We modified an optical microscope to enable quantitative ellipsometric stud
ies with I nm height and 0.9 mu m lateral resolution. A beam of polarised l
ight impinging on the object under a shallow angle of incidence is generate
d by focusing a pinhole into an off-axis point in the back focal plane of a
high-power microscope objective. The entire image of the object is focused
which greatly reduces stray light. In addition, this enables a drastic red
uction of the measuring time. For thicknesses of organic films exceeding 20
nm both the film thickness and its refractive index may be determined simu
ltaneously.