In this paper, an ellipsometric method well suited for optical propert
y measurements of a single layer, or even, a multi-layers surface film
over layed on a substrate is described. This method allows a high pre
cision on the ellipsometric angles Psi and Delta, especially when the
angle of incidence, phi(i), is fixed near the principal angle of incid
ence, phi(p). This ellipsometer is very easy to build and implement, I
t only requires classical polarimetric and electronic components. More
over, it is achromatic and easy to automate. Measurement of a very thi
n SiO2 layer on Si is presented.