FMCW heterodyne-detection lidar imager system with improved distance resolution

An FMCW lidar imager system, configured to determine a distance zsc separating it from a scene, comprising:

• a coherent light source, configured to emit a frequency-modulated continuous-wave primary signal Sp;
• a splitting and recombining optical device, configured to split the primary signal Sp into a reference signal Sr that is directed toward a photodetector and into an object signal So that is directed toward the scene, which backscatters a portion of the object signal So, which portion is called the backscattered object signal Sor;
• and configured to direct toward the photodetector, along the same optical axis, the reference signal Sr and a portion Sor,c of the backscattered object signal Sor, which portion is collected by a collecting optical element;
• the collecting optical element, configured to collect the portion Sor,c of the backscattered object signal Sor;
• the photodetector, intended to receive the reference signal Sr and the collected portion Sor,c of the backscattered object signal Sor,c, which interfere to form a heterodyne signal Sh;
• a processing unit, configured to determine the distance zsc of the scene on the basis of a beat frequency of the heterodyne signal Sh;
• a reflector configured to reflect, in the direction of the scene, a portion Sor,nc of the backscattered object signal Sor, which portion is not collected by the collecting optical element,
• the collected portion Sor,c of the backscattered object signal Sor then being formed from first light beams Sor,c(1) that have not been reflected by the reflector and from second light beams Sor,c(2) that have been reflected by the reflector then by the scene;
• the heterodyne signal Sh therefore having a principal component Sh(1) associated with said first light beams Sor,c(1), and a secondary component Sh(2) associated with said second light beams Sor,c(2);
• and wherein the processing unit is configured to determine the distance zsc of the scene on the basis of a beat frequency fb(2) of the secondary component Sh(2) of the heterodyne signal Sh.