beam splitter for splitting the first beam into a second light beam and a third light beam after the first light beam is reflected from the optical interface, the second and third light beams consisting of combined projections of mutually orthogonal polarization components on the main axes of the beam splitter; a signal processor for measuring the intensity difference between the second and the third light beams to calculate the phase difference induced by the sample material, the signal processor receiving a first intensity measurement from a first detector and a second intensity measurement from a second detector, the first and second detectors measuring the intensities of the second and third light beams, respectively.