A fully automatic optical microscope (FAOM) for on-line analysis of micro-objects is described. The system has many capabilities, such as autofocusing, autocounting, autoscanning, producing optical images corresponding to different depths in the sample, contour and edge finding, etc. The autofocusing can be achieved with more than one method. The system can be used for analysis and counting (high-density) micro-objects, such as particle tracks in plastic detectors. The processing speed of the system is adequate and it can be used in analysis of macro samples. The software of the FAOM is written in C++ and runs under Microsoft Windows operating systems. (C) 2002 Elsevier Science B.V. All rights reserved.