Fast automated scanning of OPERA emulsion films

The use of nuclear emulsions to record tracks of charged particles with an accuracy of better than 1 micron is possible in large physics experiments thanks to the recent improvements in the industrial production of emulsions and to the development of fast automated microscopes. The European Scanning System (ESS) is a fast automatic system developed for the mass scanning of the emulsions of the OPERA experiment, which requires microscopes with scanning speeds of about 20 cm$^2$/h. Recent improvements in the technique and measurements with ESS are reported.