Abstract

The most common optical technologies for surface topography measurement are coherence scanning interferometry (CSI), focus variation microscopy (FV) and imaging confocal microscopy (CM). Due to the benefits and drawbacks of each, these instruments are all suited to different measurement tasks, depending on the features present on the surface. In this paper, the surface topographies of two surfaces (an optical flat and a metal additive manufactured [AM] surface) with different slope angles were measured using CSI, FV and CM techniques, on an instrument capable of exploiting all three technologies using interferometric (CSI) and brightfield (FV and CM) 50× magnification objective lenses. Measurement noise obtained by CSI presents a significantly lower value than other technologies due to its sub-nanometre vertical resolution. The surface topography of a 30° tilted optically smooth surface shows the ability of CM to measure higher slope angles compared to CSI, due to the relatively higher numerical aperture of brightfield objective lenses. Although the contrast-based reconstruction algorithm prevents FV from reconstructing smooth surfaces for the instrument used, it makes FV a powerful means for surface topography measurement of complex AM surfaces; verified by comparing the surface topographies of an AM surface obtained by FV, CM and CSI.