Polarization effect averaging

摘要

In order to reduce polarization dependent error, the polarization state of incident light is set to at least two different states of polarization, and a first optical property is determined separately for each of said at least two states of polarization. Then, an averaging procedure is carried out in order to obtain a mean value of the first optical property or of a property derived therefrom. Alternatively, the averaging procedure can be performed with respect to a DUT property of a device under test that is determined as a function of said first optical property. <IMAGE>