The three-dimensional imaging system has been developed in the form of an attachment to a SEM, which consists of a
combined directional electron detector, a frame-grabber and a PC-based processing unit. The detector head is integrated
with the intermediate vacuum system to separate the sample chamber allowing gas pressure over 10 hPa and the electron
optical column where high vacuum must be maintained. Quantitative information about the surface topography is
obtained by digital processing of four input images acquired from four electron detectors. The multi-detector system
developed by authors comprises two quadruple backscattered electron detectors (of the semiconductor and ionisation
types) and an ionisation secondary electron one. The semiconductor detector is dedicated for imaging of nonconductive
surfaces while the ionisation one can be also used for wet or even semiliquid samples.