A relationship between Jones and Mueller matrices originally derived f
or random media is applied to incoherence effects in photometric ellip
sometry. Such effects are for example depolarization after reflection
from a sample with varying film thickness or from a layer which is thi
cker than the coherence length of the incident light. The main task is
to calculate the expectation value of a statistical ensemble. For the
important case of thick layers, this expectation value is derived in
a symbolic form. Results calculated with this method for transmission
ellipsometry, ellipsometry at the back surface of the substrate and th
e determination of the optical constants at the substrate-layer interf
ace are compared with measurements. (C) 1997 Elsevier Science S.A.