Depth From Focus (DFF) Utilizing the Large Measuring Volume of a Nanopositioning and Nanomeasuring Machine

摘要

At the Technische Universitaet Ilmenau a nanopositioning and nanomeasuring machine (NPM machine) has been developed, which allows highly exact dimensional and traceable positioning with subnanometre resolution and nanometre uncertainty within a measuring volume of 25 x 25 x 5 mm~3. The article deals with the utilization of the device’s very high precision and large effective range for an areal sensor based on the focus-variation principle. During a single measuring process the sample is moved in vertical direction through the virtual focal plane. The vertical positions of the sample at the intersectionpoints with the focal plane are corresponding with its topography. The position of maximum sharpness is indicated by the curve of a focus criterion, which is calculated around a lateral neighbourhood for every pixel by the wavelettransformation. The capabilities of exact positioning enables the stitching of adjacent measurement areas without complex registration algorithms and independent of the sample topography.