Beschreibung:
<jats:title>Abstract</jats:title><jats:p>For determination of film thickness with a reflectometer, the incident light is usually perpendicular to the film. Often, however, measuring heads are used that keep the aperture of the optical fiber constant or even microscopes are used to increase the lateral resolution in film thickness determination. Analogous to a fixed angle of incidence α the thickness determination is influenced in both cases. In contrast to a fixed angle now all angles between 0° and the aperture angle α<jats:sub>apt</jats:sub> are present for a measuring head or a microscope objective. We demonstrate here, how the aperture of the measuring head affects the thickness determination and give a quantitative estimation of the influence by assigning an effective angle of incidence α<jats:sub>eff</jats:sub> to a measuring head with aperture angle α<jats:sub>apt</jats:sub>.</jats:p>