Patent ID: 7889339

Claim:
A rotating compensator broadband spectroscopic ellipsometer for evaluating a sample comprising: a light source configured to generate a polychromatic light beam characterized by a range of useful wavelengths and a known polarization; a first compensator assembly disposed along an optical path of the light beam and a second compensator assembly disposed along the optical path of the light beam, wherein one or both of said first and second compensator assemblies includes a waveplate that is rotatable about an axis substantially parallel to a propagation direction of the light beam wherein the first compensator assembly is configured to induce at least a first effective phase retardation value of a polarization state of the light beam over a first range of wavelengths, wherein the first effective phase retardation value is within a range of effective retardations wherein the second compensator assembly is configured to induce at least a second effective phase retardation value of a polarization state of the light beam over a second range of wavelengths, wherein the second range of wavelengths is complementary to the first range of wavelengths, and wherein the second effective phase retardation value is within the range of effective retardations; an analyzer configured to interact with a portion of the light beam that interacts with the sample and with said first and second compensators; and a detector optically coupled to the analyzer, wherein the detector is configured to measure an intensity of light after interaction with the analyzer as a function of wavelength and of a rotation angle of each of the first and second compensators about its respective axis.