  In the Leidenfrost effect, liquid drops deposited on a hot surface levitate
on a thin vapor cushion fed by evaporation of the liquid. This vapor layer
forms a concave depression in the drop interface. Using laser-light
interference coupled to high-speed imaging, we measured the radius, curvature,
and height of the vapor pocket, as well as non-axisymmetric fluctuations of the
interface for water drops at different temperatures. The geometry of the vapor
pocket depends primarily on the drop size and not on the substrate temperature.
