Reed, M. G., Wilson, T., Juskaitis, R. and Neil, M. A. A.
Surface profiling of combustion chamber deposits using aperture correlation confocal microscopy. Journal of Microscopy 189: 188-191 (1998).

The depth discrimination capability of a confocal microscope can be used to generate height-coded maps of surface topography from reflective surfaces. However, this surface profiling ability is severely limited when black surfaces are examined. In this paper we describe how a new form of confocal microscopy, known as self-correlating aperture microscopy, can be used to obtain surface topographies from the black carbonaceous deposits found in the combustion chambers of internal combustion engines. The technique is nondestructive and requires no sample preparation. The stereo pair images presented show the range of different morphologies found in combustion deposits generated by different fuel chemistries.