  The Jefferson Lab CLAS12 detector will provide a world-leading facility for
the study of electron-nucleon scattering. The CLAS12 physics program is very
broad and includes studies on quarks dynamics as well as studies on the meson
and baryon spectroscopy with quasi-real photoproduction in a large variety of
final states. The particle identification will be complemented by a ring
imaging Cherenkov detector (RICH), that will provide separation of kaons from
protons and pions in the momentum range between 3 and 8 GeV/c allowing the
study of pion and kaon electroproduction in semi-inclusive deep inelastic
scattering as well as studying double and triple strange baryons. In this
article, we will focus on the new technologies developed for the RICH,
especially on the complex optical system, that allows to reduce the
photo-detection area. Particular attention is given to the characterization of
the surface in relationship with the simulation capability of GEANT4.
