| Apparatus for determining a layer thickness of a plurality of layers arranged on a body, wherein said apparatus comprises a first measuring device configured to determine a layer thickness of at least one of said plurality of layers by performing one or more measurements, preferably measurements based on time-domain reflectometry, using Terahertz, THz, radiation, wherein said apparatus further comprises a second measuring device configured to determine a layer thickness of at least one of said plurality of layers by performing one or more measurements based on an optical signal. |
