Theory of New Reflectometer Techniques
William H. Swindell · Applied Optics · 1968
The theory of new reflectometer techniques which determine the principal angle of incidence theta and the principal azimuth psi is given. To determine theta , the polarizer and analyzer angles are modulated at different frequencies. The difference frequency appears in a component of the detector output, and the amplitude of this component is directly proportional to the cosine of the relative phase of the Fresnel coefficients Consequently, theta is located by searching for a null in this component. A method for observing Psi is given in which angles rather than irradiances are compared. The effects of misalignments of the polarizing elements, imperfect polarizing elements, and source and detector polarization are investigated. The latter can be neglected if simple precautions are taken. Imperfect polarizing elements affect only the determination of psi , and misalignments affect only the determination of theta . Expressions for these effects are derived. The explicit relationships for n and k in terms of theta and Psi are stated, and the associated sensitivity curves are given.