a source of optical radiation;

an optical device optically coupled with the source of optical radiation, the optical device being configured to produce two replicas of the optical radiation propagating therethrough having an optical path length difference, the optical device including means for changing the optical path length difference for the two replicas of the optical radiation;

a delivering device configured to form and deliver an optical radiation beam to an associated sample, the delivering device including a proximal part and a distal part, the distal part of the delivering device including a reference reflector placed at a predetermined optical path length from the front boundary of a longitudinal range of interest of an associated sample;

a directional element configured to direct the two replicas of the optical radiation to the proximal part of the delivering device, and optically coupled with the optical device and with the delivering device; and

a time domain optoelectronic registering unit including a data processing and displaying unit, and optically coupled with the directional element;

wherein the optical path length difference for the two replicas of the optical radiation is generally equal to the predetermined optical path length between the reference reflector and the front boundary of the longitudinal range of interest;

wherein the reference reflector serves as a combining element for producing a combination optical radiation by combining an optical radiation returning from an associated sample with a reference optical radiation reflected from the reference reflector;

wherein the delivering device is further adapted for delivering the combination optical radiation to the directional element, and

wherein the directional element is further adapted for directing the combination optical radiation to the time domain optoelectronic registering unit.