Abstract: In an ellipsometric method and apparatus which, in order to increase the degree of measuring accuracy, uses the principle of comparative ellipsometry in measuring a characteristic such as a layer thickness, a reference surface is divided into first and second equal surface portions with respectively different reflection characteristics which are in substantially symmetrical relationship to the reflection characteristics of the testpiece, the surface portions preferably comprising two different tapering surface layers extending in parallel relationship to each other.

Abstract: An ellipsometric method and apparatus for studying physical properties of a testpiece provides that during the measuring operation the angular positions of a polarizing means and an analyzing means disposed upstream and downstream of the testpiece remain fixed. Two or more discrete, mutually different predetermined states of polarization of the radiation employed are produced between the polarizing means and the testpiece and/or between the testpiece and the analyzing means, by polarization modulating elements which are disposed in the path of the radiation. In each discrete state of polarization, the intensity of the radiation which is polarized in the analyzer is measured and evaluated for determining the polarization properties of the testpiece in a computer.