The Zygo utilises a beam splitter and reference surface to achieve the measurement of sample sur-face topography. The phase difference between the two is analysed by adjusting the height of the reference surface and analysing the effect on each pixel in the collected image. This is performed by the accompanying software, MetroPro and results in a 3D data-set where z-axis values are deter-mined interferometrically and lateral distances are calculated through objective lens calibration.