Using confocal microscopy (Microscopes|Confocal), surface profile measurements with a stated repeatability of 0.012 µm can be obtained in the height and 0.02µm for the width. For diffusively reflective surfaces, slopes up to 60° have been measured successfully. In addition, up to three interfaces can be detected allowing the characterisation of thickness profiles. In this way, one can for instance measure the thickness of a glass plate or even the air gap between glass substrates in a Hele-Shaw cell.
A thickness measurement showing three layers. These correspond to the front and back-face of a glass plate and also the front face of the other glass plate. In this way, the thickness of a mounted Hele-Shaw cell can be measured for instance.