System and process for analysing a sample

The present invention concerns a system and a process for analysing a sample (6) comprising an excitation section (1) and an analyse section (7), said excitation section (1) including a light source (2) emitting an incident measurement luminous beam (3), a polarisation state generator (PSG) (4), first optical means (5), and said analyse section (7) comprising a polarisation state analyser (PSA) (8), a detection system (10) and second optical means (9). According to the invention, the excitation section (1) comprises an illumination source (12) emitting an incident visualization luminous beam (22), superposition optical means (13) enabling to the incident visualization luminous beam (22) to be send onto the sample surface (21) through an optical path which is identical to the optical path of the incident measurement luminous beam (3) and the analyse section (7) comprises separation optical means (14) enabling to transmit a part of the reflected or transmitted visualization luminous beam (23) and a part of the reflected or transmitted measurement luminous beam towards a visualization direction (25).