Microtopometry describes the measurement of surface features, or topography, with a lateral resolution on the order of micrometers, or microns. Critical data for optical engineers, including:
- surface roughness, measured in terms of average roughness, root-mean-square, or rms, roughness, and peak-to-valley roughness, and
- step height, measured as the height above an averages rectangular substrate area,
can be provided in the form of false-color topographic maps or profiles. Such data can guide optical fabrication, substrate preparation, and thin-film development. Depending on the objective employed in the Micromap 512 Mirau inteferometer system described below, the map can cover an area roughly 1 mm square or 0.3 mm square; The horizontal resolution is roughly the wavelength of visible light; about 0.5 µm. The vertical resolution is as small as a few tenths of a nm, but the system can measure step heights and topography as large as 35 µm.